Incorrect Answers For Paper 1

Question 1

Non competitive inhibitiors

Answer 1

-Bind to allosteric site of the enzyme.
-Active site shape changes as H bonds, ionic bonds are disrupted.
-Active site no longer complementary SO less substrate can bind.
-Less enzyme substrate complexes formed.

Question 2

How can you conclude from a graph that an inhibitor is non-competitive?

Answer 2

With the inhibitor, an increase in substrate concentration does not increase the rate of reaction.

Question 3

Why may large lipid droplets not be visible with an optical microscope from a suspension with lipids and bile slats?

Answer 3

Emulsification cannot be seen DUE TO the resolution of optical microscope.

Question 4

Why does biodiversity decrease with the removal of hedgerows to make large fields for farming?

Answer 4

Large fields have relatively fewer SPECIES.

Question 5

Advantage of a farmer replanting hedgerows on her field

Answer 5

-Increase in biodiversity…..
-SO increase in predators

Question 6

How is human mass at birth affected by stabilising selection

Answer 6

-Those that weigh less than 2800g and more than 4200g are more likely to be transferred to a special care unit.
-The extreme mass babies are less likely to survive and reproduce AND so are less likely to pass on their ALLELES for extreme mass at birth.
-ALLELES for extreme mass at birth decrease in frequency in the population.

Question 7

When stating the conclusion of a statistical test, what should you always mention?
Assume the p value is 0.03

Answer 7

-The PROBABILITY that the DIFFERENCE is due to CHANCE is LESS THAN 0.05.
-Reject the null hypothesis.
-State the variable that has a significant effect.

Question 8

Describe the structure of an HIV particle

Answer 8

-Viral RNA.
-Surrounded by a capsid.
-Surrounded by a lipid envelope.
-Attachment proteins on the lipid envelope.

Question 9

How are algae that live on rocks on the seashore able to survive without xylem vessels?

Answer 9

There is a short diffusion pathway to the cells.

Question 10

Why can successful reproduction between Ulva prolifera and Ulva lactuca not occur?

Answer 10

-They are different species.
-So if fused together they would not produce fertile offspring.

Question 11

Sunflowers are not xerophytic plants. Suggest and explain one way the leaf growth of xerophytic plants would be different from the leaf growth of sunflowers.

Answer 11

-There would be slow growth.
-Due to a smaller number of stomata for gas exchange.

Question 12

Why do plants grown in soil with very little water grow only slowly?

Answer 12

-Stomata close to conserve water.
-Less carbon dioxide uptake for less photosynthesis.

Question 13

How do the differences in the oxyhaemoglobin dissociation curve for a mouse and for a horse allow the mouse to have a higher metabolic rate than the horse.

Answer 13

-Mouse haemoglobin has a lower affinity for oxygen, as the curve is further to the right.
-More oxygen can be dissociated for use in respiration.

Question 14

How does CO2 affect oxygen unloading in haemoglobin?

Answer 14

-When cells respire they produce CO2, which raises the pCO2.
-This increases oxygen unloading/oxygen dissociation, so the dissociation curve shifts to the right.
-The saturation of blood with oxygen is lower for a given pO2, meaning more oxygen is being released.
-This is called the Bohr effect.

Question 15

Properties of water

Answer 15

-Metabolite in hydrolysis reactions.
-High specific heat capacity so buffers changes in temperature.
-High latent heat of vaporisation, so it requires a lot of energy to break the hydrogen bonds between the molecules of water. A lot of energy is used up when water evaporates, so provides a cooling effect when organisms sweat.
-Cohesion so supports columns of water.
-Cohesion soproduces surface tension.

Question 16

Lipid test

Answer 16

-Add ethanol to sample and shake vigorously.
-Pour into water.
-Milky emulsion will form if a lipid is present.

Question 17

Non-reducing sugar test

Answer 17

-Add HCl, heat in boiled water bath.
-Neutralise with NaHCO3.
-Carry out Benedict’s test.
-Coloured precipitate will form.

Question 18

Test for Amylase

Answer 18

-Add Biuret reagent AND solution becomes purple.
-Add starch, leave for 5 minutes.
-Test for reducing sugar (absence of starch).

Question 19

Describe the structure of glycogen

Answer 19

-It is a polysaccharide of alpha-glucose.
-Joined by glycosidic bonds.
-Branched structure.

Question 20

What word must you always mention when talking about polymers being broken down into monomers?

Answer 20

Hydrolysed.

Question 21

2 ways the cell membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients.

Answer 21

-Membrane is folded so increased SA for fast diffusion.
-Large number of protein channels/carriers in the membrane for facilitated diffusion.

Question 22

If a question is about a co-transport mechanism, what are the key words to always mention?

Answer 22

-State that the method of transport is co-transport.
-The protein changes shape.

Question 23

For an enzyme activity graph, when explaining the shape of the different curves for enzymes that are denatured

Answer 23

-State whether the enzymes are denatured or not.
-Denatured faster at a higher temperature due to more kinetic energy
-Breaks H bonds, ionic bonds between amino acid R groups.
-Change in shape of the active site, so active site is no longer complementary, so fewer enzyme-substrate complexes are formed.

Question 24

Reaction catalysed by ATP synthase

Answer 24

ADP + Pi goes to ATP + H2O

Question 25

Why should patients be treated with both the new and current antibiotic?

Answer 25

-New/old antibiotic does not kill all the bacteria.
-Resistant bacteria will reproduce to produce more resistant bacteria.
-Use of both antibiotics will kill the bacteria resistant to the other antibiotic.

Question 26

Why is temperature kept constant in an experiment about a herbicide’s effect on plant growth?
Why are the samples of leaf disk shaken?

Answer 26

-To ensure the rate of diffusion remains the same in the different samples of plants.
-So that all the surfaces are exposed to water.

Question 27

What will a phagocyte always do when it has destroyed a pathogen?

Answer 27

Present the antigen from the pathogen on its cell membrane

Question 28

What is the first step in secretion of antibodies when a virus antigen is presented? (Humoral response)

Answer 28

T-helper cells bind to the antigen on the APC. Then the T cell stimulates the specific B cell

Question 29

Scientists have found a virus that produces a protein very similar to human
collagen.
Suggest how the immune response to this viral protein can result in the
development of RA.

Answer 29

Complementary antibodies to the protein produced by the virus will bind to the collagen and the destruction if human collagen will occur.

Question 30

Three comparisons of genetic diversity

Answer 30

-Base sequence of mRNA.
-Amino acid sequence of proteins.
-Comparisons of base sequence of DNA.

Question 31

Three ways an insects tracheal system is adapted for efficient gas exchange

Answer 31

-Tracheoles have thin walls, so short diffusion pathway to cells.
-Highly branched so short diffusion distance to cells.
-Fluid in the end of the tracheoles that moves out into the tissues during exercise so faster diffusion through air to the gas exchange surface.

Question 32

The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain
oxygen from water.
Some other species of insect have larvae that are a similar size and shape to
damselfly larvae and also live in water. These larvae do not actively hunt prey and
do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life.

Answer 32

Damselfly larvae have increased activity so are able to obtain more oxygen using their gills.

Question 33

Disadvantages of TEM

Answer 33

-Requires a more complex preparation.
-Requires thinner specimens.

Question 34

Why is it important to double check the error bars on a graph?

Answer 34

Because they may represent either standard deviation or the range.

Question 35

A student wanted to determine the rate of water loss per mm2 of surface area of the leaves of the shoot.

Outline a method she could have used to find this rate. You should assume that all
water loss from the shoot is from the leaves.

Answer 35

-Draw around each leaf on the graph paper and count the squares.
-Of both sides of the leaf
-Divide the rate of water loss by total surface area of the leaves.

Question 36

The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of the whole plant.
Suggest one reason why.

Answer 36

Xylem vessels are very narrow.

Question 37

If most of the mitochondria in a cell are faulty, this prevents many important
enzyme-catalysed reactions taking place or slows them down.
Suggest and explain one reason why.

Answer 37

Little ATP is produced.
ATP provides energy for enzyme reactions

Question 38

Binding of one molecule of oxygen to haemoglobin makes it easier for a second
oxygen molecule to bind.

Answer 38

-The binding of the first oxygen changes the tertiary structure/quaternary structure of haemoglobin.
-This uncovers a second binding site.

Question 39

When counting white blood cells, the doctor only diluted the blood sample by a factor
of 20 times, instead of 200 times when counting red blood cells.
Suggest why he only diluted the sample by a factor of 20 times.

Answer 39

There are fewer white blood cells, so no need to dilute further to see enough.

Question 40

Scientists investigated the role of a protein called CENP-W in mitosis. Their method involved cell fractionation and ultracentrifugation.
Explain how ultracentrifugation separates CENP-W from other molecules.

Answer 40

-Spin the supernatant at very high speed.
-CENP-W separates depending on molecular mass/density.

Question 41

Describe the role of micelles in the absorption of fats into the cells lining the ileum.

Answer 41

Micelles include bile salts and fatty acids.
This makes fatty acids more soluble in water.
Fatty acids are absorbed by diffusion.

Question 42

Define ‘non-coding base sequences’ and describe where the non-coding multiple
repeats are positioned in the genome.

Answer 42

DNA that does not code for a protein
Positioned between genes.

Question 43

The scientists studied five individuals from each species. Within the five individuals of
species T they found a percentage similarity of 66%.
Use Table 3 to evaluate how this information affects the validity of the
phylogenetic tree.

Answer 43

-This indicates that there is high infraspecific variation in species T.
-There is a very small sample size.

Question 44

When looking at enzyme activity graphs what are important factors to look for when “evaluating” (4 things)

Answer 44

-If the reaction is carried out in a test tube, i.e. isolated enzymes.
-What species of plant or animal the enzyme activity is tested it- may not hold true for other species.
-If a statistical test has been carried out.
-If when one increases the other also increases- what relationship does this infer? If any?

Question 45

Explain the change in ATP concentration with increasing inorganic phosphate
concentration.

Answer 45

As Pi concentration increases, more ADP reacts with Pi to produce ATP. More Enzyme-substrate complexes form.

Question 46

Model A-Oxygen uptake through system developed to the outside of the body, eg fish gills.
Model B-Oxygen uptake through system developed to the inside of the body, eg human lungs.
-Suggest how the environmental conditions have resulted in adaptations of systems using model A rather than model B

Answer 46

-Water has a lower pO2 than air.
-System on the outside gives a larger surface area in contact with the water.

Question 47

What are main things to ensure a scientific drawing has?

Answer 47

-No sketched lines.
-Use a magnification bar.
-Label the diagrams.
-Draw all parts to the same scale.
-Do not use shading/hatching.

Question 48

What is the first step when isolating chloroplasts from a sample of leaves?

Answer 48

Homogenise to release the organelles AND filter.

Question 49

In a mathematics question, what should you always make sure to do before giving your answer?

Answer 49

Check the question stem to see if any significant figures or decimal places are required.

Question 50

What other investigations should be done before a treatment is tested on human patients?

Answer 50

-Tested in other mammals to test for safety/side effects.
-Tested on healthy humans to check for safety/side effects
-See if repeat doses have any effect (if only one dose is given in the investigation in the question.)
-Investigate different concentrations of the drug to find suitable/safe dosage.

Question 51

Describe how a triglyceride is formed.

Answer 51

-One glycerol and three fatty acids;
-Condensation reactions and removal of three molecules of water;
-Ester bonds formed.

Question 52

Describe the structure of DNA.

Answer 52

-Polynucleotide;
-Each nucleotide is formed from deoxyribose, a phosphate group and a nitrogenous base;
-Phosphodiester bonds between nucleotides;
-Double helix, two strands held together by hydrogen bonds;
-Hydrogen bonds between adenine, thymine and cytosine, guanine.

Question 53

When comparing the sizes of two cells from two different images, what must you always say?

Answer 53

Magnification shows that one cell is larger/smaller than the other.

Question 54

Describe the structure and function of the nucleus

Answer 54

Structure:
-Nuclear envelope and pores.
-DNA with histones
-Nucleolus.
Function:
-Holds/stores genetic information.
-DNA replication.
-Production of mRNA.
-Production of ribosomes.

Question 55

What polymer is the cell wall of fungi made from?

Answer 55

Chitin/N-acetylglucosamine

Question 56

Scientists investigated the effect of the number of fungal species in soil on the
diversity of plant species.

Suggest one reason the scientists used biomass instead of the number of individuals
of each plant species when collecting data to measure diversity.

Answer 56

Individual organisms could not be identified.

Question 57

Clostridium difficile is a bacterial species that causes disease in humans.
Antibiotic-resistant strains of C. difficile have become a common cause of infection
acquired when in hospital.
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria
becoming a common cause of infection acquired when in hospital.

Answer 57

-Some bacteria have alleles for resistance;
-Exposure to antibiotics is the selection pressure;
-Resistant bacteria survive and reproduce;
-So high frequency of resistant allele in bacterial population.

Question 58

When looking at data for bacterial growth due to a particular substance for resistant and non resistant strains, what are some key factors to consider about the data? (5)

Answer 58

-If the experiment was carried out in the laboratory or in people.
-If any other substances affect the growth other than the one looked at.
-Other bacterial species in the body might affect bacteria.
-If there is data for the growth of both strains together.
-If there is data for different concentrations of the substance being tested.

Question 59

What is the function of cholesterol in the cell membrane? What must you never say?

Answer 59

Cholesterol stabilises the cell membrane.
You must NOT say strengthens.

Question 60

Explain how enzymes with different amino acid sequences can catalyse the same reaction.

Answer 60

-Both active sites have similar tertiary structures;
-Both for enzyme-substrate complexes with the same substrate.

Question 61

When investigating the effect of different pH on enzyme activity, what should be placed in the control tubes in the investigation?

Answer 61

-The same volume and concentration of substrate;
-The same concentration and volume of denatured enzyme;
-The same volume of buffers used in the investigation.

Question 62

What are causes of increased transpiration rate?

Answer 62

-Increased temperature; so increased kinetic energy
-Increase in light intensity;
-Decreased humidity; so increased water potential gradient.
-Increase in air movement; so increased water diffusion gradient.
-Stomata open allowing gas exchange;

Question 63

Give differences between DNA and tRNA. (7)

Answer 63

-Deoxyribose v ribose;
-Double-stranded v single-stranded;
-Many nucleotides v few;
-Thymine v Uracil;
-Linear v clover leaf;
-Does not bind to amino acid v does bind it amino acid;
-No exposed bases v anticodon.

Question 64

Differences between blood circulation of a fish and a human.

Answer 64

-2 chamber v 4 chambers;
-Blood does not return to the hearts after being oxygenated via blood returns to the hearts after being oxygenated;
-One vein carrying blood towards the heart v two veins carrying blood towards the heart;
-One artery carrying blood away from the heart v two artery carrying blood away from her heart;
-Single circulation v double circulation;
-Blood reaching body capillaries at lower pressure v blood reaching body capillaries at higher pressure.

Question 65

Describe the transport of carbohydrates in plants.

Answer 65

-Sucrose is actively transported into he phloem cell;
-By companion cells;
-Lowers the water potential in the phloem and water enters from the xylem by osmosis;
-This produces a higher hydrostatic pressure;
-Mass flow to respiring cells/storage tissue/organ;
-Unloaded/removed from phloem by active transport/facilitated diffusion.

Question 66

Compare and contrast the structure of starch and structure of cellulose.

Answer 66

-Both are polysaccharides;
-Both contain glycosidic bonds;
-Both contain C, O and H only;
-Starch has alpha-glucose whereas cellulose has beta-glucose;
-Starch molecule is helical and cellulose molecule is straight;
-Starch molecule is branched and cellulose is not branched;
-Cellulose has micro/macrofibrils and starch does not.