RESPONDING TO CHANGES IN THE ENVIRONMENT

• CONTROL OF HEART RATE

  Give two safety precautions that should be followed when dissecting a

  heart. (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
• Caffeine affects the autonomic nervous system.

  Suggest how caffeine could account for the results of Group I in Figure 2

  at 60 minutes. (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 (seen in Figure 2);
• Before taking the drink, the mean heart rate of Group J was 68 beats per

  minute.

  Fifteen minutes after taking the drink, the mean volume of blood leaving

  the hearts of Group J was 4700 cm3 per minute.

  Calculate the mean volume of blood leaving the heart at each beat fifteen

  minutes after taking the drink. (1)

  73
• The increase seen in Group I could be due to the combination of caffeine

  and sugar.

  Suggest one drink to be given to an additional group that should be

  investigated to find out if this is true.

  Give a reason for your answer. (2)

  Group to be given

  1. Sugar solution (only)

  OR

  A drink with sugar (and no caffeine);

  Accept 'glucose' for sugar

  Ignore named drinks unless qualified

  Ignore 'sugar' by itself

  Ignore references to use of a placebo tablet

  Reason

  2. To show/prove that sugar (alone) is not causing the increases

  (in HR)

  OR

  To show that sugar does not have an effect;

  Accept 'to see the effect of sugar
• Exercise causes an increase in heart rate.

  Describe the role of receptors and of the nervous system in this process.(4)

  1. Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid / fall

  in pH

  OR

  Baro / pressure receptors detect rise in blood pressure;

  2. Send impulses to cardiac centre / medulla;

  3. More impulses to SAN;

  4. By sympathetic (nervous system for chemoreceptors / CO2)

  OR

  By parasympathetic (nervous system for baro / pressure

  receptors / blood pressure);

  1. Ignore: location of receptors.

  1. Ignore: chemoreceptors detect oxygen.
• 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)

  1. Electrical activity only through Bundle of His / AVN;

  2. Wave of electrical activity passes over / through both ventricles at the

  same time;
• Damage to the myelin sheath of neurones can cause muscular paralysis

  (lines 2-4).

  Explain how. (3)

  1. (Refers to) saltatory conduction

  2. (Nerve) impulses slowed/stopped;

  3. (Refers to) neuromuscular junction
• RECEPTORS

  Q1.

  The iris in the human eye is a muscular structure. The iris changes the size of

  the pupil.

  The diagram below shows the muscles in the iris.

  (a) Suggest and explain how the interaction between the muscles labelled in

  the diagram above could cause the pupil to constrict (narrow). (2)

  1. Circular muscle contracts;

  2. Radial muscle relaxes;
• The fovea of the eye of an eagle has a high density of cones. An eagle

  focuses the image of its prey onto the fovea.

  Explain how the fovea enables an eagle to see its prey in detail.

  Do not refer to colour vision in your answer. (3)

  1. High (visual) acuity;

  2. (Each) cone is connected to a single neurone;

  3. (Cones send) separate (sets of) impulses to brain;
• The retina of an owl has a high density of rod cells.

  Explain how this enables an owl to hunt its prey at night.

  Do not refer to rhodopsin in your answer. (3)

  1. High (visual) sensitivity;

  Accept retinal convergence.

  2. Several rods connected to a single neurone;

  3. Enough (neuro)transmitter to reach/overcome threshold
• 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. (2)

  1. Membrane more permeable to potassium ions and less permeable to

  sodium ions;

  2. Sodium ions actively transported / pumped out and potassium

  ions in.
• NERVOUS COORDINATION

  Explain how a resting potential is maintained across the axon membrane in

  a neurone. (3)

  1. Higher concentration of potassium ions inside and higher

  concentration of sodium ions outside (the neurone)

  OR

  potassium ions diffuse out

  OR

  sodium ions diffuse in;

  2. (Membrane) more permeable to potassium ions (leaving

  than sodium ions entering)

  3. Sodium ions (actively) transported out and potassium ions in;

  reference to ions or Na+ and K+ is required. If

  mentioned once allow for all mark points.
• Explain why the speed of transmission of impulses is faster along a

  myelinated axon than along a non-myelinated axon. (3)

  1. Myelination provides (electrical) insulation;

  Reject thermal insulation.

  Accept description of (electrical) insulation.

  2. (In myelinated) saltatory (conduction)

  OR

  (In myelinated) depolarisation at nodes (of Ranvier);

  3. In non-myelinated depolarisation occurs along whole/length (of axon);
• A scientist investigated the effect of inhibitors on neurones. She added a

  respiratory inhibitor to a neurone. The resting potential of the neurone

  changed from -70 mV to 0 mV.

  Explain why.(3)

  1. No/less ATP produced;

  2. No/less active transport

  OR

  Sodium/potassium pump inhibited;

  Accept Na+ not/fewer moved out and K+ not/fewer

  moved in.

  3. Electrochemical gradient not maintained
• Describe the sequence of events involved in transmission across a cholinergic

  synapse.

  Do not include details on the breakdown of acetylcholine in your answer. (5)

  1. Depolarisation of presynaptic membrane;

  Accept action potential for depolarisation.

  2. Calcium channels open and calcium ions enter (synaptic knob);

  Accept Ca2+.

  3. (Calcium ions cause) synaptic vesicles move to/fuse with

  presynaptic membrane and release

  acetylcholine/neurotransmitter;

  Accept abbreviations for acetylcholine as term is in

  the question.

  4. Acetylcholine/neurotransmitter diffuses across (synaptic cleft);

  Accept abbreviations for acetylcholine as term is in

  the question.

  5. (Acetylcholine attaches) to receptors on the postsynaptic membrane;
• Dopamine is a neurotransmitter released in some synapses in the brain.

  The transmission of dopamine is similar to that of acetylcholine.

  Dopamine stimulates the production of nerve impulses in postsynaptic

  neurones.

  Describe how.

  Do not include in your answer the events leading to the release of

  dopamine and the events following production of nerve impulses at

  postsynaptic neurones.(3)

  1. (Dopamine) diffuses across (synapse);

  2. Attaches to receptors on postsynaptic membrane;

  Ignore name/nature of receptor e.g. cholinergic

  3. Stimulates entry of sodium ions and depolarisation/action potential;

  Accept Na+ for sodium ions

  Accept generator potential for action potential
• Dopamine has a role in numerous processes in the brain including pain

  relief. The release of dopamine can be stimulated by chemicals called

  endorphins produced in the brain. Endorphins attach to opioid receptors on

  presynaptic neurones that release dopamine.

  Morphine is a drug that has a similar structure to endorphins and can

  provide pain relief.

  Explain how. (2)

  1. Morphine attaches to opioid receptors;

  Reject reference to active site

  2. (More) dopamine released (to provide pain relief);

  Reject receptors release dopamine
• GABA is a neurotransmitter released in some inhibitory synapses in the

  brain. GABA causes negatively charged chloride ions to enter postsynaptic

  neurones.

  Explain how this inhibits postsynaptic neurones. (3)

  1. Less / no acetylcholine broken down;

  2. Acetylcholine attaches to receptors;

  3. (More) Na+ enter to reach threshold / for depolarisation / action

  potential / impulse;
• When a nerve impulse arrives at a synapse, it causes the release of

  neurotransmitter from vesicles in the presynaptic knob.

  Describe how. (3)

  1. Less / no acetylcholine broken down;

  2. Acetylcholine attaches to receptors;

  3. (More) Na+ enter to reach threshold / for depolarisation / action

  potential / impulse;
• Use your knowledge of how myosin and actin interact to suggest how the

  myosin molecule moves the mitochondrion towards the presynaptic

  membrane.

  Do not include the roles of calcium ions and tropomyosin in your answer. (2)

  ) 1. Myosin head attaches to actin and bends / performs

  powerstroke;

  2. (This) pulls mitochondria past / along the actin
• This movement of mitochondria happens when nerve impulses arrive at the

  synapse.

  Suggest and explain one advantage of the movement of mitochondria

  towards the presynaptic membrane when nerve impulses arrive at the

  synapse. (2)

  1. (Mitochondria) supply (additional) ATP / energy;

  2. To move vesicles / for active transport of ions / for myosin to

  move past actin
• CONTRACTION OF SKELETAL MUSCLES

  The diagram below shows the banding pattern of a single sarcomere.

  (a) Explain the banding pattern shown in the diagram above. (3)

  1. Light/I band only actin;

  2. H zone/band only myosin;

  3. Darkest/overlapping region actin and myosin;
• Another group of scientists suggested that a decrease in the force of

  muscle contraction is caused by an increase in the concentration of

  inorganic phosphate, Pi, in muscle tissues.

  Their hypothesis is that an increase in the concentration of Pi prevents the

  release of calcium ions within muscle tissues.

  Explain how a decrease in the concentration of calcium ions within muscle

  tissues could cause a decrease in the force of muscle contraction. (3)

  1. (Less/No) tropomyosin moved from binding site

  OR

  Shape of tropomyosin not changed so binding site not

  exposed/available;

  Ignore troponin.

  Reject active site only once.

  2. (Fewer/No) actinomyosin bridges formed;

  Accept actin and myosin do not bind.

  Reject active site only once.

  3. Myosin head does not move

  OR

  Myosin does not pull actin (filaments)

  OR

  (Less/No) ATP (hydrol)ase (activation);
• In muscles, pyruvate is converted to lactate during prolonged exercise.

  Explain why converting pyruvate to lactate allows the continued production

  of ATP by anaerobic respiration. (2)

  1. Regenerates/produces NAD

  OR

  oxidises reduced NAD;

  Reject NADP and any reference to FAD.

  Accept descriptions of oxidation e.g. loss of hydrogen.

  2. (So) glycolysis continues;
• Succinic acid dehydrogenase is an enzyme used in the Krebs cycle.

  Suggest one reason for the difference in the staining between the muscle

  fibres of the control mice and the trained mice. (1)

  Increase in aerobic respiration
• The scientists then compared the length of time that the control mice and

  the trained mice could carry out prolonged exercise. The trained mice were

  able to exercise for a longer time period than control mice.

  Explain why. (3)

  1. (More aerobic respiration) produces more ATP;

  2. Anaerobic respiration delayed;

  3. Less or no lactate;
• The image shows glycogen granules present in skeletal muscle.

  Explain their role in skeletal muscle. (2)

  1. As a store of glucose

  Ignore provide energy

  OR

  To be hydrolysed to glucose;

  2. For respiration / to provide ATP;
• During vigorous exercise, the pH of skeletal muscle tissue falls. This fall in

  pH leads to a reduction in the ability of calcium ions to stimulate muscle

  contraction.

  Suggest how. (3)

  ) 1. Low pH changes shape of calcium ion receptors

  Do not accept tropomyosin does not move

  2. Fewer calcium ions bind to tropomyosin;

  Accept troponin

  3. Fewer tropomyosin molecules move away;

  4. Fewer binding sites on actin revealed;

  5. Fewer cross-bridges can form
• Describe the roles of calcium ions and ATP in the contraction of a

  myofibril (5)

  1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;

  2. (Calcium ions) cause movement of tropomyosin (on actin);

  3. (This movement causes) exposure of the binding sites on the

  actin;

  4. Myosin heads attach to binding sites on actin;

  5. Hydrolysis of ATP (on myosin heads) causes myosin heads to

  bend;

  6. (Bending) pulling actin molecules;

  7. Attachment of a new ATP molecule to each myosin head

  causes myosin heads to detach (from actin sites)
• ATP is an energy source used in many cell processes. Give two ways in

  which ATP is a suitable energy source for cells to use. (2)

  1. Releases relatively small amount of energy / little energy lost as heat;

  2. Releases energy instantaneously;
• What is the role of ATP in myofibril contraction? (2)

  1. (Reaction with ATP) breaks/allows binding of myosin to actin/

  actinomyosin bridge;

  2. Provides energy to move myosin head;
• The mice that were not able to produce creatine were homozygous for a

  recessive allele of a gene. Mice that are heterozygous for this allele are

  able to produce forces similar to those of normal mice that are

  homozygous for the dominant allele of the same gene.

  Explain why the heterozygous mice can produce forces similar to those of

  normal mice (2)

  ) 1. (Heterozygous) have one dominant/normal

  allele (for creatine production);

  2. (This) leads to production of enough/normal

  amount of creatine;
• CONTROL OF BLOOD GLUCOSE CONCENTRATION

  Neonatal diabetes is a disease that affects newly born children. The

  disease is caused by a change in the amino acid sequence of insulin.

  This change prevents insulin binding to its receptor. Explain why this

  change prevents insulin binding to its receptor. (2)


  1. Changes tertiary structure;

  Reject change in tertiary structure of receptor.

  2. No longer complementary (to receptor);

  Reject 'active site' or reference to enzyme or

  substrate.
• Using your knowledge of the kidney, explain why glucose is found in the

  urine of a person with untreated diabetes. (3)

  1. High concentration of glucose in blood/filtrate;

  Accept tubule for filtrate.

  2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;

  Reject no glucose is (re)absorbed.

  3. Carrier/co-transport proteins are working at maximum rate
• Describe the role of glucagon in gluconeogenesis.

  Do not include in your answer details on the second messenger model of

  glucagon action. (2)

  1. (Attaches to receptors on target cells and) activates/stimulates

  enzymes;

  Reject 'produces enzymes'.

  2. Glycerol/amino acids/fatty acids into glucose;

  Reject 'glucagon converts' as context suggests enzyme

  action.
• Metformin is a drug commonly used to treat type II diabetes. Metformin's ability

  to lower the blood glucose concentration involves a number of mechanisms

  including:

  • increasing a cell's sensitivity to insulin

  • inhibiting adenylate cyclase.

  (c) Explain how increasing a cell's sensitivity to insulin will lower the blood

  glucose concentration. (2)

  1. (More) insulin binds to receptors;

  2. (Stimulates) uptake of glucose by channel/transport proteins
• Explain how inhibiting adenylate cyclase may help to lower the blood

  glucose concentration. (3)

  1. Less/no ATP is converted to cyclic AMP/cAMP;

  2. Less/no kinase is activated;

  3. Less/no glycogen is converted to glucose
• Each year, a few people with type I diabetes are given a pancreas

  transplant. Pancreas transplants are not used to treat people with type II

  diabetes.

  Give two reasons why pancreas transplants are not used for the treatment

  of type II diabetes. (2)

  1. (Usually)Type II produce insulin;

  2. Cells / receptors less sensitive / responsive (to insulin)
• The pancreas produces the hormone insulin.

  Put a tick (✔) in the box next to the statement which describes incorrectly

  the action of insulin.

  Activates enzymes involved in the conversion of

  glucose to glycogen.

  Controls the uptake of glucose by regulating the

  inclusion of channel proteins in the surface

  membranes of target cells.

  Attaches to receptors on the surfaces of target

  cells.

  Activates enzymes involved in the conversion of

  glycerol to glucose. (1)

  Tick in box 4
• Give two ways in which people with type 1 diabetes control their blood

  glucose concentration. (2)


  1. Treat with insulin (injection/infusion);

  2. (Control) diet/control sugar intake;

  2. Accept '(regular) exercise