Shuffle

Question 1

Describe how R groups interact to determine the tertiary structure of a protein (4)

Answer 1

1 some R groups, attract / repel ;
2 disulfide, bridges / bond ;
3 between, cysteine / SH / S (atoms) ;
4 hydrogen / H, bonds ;
5 ionic bonds between, oppositely charged / + and -, R groups ;
6 hydrophilic R groups, on outside of molecule / in contact with
water (molecules) ;
7 hydrophobic R groups,
on inside of molecule / shielded from water (molecules) ;

Question 2

What are 3 differences between the structure of glycogen and collagen? (3)

Answer 2

1 polysaccharide and protein / polypeptide ;
2 (alpha) glucose (units) amino acid (units) ;
3 identical units different amino acid units ;
4 glycosidic, bonds / links peptide, bonds / links ;
5 branched unb / linear ;
6 non-helical ;
7 one chain (per molecule) three chains (per molecule) ;
8 no cross links cross links (between
chains) ;
9 contains C H O contains C H O N ;

Question 3

State 2 properties of collagen making it suitable for ligaments (2)

Answer 3

strong
insoluble
flexible

Question 4

State two properties of cellulose making it suitable for cell membranes (2)

Answer 4

unreactive
insoluble
flexible
forms H bonds with neighbouring chains

Question 5

Why may some cells not take up a stain? (1)

Answer 5

cells, dead / not respiring ;

no, (metabolic) energy /ATP, to take up stain

Question 6

Describe the function of glycolipid in the cells surface membrance? (5)

Answer 6

1 (acting as) antigens ;
2 identification / recognition, (of cells) as, self / non-self / AW ;
3 cell signalling / described ;
4 receptor / binding site, for, hormone / (chemical) signal / (medicinal / named) drugs ;
5 ref. to receptor / binding site / trigger,on transport proteins / AW ;
6 cell adhesion / to hold cells together (in a tissue) ;
7 attach to water molecules (to stabilise membrane / cell) ;

Question 7

What is the role of the phospholipid bilayer? (1)

Answer 7

to act as a barrier (to, polar / charged, particles) / select what enters or leaves cell ;
ACCEPT selectively permeable or partially permeable membrane
ACCEPT allows small / fat soluble molecules to pass through

Question 8

Explain why new branches are seen growing just under the bark of the cut suface of the plant? (2)

Answer 8

This is where cambium / meristem / xylem / phloem / vascular bundle, is found ;
mitosis/cell division, occurs in cambium (to produce new cells for growth) ;
new cells, differentiate / specialise, (into xylem and phloem) ;
xylem supplies water for, (cell) elongation / (cell) growth ; phloem supplies, sugars / assimilates, for, energy / growth /respiration

Question 9

Suggest why plants need lenticels (cells to allow gases to diffuse into living tissues of the trunk (2)

Answer 9

allow oxygen to reach, cells / tissues (under bark) ;
for (aerobic) respiration ;
animals transport oxygen in, blood / circulation / transport system ;
plants do not transport (much) oxygen in transport system ;
idea that (oxygen not supplied from leaves as) stomata only open in day / no leaves in winter ;

Question 10

Complete this passage about the loop of Henle (6)
Electrolytes such as sodium —– are actively reabsorbed from the filtrate at the —– of the loop of Henle. This reduces the —– —– of the surrounging tissues in the —– of the kidney. The walls od the desending loop are —– to water. The result is that water is reabsorbed from the filtrate by the process of —–.

Answer 10

ions 
asending limb
water potential
medulla 
permeable 
osmosis

Question 11

Predict the effect of a non functioning glucose transport protein on the volume of the filtrate (3)

Answer 11

• volume increase
• glucose lowers water potential graident
• reduction of water potential from the filtrate and cortex
• less water absorbed from desending limb

Question 12

Where are podocytes located? (1)

Answer 12

Bowman’s capsule

Question 13

How does ornithine and citrulline move into and out of the mitrochondria? (2)

Answer 13

• AT as need to be moved more quickly than would be met by diffusion
  OR
• Facilitated diffusion as conversion of ornithine to citrulline creates concentration graidents

Question 14

Give one way in which a laser scanning confocal microscope differs from an electron microscope? (1)

Answer 14

LSCM has a …

• lower resolution
• can have a fluorescent tag
• can see movement
• can say different layers/depths

Question 15

State two reasons why a cell may look in prophase? (2)

Answer 15

• chromosomes condensed
• chromosomes not organised
• nuclear envelope is present
• no nucleolus

Question 16

Explain how the organisation of homologous chromosomes during Metaphase 1 increases genetic variation? (3)

Answer 16

• independent assortment
• (homologous chromosomes) line up along the centre of the cell/metaphase plate/equator
• either chromosome could end up in either cell
• each chromosome of the homologous pair is genetically different

Question 17

Describe a procedure to observe the positions of xylem vessels in a leaf stalk of celery? (2)

Answer 17

• cut a cross-section

- add a stain and observe under a microscope

Question 18

State 1 similarity and 2 differences between the structure of the xylem and the phloem (3)

Answer 18

Similarities: 
-both made up of cells joined end to end
-both made up of more than one cell type
-xylem vessels and sieve tube elements both lack nuclei
Differences:
X lignified P no lignin
X no sieve plated P sieve plates 
X no companion cells P companion cells 
X pits P no pits
X no cytoplasm/organelles P has cytoplasm and some organelles

Question 19

Describe how you would do a dissection of a insect gaseous exchange system? (2)

Answer 19

• cup open exoskeleton

- observe tracheoles/ tracheae using saline solution

Question 20

How is the trachea of a mammal different from that of an insect? (2)

Answer 20

• Mammals have 1 trachea and insects have multiple
• Mammals have a larger diameter
• Mammals have cartilage but insects have chitin
• Mammals have C - shaped cartilage and insects have spiral
• Mammals trachea branches into bronchi while plants into tracheoles
• Mammal trachea has smooth muscle/goblet cells and insect tracheae do not

Question 21

Explain the differences in duration between primary and secondary infection? (2)

Answer 21

Primary is slower due to clonal selection/expansion/production of antibodies.
Secondary is quicker because of memory cells/more antibodies produced/immunological memory.

Question 22

What do scientists need to control when doing biodiversity experiments? (1)

Answer 22

• same time of year/day
• same length/number of transects
• same counting/capture technique
• same place in habitat

Question 23

State 3 adaptations to hydrophytes? (3)

Answer 23

• air spaces in leaves to allow leaves to float to receive light for photosynthesis
• stomata on upper side of leaf so they have access to C02
• roots reduced/absent as not required to obtain water/not wasting resources
• waxy cuticle so water does not block stomata
• reduced vascular tissues due to high water availability

Question 24

Explain why an electrocardiogram may not be an accurate representation of a persons heart rate? (3)

Answer 24

• only 1 cardiac cycle shown
• could be anonymous/atypical
• mean of several cycles would be better

Question 25

Explain how the structure of a phospholipid allows them to form the bilayer? (3)

Answer 25

- hydrophilic head and hydrophobic tail - hydrophobic tail repelled by water - hydrophilic head forms H bonds with water - medium outside plasma membrane in aqueous - hydrophobic nature of tail results in their facing towards each other

Question 26

Suggest what roles these ions have in helping cut plants last longer? (2) H+ Na+

Answer 26

``` H+ = maintain/regulate pH Na+ = regulate water potential ```

Question 27

What causes the fluctuation of pressure in the aorta? (2)

Answer 27

- systole increases pressure - diastole decreases pressure - systole is ventricular - left ventricle

Question 28

Why does pressure have to decrease from the aorta to the capillaries? (2)

Answer 28

- capillary (wall) is, thin / only one cell thick ; - (high pressure would) burst / damage, capillary (wall) ; - reduce chance of, tissue fluid build up / oedema

Question 29

Describe and explain how the wall of an artery is adapted both to withstand and maintain high hydrostatic pressure (5)

Answer 29

``` To withstand pressure: wall is thick ; (thick layer of) collagen ; (wall / collagen) provides strength ; endothelium, corrugated / folded ; idea of: no damage to, endothelium / artery (wall) (as it stretches) ; max 3 ``` To maintain pressure: (thick layer of) elastic tissue / elastic fibres / elastin ; to cause recoil / return to original size ; (thick layer of) smooth muscle ; narrows / constricts, lumen / artery ;

Question 30

How can you tell the distance between the strands in DNA is not always the same? (1)

Answer 30

DNA creates a double helix shape which would not occur if the strands are the same length.

Question 31

How does carrying out replicates improve an investigation? (2)

Answer 31

- calculate a mean - anomalies can be identified - improves repeatability - allows statistical tests to be completed

Question 32

Explain how paralysis of the diaphragm could lead to suffocation? (2)

Answer 32

- no/little increase in volume of thorax - no/little decrease in pressure in the thorax - less air drawn into lungs

Question 33

What effect will reducing the speed of conduction of Purkyne fibres have on heart rate? (3)

Answer 33

- slows/decreases heart rate - slows transmission of impulse from AVN to ventricles - slows ventricular systole - longer delay before ventricular systole begins - increases time the heart is in diastole

Question 34

Explain why the wall of the left ventricle is thicker than the wall of the left atrium? (3)

Answer 34

``` 1 (more muscle to create) more force ; 2 (needs to create) higher pressure ; 3 push blood against greater , resistance / friction ; 4 (left ventricle) pumps blood further / pumps blood to all parts of body / supplies systemic circulation ; ```

Question 35

Explain why the curve for fetal oxyhaemoglobin is to the left of the curve for adult oxyhaemoglobin? (4)

Answer 35

1 fetal haemoglobin has a higher affinity (for oxygen) ( than adult haemoglobin) ; 2 (fetal Hb) takes up oxygen in low(er) partial pressure of oxygen ; 3 placenta has low partial pressure of oxygen ; 4 at low partial pressure of oxygen / in placenta, adult (oxy)haemoglobin will dissociate / AW ;

Question 36

Suggest the effects of kidney failure on the composition of the blood (2)

Answer 36

- higher conc of urea - higher conc of ions/salts - increase in water

Question 37

Explain the need for close matching of a donated kidney to a recipient (3)

Answer 37

Donated kidney will be recognised as foreign/non self Antigens on donated kidney will be different Causing rejection By immune system

Question 38

Explain the ways in which the Bowmans capsule and the Glomerulus are adapted (5)

Answer 38

Ultrafiltration Afferent arteriole is wider than efferent arteriole High hydrostatic pressure in glomerulus Endothelium has gaps to allow passage of substances Basement membrane stops removal of large molecules Podocytes have projections Projections ensure gaps to allow passage

Question 39

ADH is a hormone which is produced by specialised nerve cells known as ---- cells. These cells detect changes in the water potential of the blood flowing through the ----. If the water potential of the blood is too low ADH is released. ADH s not secreted immediately into the blood but passes along the ---- of the specialised nerve cells to the ---- gland where it is released. ADH acts on the cells of the ----. The ADH molecule attaches to the ---- of these cells. (6)

Answer 39

``` Osmoreceptor Hypothalamus Axon Posterior pituitary Collecting duct Cell membrane ```

Question 40

ADH is a hormone. Suggest where it is removed in the blood describing what happens to the ADH molecule (3)

Answer 40

``` Liver cells Hydrolysis of protein Deamination occurs Ornithine cycle Amino acid used in metabolic pathway Ultrafiltration from blood Urea present in urine Excreted ```

Question 41

State two processes which occur in a cell during interphase (2)

Answer 41

- ATP content of cell increased - Cell growth - Protein Synthesis - Checking genetic material - Increase in the number of organelles

Question 42

Who is cell division in a plant different to that in an animal? (2)

Answer 42

Plant: - plate/wall forms - cytokinesis starts from middle of cell - occurs in meristems - no centrioles

Question 43

What does meristematic tissue need to be stained for investigating the number of cells in each phase (2)

Answer 43

- to be able to see the individual chromosomes - to provide a contrast between cell structures - to determine the different stages of mitosis

Question 44

Before division of the nucleus of the cell, the frantic material must replicate in mitosis. State why (2)

Answer 44

- both cells are genetically identical to mother | - both cells receive a diploid number of chromosomes

Question 45

Describe how cells in a multicellular organisms are organised (5)

Answer 45

- cells are differentiated/specialised - cells form tissue - tissues form organs - a group of organs form organ systems - cells/tissues/organs/organ systems work together - named example of tissue/organ/organ system

Question 46

How might the peritoneum differ in its function from the artificial membrane in a dialysis machine used in haemodialysis? (1)

Answer 46

it can perform , active transport / facilitated diffusion

Question 47

Why does the dialysis fluid used in peritoneal dialysis contain dextrose solution rather than water alone? (2)

Answer 47

1 idea that (dialysis is replicating function of kidney and) part of kidney’s function is to remove (excess) water from blood ; 2 (dextrose / sugar) reduces , water potential /  (of dialysis fluid) or (dextrose / sugar , solution) has a lower , water potential /  (than water) ; 3 water moves from blood (into dialysis fluid) by osmosis or prevents water moving into the blood (from dialysis fluid) by osmosis ; 4 (if it was water alone) cells would , swell / burst ;

Question 48

Suggest why patients receiving peritoneal dialysis usually need to have the peritoneal dialysis fluid replaced four times a day, but those receiving haemodialysis only need treatment three times a week (2)

Answer 48

1 peritoneal dialysis can remove less (named) waste (than haemodialysis) ; 2 idea that in haemodialysis dialysis fluid is constantly , refreshed / changed (but not in peritoneal dialysis) ; 3 4 haemodialysis uses counter-current flow ; idea that haemodialysis maintains concentration gradient or in peritoneal dialysis the concentration gradient , reduces / is lower ; 5 (in peritoneal dialysis) the fluid reaches equilibrium with the blood ;

Question 49

The blood in the glomerulus has a high ....................................................... pressure, which forces small molecules, such as glucose and ..................................................... , out of the glomerulus and into the lumen of the Bowman’s capsule. This process is known as ...................................................... . In the proximal convoluted tubule, the glucose, most of the ............................................... and some of the salts are reabsorbed into blood ....................................................... that surround the nephron at this point.

Answer 49

``` hydrostatic ; water / urea / amino acids / vitamins / small proteins ; ultrafiltration ; water ; capillaries / vessels ; ```

Question 50

Suggest and explain what effect the action of aldosterone will have on the secretion of ADH (2)

Answer 50

-water potential of , plasma / blood , will , decrease / become more negative ; -(ADH secretion) will increase ;

Question 51

Which part(s) of the nephron corresponds to each of the statements in the table below? ``` walls are impermeable to water glucose is reabsorbed into the blood ADH acts on the walls contains podocytes most of the water is reabsorbed into the blood ```

Answer 51

``` ascending loop of Henle proximal convoluted tubule collecting duct Bowman's capsule Proximal convoluted tubule ```

Question 52

State the effect that the environment has on discontinuous and continuous variation (2)

Answer 52

of 1 no / little , environmental effect for , (named example of) discontinuous variation / example given for discontinuous variation in (i) as ecf ; 2 some / large , environmental effect for , (named example of) continuous variation / example given for continuous variation in (i) as ecf ;

Question 53

State one advantage and one disadvantage of using clones to test a treatment for a disease (2)

Answer 53

``` advantage (genetically identical so) all react the same or genetic variable controlled ; disadvantage expensive (to produce) or don’t see varied response to drug like in real populations (of mice) or idea that clones (of mice) may have unknown health issue (which would affect responses) ; ```

Question 54

What is meant by homozygous and gene locus? (2)

Answer 54

(individual / cat / genotype with) 2 identical, alleles / version of the gene / forms of the gene ; gene locus position / place / location, of, gene / allele, on chromosome

Question 55

Suggest why physiological problems in pedigree animals are more common than wild animals (2)

Answer 55

1 inbreeding / small or decreasing, gene pool ; 2 homozygous recessive (genotypes) ; 3 gene / allele , for desired characteristic on same chromosome as problem, gene / allele ; 4 selecting for one trait (unintentionally) selects for another ; 5 breeders select for looks not health ; 6 weaker selection against less healthy animals (than in wild) ;

Question 56

Which ions along the axon are at higher concentrations in the extra cellular compared to the intracellular space? (1)

Answer 56

Na+ and Cl-

Question 57

Which is the following brain regions is responsible for controlling balance? (1) - hypothalamus - medulla oblongata - cerebellum - temporal lobe

Answer 57

Cerebellum

Question 58

Where precisely in the body is adrenaline produced? (1)

Answer 58

Adrenal Medulla

Question 59

Are these insitu or exsitu forms of conservation? (1) - seed bank - botanic gardens - SSSI forest - marine reserve

Answer 59

Exsitu Exsitu Insitu Insitu

Question 60

Which of these is the specific location that light dependent reactions take place? (1) 1) chloroplast 2) thylakoid membrane 3) stroma 4) lumen of the grana

Answer 60

2

Question 61

``` By what mechanism is a rare disease found at high frequencies?(1) A) genetic bottleneck B) mutation C) artificial selection D) founder effect ```

Answer 61

D

Question 62

``` On a typical growth curve, what stage would penicillin be produced by the bacteria?(1) A) lag phase B) log phase C) stationary phase D) death phase ```

Answer 62

C

Question 63

Which part of the lac operon codes for the transcription factor? (1)

Answer 63

The regulatory Gene

Question 64

Why is it vital to give someone a booster dose of the same vaccine? (1)

Answer 64

The memory cells have undergone apoptosis

Question 65

Outline the reasons why insects and other animals need well-developed transport systems (3)

Answer 65

high metabolic , demands / rate  need , large oxygen / rapid oxygen , supply  diffusion , not sufficient / too slow / distance too far  (to) maintain , steep / AW , concentration / diffusion , gradient(s)  surface area to volume ratio is (usually) low  (named) metabolite(s) needed by cells / (named) waste(s) removed from cells 

Question 66

How do you know a TEM microscope has been used? (2)

Answer 66

``` 2D image  internal details visible  (named) organelles / ultrastructures , visible  high magnification  high resolution  ```

Question 67

Explain why a plant leaf is described as an organ (4)

Answer 67

organ is collection / AW , of tissues  perform / carry out / adapted to , function / role  leaves have two from: epidermis / spongy mesophyll / palisade mesophyll / vascular / phloem / xylem , (tissues)  (to carry out) photosynthesis / gaseous exchange 

Question 68

What can large standard deviations show on a graph? (1)

Answer 68

That a random error has occured

Question 69

Explain why podocytes are usually unable to undergo mitosis (3)

Answer 69

have already / are , differentiated / specialised (so cannot divide)  2 are in , G0 (phase of cell cycle) / resting phase  3 idea that shape is (too) , irregular / asymmetrical (so cannot divide)  4 cytoskeleton cannot function / spindle (fibres) cannot form 5 (if mitosis occurred) it would alter , number / size , of the , gaps / fenestrations  6 idea that it would alter an aspect of ultrafiltration

Question 70

Explain why the toxins produced by the different strains are described as immunologically distinct and how they are dealt with by the immune system (6)`

Answer 70

1) toxins produced by each strain will be slightly different 2) each toxin with have a different 3D shape 3) toxin acts as an antigen 4) immune response determined by the shape of antigen 5) APC inject antigen and display antigens on surface 6) interaction causes production of interleukins 7) B cells activated by T-Helper cells 8) Clonal selection and clonal expansion 9) B cells differentiate into plasma cells 10) plasma cells produce antibodies 11) by protein synthesis antibodies bind to and neutralise toxins

Question 71

What is meant by an autoimmune disease? (2)

Answer 71

An abnormal immune response | Against tissues normally in the body

Question 72

Suggest why antibodies specific to nuclear proteins are not normally made (1)

Answer 72

They are usually hidden in the nucleus

Question 73

Name two different types of T lymphocytes and describe their role in the immune system (2)

Answer 73

- Helper cells which produce interleukins - Killer cells secrete perforin to kill cells - Memory cells for a faster/secondary immune response

Question 74

State two possible sources of natural medicines (2)

Answer 74

plants and microorganisms

Question 75

Outline the processes that lead to the production of antibodies against an unfamiliar bacterium (3)

Answer 75

- B cells/lymphocytes carry an antibody on surface/complementary to one antigen - Selected/activated B cell clones/divides by mitosis - forms/differentiates into plasma/effector cells - which secretes antibodies/complementary to antigen

Question 76

Explain how helper T cells act to speed up B cell stimulation? (2)

Answer 76

T Helper cells are stimulated by antigen-presenting cells. Release cytokines/interleukins. Stimulate B cells/mitosis/clonal expansion

Question 77

Explain why vaccinations are an example of active immunity (2)

Answer 77

Antibodies produced Activation of lymphocytes of person being vaccinated Memory cells remain

Question 78

Explain why vaccinations are an example of active immunity (2)

Answer 78

- Different pathogens have different antigens - Antigens have a specific shape - Shape of antibody must be complementary to a specific antigen - Different antibody needed for each pathogen

Question 79

Describe the actions of the B lymphocytes in the immune response (8)

Answer 79

- Humoral response - B cells have antigen receptor/carries antibody on its surface - Matches to one antigen - Clonal selection - Selection of B lymphocyte - by macrophages/ APC / T helper cells / interleukins - Clonal expansion - Cells divide by mitosis/clones - Differentiate/specialise - B cells form plasma/effector cells - Secrete/produce antibodies - Antibodies are specific/complementary to an antigen - B cells form memory cells - Secondary response

Question 80

Explain why the response to the subsequent infection is much bigger than the response to vaccination? (3)

Answer 80

Clonal selection Clonal Expansion Differenciation

Question 81

Describe two ways in which the structure of part C is adapted to its function (2)

Answer 81

1 contain , (named) pigment (molecules) / photosystems ; 2 contain , (named) electron carriers / ETC / ATP synth(et)ase ; 3 idea that has a large surface area (in a small volume) for , light absorption / light dependent reaction(s) / light dependent stage / electron transport ;

Question 82

With reference to the biochemistry of photosynthesis, explain why the theoretical rate of photosynthesis is not achieved at higher light intensities (2)

Answer 82

1 at high light intensity other (named) factor becomes a limiting factor ; 2 idea that temperature becomes limiting as , Calvin cycle / light independent reaction , involves enzymes / relies on kinetic energy of molecules ; 3 idea that CO2 (concentration) becomes limiting as it is required for , Calvin cycle / light independent reaction / formation of (named) Calvin cycle compound / reaction with RuBP / fixation by Rubisco ;

Question 83

Suggest one way in which the structure of a leaf in shaded area will differ (1)

Answer 83

shade leaf will have 1 2 3 large(r) / more , chloroplast(s) / (palisade) mesophyll ; more , grana / thylakoids (in chloroplast) ; large(r) surface area (of leaves) ;

Question 84

State the advantage to the plant of having a range of accessory pigments in photosystems (1)

Answer 84

able to , absorb / use , a range of / different / more / other , (light) wavelengths / ;

Question 85

Name the products of the light-dependent of photosynthesis (3)

Answer 85

reduced NADP / NADPH / NADPH2 / NADPH+ ; ATP ; oxygen ;

Question 86

What stage of the DNA cycle does DNA Replication occur? (1)

Answer 86

The synthesis phase of interphase

Question 87

What are the products of DNA replication compared to transcription? (1)

Answer 87

DNA replication produces two double stranded DNA molecules and transcription produces one mRNA molecule

Question 88

What does a stop codon do to stop the formation of the polypeptide? (1)

Answer 88

A stop codon does not bring down any amino acids so the polypeptide chain stops

Question 89

Choose three words which are wrong and replace them (3) Replication takes place in the S-phase of mitosis. The DNA molecules unwinds. Free DNA nucleotides are activated. Thymine pairs with adenosine. The nucleotides are joined by DNA helicase. Cytosine pairs with guanine.

Answer 89

Mitosis - Interphase Adenosine - Adenine DNA helicase - DNA polymerase

Question 90

Outline the processes which occur in G1 and G2 (4)

Answer 90

G1 (2 marks maximum)(more) protein, synthesised / made;(more) cytoplasm volume increases;cell, grows / increases in size;(more) organelles, produced / grow anddivide / replicate; G2(more) organelles, produced / grow anddivide / replicate;energy stores, increase / AW;idea of (DNA) proofreading / checkpoin

Question 91

Outline the processes and organelles involved in the translation of these proteins from RNA (4)

Answer 91

(m)RNA transported out of nucleus (1)(m)RNA transported to / associates withribosome (1)translation / protein synthesis, occurs atribosome (1)(t)RNA brings specific amino acids or(t)RNA described (1)peptide bonds form between adjacentamino acids or peptide bonds described (1)polypeptide / protein processed through Golgi apparatus (1)

Question 92

Describe how gene expression can be regulated after transcription (3)

Answer 92

primary mRNA is modified (1)removal of introns to produce maturemRNA (1)Alternative splicing can produce differentversions of mRNA (1)protein must be activated by cAMP /phosphorylation (1)binding (of cAMP) alters shape of protein

Question 93

Explain why the rate of photosynthesis decreased at temperatures above 25 degrees (4)

Answer 93

1 denaturing of enzyme; 2 change in shape of active site; 3 named photosynthetic enzyme; 4 less photolysis; 5 less ATP produced; 6 named step in Calvin cycle which is affected; A step described 7 increase in rate of respiration; 8 respiration occurring at faster rate than photosynthesis; 9 temperature compensation point; 10 increased rate of transpiration; 11 stomatal closure; 12 less carbon dioxide uptake; 13 AVP; e.g. ref to photorespiration

Question 94

Explain why CO2 was released when CO2 concentrations were low for the plant (2)

Answer 94

ref respiration; production of carbon dioxide; R release (at low concentrations, CO2 was) diffusing / moving down a concentration gradient; respiration faster than photosynthesis / AW; AVP; e.g. below compensation point

Question 95

Suggest why it was important that the leaves remained attached to the plants while the measurement were made in photosynthesis? (2)

Answer 95

maintenance of water supply; xylem / vascular bundles, intact; water required for, photosynthesis / turgor; A water prevents wilting stomata might close if the leaf detached; leaves site of photosynthesis; AVP; e.g. ABA, water stress, sugar transport

Question 96

Outline the ways in which heterotrophic organisms are dependant on plants (3)

Answer 96

``` 1 animals / heterotrophs (need to) , eat / obtain organic material from / AW , plants / autotrophs ; 2 (plants / autotrophs) produce (named) organic molecules during , photosynthesis / Calvin cycle / light independent stage ; 3 (plants / autotrophs) produce oxygen during , photosynthesis / photolysis / light dependent stage; 4 glucose / carbohydrate / oxygen , (produced in photosynthesis) are used in respiration by , animals / heterotrophs ```

Question 97

Name two polysaccharides that can be synthesised from the end products of the light independent stage of photosynthesis (2)

Answer 97

starch / amylose / amylopectin and cellulose ;

Question 98

Define what is meant by autotroph and heterotroph (2)

Answer 98

autotroph can make , organic molecule(s) / named organic molecule(s) , from , inorganic molecule(s) / carbon dioxide ; heterotroph relies on / needs to use / has to obtain / feeds on and digests , (named) organic molecules (that have been made by another organism) ;

Question 99

Explain what fat droplets in the chloroplast might be used for (1)

Answer 99

for membrane formation or phospholipid / cholesterol / glycolipid , for membrane ; fatty acid / (named) pigment , synthesis

Question 100

Suggest the effect of the herbicide binding to the electron carriers will have on photosynthesis (2)

Answer 100

1 prevents non-cyclic photophosphorylation ; 2 no electron(s) available to form reduced NADP ; 3 idea that ATP production by cyclic photophosphorylation is not prevented ; 4 no / less , ATP and no reduced NADP available for , Calvin cycle / light independent reaction / conversion of GP to TP ;

Question 101

Describe why measuring carbon dioxide and oxygen production may both not be accurate (2)

Answer 101

``` 1 2 3 4 5 oxygen oxygen only produced in one (named) stage of photosynthesis ; oxygen produced might be used for respiration ; carbon dioxide CO2 only used in one (named) stage of photosynthesis ; CO2 produced during respiration might be used for , photosynthesis / light independent reaction / Calvin cycle ; O2 / CO2 / both , could be an underestimate or represents net production (O2) or represents net use (CO2) ; ```

Question 102

Paraquat binds to electrons in photosystem 1. Suggest how in results in death of the plant (2)

Answer 102

``` 1 prevents photophosphorylation ; 2 cyclic and non-cyclic ; 3 no / less , ATP / reduced NADP , for , light-independent stage / Calvin cycle / GP to TP ; 4 no (named) substrate made for respiration ; ```

Question 103

Suggest the role of DNA and ribosomes in the chloroplast(2)

Answer 103

1 (DNA) coding for , gene(s) / protein / enzyme or (ribosome) protein / enzyme , synthesis ; 2 (enzymes for production of / proteins for) chlorophyll synthesis / pigment synthesis / photosystem ; 3 (protein for) electron , acceptor(s) / carrier(s) ; 4 ATP synth(et)ase ; 5 (enzyme / PSII) for , photolysis / splitting of water ; 6 (enzymes for) Calvin cycle / light independent reaction ;

Question 104

Suggest why not all the oxygen produced by the plant in photosynthesis is collected (2)

Answer 104

1 would dissolve in the water ; 2 used in , respiration / oxidative phosphorylation ; 3 may escape the collection apparatus ; 4 trapped in , a bubble attached to / air spaces in , the leaf

Question 105

Why might nitrogen be collected from a plant in a photosynthesis reaction? (1)

Answer 105

1 (nitrogen) was present in the air (spaces) in the , leaf / plant ; 2 (nitrogen) leaves the plant with the oxygen ; 3 idea that (nitrogen) comes out of solution / ‘undissolved’ (as less soluble in warm water) ;

Question 106

Suggest the advantage of plants deep in water to having different accessory pigments (2)

Answer 106

intensity 1 in deeper water there is , less / lower , light intensity ; 2 (these pigments) can absorb what (little) light there is ; wavelength 3 not all wavelengths of light can penetrate or mainly shorter wavelengths can penetrate or (mostly) blue light (450 – 520 nm) penetrates ; 4 (these pigments) can absorb wavelengths of light that can penetrate (deeper water) ;

Question 107

Discuss the fate of TP in the Calvin Cycle (3)

Answer 107

1 regenerates / produces , ribulose bisphosphate / RuBP ; 2 so cycle can continue / for (further) CO2 fixation / to combine with CO2 ; 3 formation of (named) , sugar / glucose / hexose / sucrose / starch / cellulose ; 4 formation of (named) , fat / triglyceride / lipid / fatty acids / glycerol / amino acids / protein / nucleic acids / nucleotides ; 5 10x TP for RuBP and 2x TP for production or most TP used to produce RuBP and the rest for production

Question 108

Explain why the Bohr effect occurs (2)

Answer 108

- reduces affinity for oxygen - formation of haemoglobinic acid - prevents a fall in pH - alters shape of haemoglobin - more 02 released where CO2 concentration is high - Co2 binds to haemoglobin forming haemoglobinic acid

Question 109

Describe the role of haemoglobin in transporting oxygen around the body (2)

Answer 109

1 haemoglobin has a high affinity for oxygen 2 oxygen binds to haemoglobin in high partial pressures 3 oxyhaemoglobin 4 oxygen released where oxygen partial pressure is low

Question 110

Explain how selective breeding that led to this increased yield could have been done? (4)

Answer 110

- breed high yielding plants together - access/test yield - crossbreed best offspring - over many generations

Question 111

Define the term recombinant DNA (1)

Answer 111

DNA which has been combined from two sources

Question 112

State what is meant by biotechnology using examples and suggest the advantages of using microorganisms for this (6)

Answer 112

- large-scale / industrial / commercial use (of living organisms / enzymes) ; - to produce , food / named example ; - detail of , microbe / enzyme , involved ; - to produce , drugs / named example ; - detail of , microbe / enzyme , involved ; to make , (useful) enzymes / biogas / calcium citrate / - for bioremediation / for water treatment / for microbial mining ; Advantages of microorganisms - fast, growth / reproduction / products ; - microbes can be genetically engineered ; - processes occur at low , temperatures / pressures ; - low , temp / pressure , cheaper / safer , to maintain ; - products , pure / easy to separate ; - grow on unwanted, food / nutrients ;

Question 113

What is graphical evidence that a substance is a secondary metabolite? (2)

Answer 113

- it is produced after main growth cycle | - it is not needed for growth

Question 114

What is the importance of maintaining aseptic technique in fermentation? (3)

Answer 114

to avoid unwanted microbe , entry / presence ; so no competition for nutrients ; so conditions remain unchanged ; so no decrease in yield ; so no contamination of , batch / product / penicillin or batch is unusable ; to prevent escape of , microbes / fungus / Penicillium / spores ;

Question 115

State 3 physical factors in a fermenter that need to be monitored and controlled and why (3)

Answer 115

pH - enzyme activity temp - enzyme activity oxygen concentration - respiration levels

Question 116

Give 2 advantages of immobilised enzymes (2)

Answer 116

(enzyme can be removed to be) used again ; (enzyme can) to leave pure(r) product ; ora (enzyme) more stable / more efficient / works better ;

Question 117

Outline the process by which bacteria can be genetically modified (6)

Answer 117

``` Section I - Obtaining the gene use restriction, enzyme / endonuclease ; to, cut out / get / isolate, (rennin) gene / DNA coding for rennin or to, fragment / digest, DNA ; gene probe ; OR obtain rennin mRNA ; (use) reverse transcriptase ; to make cDNA ; OR sequence, rennin (protein) ; work out base code ; make this DNA sequence ; sticky ends ; Section II - Vector cut (open), plasmid / phage ; using same restriction enzyme ; annealing / base pairing of sticky ends ; join sugar-phosphate backbones ; (using DNA) ligase ; recombinant, vector / plasmid / phage / DNA ; Section III - Introduction into host cell mix with bacteria ; detail of conditions ; transformation (plasmid) / transduction (phage) ; ```

Question 118

Discuss the benefits of using immobilised enzymes for large scale production (4)

Answer 118

(enzyme) can be re-used so reduces cost ; product, pure(r) / uncontaminated ; reduced downstream processing costs ; (immobilised enzyme) works at high(er) temperature ; (immobilised enzyme) works in changed pH ; reaction, can be faster / have higher yield , because can be done at higher temperature ;

Question 119

Define the term recombinant DNA (1)

Answer 119

DNA (combined) from (two) , sources / organisms ;

Question 120

Outline the process of somatic cell therapy (5)

Answer 120

somatic / adult, cell / nucleus ; fused with / injected into ; empty / enucleate , egg cell ; from another goat ; idea of electric shock / electrostimulation ; this cell or embryo, grown on , in vitro / in tied oviduct ; (early) embryo / blastocyst , split ; idea that embryos replaced in , surrogate mothers

Question 121

Outline the process of glycolysis (4)

Answer 121

1 phosphorylation of glucose ; 2 so forming hexose (1,6) bisphosphate ; 3 (then) splitting into / formation of , two / 2 , triose phosphate(s) / TP ; 4 (for formation of pyruvate) dehydrogenation / oxidation / formation of reduced NAD ; 5 yruvate produced (from , TP / (3C) intermediate) ; 6 total production 4 ATP / net production of 2 ATP ;

Question 122

Explain what might happen to a person if the liver did not break down insulin (2)

Answer 122

1 blood glucose (concentration) would fall , too low / below normal level ; 2 idea that glucose would continue to be taken up by , cells / liver / muscle (results in low blood glucose) or idea that glucose is continually converted into glycogen / would store too much glucose as glycogen ; 3 (mitochondria eventually) cannot , release enough energy / generate enough ATP (as less available glucose in blood) ; 4 coma / death ;

Question 123

When mitochondria are extracted from cells, they are usually kept in a 0.25 mol dm-3 sucrose solution. What is the purpose of the sucrose solution? A it is used as a solvent B it maintains a constant pH by acting as a buffer C it acts as a source of food for respiration D it prevents the mitochondria from changing structure

Answer 123

D

Question 124

Which of the following is absent from prokaryotic cells? A plasmids B cell wall C rough endoplasmic reticulum D ribosomes

Answer 124

C

Question 125

``` On complete hydrolysis, which of the following would produce the fewest molecules? A phospholipid B triglyceride C sucrose D polypeptide ```

Answer 125

C (only 2 molecules produced) - 1 fructose and 1 glucose

Question 126

``` Which of the following molecules does not yield only α glucose molecules on complete hydrolysis? A amylose B glycogen C maltose D sucrose ```

Answer 126

D (produces fructose also)

Question 127

Analysis of a sample of DNA found that 20% of the bases were adenine. ``` What percentage of the bases would be pyrimidines? A 20% B 30% C 60% D 50% ```

Answer 127

D 20% thymine 30% cytosine

Question 128

``` What is the approximate temperature coefficient (Q10) of an enzyme-controlled reaction? A 50 B 10 C 2 D 1 ```

Answer 128

C - the rate of the reaction doubles with temperature going up by ten degrees

Question 129

``` When an enzyme is subjected to temperatures above the optimum, it denatures. Which of the following bonds are the first to be disrupted by high temperatures? A disulfide B hydrogen C ionic D peptide ```

Answer 129

B

Question 130

Why do we store glycogen and not glucose? (3)

Answer 130

- insoluble so no affect on water potential - metabolically inactive - compact so lots can be stored in a small place - able to store lots of energy - has lots of ends to be broken down and release glucose quickly

Question 131

Why can progesterone move through the phospholipid bilayer? (2)

Answer 131

- non polar/ lipid/ hydrophobic/ fat soluble | - it can diffuse through the phospholipid bilayer

Question 132

Explain why more is absorbed from a colorimeter when temperature increases with beetroot (5)

Answer 132

- increase in pigment causes an increase in absorption - low temperatures there is little change in absorption - the membrane is undamaged - at higher temperatures there's a higher increase in pigment - this then leaks out when the membrane gets more damaged / becomes more permeable / move further apart

Question 133

What is the point of DNA polymerase? (1)

Answer 133

Forming phosphodiester bonds between molecules

Question 134

What is one thing that needs to be done before a plant cross section can be observed? (1)

Answer 134

A stain needs to be added

Question 135

Why can expiration be a passive process? (1)

Answer 135

it does not use muscle contraction / muscles (just) relax or rib cage , falls / drops (due to gravity) or lungs (elastic so) will recoil 

Question 136

Given chitin is made from beta glucose, describe the formation of a polysaccharide (4)

Answer 136

1 (in chitin glycosidic bond(s) formed by) condensation  2 (molecule of) H2O / water , produced / released  3 alternate monomers are , upside-down / flipped / rotated through 180o  4 because of the position of the , OH / H , on carbon 1  5 forms a , straight / linear / unbranched , chain / molecule / polymer  6 similar to cellulose 

Question 137

Why might a white spotting tile be used instead of just adding a load of indicator? (1)

Answer 137

``` (looking at , a small volume / against a white background) makes it easier to see the colour change  the indicator (if added to test tube) might affect the progress of the enzyme reaction  better temperature control as test tube not taken in and out of water bath  ```

Question 138

State the structures and functions and the 3 types of muscle (6)

Answer 138

Function: - cardiac is for the pumping of blood - smooth muscle for the control of the bronchioles and blood vessels - skeletal for the movement of muscle and bones Structure: - cardiac is uni nucleated and some striations - smooth is uni nucleated and spindle shaped and not striated - skeletal is multi nucleated and striated

Question 139

Suggest why individuals have 2 allies specifically(2)

Answer 139

- humans have diploid cells - chromosomes are in pairs - one allele on each chromosome from parent

Question 140

Give two industrial uses of plant hormones (2)

Answer 140

- seedless fruits - weed killers - rooting powder - control fruit ripening - preserve cut flowers

Question 141

What properties of the mitochondrial inner membrane allows chemiosmosis to occur? (2)

Answer 141

Large surface area Presence of ATP synthase Impermeable to hydrogen ions

Question 142

State two quantitative changed which occur in the inner mitochondrial membrane which occur as a result of oxidative phophorylation (2)

Answer 142

Decrease in pH | Becomes positively charged

Question 143

What are the net products of one cycle of Krebs? (1)

Answer 143

3 NADP 2 CO2 1 ATP 1 FADH2

Question 144

Summarise the importance of coenzymes in respiration (6)

Answer 144

Coenzyme A: - transfers acetate from Links to Krebs cycle ATP: - phophorylation of glucose to heroes bisphosphate - removal of phosphate group from TP in glycolysis - dephosphoylation in the Krebs cycle - formation from substrate level phosphorylation - formation from oxidative phosphorylation NAD: - oxidises TP in glycolysis - oxidises pyruvate in Links reaction - oxidises intermediates in Krebs - addition of electrons to electron transport chain FAD: - oxidation of intermediates in Krebs

Question 145

Explain the difference from ATP made in Krebs and by ATP synthase (2)

Answer 145

Krebs = substrate level phosphorylation | ATP synthase = oxidative phosphorylation

Question 146

Why does aerobic respiration yield less ATP than expected? (2)

Answer 146

1. some ATP needed to actively transport pyruvate into the mitochondria 2. Some ATP used to transport NADH made from glycolysis 3. Some energy released in electron transport chain is to used to transport protons 4. Not all proton movement generates ATP

Question 147

Explain why having a large number of proton pores in the inner mitochondrial membrane will result in someone being less likely to gain weight (4)

Answer 147

- protons leak back into matrix - reduces yield of ATP from chemiosmatic gradients - less ATP is made from oxidative phosphorylation - more energy wasted as heat - energy yield per glucose molecule decreases to n aerobic respiration - food not converted to ATP as efficiently - less energy in take in diet - less deposition of fat - fat stores may be respire for energy

Question 148

If two sucrose solutions of different concentrations are separated by a partially permeable membrane, which one of the following will occur? A The solute will diffuse from the more concentrated to the less concentrated solution. B Both solute and solvent will diffuse until equilibrium is reached. C The volume of the less concentrated solution will increase. D The volume of the less concentrated solution will decrease.

Answer 148

D

Question 149

1 There are 40 units of DNA in the cell during stage G2. How many units of DNA are in the cell during G1? A 10 B 20 C 40 D 80

Answer 149

B

Question 150

11 A diploid cell contains three pairs of homologous chromosomes. Each pair is heterozygous for a pair of alleles, Aa, Bb and Cc respectively. If this diploid cell undergoes meiosis, how many different combinations of these genes could be produced in the haploid daughter cells? A 6 B 8 C 16 D 64

Answer 150

B

Question 151

What volume cannot be measured by a spirometer? (1)

Answer 151

Residual volume

Question 152

How does surfactant stop the lungs collapsing? (1)

Answer 152

By reducing the surface tension

Question 153

Where is the heartbeat initiated? (1)

Answer 153

In the right atrium (where is SAN is)

Question 154

Which of the following statements he molecules produced during the phosphorylation stage of glycolysis? (1) 1 two molecules of triode phosphate 2 two molecules of ATP 3 two molecules of NADHZ

Answer 154

1

Question 155

What is the equation for respiratory quotient?

Answer 155

Volume of carbon dioxide produced divided by volume of oxygen produced

Question 156

Explain how acetyl coenzyme A is formed from pyruvate (4)

Answer 156

Pyruvate is decarboxylated forming one molecule of carbon dioxide. One molecule of NAD is reduced to NADH. Pyruvate is dehydrogenated. This forms acetate. Acetate combines with coenzyme A to form acetyl coenzyme A

Question 157

Explain how glycolysis can be maintained during anaerobic respiration (3)

Answer 157

- during aerobic respiration, pyruvate is hydrogenated to lactate using NADH - this regenerates NAD - this can be used again in glycolysis to oxidise triose phosphate

Question 158

Explain how the movement of electrons down electron transport chain leads to the formation of ATP (3)

Answer 158

- electrons pass down the chain releasing energy - this energy is used to pump protons from the mitochondrial membrane into the intermembrane space - protons then move down the electrochemical gradient via ATP synthase

Question 159

Explain what the light energy absorbed by the photosystems in photosynthesis is used for (3)

Answer 159

To make ATP from ADP To make NADH from NAD To split water into protons and electrons in photolysis

Question 160

Explain why using a standard deviation is better than a range (2)

Answer 160

Standard deviation takes all data into account | SD is not affected by outliers

Question 161

State where the reduced NAD and reduced FAD molecules are reoxidised and describe what happens to the hydrogen atoms (4)

Answer 161

1 inner mitochondrial membrane/cristae; 2 ref to (NADH) dehydrogenase; 3 hydrogen split into protons and electrons; 4 ref to, electron carriers/ETC/cytochromes; 5 energy released from electrons; 6 ref to protons pumped across membrane; 7 protons accumulate in intermembranal space; 8 proton gradient/pH gradient/H+ gradient; 9 protons pass through ATPase; A ATPsynthase/ ATP synthetase/stalked particle 10 ref. to oxygen (final) hydrogen/electron acceptor; 11 formation of water;

Question 162

Explain why the incomplete breakdown of glucose in anaerobic respiration produces less ATP than aerobic respiration (4)

Answer 162

1 glycolysis / conversion of glucose into pyruvate , occurs ; 2 produces 2 molecules of ATP (net) ; 3 (only) substrate level phosphorylation (occurs) ; 4 oxygen not available as final electron acceptor ; pyruvate / ethanal , 5 used to regenerate NAD for glycolysis (to continue) ; 6 (Krebs cycle and) electron transport chain / chemiosmosis / oxidative phosphorylation , do not occur ;

Question 163

Suggest why lactate is converted to pyruvate by the hepatocytes rather than the respiring cells in which it is produced (1)

Answer 163

hepatocytes can tolerate , lactate / low pH (which would otherwise be toxic) ; 2 hepatocytes have / (other) cells do not have , enzymes , t o metabolise lactate / catalyse this reaction ; 3 (conversion of lactate) requires oxygen and , muscle cells do not have enough oxygen / 2 O is not available during anaerobic respiration

Question 164

State where in the liver cell that the excess reduced NAD is oxidised (1)

Answer 164

In the inner mitochondrial membrane

Question 165

Which reaction is catalysed by the enzyme RuBisCO? A carboxylation of ribulose bisphosphate (RuBP) B conversion of triose phosphate (TP) to ribulose phosphate (RuP) C oxidation of glycerate-3-phosphate (GP) D reduction of glycerate-3-phosphate (GP)

Answer 165

A

Question 166

Outline how a student could carry out a chromatography experiment to determine the pigments present in the leaves (4)

Answer 166

- extract the pigments from the leaves by grinding them up - place a concentrated spot on the chromatography plate - put this in a small beaker containing a small amount of solvent - when the solvent has stopped moving, remove it and mark the solvent front - calculate the retention values

Question 167

What are two safety precautions that should be taken when doing paper chromatography ? (2)

Answer 167

- wear gloves/goggles because many of the compounds are toxic - fume cupboard as the vapours are hazardous

Question 168

Give two chemical defences that plants can produce in response to be eaten by plants and explain how they work (4)

Answer 168

Alkaloids which are poisonous to many insects | Tannins which bind to protein in the animals guy making it hard for the plant to be digested

Question 169

How does ethene cause the plants to ripen? (1)

Answer 169

Breaks down cell walls / break down chlorophyll / convert starch into sugars

Question 170

State three ways in which lactate enzymes can be immobilised (3)

Answer 170

1 encapsulated in alginate beads 2 trapped in a silica gel matrix 3 covalently bonded to cellulose or collagen fibres

Question 171

Give two disadvantages of using immobilised enzymes in industry (2)

Answer 171

1 extra equipment needed 2 reduction in enzyme activity 3 expensive so not good for small scale production

Question 172

Give one example of an immobilised enzymes used in industry (1)

Answer 172

Penicillin acylase used in production of semi synthetic penicillins. Glucoamylase for the conversion of dextrin a to glucose. Glucose isomerase for the conversion of glucose to fructose

Question 173

Explain the process of somatic cell cloning and give some disadvantages (6)

Answer 173

- nuclei extracted from the organism that's being cloned - nuclei removed from the oocyte - electrofusion to stimulate the nucleus to be take up - cells stimulated to divide to produce embryos - an embryo is transplanted into a surrogate mother - reduced genetic variability - difficult / time consuming - may have health defects - unethical

Question 174

Plant growth can be reduced if the rate of the light independent reaction is limited. Explain one reason why (2)

Answer 174

Less GP converted to TP.... Less amino acids for protein production Less glucose for releasing energy

Question 175

Give one example of a phenotypic trait in plants that is only determined by the environment and explain how it is caused (2)

Answer 175

Chlorosis - leaves turn yellow due to external factors such as limited magnesium to be able to produce chlorophyll

Question 176

Why does DNA need to be amplified before producing a DNA profile? (1)

Answer 176

To be able to see the DNA bands much easier

Question 177

Explain why DNA samples from different individuals produce different bands with different patterns when DNA profiles are produced? (4)

Answer 177

1. The genome contains areas of repetitive, non-coding base sequences 2. Different individuals have a different number of repeats at each loci 3. DNA fragments corresponding to different numbers of repeats are separated according to size 4. The pattern of bands produced corresponds to the number of repeats an individual has at each locus

Question 178

Give two disadvantages of somatic cell therapy (2)

Answer 178

- effects may be short lived - multiple treatments needed - immune response may start against the virus vector - the gene may be overexpressed - may be inserted in the wrong place and could cause more problems

Question 179

A hydatidiform mole is a rare complication of pregnancy that can occur after implantation of the fertilised egg in the uterus. It results in excessive production of hCG and damage to the lining of the womb, leading to miscarriage. Suggest how a hydatidiform mole could increase hCG above normal levels (3)

Answer 179

1 idea that (hydatidiform mole) cells produce more hCG than normal  2 (due to) expression / up regulation , of genes  3 synthesising more , hCG / protein(s)  4 idea that other tissues could be stimulated to produce more hCG than normal 

Question 180

Discuss the benefits of using stains when making slides for light microscopy (3)

Answer 180

contrast is high(er)  more (internal) structures visible  some (named) organelles / cell components more visible , because they bind to stain  clearer image can be obtained 

Question 181

In a microscope image, how do you identify the islets of langerhan and the acini tissue in the pancreus? (1)

Answer 181

The islets of langerhan are in a cluster where as the acini cells are not.

Question 182

Suggest how the interdisciplinary field of bioinformatics may be useful in determining whether a newly-sequenced allele causes a genetic disease (2)

Answer 182

base sequence of normal allele and (known) alternatives held (in database)  computational analysis allows rapid comparison of sequences with newly sequenced allele  amino acid sequence / protein structures, also held (in database)  idea of computer modelling of new protein structure from base sequence 

Question 183

Suggest three ways in which the use of embryonic stem cells in research has practical benefits to biological knowledge (3)

Answer 183

(can be grown into different tissues to) test how effective new medicinal drugs are  (can be grown into different tissues to) test for side effects / toxicity of new drugs  (can be grown and) studied to see how they develop into different cell types (developmental research)  cell function can be studied to find out what can make it fail to work properly in certain (named) diseases

Question 184

Suggest one advantage and one disadvantage of a kidney transplant compared to dialysis (2)

Answer 184

advantage: does not require repeated dialysis OR diet less limited OR better quality of life / no longer chronically ill  disadvantage: idea of difficulty finding donor organ OR risks of surgery OR risks from , organ rejection / long term immunosuppressant drugs 

Question 185

State a material used as the stationary phase in thin layer chromatography (1)

Answer 185

Silica gel

Question 186

State the precise location of photosynthetic pigments in the chloroplast (2)

Answer 186

Photosystems | Thalakoid membrane

Question 187

State three differences between electrophoresis and thin layer chromatography (3)

Answer 187

- separates by absorption vs separates by size - TLC separates non charged molecules where as electrophoresis only can seperate charged molecules - electricity is used for electrophoresis compared to not in TLC - buffer solution for electrophoresis but not for TLC - electrophoresis is automated but TLC is not

Question 188

Compare DNA replication and transcription by describing the similarities and differences between the two processes (6)

Answer 188

``` Similarities • DNA unwinds and unzips • Helicase enzymes • Template DNA • Complementary base pairing • Hydrogen bonds • Free, activated nucleotides • Polymerase enzymes ``` Differences • Only a small section of DNA (where the gene is located) unzips during transcription • Both strands act as templates in replication • RNA vs DNA free nucleotides • RNA vs DNA polymerase • Different helicase enzymes • Products are two new daughter strands of DNA in replication and one mRNA strand in transcription • mRNA leaves nucleus whereas the new DNA strand remains bound to the template strand

Question 189

Suggest why proteins are heated before being placed in the electrophoresis gel (1)

Answer 189

denature / unfold , protein AND idea of exposes charges or hydrophobic region

Question 190

Define a climax community (1)

Answer 190

final / stable / not subject to further succession

Question 191

Describe the difference betwen a pioneer community and a climax community (2)

Answer 191

1 pioneers arrive, before climax / earlier; ora 2 pioneer communities subject to, greater / more, change / succession / replacement; ora 3 pioneer community (usually) has, less / lower, biodiversity; ora 4 idea that pioneer community is (often) less, stable / self-sustaining; ora 5 pioneer community has lower biomass; ora

Question 192

What is the difference between decomposition and denitrification? (2)

Answer 192

1 decomposition is break down, dead matter / waste or decomposition is conversion of organic matter to inorganic; 2 denitrification is conversion of nitrates to nitrogen (gas); 3 decomposition increases, mineral / nitrate, supply and denitrification reduces, mineral / nitrate, supply;

Question 193

What is the difference between nitrogen fixation and nitrification? (2)

Answer 193

nitrogen fixation is the conversion of (atmospheric) nitrogen into, ammonia / ammonium compounds / ammonium ions; 2 nitrification is the conversion of, ammonia / ammonium compounds / ammonium ions, into nitrite / nitrate; 3 correct ref to microorganisms involvement in both processes; - nitrogen fixation involves, Rhizobium / Azotobacter / Nostoc and nitrification involves, Nitrosomonas / Nitrobacter

Question 194

Describe how a student would use a belt transect to measure the distribution of the two buttercup species between the pond and the land (3)

Answer 194

lay tape measure out from edge of pond ✓ place quadrat beside tape measure ✓ identify species of buttercup in quadrat ✓ count number of plants of each species (in quadrat) ✓ repeat for positions of quadrat along tape ✓

Question 195

``` Which of the following statements describes a feature of peritoneal dialysis?1 Urea and mineral ions pass into the tissue fluid.2 Blood is passed over an artificial membrane to remove toxins.3 The patient receives immunosuppressant medication. A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1 ```

Answer 195

D

Question 196

Fluid is found in the tubes responsible for gaseous exchange in insects. Name this fluid (1)

Answer 196

Tracheal fluid

Question 197

Explain why is meant by a limiting factor (2)

Answer 197

the factor that will , determine / limit / AW , the rate | when at ,low(er) / sub-optimal / AW , level 

Question 198

Water can fill air spaces in the soil surrounding the roots.This prevents oxygen from reaching root hair cells. Using your knowledge of aerobic and anaerobic respiration, explain why overwatering can kill plants (6)

Answer 198

Aerobic respiration (A)(No oxygen so) no aerobic respiration occurs No , link reaction / Kreb’s cycle / ETC / oxidative phosphorylation No oxygen to act as the final , electron / hydrogen acceptor Anaerobic respiration Plant has to) switch to anaerobic respiration / only anaerobic respiration can occur Only glycolysis occurs Alcoholic fermentation occurs NAD regenerated (for glycolysis) Pyruvate to ethanal to ethanol Named enzyme e.g. pyruvate decarboxylase (Only) 2 ATP ethanol is toxic (alcoholic fermentation) is irreversible Less ATP produced / only 2 ATP from glycolysis Less / no , active transport (root hair cells) cannot take up mineral ions (by active transport) so (plant) cannot make , proteins / amino acids / DNA / chlorophyll etc cannot generate water potential gradient (into roots) / water potential (in root hair cells) is too high water cannot be absorbed (so cells cannot remain turgid) less / no , photosynthesis

Question 199

Explain why a plant leaf is described as an organ (4)

Answer 199

organ iscollection/ AW, of tissues perform / carry out / adapted to , function / role leaves have two from: epidermis / spongy mesophyll / palisade mesophyll / vascular / phloem / xylem , (tissues) (to carry out) photosynthesis/ gaseous exchange

Question 200

Nephrogenic diabetes insipidus is a disease of the kidney that affects the regulation of water potential in the blood. One cause is lithium poisoning. Lithium ions enter the kidney tubules through sodium channels.This prevents the cells of the collecting duct from responding to ADH in the blood.State and explain one symptom you would expect to observe as a result of nephrogenic diabetes insipidus (2)

Answer 200

symptom: high volume of / excess , urine OR always thirsty / AW explanation: fewer / AW , aquaporins in the (plasma) membrane (of collecting duct cells)

Question 201

Describe and explain the role of ATP in the cell (3)

Answer 201

- releases energy - phosphate group can be removed by hydrolysis - energy released in small packets - ADP can attach to a phosphate during respiration

Question 202

Describe the ways in which an endothermic animal prevents its core temperature decreasing (5)

Answer 202

- thermoreceptors detect this - hypothalamus then receives this info - vasoconstriction of arteriole story reduce heat loss - Increased metabolic rate to generate heat - adrenaline release - shivering to generate heat - erector muscles contract

Question 203

Fever is accompanied by sweating. Explain the effect that this sweating will have on the body (2)

Answer 203

1 evaporation will , have a cooling effect / reduce (body) temperature ; 2 heat , taken from / supplied by , the body / blood / skin , is , needed / used for , evaporation ; 3 idea that water has a high latent heat of , vaporisation / evaporation

Question 204

Suggest an explanation for the fact that action potentials are not generated constantly whilst wearing clothes (1)

Answer 204

``` 1 sodium (ion) channels (remain) open/ resting potential not re-established ; 2 idea of ions being in the wrong place for correct ion movement (across membrane) ; ```

Question 205

Describe and explain the difference between the functions of RNA and DNA polymerase (4)

Answer 205

RNA Polymerase: - makes mRNA - transcription - one strand used / formed DNA Polymerase: - DNA replication - semi conservative - before cell/ nuclear division

Question 206

Describe how the equation for respiration is an over simplification (1)

Answer 206

- glucose is not the only substrate - ATP is produced - ATP required - not a single step reaction - enzymes are involved - glucose does not react directly with oxygen

Question 207

Suggest three ways that farmers can maximise the efficiency of the transfer of energy up food chains from primary consumers to humans (3)

Answer 207

1 keep animals, warm / indoors; 2 reduce animal movement ; 3 feed animals high, protein / energy, food ; 4 vaccination / (routine) antibiotics, for animals; 5 selective breeding / genetic engineering, for improved animals ; 6 slaughter just before, mature / full size ;

Question 208

Which statements describe commercial uses of plant hormones? Statement 1: Auxin powder is placed on the cut stems of plants to help them root. Statement 2: Ethylene gas is used to speed up the ripening of harvested green bananas. ``` Statement 3: Gibberellin is produced by a seed during germination. A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1 ```

Answer 208

B

Question 209

Which food will require the largest volume of oxygen for it to be oxidised completely? A 1 g lipid B 1 g monosaccharide C 1 g polysaccharide D 1 g protein

Answer 209

A

Question 210

Which of the following is an example of post-translational control of gene expression? A A non-functional protein produced from edited mRNA B β-galactosidase activity in Escherichia coli exposed to lactose C Liver cells beginning glycogenolysis in response to glucagon. D A Hox gene product acting as a transcription factor for many other

Answer 210

C

Question 211

18 The polymerase chain reaction (PCR) is a laboratory technique used to amplify DNA. Which statements correctly describe aspects of this process? Statement 1: When the temperature is at 55oC single-stranded DNA anneals to primers. Statement 2: DNA copy number increases with each thermal cycle on a logarithmic scale. Statement 3: The enzyme Taq polymerase is used because it catalyses transcription in a bacterium that lives in hot water. A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1

Answer 211

B

Question 212

Which of these statements is true of natural clones in mammals? A They have identical nuclear genomes and, on average, 50% of the same mitochondrial genome. B They share the same nuclear and mitochondrial DNA genomes. C They share, on average, 50% of their nuclear genome but have identical mitochondrial genomes. D They share, on average, 50% of their nuclear and mitochondrial genomes.

Answer 212

B

Question 213

A liquid broth containing bacteria undergoes three rounds of serial dilution. In each case 1 cm3 of the starting solution is mixed with 9 cm3 of water. 1 cm3 of the final solution is plated onto agar and 39 colonies grow. Calculate the number of bacteria in 1 cm3 of the original broth. A 390 B 3 900 C 39 000 D 390 000

Answer 213

C

Question 214

What conversion is carried out by nitrifying bacteria as part of the nitrogen cycle? A Ammonium compounds are converted to nitrites and nitrates. B Atmospheric nitrogen is converted to nitrates. C Nitrates are converted to atmospheric nitrogen. D Nitrates are converted to ammonium compounds.

Answer 214

A

Question 215

State three differences in the structures of starch (amylose) and cellulose molecules (3)

Answer 215

coiled no coiling (contains) α / alpha / A / a ,-glucose (contains) β / beta / B / b , -glucose ; α / alpha / A / a 1-4 glycosidic bonds β / beta / B / b 1-4 glycosidic bonds ; all , monomers / AW , in same orientation alternate monomers at , 180° / AW , to each other ; granular / not fibrousfibrous / not granular ; H bonds within molecule / no (H) bonds (between molecules) (H) bonds between adjacent molecules

Question 216

Describe how the guard cells surrounding the leaf pores are adapted to their role (2)

Answer 216

dea of: unevenly thickened (cell) wall ; able to, change shape / bend ; transport proteins / ion pumps, in plasma membrane ; (presence of) chloroplasts (to provide, ATP / energy) ;2

Question 217

The cohesion-tension theory is often used to explain the mechanism by which water movesup the xylem from the roots to the leaves.Use this theory to explain how water moves from the roots to the leaves (4)

Answer 217

evaporation at top of, plant / xylem ; (creates) tension in xylem ; water molecules, stick together / are cohesive / form a chain or column ; (column / chain) pulled up (by tension);

Question 218

State two adaptations of sieve tubes that enable mass flow to occur (2)

Answer 218

1 elongated elements ; 2 elements , joined end to end / form column ; 3 sieve plates / pores in end walls / perforated end plates / sieve pores ; 4 little cytoplasm / cytoplasm pushed to cell edges / thin (layer of) cytoplasm; 5 no nucleus / few organelles

Question 219

State and explain two adaptations of leaves that reduce evaporation (4)

Answer 219

1] hairy leaves ;trap water vapour / moisture ; [A 2]stomata, in pits / sunken ;pits trap, water vapour / moisture ; 3] rolled leaves / presence of hinge cells;reduce surface area OR(rolled leaves) trap water vapour / moisture ; 4] high solute concentration in cells ; reduces water potential inside leaf cells ; 5] thick(er) cuticle;(which is) waterproof / (relatively) impermeable; 6] smallleaves / needles;smaller surface area; 7] fewer stomata; reduces diffusion (of water vapour) ; 8] stomata close, during the day ; reduces diffusion (of water vapour) ; 9] most stomata on lower surface ; less exposure to sun OR cooler OR reduces diffusion (of water vapour

Question 220

Some chemicals can act as allergens. If these allergens are inhaled, they can cause breathing problems. Allergens cause the smooth muscle in the walls of the airways to contract. Suggest the effects that this muscle contraction has on ventilation (2)

Answer 220

1 reduction in (lumen) diameter of, bronchi/bronchioles 2harder to exhale / more resistance to exhalation /less aircan be exhaled 3more air remains in the lungs 4harder to inhale / more resistance to inhalation /less aircan be inhaled 5harder to ventilate / more resistance to ventilation/ increased breathing rate/ gasping

Question 221

Suggest why the resistance of MRSA to existing antibiotics is of major concern to humans (2)

Answer 221

MRSA / it, is harder to treat / may become untreatable ; potential for, disease outbreak / epidemic / pandemic / killing many people ;developing new / more powerful, antibiotics, is expensive / takes time

Question 222

he wild ancestor of the domestic chicken is the red jungle fowl found in the rainforestsof South East Asia.Explain why it is important to preserve the population of the red jungle fowl (2)

Answer 222

``` 1 maintain biodiversity ; 2aesthetic (reasons) / tourism ; 3ethical (reasons) ; 4part of a food chain / web ; 5maintain / increase gene pool; 6genetic resource / availability to breed with domestic chickens ```

Question 223

State three differences in the ways in which plant and mammalian hormones operate (3)

Answer 223

1 (M) made in endocrine glands versus (P)made in many plant tissues ; 2 (M) move in blood versus(P)move, in xylem / in phloem / from cell to cell ; 3 (M) act on, a few / specific / target, tissues versus (P)act on most tissues / can act in cells where produced 4 (M) act more rapidly

Question 224

``` Define the following terms: producer consumer trophic level (3) ```

Answer 224

producer (leaves / plants) fix carbon / photosynthesise / make food / autotroph(ic) / convert light energy to chemical energy / convert inorganic, C / CO2, to organic molecules consumer (bird) eat / derives energy from / feeds on , other organisms or heterotroph(ic) trophic level stage / position / place / level , in a food , chain / web

Question 225

The farmer does not wish to use inorganic fertiliser to replace the nitrate in the soil of thecabbage field. She wishes to make use of nitrogen fixation. Suggest a crop she could plant that would allow this to occur and explain how this would add nitrate to the soil (3)

Answer 225

1 legume / any named leguminous plant ; 2 Rhizobium / nitrogen-fixing bacteria (in root nodules) 3 idea of converting nitrogen gas / N2 , into ,compounds / ammonium / ammonia / amino acids / protein (in plants) 4 plants ploughed in / plants left to decay /

Question 226

Why is the continued existence of rare breeds of farm animals desirable? (2)

Answer 226

1 genetic resource / gene bank / have (different) alleles ; 2 for , genetic engineering / genetic modification / artificial selection / selective breeding / described 3 if conditions change / in the future 4 example of useful trait 5 to maintain, biodiversity / genetic diversity / (large) gene pool

Question 227

Explain the differences between conservation and preservation (2)

Answer 227

1 conservation maintains , ecosystem / biodiversity / species / habitats or conservation involves , active / sustainable , management of , ecosystem / resource / habitat 2 preservation leaves , ecosystems / habitats undisturbed

Question 228

Describe the proccesses that lead to the release of insulin from beta cells (4)

Answer 228

1 glucose , respired / phosphorylated / metabolised , to produce ATP ; 2 ATP , blocks / closes , potassium ion channel(s) andpotassium ions / K+, build up (inside cell) / cannot leave ; 3 (voltage-gated) calcium ion / Ca2+, channels open andcalcium ions / Ca2+, enter (cell by diffusion) 4 (more) calcium ions / Ca2+, resulting in , movement of vesicles to membrane /exocytosis / described

Question 229

Outline the organisation and roles of the autonomic nervous system in mammals (6)

Answer 229

- (two parts are) sympathetic and parasympathetic - S uses noradrenaline but P uses acetylcholine - S, fight / flight / stress, but P, rest / relaxation / calm - S increases,heart rate / cardiac output / blood pressure, but P reduces this; - S increases, speed / rate / depth, of breathing, butPreduces this - S increases airway diameter but P reduces it ; - S increases blood flow to skeletal muscle but Pincreases blood flow to gut (smooth muscle) - S dilates pupils but P constricts pupils - S makes liver release glucose, but P makes liver,store / take up,glucose

Question 230

Explain why dwarfism can be described as a genetic condition (2)

Answer 230

inherited / passed to offspring / passed (down) from parents | (caused by) mutation / allele;

Question 231

Name the tissue that lines the proximal convoluted tubule (1)

Answer 231

Epithelial

Question 232

Explain how changes in concentration in the blood are brought about by the proximal convoluted tubule (3)

Answer 232

- selective reabsorption; - of glucose and amino acids ; - co-transport / facilitated diffusion / uptake described ; - water follows by osmosis so concentration of, ions / nitrogenous waste / urea / remaining substances , increases ;

Question 233

Suggest why it is necessary to add an anticoagulant to the blood in dialysis (1)

Answer 233

so that clots don’t form, whilein the(dialysis) machine / during dialysis

Question 234

Suggest why no anticoagulant is added to the blood towards the end of a dialysis session (1)

Answer 234

idea of allowing blood to clot normally after treatment

Question 235

Suggest why patients receiving peritoneal dialysis usually need to have the peritonealdialysis fluid replaced four times a day, but those receiving haemodialysis only needtreatment three times a week (2)

Answer 235

- peritoneal dialysis can remove less (named)waste (than haemodialysis) - in haemodialysis dialysis fluid is constantly ,refreshed / changed (but not in peritoneal dialysis) ; - haemodialysis uses counter-current flow ; - idea that haemodialysis maintains concentration gradient or in peritoneal dialysis the concentration gradient , reduces / is lower ; - (in peritoneal dialysis) the fluid reaches equilibrium with the blood

Question 236

(c) If oxygen is not present or is in short supply, respiration can take an anaerobic pathway afterglycolysis. In plant cells, this pathway is the same as the one used in yeast cells. (i) Name the hydrogen acceptor in this pathway. ...................................................[1] (ii) Name the intermediate compound in this pathway. .................................................[1] (iii) Name the products of this pathway. ....................................................[1]

Answer 236

1 ethanal 2 ethanal 3 ethanol and carbon dioxide

Question 237

Explain why aerobic respiration is important to plants (2)

Answer 237

1 releases NAD , to accept more H / to be reduced again / so glycolysis can continue or allows (some) ATP to be generated (in glycolysis) ; 2 (some ATP available) for named cellular process eg: (active transport, endocytosis / exocytosis , mitosis / meiosis, protein synthesis, DNA replication, Calvin cycle / light-independent stage of photosynthesis

Question 238

State the stage or stages of aerobic respiration during which: (i) carbon dioxide is produced [1] (ii) oxygen is used [1]

Answer 238

(i) link cycle and krebs cycle | (ii) oxidative phosphorylation

Question 239

Explain why there is an increased rate of respiration in soaked seeds at 25 °C compared with soaked seeds at 15 °C (2)

Answer 239

increased kinetic energy ; | (named respiratory) enzymes / decarboxylases / dehydrogenases involved

Question 240

Compare anaerobic respiration in yeast and mammals. - Name of hydrogen acceptor after glycolysis - CO2 produced? - name of final product

Answer 240

``` Mammals: - pyruvate - no - lactic acid Yeast: - ethanal - yes - ethanol ```

Question 241

Explain how the three reaction pathways (Krebs, Calvin, Glycolysis) are able to work independently of each other in the same leaf cell (3)

Answer 241

take place in different , parts / organelles , of the cell or compartmentalisation / reactions separated by membranes ; W / glycolysis , in cytoplasm ; X / Calvin cycle , in , chloroplast /stroma (of chloroplast) Y / Krebs cycle , in , mitochondrion / matrix (of mitochondrion

Question 242

Describe how the structure of the cell walls in xylem vessels would differ from the cell walls in meristematic cell tissue (2)

Answer 242

thicker ; lignified ; contain (bordered) pits

Question 243

Discuss the ways in which genetic variation is produced, including the role of nuclear division (8)

Answer 243

A1 independent assortment / random segregation , of(homologous) chromosomes / bivalents; A2 in , metaphase I / meiosis I; A3 of chromatids in , metaphase I I / meiosis I I ; A4 (so) homologous chromosomes , have different alleles / come from different parents ; A5 produces large number of allele combinations ; C1 crossing over / (formation of) chiasma(ta) ; C2 in , prophase I / meiosis I ; C3 (so) chromatids will have new combination of alleles C4 amount of variation depends on distance between crossover points ; M1 mutation ; M2 changes the (DNA) nucleotide/ base, sequence ; M3 DNA checks (during duplication) did not recognise damage ; M4 idea of differences in (named) protein(s) ; N1 non-disjunction ; N2 homologous chromosomes do not separate (in metaphase I) ; N3 one , more / less , chromosome present ; F1 random, mating / fusion of gametes/fertilisation ; F2 gametes are not genetically identical; F3 produces large number of (allele) combinations

Question 244

Explain what is meant by a homologous pair of chromosomes (3)

Answer 244

``` 1 one maternal and one paternal / 2 carry same genes; 3 carry, same / different, alleles ; 4 (usually) same / similar, length ; 5 centromere in same position ; 6 same banding pattern ; 7 pair up in meiosis / form bivalent ```

Question 245

Name two parts of a plant where meristematic tissue can be found (2)

Answer 245

(just behind) tip / apex , of root ; (just behind) tip / apex , of shoot ; cambium / pericycle / vascular bundle ; bud ;

Question 246

State three reasons why mitosis is important to organisms (3)

Answer 246

growth (of tissue / organism) ; replace (cells) / repair (tissues) ; asexual reproduction/cloning / producing genetically identical cells; maintain chromosome number in all cells

Question 247

Suggest why it is not possible to expel all the air from the lungs (2)

Answer 247

thorax / rib cage / lungs, cannot be completely , compressed / flattened ; trachea / bronchi, held open by cartilage ; bronchioles / alveoli, held open by elastic fibres

Question 248

State the name of the process by which new species arise and suggest the mechanisms necessary for this process to occur (3)

Answer 248

- speciation; - isolation / separation, (of populations) - further detail of isolating mechanism e.g. volcano/ river - mutation / genetic variation - natural selection / description of natural selection - different selection pressure(s) (in different environment) - (enough) time to allow changes in population to prevent interbreeding

Question 249

Outline the main steps involved in cloning plants via tissue culture (5)

Answer 249

- meristematic/ totipotent/ undiffernciated tissue - sterile conditions - nutrient medium to encourage mitosis - produces a callus - subdivided - grows into plantlet

Question 250

State 3 advantages of tissue culture (3)

Answer 250

- can be done at any time of year - deseribale characteristics always passed on - faster method - produces many plants - disease free

Question 251

List 3 constituents of the culture medium (3)

Answer 251

1. sucrose 2. amino acids 3. vitamins 4. water 5. auxins

Question 252

Suggest 3 reasons why micropropagation may be more expensive than other methods (3)

Answer 252

- specalist workers needed - special equipment - labour intensive - sterile conditions

Question 253

State the meaning of an immobolised enzyme (1)

Answer 253

An enzyme which is attached to an insoluable material

Question 254

Describe two practical considerations to ensure the S. cerevisiae population grows successfully when the initial culture is established (2)

Answer 254

aseptic techniques / avoid contamination provide (sources of) nutrients / respiratory substrates (incubate at) suitable temperature use (pH) buffer agitation / stirring / shaking

Question 255

A diploid cell contains three pairs of homologous chromosomes. Each pair is heterozygous for a pair of alleles, Aa, Bb and Cc respectively. If this diploid cell undergoes meiosis, how many different combinations of these genes could be produced in the haploid daughter cells? A 6 B 8 C 16 D 64

Answer 255

B

Question 256

``` How many mitotic divisions of a meristematic cell in a root tip are needed to produce 256 daughter cells? A 8 B 16 C 32 D 64 ```

Answer 256

8 (2^8)

Question 257

Explain why glucose is needed for contraction of skeletal muscle (3)

Answer 257

(glucose) for respiration / as respiratory substrate / to release energy  to produce ATP  ATP needed (in muscle contraction) for breaking cross-bridges between myosin and actin / AW  ATP , hydrolysed / to ADP and Pi , to reset myosin heads  ATP for active transport of calcium ions (back) into sarcoplasmic reticulum 

Question 258

Outline the importance of photosynthetic pigments in photosynthesis (4)

Answer 258

- pigments absorb light/photos - accessory pigments pass energy to , reaction centres / primary pigments  - primary pigments , become oxidised / lose electrons / pass electrons to ETC  - for light dependent reaction / photophosphorylation

Question 259

State and explain how one feature of the plasma membrane contributes to its stability (2)

Answer 259

``` property - hydrophobic (region / fatty acid tails)  explanation - (helps to) form bilayer / separates two aqueous regions  property - (region) contains cholesterol  explanation - regulates (membrane) fluidity ```

Question 260

Outline the role of membranes within cells (2)

Answer 260

compartmentalisation OR form / surround , (named) organelles  purpose of / need for , compartments / separation  sites of , chemical reactions / electron carriers / photophosphorylation / chemiosmosis / oxidative phosphorylation  provide attachment sites for , enzymes / pigments  allow formation of concentration gradients

Question 261

Outline the processes involved in the generation of ATP through chemiosmosis (6)

Answer 261

Points mentioned - involves inner membrane and matrix - involves movement of H+ across the membrane - use of enzyme / ATP synthase - H+ pumped out of the matrix - H+ gradient - ATP synthase produces ATP from ADP and an inorganic phosphate Points missed out - occurs in mitochondria - H+ ions pass through hydrophilic transmembrane protein - H+ ions move from area of high concentration to low concentration - Some H+ ions leak back into matrix / process is not completely efficient - cristae

Question 262

Explain how TTX affects the activity of neurones if it binds to voltage - gated sodium ions and stops them opening (4)

Answer 262

- sodium ions / Na ions / Na+ , cannot enter  - no / prevents , depolarisation of membrane  - (membrane) remains at resting potential  - prevents action potential being generated  - impulse not conducted (along axon)  - (so) no release of neurotransmitter 

Question 263

``` Which of the following types of cells will not be involved in the primar immune response? (1) A T - Memory B T - Helper C T - Killer D plasma cells ```

Answer 263

A

Question 264

Desribe and explain how one feature of the lungs provides an efficent gas exchange surface (2)

Answer 264

large surface area for (maximum) diffusion squamous, epithelium / cells OR alveolar wall, only 1 cell thick / thin (providing) a short diffusion distance Good, blood supply / ventilation maintaining / creating a (steep) concentration gradient

Question 265

Suggest two ways in which the student could have ensured confidence in their results (2)

Answer 265

- repeats - calculate mean - identify anomolies - use statistical test to identify differences

Question 266

Explain why the surface area to volume ratio of an organism determines whether it needs a circulatory system (3)

Answer 266

large(r) organism has small(er) SA : Vol ratio (rate of) diffusion (too) slow / diffusion distance (too) long for (sufficient), delivery / uptake of, oxygen / nutrientsOR for (sufficient) removal of (named) waste products for, (aerobic) respiration / metabolic demand

Question 267

Name 3 functions of triglycerides in living organisms (3)

Answer 267

- thermal insulation - electrical insulation - protection for organs - energy storage - buoyancy

Question 268

Explain the melting points of three molecules decreasing when the number of hydrogen atoms decreases (2)

Answer 268

- less saturated molecule means more kinks | - less uniformly packed together

Question 269

Outline a practical method that could be used to determine the density of hairs on the underside of the leaf (3)

Answer 269

``` use a microscope use a graticule/ calibrate count number hairs per (unit) area repeat (measurements on same leaf) calculate mean(leaf hair density) divide by area used (to calculate density) ```

Question 270

Why do plants further away from the river have an increased number of leaf hairs? (2)

Answer 270

- further away from the river means less water (available) - transpiration causes water loss - hairs,trap water vapour/ reduce transpiration / reduce loss of water (vapour) - reduced water (vapour) potential gradient from inside to outside leaf

Question 271

Explain why transcription is needed for long polypeptide synthesis (2)

Answer 271

1 gene / DNA, copied/ transcribed,to (m)RNA 2 (idea that RNA goes to / translation is at) ribosome(s) / RER 3 DNA,is too large to/ cannot / is not able to,leave nucleus / cross nuclear envelope / fit through nuclear pores

Question 272

Compare the properties and functions of fibrous and globular proteins (6)

Answer 272

FIBROUS PROTEINS Properties:• insoluble• elongated / long / rods / filaments / ropes / strands• strong / tough• flexible IGNORE size refs / compact / coiled / bond types / hard Functions: (structure) collagen in, bone / cartilage / connective tissue / tendons / ligaments / skin / blood vessels fibrin + role described• for protection• keratin in, skin / hair / nails• to give, elasticity / elastic properties• elastin in, (named) blood vessels / alveoli / cartilage• for, contraction / mechanical movement• actin / myosin, in muscle• microtubules in, cilia / flagella / spindle / cytoskeleton GLOBULAR PROTEINS Properties:• soluble• spherical / ball-shaped• have, 3D / tertiary / 3o, shape / structure• specific / complementary (to another molecule)• ref. conjugated / contain prosthetic group• temperature / pH, sensitive• hydrophilic on outside Functions: enzymes / metabolic role / to catalyse reaction(s) / to lower activation energy• named enzyme + its specific role described• hormones / receptors / for cell signalling• named hormone / insulin + role described• antibody / for immunity / defence against infection• opsonin / antitoxin / agglutinin + role described• fibrinogen in bloodclotting• to transport substances across cell membranes• carrier / channel / pump + role described• to transport substances in blood• haemoglobin + role described e.g. carry oxygen•

Question 273

A student did a method to work out which amino acids were in a sample. This is the method used: 1 Draw a pencil line 1cm from the bottom of the chromatography plate, put solvent to 0.9cm 2 Hold the paper in your hand and lower it into the beaker Suggest 4 improvements which could be made (4)

Answer 273

1 put pencil line / origin / amino acids, higher (than the solvent / 1cm) +1 R to stop, spots / samples / amino acids,dissolving into / mixing with / touching, solvent 2 put, amino acids / spots / them, further apart / on separate plates+2R to stop them, merging / touching / clashing / AW 3 touch plate edges / wear gloves / use forceps / don’t touch middle, to prevent, contamination / transfer of substances from hands 4 place, lid / cover, over beaker to prevent evaporation (of solvent) 5 support the plate / attach plate to beakerto keep plate, vertical / still / at constant height 6 use ninhydrin to, see / visualise, amino acids 7 repeat and find, mean / average (Rf value) to improve, accuracy / check for repeatability / exclude anomalies 8 label, amino acids / spots / samples (in pencil / on beaker) to know which is which / avoid confusion

Question 274

Explain how electricty activity controls ventricular systole (2)

Answer 274

1 impulse OR(wave of) depolarisation ORwave of excitation 2correct ref.atrioventricular node / AV node / AVN 3 (through / along)bundle of His/ Purkyne fibres,to (cause contraction of) ventricles

Question 275

State how the cytoskeleton moves organelles around the cell (1)

Answer 275

microtubules/ tubulin / motor protein

Question 276

Explain the function of the epithelial cells in the airways of mammals and the importance of the cytoskeleton in carrying this out (4)

Answer 276

1 goblet cells,secrete / release / make / produce / form, mucus 2mucus traps, pathogens/ microorganisms / bacteria 3ref. phagocytes / neutrophils / macrophages / lysozyme 4cilia/ ciliated cells / ciliated epithelium, sweep / brush / waft / move / AW, mucus 5cytoskeleton / microtubules / tubulin, move(s) / make(s) up, the cilia

Question 277

``` In which of the following processes do bacteria not play an active role? A Bioinformatics B Bioremediation C Cheese - Making D Manufacturing human insulin ```

Answer 277

A

Question 278

How do you know if something is a light microscope? (2)

Answer 278

magnification , (only) 1000 / < 2000 / within LM range • colour visible • (other) subcellular structures / (named) organelles , not visible • wide field of view

Question 279

Apart from growth and repairs, what are the other roles of mitosis in multicelluar organisms? (1)

Answer 279

- asexual reproduction - development of body plan - proliferation of white blood cells (clonal expansion) - producing gametes from haploid cells - production of new stem cells

Question 280

Explain, with refernce to selective breeding, why it is important to maintain viable wild populations of crop plant species (6)

Answer 280

``` genetic variation genetic resource / gene bank source of useful alleles can be cross bred with crop varieties allows introduction of different traits unknown future requirements potentially useful in changing climate prevention of inbreeding depression promotion of hybrid vigour prevent dwindling gene pool source of replacement if cultivated population is in danger ```

Question 281

Explain the purpose of a control bacterial plate which contains no bacterial broth (2)

Answer 281

- control | - shows that bacterial growth is only due to the bacteria being cultered (idea of checking for contamination)

Question 282

Suggest why the teacher told the students not to grow the bacteria at 35 degrees (1)

Answer 282

- human pathogens / harmful pathogens can grow

Question 283

Suggest why doing repliates helps to improve an investigation (3)

Answer 283

- reduces impact of anomolies - measure repeatability - allows a calculation of a statistical test - mean is more likely to be close to the true value

Question 284

Explain why a gentic bottleneck can lead to low genetic diversity (2)

Answer 284

``` alleles lost (when population dropped) (modern population) descended from few survivors ```

Question 285

Explain how DNA sequencing allows the sequence of amino acids in a polypeptide to be predicted 92)

Answer 285

- 3 bases/a codon codes for an amino acid | - order of bases codes for order of amino acids

Question 286

Outline how DNA sequencing and bioinformatics could be used toincrese the effectiveness of a vaccination programme against ebola (4)

Answer 286

Sequencing - high) mutation (rate) means many , strains / AW , of virus exist can predict (viral) , strain / protein / antigen vaccine contains correct antigen Bioinformatics facilitates access to large amount of data facilitates access to data on DNA and proteins idea that format (of information) is universal can identify source of outbreak can identify vulnerable populations vaccination program can target certain , area / individuals

Question 287

What is the normal function of IAA in a plant? (1)

Answer 287

cell enlongation

Question 288

The herbicide atrazine works by disabling plastoquinone, one of the proton pumps in photosystem II. Explain how atrazine would kill a susceptible plant (5)

Answer 288

1reduced / no,proton pumping / proton motive force / chemiosmosis 2photophosphorylation stops 3less / no,ATP produced 4less / no,reduced NADP produced 5no,Calvin cycle / carbon fixation / light independent stage 6no,TP / (hexose) sugars,made 7no respiratory substrate / respiration ceases

Question 289

What are 2 examples of non reversible enzyme inhibitors? (2)

Answer 289

- cyanide | - aresenic

Question 290

What is the name of the action where animals synapes have multiple stimuli which result in one response? (1)

Answer 290

- spatial summation

Question 291

By appearance, how can yo tell the difference between the hepatic portal vein and the hepatic artery? (1)

Answer 291

Hepatic artery as blood entering liver through narrow vessel Hepatic portal vein as blood (from gut) entering liver through branched vessel

Question 292

Suggest 2 ways in which the ultrastructure of the chloroplast can be altered by high temperatures? (4)

Answer 292

1a damage to chlorophyll / reduction in pigment 1b which will reduce the light dependent stage 2a damage to membranes in chloroplast / reduction in sites for light capture 2b which will reduce the light dependent stage 3a damage to membranes in chloroplast / reduction in reaction sites for electron transfer 3b which will reduce,photophosphorylation / ATP production in the light dependent stage 4a damage to membrane around chloroplast / release of enzymes 4b which will reduce,light independent stage / Calvin cycle

Question 293

Suggest why is is beneficial for a plant to transfer their carbohydrate to be transferred as sucrose rather than another carbohydrate (2)

Answer 293

1 soluable | 2 metabolically inactive

Question 294

How is transport in the phloem similar and different to that in the xylem? (2)

Answer 294

similar - solutes carried in solution in both both carry mineral salts both use, mass flow / generated hydrostatic pressure different – transport in phloem can take place in different directions and transport in xylem only takes place up the plant phloem carries carbohydrates and xylem does not phloem transport uses living cells and xylem does not xylem uses, capillary action / cohesion and adhesion,and phloem does not

Question 295

Describe the sequence of actions that occur once adenylyl cyclase is activated in liver cells? (2)

Answer 295

catalyses synthesis of cyclic AMP from ATP | cyclic AMP activates enzymes responsible for conversion of glycogen to glucose

Question 296

Suggest how an allele may inhibit the expression of another allele by epistasis (2)

Answer 296

B, produces / codes for, repressor protein / repressor polypeptide / enzyme / transcription factor  (protein / polypeptide / product of B) binds to, promoter (of A) / mRNA / ribosome  (product of allele B) stops, transcription / translation (of allele A) / protein synthesis / described product of B inhibits the enzyme (encoded by A)

Question 297

Describe the production of ATP by substrate - level phosphorylation in different stages of respiration with reference to the number of ATP produced (4)

Answer 297

-2 (ATP molecules per glucose) from, glycolysis -(when) triose (bis)phosphate / TP, converted / broken down, to pyruvate  -ref to net yield of 2 (ATP) / 4 (ATP) made but 2 used up ( in glycolysis)  -1 ATP (produced) per, (turn of the) Krebs cycle / acetyl (coA)  -when 5-carbon compound is converted to, 4-carbon compound / oxaloacetate

Question 298

Explain how temperature has a greater effect on the light independent stage rather than the light dependant stage (2)

Answer 298

1 light-independent stage is) controlled by (named) enzymes  2 idea that higher temperature will increase, kinetic 3 energy of enzyme molecules / number of successful collisions /ESCs formed / ora  4 enzymes may be denatured at high temperatures / described

Question 299

Complete. The tissue sample removed from a plant is called the _____ ? (1)

Answer 299

Explant

Question 300

Explain why PCR may not be able to complete as much cycles in practice (1)

Answer 300

-temperature damage to, template / strand / fragment -(sometimes, once separated) template / strands, may rejoin (rather than bonding to primers)  -lack of, primers / (free) nucleotides  -primers fail to, join / attach / anneal (to fragment

Question 301

What is one differnce between the action of somati cell therpay compared to germ line therapy? (1)

Answer 301

- somatic tissue can target specific tissue in need of treatment which germ line therapy cant do

Question 302

Outline the processes which lead to the production of antibodies against an unfamilar bacterium (3)

Answer 302

- B cells/ lymphocytes, have,antigenreceptor / carry antibody,on surface,specific / complimentary to, only one antigen - selected / activated, B cell, proliferates / clones/ divides by mitosis - forms/ differentiates into, plasma / effector, cells - which secrete antibodies specific / complementary, to antigen

Question 303

Describe 2 economic advantages of immobolising enzymes for large - scale production

Answer 303

- reused so less money/cost - purifying cost reduced - more profit from faster yield

Question 304

Give comparisons of cuttings compared to micropropagation (2)

Answer 304

- cuttings needs less and propogation needs more equipment - microprogogation needs more staff - cuttings roduces less offspring

Question 305

What are the steps that occur to ammonia for plants to be able to take up the nitrogen and what bacteria are involved? (4)

Answer 305

Nitrosomonas ammonia to nitrite Nitrobacter nitrile to nitrate

Question 306

What is the hydrostatic pressure and oncotic pressure like at the arterial end of the capillary and the venous end? (1)

Answer 306

The hydrostatic pressure is higher at the arterial end. | The oncotic pressure is the end at both ends.

Question 307

What are some adaptations of hydrophytes? (2)

Answer 307

no / thin, (waxy) cuticle and idea that wax production is a waste (1) large surface area to, increase / maximise, photosynthesis, as transpiration is not an issue (1) many stomata to, increase / maximise, gas exchange (1) stomata on the top surface, as gas concentration is higher in air than water

Question 308

Explain how the casparian strip stops ions from passing through the endodermis layer? (2)

Answer 308

strip is impervious to, water / solutions (1) forces water / solutions, to pass through, plasma / cell surface, membrane (1) phospholipid (bilayer), repels / AW, ions / charged particles (1)

Question 309

Explain how mass flow of the phloem sap occurs in plants with a vascular system (3)

Answer 309

1 sugar / sucrose / assimilates, in the sieve tube (elements) ✓ 2 (assimilates) enter, sieve tube / phloem (at source) and lowers water potential (in sieve tube)✓ 3 water enters (sieve tube), by osmosis / down water potential gradient / described and increases hydrostatic pressure ✓ 4 (assimilates) leave, sieve tube / phloem (at sink) and increases water potential (inside sieve tube) ✓ 5 water leaves (sieve tube), by osmosis / down water potential gradient / described and lowers hydrostatic pressure ✓ 6 (assimilates) move, from high to low (hydrostatic) pressure / down pressure gradient

Question 310

Explain why water molecules can form hydrogen bonds with nitrate (NO3–) ions (2)

Answer 310

``` water is (a) polar (molecule) ✔ nitrate (ion) / NO3–, is, charged / negative ✔ (hydrogen bonds form) between H on water and O on nitrate ```

Question 311

Describe the roles of the sinoatrial node (SAN) and the atrioventricular node (AVN) incoordinating the cardiac cycle (3)

Answer 311

SAN, is pacemaker/initiates heart beat ; (SAN sends) impulse / wave of excitation, over atria (walls) ; AVN delays impulse ; (AVN) sends impulse down, septum / bundle of His / Purkyne fibres

Question 312

Describe how the action of the heart is initiated and coordinated (5)

Answer 312

- T / SAN, creates / initiates / starts / originates, excitation - wave (of excitation) spreads over atrial, wall / muscle; ref to, AVN / U ; - atria contract / atrial systole ; contraction is synchronised / AW - delay at AVN - (excitation spreads) down septum - ref to, bundle of His / Purkyne fibres - ventricles contract / ventricular systole, from, apex / bottom

Question 313

Explain why a protein that is 175 amino acids long is coded for by 528 base pairs of DNA (3)

Answer 313

triplet code or 3 bases = 1 amino acid ; 525 ; 3bases are , stop / (chain) termination , codon

Question 314

Describe two ways in which hormones may alter a plant’s growth in response too overcrowding by other plants (4)

Answer 314

auxin / IAA (positive) phototropism plants / shoots, bend towards light etiolation / plants grow taller climbing plants climb, up / over, other plants (positive) thigmotropism / sense of touch grow roots towards, water / minerals

Question 315

Suggest how hormones alter a plant’s growth if the top of the plant shoot is eaten by an animal (3)

Answer 315

less auxin / auxin production stopped apical dominance, stopped / removed side shoots grow / lateral buds develop / ora plant becomes bushy

Question 316

The number of small squirrels increases initially, but then decreases. Explain, using your knowledge of factors affecting population growth, why the small squirrel population in this rainforest does not increase in size indefinitely (4)

Answer 316

``` limiting / density-dependent, factors ; carrying capacity; intraspecific competition ; for, food / nesting sites ; interspecific competition parasites spread more easily ```

Question 317

Outline three reasons for conserving biological resources, such as the rainforest in Sarawak (3)

Answer 317

aesthetic / amenity / recreational, value (eco)tourism to, preserve biodiversity / preserve genetic diversity / stop extinction ref. interactions between species / need to preserve whole habitat ; (rainforest species / preserve gene pool as could be useful, in future / as potential, for, medicine / genetic engineering / AW ; to support indigenous peoples / AW ; to stop effect of deforestation on, atmosphere / climate / soil

Question 318

As the sugar concentration decreases the ethanol concentration increases in a yeast fermentor increases. Explain this relationship (3)

Answer 318

1 sugar converted to ethanol ; 2 in anaerobic respiration ; 3 sugar , undergoes glycolysis / converted to pyruvate ; 4 pyruvate , loses carbon dioxide / decarboxylated / forms ethanal ; 5 reduced NAD giving hydrogen to ethanal ; 6 idea of NAD being , regenerated / recycled , (so) glycolysis continues ; 7 correct ref to , pyruvate decarboxylase / ethanol dehydrogenase ;

Question 319

Discuss the benefits of using immobilised enzymes for large-scale production (4)

Answer 319

(enzyme) can be re-used so reduces cost ; product, pure(r) / uncontaminated ; reduced downstream processing costs ; (immobilised enzyme) works at high(er) temperature ; (immobilised enzyme) works in changed pH ; reaction, can be faster / have higher yield , because can be done at higher temperature

Question 320

HGH made in this way is given by injection to some children who have a genetic mutation. The mutation means that they do not produce enough HGH to enable them to grow atthe normal rate.Explain why injecting recombinant HGH in this way is not an example of gene therapy (3)

Answer 320

cells / DNA / genes / alleles ,not changed; vector not used (in child) ; child / cells , not producing , HGH / hormone ; HGH / drug / injection , has to be given repeatedly / is a short term solution / not a cure

Question 321

Describe how a method that uses a colorimeter and Benedict's reagent could be calibrated to measure the concentration of lactose in an unknown sample (4)

Answer 321

``` 1 zero the colorimeter / set to zero 2 using blank 3 use red filter 4 use known concentrations (of lactose) 5 (produce) serial / series, dilutions 6 construct calibration curve 7 test unknown sample (using the same method) 8 use / read from, graph / calibration curve, to determine (unknown) concentration ```

Question 322

Explain the mechanism by which competitive inhibition by enzymes work (3)

Answer 322

competes (with substrate) / competitive (1) enters / fits in / binds to / blocks, active site (1) prevents substrate from entering active site (1) (binds to active site) temporarily (1)

Question 323

Explain the importance of species evenness in determining the biodiversity in a habitat (3)

Answer 323

measures), abundance / numbers, of individuals in each species ; species evenness is more quantitative than species richness ; high(er) species evenness indicates high(er) biodiversity ;oralow species evenness indicates, dominance by / high abundance of, one / few, species ;ora used to calculate (Simpson’s) Index of Diversity ; example used to illustrate explanation of mp 3 or 4

Question 324

Suggest the implications of high Simpsons index on planning decisions (2)

Answer 324

many species present / high species richness / all species evenly represented / high species evenness / high biodiversity ;(so) should not be developed / development should be modified / development should be reconsidered / should be conserved /

Question 325

Describe how it is possible to use selective breeding to improve the overall disease resistance of a crop (6)

Answer 325

1. cross / breed, with disease resistant variety ; 2. method to test offspring for disease resistance ; 3. select , best offspring / offspring with resistance 4.(inter)breed, offspring with resistance / best offspring 5.(continue process) for (many) generations ; 6. dea of avoid breeding, closely related / AW , individuals to preserve genetic diversity ; 7. ora (regularly back) cross with, wild variety ; 8. idea of preserving rare varieties in case they are needed in the future

Question 326

Describe the way in which an endothermic animal prevents body temperature decreasing (5)

Answer 326

1. peripheral / skin ,thermoreceptors/ (heat) receptors ,stimulated (by decrease in external temp) ; 2. (impulses sent to / blood temperature monitored in )hypothalamus / sensory cortex; vasoconstriction of , arterioles / small arteries , to reduce heat loss ; 3. (prevents heat loss by) radiation / conduction / convection ; 4. increased,metabolic rate / metabolism / respiration , to generate heat (energy) ; 5. (release of) adrenaline / thyroxine ; shivering / (involuntary) muscle spasms , to generate heat (energy) ; 6.erector / hair , muscles raise , (skin) hair / fur , to trap , air / heat 7. reduce sweating

Question 327

Explain how the structure of galactose allows it to be used as a respiratory substate (3)

Answer 327

Bonds contain energy (bonds) can be broken by (respiratory) enzymes soluble so , can move (within cell) H / OH , (groups) can form H bonds with water / allow solubility