Bio exam questions Flashcards
A student suggested that details of component C could clearly been seen with a very good light microscope
Explain why the student is not correct (2 marks)
(By the way component c is mitochondria)
May 2013 unit 1
The mark scheme says
1- Component C is too small
2-The student would need a microscope with higher resolution
3-The wavelength of light is too long
It says to ignore references about magnification (I’m assuming that’s because it says could not be seen clearly)
New growth in a stem or trunk comes from the cambium which is situated between xylem and phloem tissue
Explain why the new branches in fig 3.2 are seen going from a position just under the bark of the cut surface (2 marks)
May 2013 (unit 1)
- Where cambium/meristem/vascular bundle/xylem/phloem found
- Mitosis occurs in cambium to produce new cells for growth
New cells can differentiate in cambium into xylem and phloem (learnt that in differentiation and stem cells)
Suggest what lenticels are essential to the survival of large multicellular organisms and explain why similar structure are not found in large multicellular animals (2 marks)
Picture shows small holes in branch
(May 2013 unit 1)
- Allows oxygen to reach cells under bark
For aerobic respiration - animals transport oxygen in blood/circulatory/or transport system
Plants do not transport as much oxygen
Name a location where growth occurs in plant
Meristem
Tip/apex of root or shoot
Explain why fetal haemoglobin curve is on the left of the adult haemoglobin curve
(3 marks)
May 2013 unit 1
- Fetal haemoglobin has a greater affinity for oxygen than adult haemoglobin
- This is because the placenta has a low PO2
- so oxygen is more likely to dissociate from haemoglobin there
Sickle cell anaemia is an inherited disorder in which haemoglobin crystallises when the
partial pressure of oxygen (pO2) is low. The red blood cells change shape and oxygen
transport is disrupted.
Treatment with drugs, such as hydroxyurea, can stimulate adults to produce fetal
haemoglobin rather than adult haemoglobin.
Suggest why this treatment might be of benefit to adults with sickle cell anaemia.(2 marks)
May 2013 unit 1
(fetal) haemoglobin may not crystallise as much
(at low pO2) ;
- So (fetal) haemoglobin can pick up more oxygen at low pO2 (than sickle haemoglobin)
So more oxygen can be transported/delivered
around the body
Describe and explain how substances that are dissolved in the blood plasma, such as oxygen
or glucose, enter the tissue fluid from the capillaries.
3 marks + QWC so 4 marks
May 2013 unit 1
There is more hydrostatic pressure in the capillaries than in the tissue,
this makes the capillaries walls leakier.
Fluid is then forced out of the capillaries.
Only small molecules such as glucose and oxygen can leave the capillaries
Plus 1 QWC mark. Also, there are marks for mentioning diffusion and its gradients
What is the function of the phospholipid bilayer?
(1 mark)
May 2013 unit 1 part of a larger question
To provide a barrier to large polar molecules, or to only allow small non-polar molecules through
Distinguish between the term transpiration and the transpiration stream
3 marks
May 2013 unit 1
Transpiration is the loss of water vapour from stomata
Transpiration stream is the movement of water from roots to leaf
Liver cells contain membrane-bound organelles called peroxisomes. These organelles
contain catalase, an enzyme that breaks down hydrogen peroxide to release oxygen
gas.
A student carried out an investigation on catalase using the following procedure:
• two identical sized cubes were cut from a piece of fresh liver
• one cube was frozen overnight and then defrosted
• the other cube was stored in the refrigerator
• both cubes were returned to room temperature and were placed in separate
test tubes containing equal volumes of 2% hydrogen peroxide solution.
The student observed that the cube of the liver that had been frozen and defrosted, bubbled
significantly more than the cube that had been refrigerated.
Suggest an explanation for this result (2 marks)
May 2013 unit 1.
The reason is that when deforested the membrane was damaged (you wrote ice crystals pierced it)
Mark 2
this increases the permeability of the membrane
DNA codes for the structure of polypeptides.
State the role of messenger RNA (mRNA)
mRNA carries a section of or copy of a gene
- out of the nucleus/ transfers to a ribosome
Describe the actions of b-lymphocytes in the immune system ( 6 marks)
- Part of the humoral response ;
- (B) cell/lymphocyte has antigen receptor / carries antibody on its surface
- This is specific to / matches / complementary to, only one antigen ;
- clonal selection happens when
- the correct macrophage selects the b-lymphocyte
- with the complimentary receptor
- Then clonal expansion ;
by (selected cell) divides by mitosis/clones; - (B) cells , differentiate / specialise ;
- (B cells) form, plasma/effector, cells ;
- (which) secrete/produce, antibodies ;
- antibodies are, specific/complementary, to antigen ;
(B cells) form memory cells
this (provides) secondary response
they are long-lasting
suggest why adults who have survived malaria may lose their immunity when they leave a malarial area ( 2 marks)
Because
no further exposure means that you lose immunological memory
their b memory cells are limited/may reduce/get lost
Explain why the decision was made to conserve the species in captivity (ex-situ) rather than in the wild(in-situ) ( 3 marks)
Note: can probably use this template for any question really
- Can monitor the health of organisms/prevent disease
- protection from predation/hunting
- manipulate breeding
- reduce competition between organims
Explain why the white backed vultures in the captive breeding programme were (3 marks)
- collected from different areas
- housed in seperate centres
- Maintains genetic biodiversity
- reduces the risk of inbreeding
- different races of vultures
- less likely to risk losing organims (vultures) to disease
Outline three reasons why the conservation of the white backed vultures is important (3 marks)
Any of the points below, im guessing it can be generic
maintains biodiversity
part of food chain / part of ecosystem / part of food web /
scavengers
have a right to existence / moral reason
specific religious reason
give pleasure / beautiful creatures
ecotourism
useful product / source of medicine / medical research
genetic resource
saves clearing up / remove carcasses
prevents disease
keeps , rat / dog , population down
Suggest three measures that could be taken in the long term to preserve the numbers of
white-backed vultures, once the captive bred individuals have been released into the wild. ( 3 marks)
Any of the points below ban / make illegal , use of this painkiller ; provide alternative painkillers (that do not have the same ecological impact) ; no hunting / no killing / legal protection, of white-backed vultures ; protected areas / sanctuary / reserves ; provide breeding sites ; prevent habitat destruction ; monitoring (of vultures) / tagging ; feeding programme (for released birds) / provide uncontaminated carcasses ; qualified ref. to education ; promotion of ecotourism ; in case the population falls again, sperm and egg banks / frozen embryos ;
State the type of variation shown in figure 5.2 and describe its characteristics
Type of variation: it’s discontinuous btw
Any points below Influenced by single / few, genes It is qualitative ; It has discrete categories There are no intermediates ; no / small / little , environmental effects ;
Outline how a breeding programme could be carried out to produce wheat plants that have both high yield and resistance to mildew (which is a bad fungus that infects them)
artificial selection / selective breeding ;
cross / breed , Iranian / resistant , wheat with ,
high yield / UK , wheat ;
method to prevent self , pollination / fertilisation ;
select , best offspring / offspring with good yield and resistant ;
(back) cross to high yield (UK) wheat / interbreed best offspring
/ interbreed offspring with both characteristics ;
idea of breeding (and selecting) for many generations ;
Over a period of time mildew can overcome the resistance bred into the wheat.
Using the theory of natural selection explain how the mildew fungus adapts to overcome resistance
Mark points below
- There is genetic variation, due to a mutation.
- Wheat resistance acts as a selection pressure
- Mildew fungus that has the overcome resistance are more likely to survive
- The mildew fungus reproduce
- They will then pass on their successful allele to their offspring
- increased frequency in the allele
An investigation was conducted into the effect of smoking on lung function. One measure of
lung function is peak flow rate.
The peak flow rate is the maximum volume of air expelled from the lung in one minute
(dm3 min–1).
Two male volunteers, one a smoker and one a non-smoker, had their peak flow measured
once a year for seven years.
Using the information above suggests three ways of improving the reliability of this investigation
- more individuals (male) should be used
- replicates / repeat measurements (at one time)
- calculate, mean/average
- identify/deal with, anomalous results ;
- take measurements at more frequent intervals;
controlled variable ;
State what benedicts solution tests for and what a positive test is.
June 2010 unit 2
(2 marks)
tests for reducing sugars
blue to red, green, yellow
Describe the structure of a triglyceride molecule (3 marks)
June 2010 unit 2
You could draw it or
- one) glycerol
3 fatty acids
ester bond (between glycerol and fatty acid)
State three roles of lipids in living organisms
(3 marks)
June 2010 unit 2
(thermal) insulation energy, store / source / release protection membranes / phospholipid bilayer / control entry and exit into cells (steroid) hormones / named steroid hormone buoyancy waterproofing source of water (from respiration) ; (electrical insulation) in myelin / around neurones / around axons / around dendrons aid, absorption / storage / production, of, fat soluble / A / D / E / K, vitamins
Define the term classification (2 marks)
June 2010 unit 2
A method of grouping organisms (1) can also say classifying/taxa/categories
based on similarities/or differences
Human populations with diets high in animal fats have a lower life expectancy than those with
diets high in vegetable oils.
Suggest one difference between lipids from animals and those from plants. (1 mark)
June 2010 unit 2
At room temperature animal lipids are solid
they are saturated
they contain only single bonds
can allow vice versa if talking about plants
Suggest what criteria a taxonomist may take into account when classifying a new species (3 marks)
June 2010 unit 2
Anatomical features/morpholpgy/ biochemistry/ cyctochrome C genes dna etc embryological/behavioural idea of shared evolutionary relationship
Describe the differences between a classification system based on domains and one based on kingdoms
( 4 marks) June 2010 unit 2
- 3 domains AND 5 kingdoms ;
- domains are, bacteria / eubacteria, AND,
archaea / archaebacteria, AND,
eukarya / eukaryotes ; - kingdoms are prokaryotes AND protoctists
AND fungi AND plants AND animals ; - eukaryotes split into different kingdoms /
all eukaryotes are in the same domain ; - all prokaryotes are in the same kingdom /
prokaryotes split into different domains ; - domain classification based on,
rRNA / ribosomes / RNA polymerase /
protein synthesis / enzymes /
flagella / membrane structure ;
The food poisoning outbreak involved the bacterium Escherichia coli 0157 (E. coli 0157) which
had been responsible for contaminating meat products. The meat had been stored at 11 °C
rather than the recommended 5 °C and this led to meat spoilage.
Explain how bacteria cause food spoilage. ( 3 marks)
June 2010 unit 2
- Bacteria reproduce
- secrete enzymes
- which then digest food
- Bacteria release toxins
- which causes a change in smell, appearance etc
Food normally spoils much faster if stored at temperatures higher than 5 °C.
Explain why food spoils faster at higher temperatures
(3 marks)
Unit 2 June 2010
- Bacetria reproudce rapidly
- more bacteria present
- more toxins are released
- more enzymes are secreted.
Explain why the mRNA molecule is shorter than a DNA molecule
- mRNA is a copy of a section of gene
2. DNA has many genes
Given some context that one enzyme involved in the production of mRNA is inhibited by α-amanitin., then we are told
The Roman Emperor Claudius was poisoned by his wife Agrippina when she gave him
death cap fungus to eat. The death cap fungus contains α-amanitin.
Suggest how the toxin α-amanitin may lead to the death of an organism. (2 marks)
Unit 2 June 2010
- mRNA production would be inhibited
- which prevents protein synthesis
(said they would accept translation for second mark and transcription for the first mark)
Smoking increases the risk of lung infections.
Explain how the mucus and the cilia in the air passages reduce the chance of developing
lung infections. ( 2 marks)
Unit 2 June 2010
- Mucus traps microorganism/pathogens/bacteria/virus etc
2. Cillia waft/sweep/move bacteria, pathogens, mucus etc
Describe how the structure of an antibody molecule is related to its function. (7 marks)
June 2010 unit 2
- Structure:Y-shaped molecule / light and heavy chains
disulfide bonds / 4 polypeptide chains ; - Structure: constant region ;
- Function: marker for / binds to, phagocytes / AW ;
- Structure: variable region ;
- Function: (antibody) specificity ;
- Function: (has) complementary shape to antigen (on pathogen)
- structure: hinge (region)
- function: allows flexibility ;
- Structure: more than one variable region :
- Function: agglutination / description of agglutination
or attachment to more than one, pathogen / antigen ;
neutralisation / blocking pathogen’s binding sites ;
QWC mark
When proteins are heated to a high temperature, their tertiary structure is disrupted.
Explain how this occurs. (3 marks)
June 2010 unit 2
- Increased kinetic energy
- the molecule vibrates
- hydrogen/ionic/hydrophilic- hydrophobic interactions break
- Causes a change in 3D shape or tertiary structure
- the protein denatures
Before any major development can take place, an Environmental Impact Assessment (EIA)
needs to be carried out. One such development is the proposed extension to the M27 motorway in Hampshire. This extension would cut through an important heathland ecosystem.
Suggest three aspects of this development that would need to be considered when carrying out the EIA. ( 3 marks)
June 2010 unit 2
- Need to consider how it will affect the biodiversity of heathland
- consider whether there are rare/endangered species present in
- consider how rare the habitat is
- the effect of moving organisms
- how reducing the size of the habitat will affect life
An ecologist carried out a survey of butterfly species on the heathland.
The ecologist walked along a marked path on four different days in June. She counted
• the number of butterfly species
• the number of individual butterflies of each species.
Suggest how this method of collecting data could be improved. (3 marks)
June 2010 unit 2
The mark scheme says
- collect in a wider area
- use a sweep net/or take photographs
- collect at different times of the day
- could do mark, capture, recapture
Suggest the implications of a high value of Simpson’s Index of Diversity on planning decisions. ( 2 marks)
June 2010 Unit 2
- There is a high biodiversity/species richness/species evenness/ many species present
- therefore area should not be developed, or development should be modified, or habitat should be conserved, or development should be reconsidered
State why Small Heath and Large Heath butterflies both share part of their scientific name. (2 marks)
by the way, they share the same genus so what’s the next mark
June 2010 unit 2
- have similar features, appearance, behaviour, biochemistry,
or
- share a common ancestor, have similar phylogeny
Before the division of the nucleus of a cell, the genetic material must replicate.
Explain why this is essential. (2 marks)
May 2012 unit 1
- Each daughter cell are genetically identical/same DNA
2. Each daughter cell have a full copy of DNA/46 chromosomes
Explain what is meant by a homologous pair of chromosomes (3 marks)
May 2012 Unit 1
- One chromosome is from the mother one and from the father
2 they both carry the same genes ;
3 they both 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 ;
What is the function of the ciliated tissue
1 mark
To waft mucus or to secrete mucus
Suggest a type of extracellular protein that can be secreted at the cell surface membrane
(1 mark)
- Enzyme, hormone
can accept things like insulin, amalyse, collagen,
The pressure fluctuates as the blood flows along the aorta, as shown in Fig. 3.1.
Explain what causes this fluctuation.
(2 marks)
May 2012 unit 1
- ventricular systole increases pressure
- Diastole decreases pressure
other marks
- contraction of ventricle/muscle/wall
- ventricle
State the term used to describe the number of fluctuations per minute ( 1 mark)
May 2012 unit 1
Heart rate
Using the information in Fig. 3.1, explain what causes the overall change in pressure as
blood flows from the aorta to the arteries and from the arteries to the capillaries.
(3 marks)
May 2012 Unit 1
- blood flows into a larger number of vessels ;
- (total) the cross-sectional area of the arteries is
greater than the aorta - (total) the cross-sectional area of the capillaries is greater than the, aorta/arteries
When you did this it said to ignore any comments about the lumen
A student wanted to observe some red blood cells under the microscope. The student placed
a small sample of blood onto a microscope slide and added a drop of distilled water. When viewed at high power, the student observed that the red blood cells had burst.
In a similar procedure using plant epidermis, the student observed that the plant cells did not
burst.
Explain these observations. ( 4 marks)
May 2012 Unit 1
- the RBC has a lower water potential than distilled water
- so water moves into the red blood cell by osmosis
- The cell surface membrane is weak, so it will burst due to pressure
- For a plant cell the water will also move I to the cell by osmosis
- because the water potential in the plant cell is lower the water potential outside the cell
- the inelastic cellulose cell wall prevents the plant from bursting
- So the plant cell becomes turgid
Suggest how the student could modify the procedure to observe red blood cells without them bursting. (1 mark)
May 2012 Unit 1
- Use a salt/sugar solution
2. Use a solution with a lower water potential than the blood
About 1 dm3 of air cannot be expelled from the lungs. This is known as the residual volume.
Suggest why it is not possible to expel all the air from the lungs. ( 2 marks)
May 2012 Unit 1
- the trachea contains cartilage
- It would be hard to compress the ribcage or intercoastal muscles
- bronchioles/alveoli are held open by elastic fibres
Sugar molecules are actively loaded into the transport tissue.
Describe how active loading takes place. ( 3 marks)
May 2012 Unit 1
- Hydrogen ions are loaded into the companion cells
- the concentration of hydrogen ions is lower outside of the cell than inside
- The hydrogen ions re-enter the cell
- and the sucrose molecules flow/move with the H+ ions
- down the concentration gradient
- by facilitated diffusion
- through a co-transporter
Suggest why the base sequence in the genes for human antibodies is more similar to that found in a chimp than to that found in a mouse. ( 2 marks)
Mixed question Unit 2 PMT
- Chimps and humans are common ancestors
- Common ancestor is more recent
- Less time for mutations
Fungi such as Fusarium venenatum are grown in huge batch cultures to manufacture
protein for food products.
Explain why these cultures are often maintained at the optimum temperature for protein production and not at a temperature above the optimum. ( 8 marks)
So you split the question into 2
First is what happens for the optimum temperature
- At the optimum temperature molecules have more kinetic energy
- more frequent successful collisions occur with more energy
- so more enzyme-substrate complexes form
- Until Vmax is reached
After passing the optimum temperature
- at higher temp more molecules have higher kinetic energy
- this leads to molecules vibrate more
- this causes hydrogen and ionic bonds to be broken
- this causes a change in the tertiary structure
- which leads the active site to lose its shape
- enzymes become denatured
- the substrate no longer fits into the active site
State what is meant by species richness ( 1 mark)
Number of different species present in an area
Describe how the students may have determined the numbers of individuals of each species in each habitat. (5 marks)
Its about insects i think
- They could have randomly chosen an area to observe, by diving up the habitats (elaborate obvs)
- then using a sweep net
- Repeat this same technique in every habitat
- then classify each insect caught
Discuss the role of an EIA as part of a local planning decision. (3 marks)
- they look at whether there is a need for conservation or whether to maintain biodiversity
- To see whether there are any endangered animals that need protection
- they may look at laws to see
- they plan whether to relocate species
Suggest why some conservationists might object to these studies. ( 2 marks)
btw they are talking about EIA studies
- They believe that habitats should be left alone
- they don’t want to damage the environment when animals are being studied
- sampling in the area would mean that they would disturb the natural environment
Historically, all organisms were classified into just two kingdoms. In 1988 a five-kingdom system of classification was accepted. In 1990 a three-domain system was proposed.
Discuss, with reference to the Prokaryotes, the reasons why classification systems are not universally accepted and why they change over time. ( 4 marks)
A reason why they change over time is that…
- New scientific evidence has been found
- New technology has been developed like new microscopes
- for examples they have noticed differences between archaea and bacteria in terms of RNA polymerase/histones/membrane structure etc
Not universally accepted because
- there is a difference of opinion between scientists
Staphylococcus aureus is a species of bacterium that is found on the skin.
Describe how variation may arise within a species of bacterium such as S. aureus. (1 marks)
- Spontaneous mutation
Suggest why such variation alters the characteristics of the individual organism. ( 2 marks)
- It happens because of a change in the DNA structure
- DNA determines your protein structure
- so a mutation happens when there is a change in DNA structure
Discuss the difficulties that variations arising in S. aureus may cause to the medical profession. ( 4 marks)
- resistant strains will reproduce quickly
- so scientists would need to develop new antibiotics because old ones will no longer work
- they won’t work because s.aurus will be resistent to the antibiotics
- we will need a wider range of antibiotics to work on several species of bacteria
- Vaccines will no longer be affected
The percentage of people infected with HIV is much higher in Sub-Saharan Africa than in much of Europe.
Suggest three reasons why the percentages are so much higher in Sub-Saharan Africa. ( 3 marks)
- Lack of education on HIV
- Poverty
- there may not be that many condoms available
- less primary healthcare so people will be less likely to be diagnosed
- using unsterilised needles
- could have things like war, rape,
Explain why it is useful to collect information, such as that shown in the figure above. ( 4 marks)
I think the figure was about rates of diseases in different countries around the world
- To keep track of infection rates around the world
- to see where an epidemic is more likely to spread
- to help research into what drugs are effective
- it allows organisations to educate people where ist most needed
- it allows organisations to give things like aid where needed
Explain what is meant by the term endangered species (2 marks)
- A species that numbers are low/ or habitat reduced/ whose population is critically low
- At the risk of extinct
Suggest why the black rhinonoscouros is going to be extinct ( 2 marks)
- Hunting
- poaching
- shot to prevent damage to farmland
- killed for horns
State two ways in which the CITES agreement is helping to save endangered species, such as the black rhinoceros. ( 2 marks)
- Ban the sales of ivory
- have international agreements to protect the rhinos
- countries can make it illegal to kill rhinos
- use education or raise awareness
Outline the potential benefits to agriculture of maintaining the biodiversity of wild animals and plants.
(4 marks)
- instead of using insecticides farmers can have natural predators
- it will be a source of plant variety for cross breeding
- A source of a variety of foods
- you can breed resistant to disease or insect crops
Describe the molecular structure of glycogen. ( 4 marks)
- Made from alpha glucose monomers
- has 1,4 glycosidic bonds
- has 1,6 glycosidic bonds where branches attach
- has branching
- it is a polymer
Explain why the part of the antibody molecule incorporating the binding site is often called the variable region. ( 2 marks)
- it is specific to the antigen
- as different have different shapes
- different antibodies fit different antigens
- have different amino acid sequences
Explain why there is a delay between the first infection by the pathogen and the appearance of antibodies in the blood. ( 2 marks)
- there is a delay due to clonal selection,
- due to clonal expansion
- due to antigen-presenting
- time taken for cells to differentiate
- production of antibodies
- there are no b memory cells
Suggest two measures, apart from the use of antibiotics, that could be taken in a hospital to combat possible infection with MRSA. ( 2 marks)
- washing hands bwteen diffnet pateints
- sterilising equipment
- isolating patients
- restricted visiting
- screen patients at the hospital regularly
List three features of organisms belonging to the Kingdom Fungi ( 3 marks)
- chitin cell wall
- eukaryotic
- saprotrophic/heterotophic
- reproduce by spores
State two features that fungi have in common with plants. (2 marks)
- both have a cell wall
- both eukaryotic
- both have membrane-bound organelles
- both reproduce by spores
State two advantages of asexual reproduction to a parasite such as Plasmodium ( 2 marks)
- only need one gamete
- reproduce quickly
- only need one parent
In order to reproduce asexually, Plasmodium needs to obtain amino acids from the red blood cells of its host.
Suggest how Plasmodium obtains amino acids from haemoglobin within red blood cells. ( 3 marks)
- they hydrolyse haemoglobin
- by using enzymes (proteases)
- these break the peptide bonds
- which removes the haem group
using fig 1.1 and your knowledge, explain why nitrogen fertiliser needs to be applied to farmland
(June 2011, 3 marks)
fertiliser maintains yield
application of firtiliser replaces lost nitrogen
nitrogen is required for amino acids/ proteins
nitrogen is removed from plant by harvesting
Long story short there is a practical with the same disc of potato tuber tissue, it was placed in a solution with different sugar concentrations
State two details of the procedure that must be followed to obtain valid results (2 marks)
June 2016 paper 1
- discs same , size / thickness / surface area /
surface area to volume ratio / diameter
2 same (variety / part , of) potato
3 no skin on potato
4 ref to removing excess water before (re)weighing
5 same , number / amount , of discs (in each solution)
6 same volume (sucrose) solution
7 same temperature
8 cover the tubes
Explain how the student could use the data in the table to work out the water potential of the potato tuber tissue
June 2016 paper 1
You would say
- no change in mass when wp of sucrose is equal to the water potential of the potato
- say there would be no change in mass between 0.2 to 0.3
- plot a graph of your results with x being sugar conc and y being wp and with a line of best-fit work out wp
June 2016 paper 1
- Lower water potential inside the root hair cell
2. because root hair cells actively pump minerals into themselves
A DNA molecule contains two polypeptide chains
Describe how these chains are held together (3 marks)
June 2016 paper 1
- Nitrogenous bases are held together by hydrogen bonds
- Adenine binds to thymine with 2 hydrogen bonds and cytosine to guanine with 3 hydrogen bonds
- purine binds to pyrimidine
- phosphodiester bond hold sugar phosphate backbone together
state an advantage of using the binomial system to name organisms (1 mark)
June 2016 paper 1
- it is universal so many people can understand it
- there is a common name for each species
- we know what genus or species it belongs to
Suggest two reasons why this species is critically endangered in the wild (2 marks)
June 2016 paper 1
- deforestation
2. hunting
The remaining population of the rhinos are small and scattered and isolated, explain how these factors might speed up extinction (2 marks)
June 2016 paper 1
- hard to find a mate / may be gender imbalance
- (inbreeding leading to) low genetic diversity /
small gene pool / genetic bottleneck
3 .cannot / less likely to , cope with / adapt to ,
(named) environmental change
4.all wiped out by the same disease
5.more vulnerable to , predators / poachers - natural disaster could wipe out , one / some ,
of the small populations
Suggest one other way that zoos can contribute to the conservation of rhinos (1 mark)
btw breeding programmes were unsuccessful
June 2016 paper 1
- they could educate people or raise awareness
2. promote conservation projects
Explain why RBCs do not use any of the oxygen they are carrying ( 2 marks)
June 2016 paper 1
- they lack mitochondria
- so no aerobic respiration
- oxygen is bound to haemoglobin
- moved by mass flow so it doesn’t need ATP
Explain why the blood offloads more oxygen to regularly respiring tissues than resting tissues ( 2 marks)
June 2016 paper 1
- there is an increase in the PCO2
- so haemoglobin has a lower affinity for oxygen
or
3. (CO2 results in) dissociation of carbonic acid / increase of H+ leading to the release of oxygen 4. more oxygen released at same pO2 / suitable data quote from graph
Explain how mass flow in the phloem sap occurs in plants with a vascular system
( 3 marks)
June 2016 paper 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
Explain how mass flow in the phloem sap occurs in plants with a vascular system
( 3 marks)
June 2016 paper 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
Explain why onion root tips were used to view cells undergoing mitosis ( 2 marks)
June 2017 Paper 1
- There is meristem
2. this is where you’ll see lots of mitosis happening
Describe how the molecule is prepared and secreted by cells of the salivary gland after translation has taken place ( 3 marks)
June 2017 paper 1
1. transport vesicle from RER (must say transport) 2 modification / processing / folding 3 in / at , Golgi (body / apparatus) 4 (packaged into) secretory vesicle (must say secretory) 5 vesicles move along the cytoskeleton 6 (vesicle) fuses with , cell surface / plasma , membrane 7 (secretion occurs by) exocytosis
Theres a whole bunch of writing so like progesterone can easily diffuse across the plasma membrane, produced in ovaries from cholesterol
Explain why progesterone can move across membranes (2 marks)
June 2017 paper 1
- It is fat-soluble
- therefore can diffuse through phospholipids bilayer
must say diffuse through not move passes or across
Suggest two ways in which the scientific community are likely to have validated Woose research. ( 2 marks)
Btw he suggested the domain system in 1990
June 2017 paper 1
- scientific conferences, meetings
- peer review
- replication of works
- looks for supporting evidence
DNA ligase is one enzyme involved in the replication of DNA
State two other enzymes involved and describe their functions
June 2017 paper 1
- DNA helicase
- it unzips the DNA molecule
- DNA polymerase
- forms phosphodiester bonds, or sugar phosphate backbone
The cytoskeleton in cells consists of microtubules and microfilaments.
Describe the roles of the cytoskeleton. ( 3 marks)
May 2014 Unit 1
- To provide support/scaffolding for the cell
- to transport vesicles around the cell or to hold organelles in place
- to help the movement of flagella
- to help the movement of chromosomes
- helps change the shape of the cell
Outline how the organelles in pancreatic cells work together to produce and release these protein molecules from the cells. (5 marks)
May 2014 unit 1
- Transcription occurs at the nucleus
- translation occurs at the ribosome
- vesicles transport protein to Golgi apparatus
- the Golgi apparatus processes and packages the vesicle
- a secretory vesicle fuses with the plasma membrane
- the protein is secreted through exocytosis
Explain the meaning of the term tidal volume. ( 2 marks)
May 2014 unit 1
The volume of air in each breath
Explain the meaning of the term vital capacity. ( 2 marks)
May 2014 Unit 1
the maximum volume of air that can be breathed in
Erythrocytes are full of haemoglobin.
Describe the role of haemoglobin in transporting oxygen around the body. ( 3 marks)
May 2014 Unit 1
- haemoglobin was a high affinity for oxygen
- at the lungs oxygen binds with haemoglobin this forms oxyhaemoglobin
- then at repairing tissues oxygen dissociates from haemoglobin because there is a low po2
High concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin.
Name this effect and explain why it occurs. ( 3 marks)
May 2014 unit 1
Bohr shift
- it reduces the affinity of oxygen for haemoglobin
- so more haemoglobin acid is formed
more points but I didn’t get them so
Suggest what evidence the scientist might expect to see in companion cells, using an electron microscope. ( 2 marks)
May 2014 unit 1
- many mitochondria
- many ribosomes
- many proteins in the plasma membrane
- plasdostomata
Complete the paragraph. ( 5 marks also learn this paragraph)
At step A, charged particles are moved out of the companion cells by the process of
………………………………………………… . This creates a …………………………………………………gradient between the companion cell and its surroundings. At step B, the charged particles and assimilates are co-transported by …………………………………………………
diffusion into the companion cells. The assimilates build up in the companion cells and move by ………………………………………………… into the sieve tube elements at step C.
Assimilates, such as sucrose and …………………………………………………, can be loaded in
this way.
- active transport
- concentration gradient
- facilitated diffusion
- diffusion
- amino acids
describe the functions of glycoproteins in the cell surface membrane
(Jan 2010, 5 marks)
acting as antigens
recognition of cells as self or non self
cell signalling ( describe it)
receptors as a binding site for hormones
cell adhesion- to hold cells together
forms bonds with water molecules to stabilise membrane
describe three steps a student should take when setting up the potometer to ensure that the apparatus works properly
(Jan 2010, 3 marks)
make sure shoot is healthy cut shoot under water cut at an angle check that there are no air bubbles leaves need to be dry make sure screw clip is tightly shut
suggest two possible reasons, other than light and temperature, why the rate of transpiration was lower in the afternoon than in the morning
( Jan 2010, 2 marks)
in the afternoon…
plant is less healthy
stomatal closure
more humid so higher water potential
less air movement
explain why potometer only gives an estimate of the rate of transpiration
(Jan 2010, 2 marks)
measures water uptake
not all water taken up is lost
some used for photosynthesis
state two other ways in which the wall of an artery is different form the wall of a vein
(Jan 2010, 2 marks)
endothelium is folded
thicker muscle
thicker elastic tissue
thicker collagen
explain why hydrostatic pressure of the blood drops as blood moves away from the heart
(Jan 2010, 2 marks)
vessels have a larger total lumen
reduced resistance to blood flow
arteries stretch
loss of fluid from capillaries
describe and explain what happens to the blood plasma at point A along the capillary tube
(Jan 2010, 3 marks)
plasma moves out of capillary enters tissue fluid plasma proteins remain in the capillary fluid moves down pressure gradient hydrostatic pressure greater than water potential
describe the methods the student used to:
collect both samples of fleas
find out the proportion of fleas that are resistant
process the data
(classification and evolution 2, 7 marks)
named equipment for collecting from dogs ( pooter, forceps, tweezers, pipette, flea comb, sweep net, sticky traps) get large number of fleas use several dogs - random sampling named container ( tank, jar, boiling tube, petri dish) control without flea killer leave for a set amount of time count number of dead/ live fleas calculate % of live/ dead
living organisms can be classified into three groups called domains.
outline the features of this system of classification compared to the five kingdoms system
(classification and evolution 2, 3 marks)
based on differences in RNA/ DNA/ nucleus acids
domains more accurately reflect origin of prokaryotes
divides it into bacteria and archaea
(explain differences e.g. RNA polymerase)
domain reflects that there are similarities between eukaryotic kingdoms
describe how it’s possible to confirm, over a long period of time, whether two organisms belong to different species or the same species
(classification and evolution 2, 2 marks)
INTERBREED
determine if offspring are fertile
if not, then different species
species that are more closely related in evolutionary terms have more genes in common than species that are less closely related
using the information provided, suggest the likely genetic relationship between the three parrot species
(answer more specific to the question)
they are all in the same family
kea and kaka are both in the same genus (nestor)
kea and kaka are more closely related
share more recent common ancestor
define the term parasite
( communicable diseases 1, 3 marks)
lives on host
gains food from host
at the expense of the host being harmed
suggest two reasons why governments in parts of the world other than tropical areas, are also becoming increasingly concerned about malaria
(communicable diseases)
climate change results in spread to other parts of the world
increased movement of infected people
outline the mode of action of antibodies in defending the body against pathogens by describing the process of naturalisation and agglutination
( communicable diseases)
neutralisation:
block bonding site on pathogen
bind to toxins
prevent binding to host cell
agglutination:
clump together
clump is too large to enter host cell
increase likelihood of being consumed by phagocyte
explain why the students use of the word ‘immune’ was incorrect
immunity involves lymphocytes that bacteria do not have
correct term is resistant
bacteria are unicellular
explain how phagocytes are able to pass from the blood into the tissue fluid
(communicable diseases)
lobed nucleus
can change shape
can squeeze between cells through pores
histamines make capillary walls more leaky
describe the process by which a pathogen is destroyed after it has become attached to the surface of a phagocyte
pathogen engulfed by cytoplasm phagocytosis formation of phagosome lysosomes fuse with phagosome making phagolysosome enzymes are in lysosome hydrolyse pathogen to amino acid/ sugar breaks down products into cytoplasm
state what a gene codes for
sequence of amino acids
state the role of a gene
codes for one or more polypeptide
explain how the structure of DNA allows replication
double stranded
both strands act as template
hydrogen bonds easily break and form between bases
purine binds to pyramidine die to different sizes of purines and pyramidines
3 h bonds between C and G
2 h bonds between A and T
suggest how changing the sequence of DNA nucleotides could affect the final product that DNA codes for
different sequence of amino acids- primary structure
different tertiary structure
no longer function
Outline how the percentage efficiency of energy transfer between producers and herbivores
can be estimated.
herbivore / primary consumer,energy x 100 ; producer energy
last 3 marks
sample primary consumers
sample producers
measure biomass
using a calorimeter
Suggest three ways that farmers can maximise the efficiency of the transfer of energy up food chains from primary consumers to humans.
- 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 ;
Define producer
autotrophic/change light energy into chemical energy
Define consumer
eats other organisms
Define trophic level
level on a food chain
What is a dynamic ecosystem
biotic and abiotic factors vary over time
Suggest two reasons why the large scale removal of peat from bogs for use in gardens is
discouraged by conservation groups.
- peat bogs take a long to form
2. reduces biodiversity
what is humus
type of soil that contains microorganisms animals etc
What does decomposition mean
to break down dead matter
What does denitrification mean
denitrification is conversion of nitrates to nitrogen (gas)
what does conservation mean
conservation maintains , ecosystem / biodiversity /
species / habitats
what does preservation mean
preservation leaves , ecosystems / habitats ,
undisturbed
what does niroegen fixtaion mean
nitrogen fixation is the conversion of (atmospheric)
nitrogen into ammonia
what does nitrification mean
nitrification is the conversion of ,ammonia / ammonium compounds /ammonium ions , into nitrite / nitrate
Resistance to antibiotics has evolved in some pathogenic bacteria, such as MRSA.
Suggest why the resistance of MRSA to existing antibiotics is of major concern to humans.
- there is a risk of a disease outbreak
2. creating new antibiotics takes time
The evolution of antibiotic resistance in bacteria is evidence to support the theory of evolution.
How does fossil evidence support the idea that evolution has taken place?
- fossil show development of organisms over time
- these can be dated
- they can show a sequence of evolution
Describe three characteristics of continuous variation.
- controlled by many types of genes/ influenced by the environment
- qualitative
- has no distinct categories
Suggest two undesirable consequences of selective breeding
- inbreeding
- more suspectable to disease
- low genetic variety
The wild ancestor of the domestic chicken is the red jungle fowl found in the rainforests
of South East Asia.
Explain why it is important to preserve the population of the red jungle fowl.
maintain biodiversity ; aesthetic (reasons) / tourism ; ethical (reasons) ; part of a food chain / web ; maintain / increase gene pool ; genetic resource / availability to breed with domestic chickens
what do you do if your t value is above the critical value
you reject the null hypotheses and say the difference (between the means) is significant / not due to chance
Describe three steps a student should take when setting up the potometer to ensure that the apparatus works correctly
- potomtere is airtight
- there is no water on the leaves
- cut the shoot underwater
- cut it at an angle
Xerophytes have various modifications that reduce water loss from their leaves.
State two such adaptations that reduce water loss and explain how the reduction in loss is achieved.
- covered in hair, this traps water vapour
- thick waxy cuticle, reduces evaporation of from leaves
- have spikes for leaves, which reduces the surface area
- sunken stomata traps water vapour
- rolled up leaves less surface area
what does habitat mean
a place where an organism lives
what does biodiversity mean
variety of life / the range of living organisms found
or a variety of habitats
basically the question talks about the last male Spix Macaw mating with a Blue-winged Macaw
explain why the eggs produced did not hatch
2 marks
different species
different genus
genetically incompatible
(may have) different number of chromosomes
physical / behavioural , reason for reproductive
incompatibility
describe three ways in which the sweep net sampling procedure could be designed to try and make sure that a representative sample was obtained
idea of: unbiased method to selecting sampling area
sample many times / AW, and calculate mean / average
standardised sweeping procedure
ensure insects do not escape (before being identified)
method to prevent recounting
sample at different times of, day / month / year / weather
conditions
state two of the aims of the CITES agreement
regulate / monitor , trade in selected ,
species / animals / plants / animal products
idea of ensuring trade does not put wild populations at
risk
idea of prohibiting commercial trade in wild plants
idea of allowing trade in artificially propagated plants
idea of allowing trade in less endangered species
subject to permit
suggest two factors to be taken into account when selecting individuals for the breeding programme
unrelated individuals
healthy
selecting individuals of the opposite sex for breeding
describe three ways in which the sweep net sampling procedure could be designed to try and make sure that a representative sample was obtained
idea of: unbiased method to selecting sampling area ;
sample many times / AW, and calculate mean / average
standardised sweeping procedure
ensure insects do not escape (before being identified)
method to prevent recounting
sample at different times of, day / month / year / weather
conditions
In this study, a student placed his quadrat on areas he considered to have the most biodiversity.
Explain what is wrong with this technique
- sameple he collects will be biased
2. it may be under representative or certain species and over representative of others
The Millennium Seed Bank Project (MSBP) is a global conservation programme
conceived, developed and managed by the Seed Conservation Department at the
Royal Botanic Gardens, Kew. The aims of the project are to collect and conserve 10%
of the world’s seed-bearing plants by 2010.
The project aims to make seeds available for research and species re-introduction into
the wild. Scientists working in seed banks have to maintain the viability and genetic
variability of the seeds they store. Samples of seeds stored are germinated to assess
their variability.
Describe how scientists working in seed banks maintain the viability and genetic
variability of seeds.
viability- ensures seeds germinate or collect new seeds that are produced
genetic variability: collect many different types do seeds, collect them from different parts of teh world
Zoos and botanic gardens, such as Kew Gardens, are involved in many conservation projects throughout the world.
Outline the problems experienced by zoos and botanic gardens in managing such projects and explain why it is important for such projects to be successful.
Problems
- capture of species/AW;
2 numbers of species caught ref to extinction;
3 ref to named example e.g. elephants;
4 maintenance of genetic variability/gene pool;
5 ref to funding;
6 ref to species ownership/AW;
7 problems of storage and maintenance;
8 ref to specific example of problem; e.g. inbreeding/altered breeding/seed
preparation;
Need for success
- stop extinction/maintain gene pool;
11 potential medical benefits;
12 agricultural benefits/artificial selection;
13 named example of crop improvement;
14 ethical/moral responsibility for future generations;
state reasons for the domain prokaroytae being split into bacteria and archaea
molecular evidence:
RNA polymerase is different in archaea and bacteria
archaea and eukarya have similar histones
cellular evidence:
bonds of lipids in cell membranes of B and A are different
flagella is different
explain the importance of species evenness in determining the biodiversity in a habitat
(measures), abundance / numbers, of individuals in each
species
species evenness is more quantitative than
species richness
high(er) species evenness indicates
high(er) biodiversity
low species evenness indicates, dominance by / high
abundance of, one / few, species
used to calculate (Simpson’s) Index of Diversity
suggest what is meant by critically endangered
likely to become extinct / on the verge of extinction /
numbers are not sustainable /
numbers too low for survival of species /
numbers drop below 10% of (original) population
describe how it is possible to use selective breeding to improve the overall disease resistance of a crop such as potatoes in both the short and long term
7 marks
cross / breed, with disease resistant variety
method to test offspring for disease resistance
select , best offspring / offspring with
resistance
(inter)breed, offspring with resistance / best
offspring
(continue process) for (many) generations
idea of avoid breeding, closely related
individuals to preserve genetic diversity
(regularly back) cross with, wild variety
idea of preserving rare varieties in case they
are needed in the future
suggest two reasons why the number of species identified is likely to be lower than the actual number of species present on earth
idea that:
not all , areas explored / species yet discovered ;
microscopic / small / nocturnal / camouflaged , species
difficult to see
sampling might miss rare species
organisms mistakenly identified as one species may
actually be two (or more) species
concept of species is difficult to define
state two aims for each of the conventions
RIO & CITES
CITES 2 max
regulate / monitor / prevent , trade in , selected / certain
endangered , species
ensure (international) trade does not endanger , wild
populations
prohibit (commercial) trade in wild plants
allow trade in , artificially propagated plants
allow (some) trade in less endangered , wild species /
organisms / animals and plants
Rio Convention 2 max
sustainable use of , organisms / habitats / ecosystems ;
share genetic resources
share access to , scientific knowledge / technology ;
idea of promoting (named) ex situ conservation
method(s)
idea of raising profile of (biodiversity) with , governments
public bodies / general public
idea of international cooperation (on biodiversity issues)
suggest how organic fertilisers improve yield of plant crops
broken down by, decomposers / bacteria / fungi
add (named) mineral(s) to soil
nitrate and phosphate and potassium / NPK
specific use of (any) named mineral
lack of (named) , mineral(s) / nutrient(s) / ion(s), is
limiting factor (for growth)
example of way in which soil quality is improved
explain how excessive use of inorganic fertilisers on farmland can cause a reduction in its biodiversity
(fertiliser) promotes growth of, one / few, (plant)
species
other (plant) species , out-competed (as a result
of competition from crop species)
idea of disruption of food chains
idea of reduction in , soil quality / humus , over time so
plants cannot grow
explain why a reduction in biodiversity may present problems for agriculture in the future
loss of genetic , diversity / variation (in wild
population)
environment / agricultural requirements, may change
(in future)
(lost) genes / alleles , may have been useful
e.g. of gene useful to agriculture
fewer pollinators
loss of (pest) predators
outline an advantage of using a seed bank as opposed to adult plants in order to conserve an endangered plant species
most plants produce an excess
(so) can be collected (from wild) without damaging
(wild) , plants / organisms / population / habitat
take up little space
able to store, large numbers / more species
easy / cheaper, to transport
idea of remaining viable for long periods
less susceptible to, disease / pests / environmental
change
suggest why its important to ensure that for each species, the seeds in a seed bank have been collected from several different sites in the world
(maintain / increase) genetic variation / gene pool
reduced chance of (future), disease / environmental
change, affecting (whole) population
reduces chance of inbreeding
maintain, geographical variation / varieties / races /
strains / subspecies
suggest why bacteria cannot break down agrose (polysaccharide)
(bacteria) do not, make / have, correct enzyme (to digest agarose)
agarose, does not fit / not complementary to, active site
(of bacterial enzymes)
suggest how the effects of insecticide use on a population of mosquito could be measured and state the steps that should be taken in order to produce valid and reliable results
Field investigation
(sampling) before and after insecticide treatment
idea of , unbiased / random, sampling of population
example of sampling technique
(sampling in) different, times / weather
large number of samples taken
idea of standardised sampling procedure
idea of preventing counting same individual more than
once
idea of capture – recapture
calculate mean / calculate standard deviation / apply
statistical test
state what is meant by the term recessive
only expressed , when homozygous /
in absence of dominant (allele)
outline the events that lead to genetic variation in gametes and in the plant grown from seed
mutation meiosis cross(ing)-over between non-sister chromatids (in) prophase I independent / random , assortment / segregation (in) metaphase idea of random , fertilisation / fusion of gametes
outline the role of decomposers in breakdown of leaves
bacteria / fungi idea of external digestion by , enzymes / named enzymes absorption of breakdown products release of carbon dioxide and water (breakdown of protein) makes , ammonium , ions / compounds or NH4+
State why the structure of enzyme molecules allows them to be detected in solution using the biuret test
(enzymes are) globular, proteins / polypeptide;
hydrophilic / water soluble, (R-)groups on outside (of enzyme
With reference to Fig. 2.1, discuss the factors that may have affected the size of the elk population:
before 1995
after 1995
7 marks
idea that population size is determined by limiting factor(s);
Before 1995, population increases due to
2 example of factor that is not limiting population
Before 1995, population levels off because
3 reaches carrying capacity;
Before 1995, population becomes limited by
4 intraspecific competition for named resource;
5 interspecific competition for named resource;
Population can decline at any time/ dips, due to
6 severe weather / natural disaster;
7 decrease before 1995 not due to wolves (as none present);
8 decrease after 1995 (probably) due to wolves;
9 idea that effect of wolves on population may be debatable
Outline how the percentage efficiency of energy transfer between producers and herbivores can be estimated.
a sample of) producers collected;
(a sample of) herbivores /primary consumers collected;
(collected from) the same area;
(measure) biomass / dry mass (of individual or population);
energy content calculated of producer and herbivore;
use of calorimeter / described
Describe the differences between the following biological terms:
a) pioneer community and a climax community
b) decomposition and denitrification
c) conservation and preservation
d) nitrogen fixation and nitrification
pioneers arrive, before climax / earlier pioneer community (usually) has, less / lower, biodiversity
decomposition is break down, dead matter / waste
denitrification is conversion of nitrates to nitrogen (gas)
conservation maintains, ecosystem / biodiversity / species / habitats
preservation leaves, ecosystems / habitats, undisturbed
nitrogen fixation is the conversion of (atmospheric) nitrogen into, ammonia / ammonium compounds / ammonium ions
nitrification is the conversion of, ammonia / ammonium compounds / ammonium ions, into nitrite / nitrate
The woodland in the figure can supply timber continuously, sustainably and economically.
Discuss some social, aesthetic and ethical benefits of managing woodland in this way compared to coniferous monoculture
4 marks
social
amenity / recreation / (eco)tourism;
educational benefit (to visitors / children);
improve (mental) well-being;
aesthetic
landscape more attractive / AW (for local people / visitors);
ethical
(continuous management) better for local employment;
duty of care for, habitat / environment / biodiversity / food webs /ecosystems;
Why is it important to calibrate a colourimeter
idea that values are, all measured to the same standard /
comparable / accurate / valid
State how the student could reduce uncertainty of their data
use more, accurate / precise apparatus / described
What is meant by the term autoimmune disease
-abnormal immune response
against bodies own tissues
Scientists often use natural substances to help them develop new medicines
State two possible sources of such natural substances
Plants
Microorganisms
Suggest how water is lost from the cut stem when all the leaves were treated with petroleum jelly
Evaporation from the leafs upper surfaces
Suggest two possible sources of error in an investigation involving a potometre
- Leaks in apparatus
- shoots not cut underwater
- error reading mensicus
Explain why onion root tips were used to view cells undergoing mitosis
- roots tips have meristem tissue
- cell division, growth, replication
Suggest a stain that the student could have used to highlight the nucelli of these cells
Methylene blue, acetic orcein, toluidine blue
Explain why mammals store glycogen instead of glucose
- Can store lots of energy
- metabolically inactive
- glycogen is insoluble so won’t change wp of cells
- compact
Describe how the molecule is prepared and secreted by cells of the salivary gland after translation has taken place (3 marks)
1.transport vesicle from RER
2. modification / processing / folding
3. in / at , Golgi (body / apparatus)
4 .(packaged into) secretory vesicle
5. vesicles move along the cytoskeleton
6. (vesicle) fuses with ,
cell surface / plasma , membrane
7. (secretion occurs by) exocytosis
How does the fluid mosaic model describe the structure of plasma membranes (2 marks)
- phospholipid bilayer
- describe the structure of the bilayer, so hydrophilic heads face out towards the environment and hydrophobic tails face inwards away from the environment
- phosphlipds/proteins move around
- protiens are randomly scattered
Why can progesterone move across the membrane (2 marks)
- Progesterone is fat soluble/lipid/hydrophobic
2. diffuses through phospholipid bilayer
ATP is made up of a phosphate groups and two other molecules
Name the two other molecules
- Adenine
2. ribose sugar
State how the structure of the cell surface membrane allows potassium ions to enter or leave a cell
-protein channels
In 1990, Carl Woese suggested a new top level taxon to the current system of classification of living organisms, which he termed a domain. He used his results from studying RNA to organise organisms into three distinct groups.
Name the cell component that appears in organisms of all three domains that Woese
suggested.
Ribosomes
Explain the meaning of semi conservative replication (1 mark)
The DNA molecule has has 1 old and one new strand
or
Each strand acts like a template strand
DNA ligase is one enzyme involved in the replication of DNA.
State two other enzymes involved and describe their functions. ( 4 marks)
DNA polymerase (1) forms phosphodiester bonds/joins sugar-phosphate backbone/joins adjacent nucleotides (1)
DNA helicase (1) unzips the DNA molecule /breaks hydrogen bonds between base pairs (1)
Mark scheme says to ignore unwinds DNA strand
The protease enzyme bromelain can be extracted from pineapples. A student investigated the effect of changing the concentration of the enzyme and measured the time taken to break down the protein gelatine.
State three variables that the student would need to control in order to make the results of this investigation valid. ( 3 marks)
- temperature
- pH
- concentration of , protein / gelatine
- volume / mass / surface area , of , protein / gelatine
- volume of , protease / bromelain / enzyme
- same source of , enzyme / gelatine
- same reaction end point
