all5

Question 1

difference between the structure of a triglyceride molecule and the structure of a phospholipid molecule

Answer 1

-In phospholipid, one fatty acid replaced by a phosphate

Question 2

how you would test for the presence of a lipid in a sample of food

Answer 2

1. Add ethanol, then add water;

2. White (emulsion shows lipid);

Question 3

how a saturated fatty acid is different from an unsaturated fatty acid

Answer 3

Saturated single/no double bonds
(between carbons)
OR
Unsaturated has (at least one) double
bond (between carbons);

Question 4

how ATP is resynthesised in cells

Answer 4

1. From ADP and phosphate;
2. By ATP synthase;
3. During respiration/photosynthesis;

Question 5

ways in which the hydrolysis of ATP is used in cells

Answer 5

1. To provide energy for other reactions/named process;

2. To add phosphate to other substances and make them more reactive/change their shape;

Question 6

evidence that a scanning electron microscope was used to take this photograph

Answer 6

(Can see) 3D image

Question 7

products of the hydrolysis of sucrose

Answer 7

1. Glucose;

2. Fructose;

Question 8

Describe the induced-fit model of enzyme action

Answer 8

1. (before reaction) active site not complementary to/does not fit substrate;
2. Shape of active site changes as substrate binds/as enzyme substrate complex forms;
3. Stressing/distorting/bending bonds (in substrate leading to reaction);

Question 9

The scientist used quantitative Benedict’s tests to produce a calibration curve of colorimeter reading against concentration of maltose.
Describe how the scientist would have produced the calibration curve and used
it to obtain the results in

Answer 9

1. Make/use maltose solutions of known/different concentrations (and carry out quantitative Benedict’s test on each);
2. (Use colorimeter to) measure colour/colorimeter value of each solution and plot calibration curve/graph described;
3. Find concentration of sample from calibration curve;

Question 10

Human papilloma virus (HPV) is the main cause of cervical cancer. A vaccine has been developed to protect girls and women from HPV.
Describe how giving this vaccine leads to production of antibody against HPV

Answer 10

1. Vaccine/it contains antigen (from HPV);
2. Displayed on antigen-presenting cells;
3. Specific helper T cell (detects antigen and) stimulates specific B cell;
4. B cell divides/goes through mitosis/forms clone to give plasma cells;
5. B cell/plasma cell produces antibody;

Question 11

ways doctors could use base sequences to compare different types of
HPV- genetic diversity

Answer 11

1. Compare (base sequences of) DNA;
2. Look for mutations/named mutations (that change the base sequence);
3. Compare (base sequences of) (m)RNA;

Question 12

Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue

Answer 12

1. How to break open cells and remove debris;
2. Solution is cold/isotonic/buffered;
3. Second pellet is chloroplast;

Question 13

Structures in a eukaryotic cell that cannot be identified using an optical microscope.

Answer 13

Mitochondrion/ribosome/endoplasmic reticulum/lysosome/cell-surface membrane

Question 14

Other factor the technician would have controlled- investigating the effect of temperature on the rate of an enzyme-controlled reaction.

Answer 14

Concentration of substrate solution / of enzyme solution / pH;

Question 15

ways in which meiosis produces genetic variation

Answer 15

1. Independent segregation (of homologous chromosomes);

2. Crossing over / formation of chiasmata;

Question 16

The arrows in Figure 5 show the directions in which each new DNA strand is being produced.
Use Figure 4, Figure 5 and your knowledge of enzyme action to explain why the arrows point in opposite directions.

Answer 16

1. (Figure 4 shows) DNA has antiparallel strands/described;
2. (Figure 4 shows) shape of the nucleotides is different/nucleotides aligned differently;
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary
   shape/only the 3’ end can bind with active site of enzyme/active site of DNA polymerase;

Question 17

The scientists obtained DNA from otters that were alive before hunting started.
Suggest one source of this DNA

Answer 17

Bone/skin/preserved remains / museums;

Question 18

reasons why populations might show very low levels of genetic diversity

Answer 18

1. Population might have been very small/genetic bottleneck;
2. Population might have started with small number of individuals / by one pregnant female / founder effect;
3. Inbreeding;

Question 19

The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why.

Answer 19

Loss of water/loss of fluid/friction (against capillary lining);

Question 20

High blood pressure leads to an accumulation of tissue fluid. Explain how

Answer 20

1. High blood pressure = high hydrostatic
   pressure;
2. Increases outward pressure from (arterial) end of capillary/reduces inward pressure at (venule) end of capillary;
3. (So) more tissue fluid formed /less tissue fluid is reabsorbed;

Question 21

The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why.

Answer 21

1. Water has left the capillary;
2. Proteins (in blood) too large to leave capillary;
3. Increasing/giving higher concentration of blood proteins (and thus wp)

Question 22

Describe how you would test a piece of food for the presence of lipid

Answer 22

1. Dissolve in alcohol, then add water;

2. White emulsion shows presence of lipid;

Question 23

Cholesterol increases the stability of plasma membranes. Cholesterol does this by making membranes less flexible.
Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum.

Answer 23

Red blood cells free in blood/not supported by other cells so cholesterol helps to maintain shape;

Question 24

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.

Answer 24

1. Cell unable to change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid/made of peptidoglycan/murein;

Question 25

HSV infects nerve cells in the face (line 1). Explain why it infects only nerve cells- specificity

Answer 25

1. Outside of virus has antigens/proteins; 2. With complementary shape to receptor/protein in membrane of cells; 3. (Receptor/protein) found only on membrane of nerve cells;

Question 26

Endopeptidases and exopeptidases are involved in the hydrolysis of proteins. Name the other type of enzyme required for the complete hydrolysis of proteins to amino acids.

Answer 26

Dipeptidase/s;

Question 27

Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own.

Answer 27

1. Endopeptidases hydrolyse internal (peptide bonds) OR Exopeptidases remove amino acids/hydrolyse (bonds) at end(s); 2. More ends or increase in surface area (for exopeptidases);

Question 28

the co-transport mechanism for the absorption of amino acids into the blood by a cell lining the ileum. The addition of a respiratory inhibitor stops the absorption of amino acids. explain why

Answer 28

1. No/less ATP produced OR No active transport; 2. Sodium (ions) not moved (into/out of cell); 3. No diffusion gradient for sodium (to move into cell with amino acid) OR No concentration gradient for sodium (to move into cell with amino acid);

Question 29

appropriate units the student should use to compare the distribution of stomata on leaves

Answer 29

Stomata per mm2 or cm2 OR Number per mm2 or cm2

Question 30

The pieces of leaf tissue examined were very thin. Explain why this was important.

Answer 30

1. Single/few layer(s) of cells; | 2. So light can pass through;

Question 31

reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue.

Answer 31

1. Distribution may not be uniform OR So it is a representative sample; 2. To obtain a (reliable) mean;

Question 32

Other than the distribution of stomata, suggest and explain two xerophytic features the leaves of this plant might have.

Answer 32

1. Hairs so ‘trap’ water vapour and water potential gradient decreased; 2. Stomata in pits/grooves so ‘trap’ water vapour and water potential gradient decreased; 3. Thick (cuticle/waxy) layer so increases diffusion distance; 4. Waxy layer/cuticle so reduces evaporation/transpiration. 5. Rolled/folded/curled leaves so ‘trap’ water vapour and water potential gradient decreased; 6. Spines/needles so reduces surface area to volume ratio;

Question 33

The student then compared the rate of transpiration (evaporation of water) from the two species of plant. She did this by measuring the rate of water uptake by each plant species. Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration.

Answer 33

1. Water used for support/turgidity; 2. Water used in photosynthesis; 3. Water used in hydrolysis; 4. Water produced during respiration;

Question 34

Explain the importance of the sites being chosen at random.

Answer 34

No bias;

Question 35

Explain why the removal of hedges caused a decrease in the diversity of birds.

Answer 35

1. Removes species/types of plant/insect; 2. Fewer food sources; 3. Fewer habitats/niches;

Question 36

Name the type of reaction used to break down phospholipids to release phosphate.

Answer 36

Hydrolysis (reaction);

Question 37

Suggest two reasons why an increase in phosphate can be linked to growth of the embryo

Answer 37

1. (Phosphate required) to make RNA; 2. (Phosphate required) to make DNA; 3. (Phosphate required) to make ATP/ADP; 4. (Phosphate required) to make membranes; 5. (Phosphates required) for phosphorylation;

Question 38

Suggest how this adaptation may enable these plant species to survive and respond to seasonal changes.

Answer 38

1. Seeds/embryo remain dormant/inactive in winter/cold OR Growth/development of seed/embryo during winter/cold; 2. Seeds/plants develop in spring/summer OR Seeds/plants develop whentemperature/light increases; 3. Plant photosynthesise (in spring/when warm); 4. Produce (more) seeds/offspring in spring/growing season;

Question 39

Suggest two precautions that should have been taken to ensure that this mean FEV1 value was reliable.

Answer 39

1. Large sample size; 2. Individuals chosen at random; 3. Are healthy; 4. Equal number of males and females; 5. Repeat readings;

Question 40

Explain the importance of determining a mean FEV1 value of 25-year-olds in this investigation.

Answer 40

1. (For) comparison; 2. To see effect of age/emphysema/smoking OR Takes into account outliers/anomalous results;

Question 41

The mean FEV1 value of non-smokers decreases after the age of 30. Use your knowledge of ventilation to suggest why.

Answer 41

1. Internal intercostal muscle(s) less effective OR | - Less elasticity (of lung tissue);

Question 42

One of the severe disabilities that results from emphysema is that walking upstairs becomes difficult. Explain how a low FEV1 value could cause this disability.

Answer 42

1. Less carbon dioxide removed; 2. Less oxygen (uptake/in blood); 3. Less (aerobic) respiration/ATP OR (More) anaerobic respiration;

Question 43

HIV attaches to a specific protein receptor on helper T cells. A low percentage of people have a mutation of the CCR5 gene which codes for this protein receptor. This mutation results in a non-functional protein receptor. Explain how this mutation can result in the production of a non-functional protein receptor

Answer 43

1. Change in DNA base/nucleotide (sequence); 2. Change in amino acid (sequence)/primary structure; 3. Alters (position of) hydrogen/ionic/disulfide bonds; 4. Change in tertiary structure (of receptor)

Question 44

People with the CCR5 mutation show a greater resistance to developing AIDS. Explain why.

Answer 44

1. (Receptor) is not complementary OR (HIV) cannot bind/attach and enter/infect (helper) T cell; 2. No replication (of virus) OR No destruction of (helper) T cell;

Question 45

Some people produce a much higher ventricular blood pressure than normal. This can cause tissue fluid to build up outside the blood capillaries of these people. Explain why

Answer 45

1. More fluid forced/filtered out of capillary/blood (due to high pressure); 2. Less return of fluid (into capillary/blood) due to pressure OR Lymph(atic) (system) cannot drain away all excess fluid;

Question 46

Some drugs used to reduce high ventricular blood pressure cause widening of blood vessels. Suggest how widening of blood vessels can reduce ventricular blood pressure.

Answer 46

1. Larger lumen/volume (of blood vessels); 2. Reduces (blood) pressure (in blood vessels); 3. Less friction/resistance (in blood vessels);

Question 47

Describe how the structures of starch and cellulose molecules are related to their functions.

Answer 47

Starch (max 3) 1. Helical/ spiral shape so compact; 2. Large (molecule)/insoluble so osmotically inactive; 3. Branched so glucose is (easily) released for respiration; 4. Large (molecule) so cannot leave cell/cross cell-surface membrane; Cellulose (max 3) 5. Long, straight/unbranched chains of β glucose; 6. Joined by hydrogen bonding; 7. To form (micro/macro)fibrils; 8. Provides rigidity/strength;

Question 48

Describe the processes involved in the transport of sugars in plant stems.

Answer 48

1. (At source) sucrose is actively (transported) into the phloem/sieve element/tube; 2. By companion/transfer cells; 3. Lowers water potential in phloem/sieve element/tube and water enters by osmosis; 4. (Produces) high (hydrostatic) pressure; 5. Mass flow/transport towards sink/roots/storage tissue; 6. At sink/roots sugars are removed/unloaded;