Jun 2016 Paper 1

Question 1

Describe the 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

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

Answer 2

Add ethanol, then add water

White (emulsion shows lipid);

Question 3

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

Answer 3

Saturated single/no double bonds

between carbons

Question 4

This fat substitute cannot be digested in the gut by lipase.

Suggest why

Answer 4

(Fat substitute) is a different/wrong shape/not complementary
Unable to fit/bind to (active site of) lipase/no ES complex formed

Question 5

Suggest why the fat substitute cannot cross cell-surface membranes.

Answer 5

It is hydrophilic

Question 6

Describe how ATP is resynthesised in cells.

Answer 6

From ADP and phosphate
By ATP synthase;
During respiration/photosynthesis

Question 7

Give two ways in which the hydrolysis of ATP is used in cells.

Answer 7

To provide energy for other reactions/named process

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

Question 8

What is the evidence from Figure 2 that a scanning electron microscope was used to take this photograph?

Answer 8

because it’s a 3D image

Question 9

Name the part of the mitochondrion labelled X in Figure 2.

Answer 9

Cristae

Question 10

P – diffusion through the phospholipid bilayer
Q – facilitated diffusion
R – active transport
S – co-transport
T – osmosis 

Transport through a channel protein
Transport of small, non-polar molecules
Transport of glucose with sodium ions

Answer 10

Transport through a channel protein : Q

Transport of small, non-polar molecules : P

Transport of glucose with sodium ions : S

Question 11

Y is a protein. One function of Y is to transport cellulose molecules across the phospholipid bilayer.
Using information from Figure 3, describe the other function of Y.

Answer 11

Makes cellulose

From β glucose

Question 12

What is the evidence in Figure 3 that the phospholipid bilayer shown is part of the cell-surface membrane?

Answer 12

because the cell-surface membrane has cellulose on it

Question 13

Describe the type of bond that holds the cellulose

molecules together side by side.

Answer 13

Hydrogen

Question 14

Name the products of the hydrolysis of sucrose

Answer 14

Glucose

Fructose

Question 15

What can you conclude about the growth of the plant cells from these data?
Explain how you reached your conclusions.

Answer 15

Sucrose hydrolysis linked to some
aspect of growth;
Greater the rate of/faster
hydrolysis/more SPS activity as
plant grows/cells divide (up to 8/10
days);
Growth/division remains the
same/slows after 8/10 days (because SPS activity is levelling off);

Question 16

Describe the induced-fit model of enzyme action.

Answer 16

active site not complementary to/does not fit substrate;
Shape of active site changes as substrate binds
distorting it

Question 17

A scientist investigated the hydrolysis of starch.
He added amylase to a suspension of starch and measured the concentration of maltose in the reaction mixture at regular intervals.
Explain the results shown in Figure 4.

Answer 17

High initial rate as plenty of starch/substrate/more E-S complexes;
No increase after 25 minutes/at end/levels off because no substrate/starch left;

Question 18

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 Figure 4.

Answer 18

Make/use maltose solutions of known/different concentrations (and carry out quantitative Benedict’s test on each);

(Use colorimeter to) measure colour/colorimeter value of each solution and plot calibration curve/graph described;

Find concentration of sample from calibration curve;

Question 19

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 19

Vaccine/it contains antigen (from HPV);

Specific helper T cell (detects antigen and) stimulates specific B cell;

B cell divides/goes through mitosis/forms clone to give plasma cells;

B cell/plasma cell produces antibody;

Question 20

What do these results suggest about whether it is better to give two or three doses of the vaccine? Give reasons for your answer.

Answer 20

Two (doses) because got more
antibody;
Also three doses would be more expensive

Question 21

The doctors carried out a statistical test to determine whether the antibody concentrations were significantly different in girls given two doses of the vaccine,
compared with those given three doses. They determined the mean concentrations of antibody 9 months after the first dose of vaccine.
What statistical test should the doctors have used? Give the reason for your choice.

Answer 21

t-test

because they are comparing two means

Question 22

There is genetic diversity within HPV.

Give two ways doctors could use base sequences to compare different types of HPV.

Answer 22

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

Question 23

Chromosomes line up on the equator of the mitotic spindle in…

Answer 23

metaphase

Question 24

Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis

Answer 24

No separation of chromatids/chromosomes/centromeres;

Chromatids/chromosomes all go to one pole/end/sides of cell/not pulled to opposite poles

Question 25

A student who saw these results concluded that in any future trials of this kinesin inhibitor with people, a concentration of 100 nmol dm–3 would be most
appropriate to use.
Do these data support the student’s conclusion? Give reasons for your answer.

Answer 25

(No, because) at 100 there are still
some (7%) cancer cells
dividing/undergoing mitosis;

So, cancer not destroyed/may continue
to grow/spread/form tumours;

This research has been carried out in culture, we don’t know effect of Kinesin inhibitor on people;

Best concentration may be between
100 and 1000/need trials between 100
and 1000;

Question 26

Describe how they made 100 cm3 of 1000 nmol dm–3 solution of kinesin inhibitor.

Answer 26

10 cm3 of 10 000 nmol dm–3 of original solution;

and 90 cm3 of water;

Question 27

Suggest how amyloid-precursor protein can be the substrate of two different enzymes, α-secretase and β-secretase (lines 3–5).

Answer 27

Different parts/areas/amino acid sequences (of amyloid-precursor) protein;
Each enzyme is specific /fits/binds/ complementary to a different part of the APP;

Question 28

Describe what happens in the hydrolysis reaction that produces the smaller protein from amyloid-precursor protein.

Answer 28

Hydrolysis occurs and the peptide bond is broken using water

Question 29

Use the information provided to explain how these mutations can lead to Alzheimer’s disease.

Answer 29

Mutations prevent production of enzyme(s)/functional enzyme;
(Increase in β-secretase) leads to faster/more β-amyloid production
(Leads to) more plaque formation;

Question 30

Using the information provided, suggest why some patients developed serious side effects.

Answer 30

Accept build-up of amyloid-precursor protein (leads to harm)

Question 31

Explain how this type of drug could prevent Alzheimer’s disease becoming worse.

Answer 31

(Inhibitor) binds to/blocks active site of β secretase/enzyme;
Stops/reduces production of β- amyloid/plaque;