Edexcel A-Level Biology AS 1 Molecules Transport and Health Questions

Identify the molecule, vessel or physiological process first, then use labelled structures, mark-scheme terminology and quantitative evidence to build the explanation.

Exam points

Describe biological molecules through monomers, bonds, functional groups and structure.
Interpret vessel, heart and dissociation evidence to explain transport and exchange.
Apply practical methods, calculations and health data with correct variables and units.

Covered syllabus points

1.1—Water as a transport solvent 1.2—Monosaccharides, disaccharides and polysaccharides 1.3—Core Practical 1 - reducing sugars and starch 1.4—Glycosidic bonds, condensation and hydrolysis 1.5—Triglycerides and saturated or unsaturated lipids 1.6—Need for hearts and circulation 1.7—Blood vessel structure and function 1.8—Cardiac cycle and mammalian heart function 1.9—Haemoglobin, oxygen dissociation and Bohr effect 1.10—Atherosclerosis 1.11—Blood clotting and cardiovascular disease 1.12—Cardiovascular disease risk factors 1.13—Antioxidants and cardiovascular disease risk 1.14—Core Practical 2 - vitamin C content 1.15—Health risk data, correlation and causation 1.16—Study design for health risk factors 1.17—Perceived risk and actual risk 1.18—Cholesterol, HDL, LDL and CVD evidence 1.19—Scientific knowledge and CHD risk reduction 1.20—Treatments for cardiovascular disease

[Maximum number: 2]

The structure and properties of the cell membrane are important in controlling which molecules can enter and leave a cell.

The diagram shows the permeability of cell membranes to some chemicals.
sodium and chloride ions

Figure for Question 1 — Edexcel A-Level Biology AS

The sodium and chloride ions, glucose and water are polar chemicals.
A steroid is a non-polar chemical.

Describe the dipolar nature of water.

[Maximum number: 11]

The structures of polysaccharides, disaccharides and monosaccharides relate to their roles in living organisms. They are all types of carbohydrate.

(a)

The table shows the main type of carbohydrate present in some foods.

Table for Question (a) — Edexcel A-Level Biology AS

[ 5 ]

(i)

Which row of the table shows an example of a polysaccharide, a disaccharide and a monosaccharide?

Table for Question (i) — Edexcel A-Level Biology AS

[ 1 ]

(ii)

Lactose is a disaccharide composed of galactose and glucose. Complete the diagram to show a molecule of lactose.

Figure for Question (ii) — Edexcel A-Level Biology AS

[ 2 ]

(iii)

Glycogen is another carbohydrate.

Describe the structure of glycogen.

[ 2 ]

A description that makes reference to the following points:

- {polymer of / polysaccharide of / made of many} ( $\alpha$ ) glucose (1)

- branched with (1-4 and 1-6 / together with 1-4) glycosidic bonds (joining glucoses) / has 1-4 and 1-6 glycosidic bonds (1)

DO NOT ACCEPT made of amylose
and amylopectin

(b)

Carbohydrate metabolism includes the group of chemical reactions that break down carbohydrates. Some of these reactions convert one type of carbohydrate into another type. The flowchart shows what happens to some of the carbohydrates that we eat.

Figure for Question (b) — Edexcel A-Level Biology AS

Explain how carbohydrates are metabolised, transported and used in the cells of the body and stored in liver cells. Use the information in the question and your own knowledge of the structures, roles and properties of carbohydrates and transport mechanisms.

[ 6 ]

1. Carbohydrate metabolism:

- carbohydrates broken down by hydrolysis

- by enzymes

- to speed up rate of reaction / to lower activation energy (E)

- starch to maltose / glucose, lactose to glucose and galactose, maltose to glucose, sucrose to glucose and fructose

- because starch is insoluble (so cannot move into blood) (E)

- so that sugars are soluble (and can be moved into the blood stream) (E)

2. Carbohydrate transport:

- monomers / named monomer pass into blood by facilitated diffusion / channel proteins / carrier proteins

- because it is a large / polar molecule (E)

- as there is more glucose in digestive system than in blood (E)

- transported in blood by mass transport

- to overcome the limitations of diffusion (E)

- because dissolves in blood plasma (E)

- because they are polar molecules (E)

3. Carbohydrate usage in cells:

- glucose passes into cells by facilitated diffusion / channel proteins / carrier proteins

- because more glucose in blood than cells (E)

- used as a respiratory substrate / respiration

- respiration to release energy (for cells) (E)

- used to form glycoproteins

- glycoproteins for cell membranes (E)

4. Carbohydrate storage in liver:

- liver stores carbohydrate as glycogen

- to lower blood sugar levels / glucose is in excess (E)

- glucoses joined by condensation reactions

- glycogen is insoluble (so can be stored) (E)

- glycogen does not have osmotic effect (E)

- glycogen broken down to re-enter blood stream

- as glycogen too large / insoluble to pass out of cells (E)

- when blood sugar levels are too low (E)

Additional guidance

Level 0

0

No awardable content

Level 1

1-2

An explanation may be attempted but with limited interpretation or analysis of the scientific information and with a focus on mainly just one piece of scientific information. The explanation will contain basic
information, with some attempt made to link knowledge and understanding to the given context.

Simple descriptions of data with no real attempt of an explanation

1 mark = one description made

2 marks = three descriptions made

Level 2

3-4

An explanation will be given, with occasional evidence of analysis,
interpretation and/or evaluation of both pieces of scientific information.
The explanation shows some linkages and lines of scientific reasoning, with some structure.

Some explanation given (E)

3 marks = explanation for one aspect of question

4 marks = explanation for two aspects of question

Level 3

5-6

An explanation is made that is supported throughout by sustained application of relevant evidence of analysis, interpretation and/or evaluation of both pieces of scientific information. The explanation shows a well-developed and sustained line of scientific reasoning, which
is clear and logically structured.

Extended explanation given (E)

5 marks = explanation for three aspects of question

6 marks = explanation for four aspects of question

[Maximum number: 4]

A simple test can be used to assess the quantity of sugar in liquids, such as food extracts and urine.

(a)

Describe how a urine sample can be tested for glucose.

[ 2 ]

(b)

Complete the table of results from tests on standard glucose solutions.

Table for Question (b) — Edexcel A-Level Biology AS

[ 2 ]

[Maximum number: 2]

The enzyme invertase breaks down sucrose into its two component monosaccharides.

Describe the structure of sucrose.

[Maximum number: 1]

The butterfly is an insect that feeds on nectar produced by flowers.
The photograph shows a butterfly feeding on a flower.

Figure for Question 5 — Edexcel A-Level Biology AS

The nectar in flowers contains nutrients including sugars, amino acids and lipids.

Which row of the table describes a saturated lipid?

□ A
□ B
□ C
□ D

Table for Question 5 — Edexcel A-Level Biology AS

[Maximum number: 2]

The butterfly is an insect that feeds on nectar produced by flowers.
The photograph shows a butterfly feeding on a flower.

Figure for Question 6 — Edexcel A-Level Biology AS

The circulatory system of an insect is described as an open system. This means that the blood is not contained inside blood vessels but flows through cavities called sinuses.

The diagram shows part of the circulatory system of an insect.

Conducting vessel: blood flows out of the

Explain why the circulation of a butterfly is different from the circulation of a mammal.

[Maximum number: 2]

(a)

The diagram shows the internal structure of a mammalian heart.

Figure for Question (a) — Edexcel A-Level Biology AS

[ 2 ]

(i)

How many of the following are correct for blood vessel P?
- carries blood to the heart
- has valves along its length
- has an endothelial lining

[ 1 ]

(ii)

Why is blood vessel Q classified as an artery?

because it carries deoxygenated blood

because it carries oxygenated blood

because it carries blood away from the heart

because it carries blood back to the heart

[ 1 ]

(iii)

Which blood vessel does the coronary artery branch from?

[ 1 ]

(iv)

When in the cardiac cycle is valve T open?

atrial systole and cardiac diastole

atrial systole only

cardiac diastole and ventricular systole

ventricular systole only

[ 1 ]

[Maximum number: 5]

Sickle cell disease is caused by a gene mutation affecting the $\beta$ -globin chain of haemoglobin.

(a)

The red blood cells in a person with sickle cell disease are sickle shaped and less elastic. They also have a shorter lifespan than healthy red blood cells.

These sickle shaped red blood cells cannot carry as much oxygen as healthy red blood cells and they get stuck in the capillaries.

The graph shows oxygen dissociation curves for groups of people with sickle cell disease and those without the disease.

The shaded areas represent the range of values for each group of people.

Percentage of haemoglobin saturated with oxygen (\%)

[ 5 ]

(i)

Identify two conclusions, other than the difference in p50 values, that can be made from this graph.

Conclusion 1

Conclusion 2

[ 2 ]

(ii)

Sickle cell disease can result in death.

Explain why the changes in the structure of haemoglobin and the shape of the red blood cells could result in death in a person with sickle cell disease.

[ 3 ]

[Maximum number: 4]

Stents are used in the treatment of atherosclerosis.
Stents widen the diseased coronary artery so that blood can flow through to the heart muscle.

The diagram shows a stent.

Figure for Question 9 — Edexcel A-Level Biology AS

Stents can damage the endothelial cells lining the artery and trigger the formation of a blood clot.

Patients who have a stent fitted are given anticoagulants.

(a)

Explain how damage to the endothelial cells results in the formation of thrombin.

[ 2 ]

(b)

The photograph shows a tropical bont tick.

This bont tick produces a peptide called variegin.
Variegin binds to the active site of thrombin and prevents blood clotting.

[ 2 ]

(i)

Explain how variegin prevents blood clotting.

[ 2 ]

[Maximum number: 1]

Several factors increase the risk of cardiovascular disease (CVD).

The diagram shows some factors that increase the risk of CVD.

Complete the diagram with one lifestyle risk factor and one non-lifestyle risk factor.

Figure for Question 10 — Edexcel A-Level Biology AS

[Maximum number: 3]

Several factors increase the risk of cardiovascular disease (CVD).

Dietary antioxidants may reduce the risk of CVD.

Explain how dietary antioxidants reduce the risk of CVD.

[Maximum number: 4]

Vitamin C is an antioxidant.

The concentration of vitamin C in a variety of locally sourced and imported fruits was measured.

Describe how vitamin C content in an extract of a fruit can be measured.

A description that includes four of the following:

- use of DCPIP (1)

- use known volume DCPIP (1)

- add \{extract / stock Vitamin C\} until no blue colour remains / becomes colourless / decolourises (1)

- record volume of \{extract / stock Vitamin C\} used (1)

- do titration again with (stock Vitamin C / extract) (1)

- compare the volume of extract added with the volume of stock added / stated correct equation to calculate Vitamin C content

accept titration of DCPIP into extract in mps 2, 3, 4 and 6

accept other appropriate redox dyes throughout, e.g. methylene blue

ignore add drops ignore amount

accept known Vitamin C concentration = stock

accept known Vitamin C concentration = stock

concentration of vitamin C in fruit juice = volume of standard solution added ÷ volume of fruit juice added x concentration of standard solution $\mathrm{V}_{1} \mathrm{C}_{1}=\mathrm{V}_{2} \mathrm{C}_{2}$

[Maximum number: 2]

Several factors increase the risk of cardiovascular disease (CVD).

The graph shows the effect of exercise on the relative risk of death from CVD.

Relative risk of death from CVD

Figure for Question 13 — Edexcel A-Level Biology AS

Energy needed for exercise / kJ per week

Describe the conclusions that can be made from the information shown in this graph.

[Maximum number: 3]

Several factors increase the risk of cardiovascular disease (CVD).

Dietary antioxidants may reduce the risk of CVD.

Devise a study to confirm that antioxidants reduce the risk of CVD.

[Maximum number: 2]

The diagram shows a coronary heart disease (CHD) risk calculator.

Coronary Heart Disease Risk Calculator

Sex: Female
Ethnicity: Native American
Age: 50
Total Cholesterol: $\sqrt{196} \mathrm{mg} / \mathrm{dL}$
HDL Cholesterol: 49 mg / dL
Systolic BP: 110 mmHg
Patient taking blood pressure medication: $\checkmark$
Patient has diabetes: $\checkmark$
Patient smokes: □

10 Year CHD Risk: 6.62%

Explain why the risk calculator takes into account total cholesterol and HDL cholesterol levels.

[Maximum number: 6]

Obesity increases the risk of cardiovascular disease (CVD).
Body mass index (BMI), waist-to-hip ratio (WHR) and skinfold thickness are indicators of obesity.

(a)

The table shows some measurements taken from two females, female J and female K.

[ 4 ]

(i)

Comment on the risk of developing CVD in these two women.

[ 2 ]

(ii)

The diagram shows how the waist and hip measurements should be taken, using a tape measure.

Explain how the way a person takes these measurements could produce an underestimate of their risk of CVD.

[ 2 ]

(b)

The diagram shows how a skinfold thickness measurement is taken over the triceps muscle at the back of the arm.

Skinfold thickness measures the thickness of the layer of fat under the skin.
Measurements are taken from several sites on the body.
The table shows the skinfold thickness at four sites on a 42-year-old female.

[ 2 ]

(i)

Suggest two reasons why the skinfold thickness values are different at each site on the body.

Assume that the skin callipers have been used correctly.

[ 2 ]

[Maximum number: 1]

Stents are used in the treatment of atherosclerosis.
Stents widen the diseased coronary artery so that blood can flow through to the heart muscle.

The diagram shows a stent.

Figure for Question 17 — Edexcel A-Level Biology AS

Stents can damage the endothelial cells lining the artery and trigger the formation of a blood clot.

Patients who have a stent fitted are given anticoagulants.

Give one risk of treating patients with anticoagulants.

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (b)

Question 3

Question (a)

Question (b)

Question 4

Question 5

Question 6

Question 7

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question 8

Question (a)

Question (i)

Question (ii)

Question 9

Question (a)

Question (b)

Question (i)

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question (a)

Question (i)

Question (ii)

Question (b)

Question (i)

Question 17