Communication, Homeostasis and Energy Exam Questions

Question 1

Kendal Mint Cake is made from sugar, flavoured with peppermint, and was famously taken on the
1953 ascent of Mount Everest.
Which statement describes why climbers now prefer to take chocolate?
A Chocolate contains fat. Fat stores and releases less energy per gram than sugar.
B Chocolate contains fat. Fat stores and releases more energy per gram than sugar.
C Fat contains more oxygen than glucose.
D Glucose can be digested more rapidly than fat.

Answer 1

B

Question 2

Which process is an example of cell signalling?
A Binding of a virus to a receptor on the cell surface membrane of an epithelial cell in the
upper respiratory tract
B Binding of acetylcholine to cell surface receptors on sodium ion channels in the
post-synaptic neurone
C Co-transport of glucose and Na+ ions across the cell surface membrane of an epithelial cell
in the proximal convoluted tubule
D Operation of the Na+/K+ pump in the cell surface membrane of the axon

Answer 2

B

Question 3

Which statement describes an aspect of homeostasis?
A Effectors detect a change and cause release of hormones that bind to target cells.
B Homeostasis maintains the internal body temperature of animals at a constant level.
C Homeostasis involves both positive and negative feedback.
D Receptors coordinate nervous and hormonal responses.

Answer 3

B

Question 4

Linoleic acid is a fatty acid found in sunflower oil.
The equation for oxidation of linoleic acid is:
Linoleic acid: C18H32O2 + 25 O2 18 CO2 + 16 H2O
What is the respiratory quotient (RQ) of linoleic acid?
A 0.33
B 0.72
C 1.00
D 1.39

Answer 4

B

Question 5

Which of the statements about the relationship between photosynthesis and aerobic respiration
in plants is/are correct?
1 During the day, photosynthesis produces all the ATP that cells in the leaves require.
2 Carbon dioxide produced in respiration can be used as a carbon source in photosynthesis.
3 Oxygen produced in photosynthesis can be used in aerobic respiration.
A 1, 2 and 3 are correct
B Only 1 and 2 are correct
C Only 2 and 3 are correct
D Only 1 is correct

Answer 5

C

Question 6

Erythrocytes are formed from bone marrow stem cells. During this process they lose most of their
organelles.
Which statement about respiration in erythrocytes is correct?
A Oxygen bound to haemoglobin is used by erythrocytes in aerobic respiration.
B They do not respire because their cell surface membrane is impermeable to glucose.
C They respire aerobically because they always have adequate supplies of oxygen.
D They respire anaerobically because they do not have mitochondria.

Answer 6

D

Question 7

Dicotyledons are a large and diverse group of multicellular plants that includes oak trees and
dandelions.
(a) Explain, using examples of transported substances, why multicellular plants need transport
systems. (3 marks)

Answer 7

• Their large size requires transport over long distances.
• The diffusion distance is too great to rely on diffusion alone.
• They have a small SA:V ratio.
• Transport systems are required to transport water from roots to cells and sucrose from source to sink.

Question 8

Identify three proteins that make up the filaments labelled Z on Fig. 19.1. (tissue in the centre of striated muscle tissue)

Answer 8

• Actin
• Tropomyosin
• Troponin

Question 9

Use your knowledge of the sliding filament model of muscle contraction to explain why
Fig. 19.2 represents contracted muscle. (3 marks)

Answer 9

-light/I band is smaller
- dark/A band remains the same
- sarcomeres are shorter
- H zone becomes smaller
- there is greater overlap between actin and
myosin filaments

Question 10

After death, the concentration of ATP in muscle cells decreases. During this time, the
muscles become rigid in a process called rigor mortis.
Suggest why a lack of ATP leads to muscle rigidity (2 marks)

Answer 10

• ATP is required to break cross-bridges/detach myosin from actin
• actin and myosin filaments remain cross-linked
• prevents relaxation of muscle/muscle stays contracted

Question 11

Muscle contraction requires energy in the form of ATP.
Describe the different sources of the ATP that is used in muscle contraction during strenuous
exercise. (6 marks)

Answer 11

Sources of ATP:
- Free ATP in muscle cells/sarcoplasm
- ATP formed from creatine phosphate or phosphocreatine
- runs out quickly

Aerobic respiration:
- occurs if oxygen available
- oxidative phosphorylation produces ATP
- greater yield of ATP
- delivery of oxygen to tissues does not meet
demand
* oxygen is limited during strenuous exercise

Anaerobic respiration:
- needed during strenuous exercise
- anaerobic only involves glycolysis
- ATP formed by substrate level
phosphorylation
- net yield of 2 ATP/smaller yield of ATP
- NAD regenerated so glycolysis can
continue
- cannot continue indefinitely due to lactic
acid build-up

Question 12

A constant flow of water past the oxygen probe allows continuous monitoring of oxygen
concentration of water containing a fish.
Explain one other reason why it is necessary to maintain a constant flow of water in the
respirometer. (2 marks)

Answer 12

• To maintain an adequate supply of oxygen so that fish can respire aerobically
• To remove waste products (eg. carbon dioxide) that could, damage/kill the fish.

Question 13

Calculate the Q10 for respiration in the largest fish.
Give your answer to 3 significant figures.
Oxygen consumption:
- 200 at 23 degrees
- 175 at 18 degrees
- 90 at 13 degrees

Answer 13

200 / 90 = 2.22222
2.22

Question 14

Describe what is meant by an endocrine gland. (2 marks)

Answer 14

• a group of cells that secretes/releases hormones
• directly into the blood stream

Question 15

The pancreas contains endocrine glands such as the Islets of Langerhans. It also
contains cells that produce digestive enzymes.
Suggest why the cells that produce digestive enzymes are described as exocrine rather
than endocrine. (1 mark)

Answer 15

Because digestive enzymes are released into ducts, not straight into the blood.

Question 16

Hormones can be classed as either steroid or non-steroid. Steroids are lipid soluble.
Suggest the location of the receptors for steroid hormones and state a reason for your
suggestion. (2 marks)

Answer 16

• inside cells/in cytoplasm/ in the nucleus
• because steroids can cross the plasma membrane

Question 17

The Society for Endocrinology has produced a booklet about adrenal failure to help patients
understand their illness.
The following statements are adapted from this booklet.
* Adrenal failure is caused by inability of the adrenal glands to produce sufficient amounts
of cortisol and aldosterone.
* In healthy people, the hormone ACTH is produced by the pituitary gland and causes the
adrenal cortex to release more cortisol and aldosterone.
* A pituitary tumour can stop ACTH production by the pituitary. This leads to adrenal
failure.
* Symptoms of adrenal failure include severe fatigue and weakness, weight loss, low
blood pressure and salt craving.
(i) Explain the symptoms of adrenal failure. (2 marks)

Answer 17

• cortisol regulates
  carbohydrate metabolism
• lack of aldosterone/mineralocorticoids cause low
  blood pressure/salt craving, as they regulate ion concentration

Question 18

The Society for Endocrinology has produced a booklet about adrenal failure to help patients
understand their illness.
The following statements are adapted from this booklet.
* Adrenal failure is caused by inability of the adrenal glands to produce sufficient amounts
of cortisol and aldosterone.
* In healthy people, the hormone ACTH is produced by the pituitary gland and causes the
adrenal cortex to release more cortisol and aldosterone.
* A pituitary tumour can stop ACTH production by the pituitary. This leads to adrenal
failure.
* Symptoms of adrenal failure include severe fatigue and weakness, weight loss, low
blood pressure and salt craving.
Explain why patients with a pituitary tumour have adrenal failure but still respond
normally to situations of danger or excitement. (3 marks)

Answer 18

• ACTH only affects the adrenal cortex
• adrenaline is produced by the adrenal medulla
• adrenaline is responsible for the response to danger/flight or fight response
• the response to danger/fight or flight response is also
  mediated by the autonomic/sympathetic nervous system

Question 19

Complete the sentences using the most appropriate terms.
Carbon fixation occurs in the Calvin cycle when CO2 combines with the five-carbon
molecule ……………………………………………………………….. . This forms an unstable six-carbon
molecule that immediately breaks down into two molecules of …………………………………………
These are reduced to triose phosphate using …………………………………………………………. and
……………………………………………………………… that are formed in the light-dependent stage of
photosynthesis. Triose phosphate is used to form hexose phosphates which can be
converted to ………………………………………………………….. for transport elsewhere in the plant

Answer 19

• RuBP/ribulose bisphosphate
• GP/glycerate phosphate
• ATP
• NADPH/reduced NADP
• sucrose

Question 20

Which of the options is not a function of the liver?
A production of urea in the ornithine cycle
B removal of amino groups from amino acids
C storage of excess amino acids as protein
D storage of glucose as glycogen

Answer 20

C

Question 21

Which of the statements about the control of blood glucose is correct?
A Pancreas cells increase their release of glucagon when blood glucose concentration rises
above a set level.
B Glucagon stimulates the conversion of glycogen to glucose by liver cells.
C Insulin increases blood glucose concentration by stimulating glycogenesis and
gluconeogenesis.
D The interaction of insulin and glucagon keeps the blood glucose concentration constant.

Answer 21

B

Question 22

Which of the following statements about nervous transmission is not correct?
A Breakdown of the myelin sheath can lead to uncoordinated movement.
B Saltatory conduction increases the rate of propagation of a nerve impulse.
C The myelin sheath is formed from Schwann cells.
D The nodes of Ranvier act as electrical insulators.

Answer 22

D

Question 23

Which of the following statements is/are correct?
1 The autonomic nervous system contains sensory and motor neurones.
2 Somatic and parasympathetic motor neurones use different neurotransmitters.
3 Somatic motor neurones stimulate skeletal muscles whereas autonomic motor neurons
stimulate only glands.
A 1, 2 and 3 are correct
B only 1 and 2 are correct
C only 2 and 3 are correct
D only 1 is correct

Answer 23

D

Question 24

NAD, FAD and Coenzyme A (CoA) are molecules that are involved in cellular respiration.
Which of the following statements about these molecules is/are correct?
1 NAD and FAD are examples of coenzymes.
2 NAD is reduced by accepting hydrogen atoms.
3 CoA delivers the three carbon atoms of pyruvate to the Krebs cycle in the form of an acetyl
group.
A 1, 2 and 3 are correct
B only 1 and 2 are correct
C only 2 and 3 are correct
D only 1 is correct

Answer 24

B

Question 25

A respirometer, shown below, can be used to investigate respiration (capillary U-tube containing coloured liquid). A student placed 5 cm3 of potassium hydroxide solution in the left-hand tube of the respirometer. The student suspended a basket above the liquid and placed 10 g of respiring seeds in the basket. Which of the following statements about this investigation is not correct? A The level of the liquid in the left-hand arm of the capillary tube would decrease (move downwards) with time. B The potassium hydroxide solution absorbs carbon dioxide. C The rate of movement of the liquid in the capillary tube is a measure of the rate of respiration. D The tap can be opened to equalise the pressure in each tube.

Answer 25

A

Question 26

State which subdivision of the peripheral nervous system supplies the SAN (1 mark)

Answer 26

Autonomic

Question 27

Normal human resting heart rate is approximately 70 beats per minute (bpm). Cutting the parasympathetic nerve to the heart increases this to approximately 100 bpm. Suggest two conclusions that could be made from this observation about the control of resting heart rate in normal humans. (2 marks)

Answer 27

- the heart rate controlled by the nervous/autonomic system - parasympathetic/vagus , nerve reduces heart rate - heart rate reduces by approximately 30 bpm

Question 28

i) Injury to the parts of the brain (hypothalamus and pituitary gland) can lead to a range of symptoms including: * fatigue * weight gain * menstrual irregularities * low blood pressure or dizziness * increased sensitivity to cold. Outline how injury to the hypothalamus and pituitary gland is able to cause such a wide range of symptoms. (2 marks) ii) Suggest why it can be difficult for a doctor to conclude that the symptoms described in part (i) are definitely caused by damage to parts of the brain. (1 mark)

Answer 28

i) - the hypothalamus and pituitary gland produce a wide range of hormones - they affect other , endocrine/hormone-producing glands ii)- damage to other endocrine glands could cause similar symptoms - symptoms may be caused by underlying conditions/other disease - symptoms may be result of epigenetic factors

Question 29

Complete the following passage using the most appropriate terms. The knee-jerk reflex is an example of a spinal reflex as it only goes through the .......................................... whereas the blinking reflex is a cranial reflex as the pathway goes through the brain. Reflexes are very fast as they only involve one or two .......................................... , which are the slowest parts of nerve transmission. This is one reason why reflexes give a survival advantage.

Answer 29

Spinal cord Synapses

Question 30

Name the cells that secrete insulin. (1 mark)

Answer 30

Beta cells

Question 31

Scientists investigated the effect of the drug nifedipine on the secretion of insulin from pancreas cells in culture. Pancreas cells were first incubated with glucose at a concentration of 3 mmol dm–3. The concentration of glucose was then increased to 20 mmol dm–3 in the presence or absence of nifedipine. The scientists then measured the amount of insulin secreted by the cells. They recorded their results as a percentage of the total insulin content of the cells. Each experiment was repeated seven times, and calculated means. i) Explain why it was necessary to increase the concentration of glucose surrounding the cells before they measured insulin secretion. (2 marks) ii) Suggest and explain which statistical test the researchers would have used to analyse their data. (2 marks) iii) The statistical test gave a value of p < 0.001. Use the words ‘chance’ and ‘probability’ to draw a conclusion from the result of the statistical test. (2 marks)

Answer 31

i) - glucose causes release of insulin - ensures the change in insulin secretion is high enough to be measured ii) - t-test - because they are comparing means iii) - probability is less than 0.001 - therefore differences in means were due to chance

Question 32

Nifedipine blocks Ca2+-channels. Explain how blocking calcium channels could inhibit insulin secretion. (2 marks)

Answer 32

- calcium ions do not enter cells - therefore there is less/ \no exocytosis (less movement of vesicles)

Question 33

Type 1 diabetes has been treatable for many years, but treatments are always improving. Evaluate the treatments for type 1 diabetes that have been used in the past as well as current and potential future treatments. (6 marks)

Answer 33

Insulin treatments: - from animal pancreas e.g. pig (past) - from GM/ recombinant bacteria (current) Other current/potential treatments: - transplant of pancreas/islets - transplant of pancreatic stem cells - immunotherapies/gene therapy Advantages of insulin: - animal-derived insulin: * tried and tested method * early treatment kept people alive - human insulin; * high purity * less risk of allergic reaction * lower production cost * overcomes religious/ethical issues of animal products * use of smart pens / pumps * detail of pump use e.g. monitored by apps Disadvantages of insulin: - animal-derived insulin: * needs to be purified * risk of allergic reaction * high production cost * religious / ethical issues of animal products - human insulin: * people persuaded to change from previous insulin regime e.g. animal insulin * some may not understand technology of injection routine * side effects of pumps e.g. hard lumps forming under skin Advantages of other treatments: e.g. transplants * less/no need for insulin injections * more physiological control of blood glucose compared with injection * reduce risk of ‘hypos’ * improved quality of life * stem cells turned into functioning β-cells e.g. immunotherapies * reprograms immune system * prevents / stops damage to β-cells Disadvantages of other treatments: e.g. transplants * requirement for immunosuppression * availability of donor tissue * ethical issues associated with stem cells * risk of cancer with stem cells * not suitable for certain people e.g. those with poor kidney function * may still need low dose of insulin * initial high costs e.g. immunotherapies * still in early stages * need clinical trials

Question 34

State the name of the final electron acceptor in the light-dependent stage of photosynthesis. (1 mark)

Answer 34

NADP

Question 35

The Hill reaction is a model system used to study the light-dependent stage of photosynthesis. It uses a blue dye, DCPIP, which is colourless when reduced. DCPIP is reduced in the Hill reaction. Suggest and explain the function of DCPIP in the Hill reaction. (2 marks)

Answer 35

- acts as the final electron acceptor - replaces NADP/the usual electron acceptor - allows photolysis to continue

Question 36

The Hill reaction is a model system used to study the light-dependent stage of photosynthesis. It uses a blue dye, DCPIP, which is colourless when reduced. A student was provided with the following method: * Cut three small spinach leaves into small pieces and place in a mortar containing 20 cm3 of 0.5 mol dm–3 sucrose solution. * Homogenise by grinding vigorously. * Filter the mixture and pour the filtrate into a centrifuge tube. * Centrifuge at high speed for 5 minutes. * Gently pour the supernatant (liquid part) into a clean tube labelled A. * Resuspend the pellet (sediment) in 20 cm3 of pH 7.0 buffer. * Add 5 cm3 of resuspended pellet to each of tubes labelled B – D. * Boil tube B for 5 minutes and then cool. * Add 10 cm3 DCPIP solution to each of tubes A – E. * Transfer tube C to a dark cupboard. * Observe colour of the tubes after 5 minutes. i) The student knew that it was important to use sucrose solution when homogenising the leaves. Explain why it was important that the pellet was suspended in buffer solution and why it did not contain sucrose. (2 marks) ii) Suggest and explain two improvements that would increase the validity of the method. (2 marks)

Answer 36

i) - the buffer maintains optimum pH - there is no sucrose as there is no need to prevent damage to chloroplasts/damage to chloroplasts increases access of DCPIP to reaction components ii) - use ice-cold solutions as it prevents damage to components/reduces rate of enzyme reactions - centrifuge at different speeds to obtain different fractions - use a water bath so that the temperature of all tubes is controlled/kept constant - use the same light source/distance from light source for illuminated tubes so that light intensity/wavelength , is controlled/kept constant

Question 37

Terrariums are popular for growing houseplants. A terrarium is a glass container containing soil and small plants. Once established, a terrarium can be sealed and the plants will be able to grow for months or even years despite not being in contact with the outside atmosphere. The terrarium maintains moist conditions for the plants. (i) Suggest one other reason why the plants in a sealed terrarium continue to grow. (1 mark) (ii) Cacti are popular house plants. Suggest why cacti do not grow well in a terrarium. (1 mark)

Answer 37

i) - respiration produces carbon dioxide that is used in photosynthesis - photosynthesis produce oxygen that is used in respiration ii) - because they are xerophytes - therefore the conditions are too moist

Question 38

Besides safety precautions, explain one practical precaution that should be taken when using a potometer. (2 marks)

Answer 38

- do not allow air to enter (cut end/shoot) to ensure a continuous column of water - keep temperature abiotic factor constant as it affects, rate of transpiration/evaporation of water - keep screw clip closed to prevent the entry of water whilst measuring

Question 39

What can you conclude from comparing the standard deviations of the two means if one is greater? (1 mark)

Answer 39

- data for the mean with a greater standard deviation are more spread about the mean/less precise

Question 40

The student wanted to estimate the total leaf surface area of the shoot. At the end of the investigation they removed all the leaves from the shoot. They placed the leaves on graph paper and then counted squares to obtain an estimate of leaf area. State two things the student would have to do to ensure that the estimate of leaf area was accurate. (2 marks)

Answer 40

- flatten leaves on to graph paper - account for partially covered squares - double leaf area to give total of both surfaces

Question 41

A student set up the respirometer to measure oxygen consumption. * The narrow tube contained coloured water. * The position of the meniscus was noted at the beginning of the experiment. * The tube was left for 20 minutes. * The new position of the meniscus was noted. * The experiment was repeated with the other type of seed. Which of the following would be necessary to ensure valid results? 1 Keeping the respirometer in the dark during the experiment. 2 Keeping the respirometer at the same temperature during the experiment. 3 Using the same dry mass of seeds each time. A 1, 2 and 3 B only 1 and 2 C only 2 and 3 D only 1

Answer 41

C

Question 42

A student set up the respirometer to measure oxygen consumption. * The narrow tube contained coloured water. * The position of the meniscus was noted at the beginning of the experiment. * The tube was left for 20 minutes. * The new position of the meniscus was noted. * The experiment was repeated with the other type of seed. The student investigated two types of seed, pea and sunflower: * pea seeds store mainly starch * sunflower seeds store mainly lipid. Which of the following, A to D, describes the results you would expect with each type of seed? A The meniscus would move to the left with pea seeds and further to the left with sunflower seeds. B The meniscus would move to the left with sunflower seeds and to the right with pea seeds. C The meniscus would move to the right with pea seeds and further to the right with sunflower seeds. D The meniscus would not move.

Answer 42

C

Question 43

Which of the following statements, A to D, describes and explains the relative yield of ATP in anaerobic and aerobic respiration? A Anaerobic respiration produces less ATP per molecule of glucose because lactate is converted to pyruvate. B Anaerobic respiration produces less ATP per molecule of glucose because NAD is not regenerated in oxidative phosphorylation. C Anaerobic respiration produces more ATP per molecule of glucose because NAD is regenerated in oxidative phosphorylation. D Anaerobic respiration produces more ATP per molecule of glucose because pyruvate is converted to lactate.

Answer 43

B

Question 44

Describe two ways in which the structure of mitochondrial membranes is related to the function of a mitochondrion. (2 marks)

Answer 44

- contain electron carriers/ ATP synthase/proton pumps - provide surface for chemiosmosis/ATP synthesis/oxidative phosphorylation - allow formation/maintenance of proton gradient - outer membrane is highly permeable to allow movement of (named) molecules