5 Energy transfers in and between organisms (A-level only)

Question 1

6.1 control of heart rate

Give two safety precautions that should be followed when dissecting a
heart. (1 mark)

Answer 1

Use a sharp scalpel/scissors
Wash hands/wear gloves
Disinfect bench/equipment
Cover any cuts
Cut away from self/others/on a hard surface
Safe disposal

only 2 required for one mark

Question 2

6.1 control of heart rate

When the heart beats, both ventricles contract at the same time.
Explain how this is coordinated in the heart after initiation of the heartbeat
by the SAN (2 marks)

Answer 2

1. More impulses/action potentials along sympathetic (nervous
   system pathway/branch);
   Ignore signals/information/ messages
   Idea of more impulses/action potentials is required
2. To SAN increasing the heart rate

Question 3

6.1 Survival and Response

Give one similarity and one difference between a taxis and a tropism (2 marks)

Answer 3

1. Similarity − directional response (to a stimulus) / movement
   towards / away from a stimulus;
2. Difference − taxis (whole) organism moves and tropism a growth
   (response).

minimum 2 points for full marks

Question 4

6.1 Survival and Response

Explain how this distribution of IAA causes the root to bend (2 marks)

Answer 4

1. (IAA) at bottom of root / where IAA concentration high inhibits expansion
   / elongation (of cells);
   2 and 3 need reference to expansion / elongation, not just
   growth
2. (IAA) at top of root / where IAA concentration low leads to expansion /
   elongation (of cells);

minimum 2 points for full marks

Question 5

6.1 Survival and Response

Suggest two advantages of simple reflexes.(2 marks)

Answer 5

1. Rapid;
2. Protect against damage to body tissues;
3. Do not have to be learnt;
4. Help escape from predators;
5. Enable homeostatic control

minimum two points for full marks

Question 6

Multiple sclerosis is a disease in which parts of the myelin sheaths
surrounding neurones are destroyed. Explain how this results in slower
responses to stimuli

Question 7

How is the structure of leaves adapted for photosynthesis?

Answer 7

• large s/a
• arrangement of leaves on a plant prevent overlapping (so no leaves are covered by shade)
• thin - most light observed in the first few micrometers
• many stomata- open and close in response to light intensity
• many interconnected air spaces - rapid diffusion of gases
• transparent cuticles and epidermis- let light through to photosynthetic mesophyll cells

Question 8

Describe the structure of chloroplasts

Answer 8

Thylakoids- contain chlorophyll pigment.
Grana - stacks of up to 100 thylakoids
Stroma - where rubisco is found. Gel like substance containing - enzymes,organic acids and sugars
Carbohydrates are stored as grains in the stroma
- double membrane
- disc shape

Question 9

What is oxidation?How is it different from reduction?

Answer 9

Oxidation
- loss of electrons
- loss of hydrogen
- gain of oxygen
- energy given out
Reduction
- gain of electrons
- gain of hydrogen
- loss of oxygen
- energy taken in

Question 10

What three pigments are found in chloroplast?

Answer 10

Chlorophyll a
Chlorophyll b
Carotene

Question 11

Where are chlorophyll a,b and carotene found in the chloroplasts?

Answer 11

In thylakoids membranes attached to proteins
Protein+pigment=photosystem

Question 12

What are the two types of phosphorylation?

Answer 12

Cyclic phosphorylation - PSI only
Non-cyclic phosphorylation - PSI an PSII

Question 14

Where precisely is rubisco found in a cell?

Answer 14

Stroma of the chloroplasts