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paper 2 Flashcards

1
Q

Describe and explain how nitrogen held in a polymer in a dead animal can be incorprated into a polymer in a plant.

A

1) saprobiotic bacteria and fungi decompose
2) DNA and protein
3) Saprobiotic bacteria carry out ammonification
4) releases ammonia into the soil
5) ammonium converted into nitrite then nitrate
6) by nitryfying bacteria
7) in a process called nitrification
8) plants absorb nitrate via the root hair cell
9) via active transport

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2
Q

Stage A represents the conversion of organic nitrogen containing compounds to inorganic compounds.

Describe the role of micro-organisms in this process. (4)

A

1) putrefying bacteria convert nitrogen compounds
2) into ammonium ions.
3) Nitrifying bacteria convert
4) Ammonium into nitrate

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3
Q

Explain how farming practices might be responsible for the change in nitrate concentration in the water. (2)

A

1) Excessive use of fertilisers

2) can cause run off/leeching

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4
Q

Describe the effect eutrophication may have in the river(5)

A

1) Increased growth of algae/plants
2) Death of algae/plants
3) More bacteria respire
4) Removes O2
5) Animals die from lack of O2

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5
Q

A clover plant has root nodules which contain nitrogen fixing bacteria
Describe the nutritional advantage gained as a result of this relationship by the clover plant and the nitrogen-fixing bacteria. (2)

A

clover plant: gains ammonium compounds

nitrogen fixing bacteria: gains ATP

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6
Q

The processes which naturally form part of the nitrogen cycle can make nitrogen contained in urine and faeces available to crop plants.
Describe how these processes occur. (6)

A

1) organic compound of nitrogen
2) converted to ammonia
3) By saprobiotic bacteria
4) then into nitrites
5) and then nitrates
6) By nitrigying bacteria
7) uptake by roots

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7
Q

Explain the advantage in the system of growing leguminous plants such as groundnuts or beans.

A

1) nitrogen fixing bacteria in root nodules
2) convert nitrogen to ammonium
3) ammonium released on decompisition
4) and converted to nitrate (less need for fertiliser)

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8
Q

Explain the advantage in the system of stocking the pond with fish that feed on algae rather than with carnivorous fish

A

1) shorter food chain
2) greater yield of fish
3) less energy lost in respiration/heat
4) fish prevent algal blooms

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9
Q

Explain how the change in phosphate concentration may have resulted in this decrease in the fish
population. (6)

A
  1. Increased phosphate causes increase in plant growth / algal bloom;
  2. Plants (cover surface and) block out light so plants (under surface) die;
  3. Increase in (aerobic) bacteria / decomposers (which break down plants);
  4. Bacteria / decomposers use up oxygen / reduce oxygen conc. in water;
  5. In respiration;
  6. Plants unable to photosynthesise so less oxygen produced
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10
Q

apart from nitrification
Describe another process carried out by microorganisms which adds ammonium
ions to soil. (2)

A
  1. Protein / amino acids broken down (to ammonium

2. By saprobionts / saprobiotic (microorganisms).

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11
Q

Denitrification requires anaerobic conditions. Ploughing aerates the soil.
Explain how ploughing would affect the fertility of the soil.(2)

A
  1. (Fertility increased as) more nitrate formed / less nitrate removed / broken down
  2. Less / no denitrification / process P is decreased / fewer denitrifying bacteria
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12
Q

Suggest two ways in which crop rotation may lead to high crop yields. (2)

A
  1. Grow crops / plants with nitrogen-fixing (bacteria);
    Accept: use different amounts of ions / nutrients
  2. (Different crops use) different minerals / salts / nutrients / ions (from the soil);
  3. (Different crops have) different pests / pathogens / diseases.
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13
Q

Explain how farming practices increase the productivity of agricultural crops (5)

A
  1. Fertilisers / minerals / named ion (added to soil);
  2. Role of named nutrient or element e.g. nitrate / nitrogen for proteins / phosphate / phosphorus for ATP / DNA;
  3. Selective breeding / genetic modification (of crops);
  4. Ploughing / aeration allows nitrification / decreases denitrification;
  5. Benefit of crop rotation in terms of soil nutrients / fertility / pest reduction;
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14
Q

Describe the role of glucagon in gluconeogenesis.

Do not include in your answer details on the second messenger model of glucagon 
action. (2)

A
  1. (Attaches to receptors on target cells and) activates/stimulates enzymes that turn
  2. Glycerol/amino acids/fatty acids into glucose;
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15
Q

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose 
concentration (2)

A

1.(More) insulin binds to receptors;
2.Stimulates) uptake of glucose by channel/transport proteins
OR
Activates enzymes which convert glucose to glycogen;

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16
Q

Explain how inhibiting adenylate cyclase may help to lower the blood glucose 
concentration (3)

A
  1. Less/no ATP is converted to cyclic AMP/cAMP;
    2.Less/no kinase is activated;
  2. Less/no glycogen is converted to glucose
    OR
    Less/no glycogenolysis;
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17
Q

Describe how ultrafiltration occurs in a glomerulus (3)

A
  1. high blood/hydrostatic pressure
  2. water/glucose/ions/urea pass out through small pores in the capillary endothelium.
  3. and through the capillary basement membrane.
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18
Q

Thickness of medulla increases. concentration of urine increases.
Explain the pattern shown (3)

A
  1. Thicker medulla=longer loop of henle
  2. longer loop of henle= increase in Na+ concentration
  3. More water is re absorbed from the loop of henle and collecting duct by osmosis.
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19
Q

Binding of insulin leads to an increase in the rate of respiration in cells
exaplain how

A
  1. insulin leads to more transport proteins for glucose

2. more glucose for respiration enters the cell

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20
Q

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes (2)

A
  1. type 2 usually produces insulin
  2. however, their cells/receptors are less sensitive/responsive to insulin
  3. This can be treated/controlled by diet and exercise.
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21
Q

More than 99% of biological molecules are reabsorbed from the filtrate in the 
proximal convoluted tubule.
Despite this, the concentration of fluid in this tubule remains constant.
Explain why (1)

A

water is also reabsorbed

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22
Q

Explain the shape of the curve in the loop of Henle in the graph.

A
  1. concentration rises in descending limb because Na+ enters and water is lost
  2. concentration falls in ascending limb because Na+ and chloride ions are actively removed.
  3. Water remains in ascending limb because its walls are impermeable to water.
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23
Q

What is the evidence in the graph that this person was secreting antidiuretic 
hormone (ADH)?
Explain your answer. (2)

A
  1. Concentration rises in collecting duct because it loses water by osmosis;
  2. ADH increases permeability (of walls of collecting duct) to water.
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24
Q

Give the location of osmoreceptors in the body of a mammals

A

Hypothalamus

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25
Q

When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why. (2)

A
  1. Water potential of blood will decrease;

2. Water moves from osmoreceptor into blood by osmosis.

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26
Q

Stimulation of osmoreceptors can lead to secretion of the hormone ADH. Describe 
and explain how the secretion of ADH affects urine produced by the kidneys. (4)

A
  1. Permeability of membrane / cells (to water) is increased;
  2. More water absorbed from / leaves distal tubule / collecting duct;
  3. Smaller volume of urine;
  4. Urine becomes more concentrated.
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27
Q

Apart from age and gender, give two factors that could affect the concentration of creatinine in the blood. (2)

A

Muscle / body mass
Ethnicity
Exercise
Kidney disease

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28
Q

Explain how the normal mice prevented their blood glucose concentration falling 
when they had not eaten for 48 hours. (3)

A
  1.   Release of glucagon;
  2.   Leads to formation of glucose in liver (cells);
  3.   From non-carbohydrates / amino acids / fatty acids.
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29
Q

A glucose biosensor is an instrument used to measure glucose concentration. It contains an enzyme called glucose oxidase.

(a)  A glucose biosensor detects only glucose. Use your knowledge of the way in which enzymes work to explain why. (3)

A

Enzyme / active site has a (specific) tertiary structure;
Only glucose has correct shape / is complementary / will bind / fit to active 
site;

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30
Q

It is better to use a biosensor than the Benedict’s test to measure the concentration of glucose in a sample of blood. Suggest two reasons why.

A
  1. (Only detects glucose whereas) Benedict’s detects (all) reducing sugars
  2. provides a reading, benedicts only gives a colour
  3. More sensitive/detects low concentrations
  4. Can monitor blood glucose concentration continuously
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31
Q

Insulin is a protein so it 

cannot be taken orally. Suggest why insulin cannot be taken orally

A

Broken down by enzymes / digested / denatured (by pH) too large to be 
absorbed;

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32
Q

a woman was given a solution of sucrose to drink and her blood glucose concentration was measured over 90 minutes.
Increase, reach peak, then decrease

explain the results shown in the graph.

A

Glucose (produced by digestion) is absorbed / enters blood;

Decrease as used up / stored

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33
Q

Describe how ultrafiltration produces glomerular filtrate. (5)

A
  1.   Blood pressure / hydrostatic pressure;
  2.   Small molecules / named example;
  3.   Pass through basement membrane / basement membrane acts as filter;
  4.   Protein too large to go through / large so stays behind;
  5.   Presence of pores in capillaries / presence of podocytes;
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34
Q

Some people who have diabetes do not secrete insulin. Explain how a lack of insulinaffects reabsorption of glucose in the kidneys of a person who does not secrete insulin.(4)

A
  1.   High concentration of glucose in blood;
  2.   High concentration in tubule / in filtrate;
  3.   Reabsorbed by facilitated diffusion / active transport;
  4.   Requires proteins / carriers;
  5.   These are working at maximum rate / are saturated;
  6.   Not all glucose is reabsorbed / some is lost in urine
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35
Q

Some desert mammals have long loops of Henle and secrete large amounts of 
antidiuretic hormone (ADH). Explain how these two features are adaptations to living
in desert conditions. (6)

A

1.  More water (from filtrate) reabsorbed 
2.  By osmosis;
3.  From collecting duct 
4.  Due to longer loop of Henle;
For loop of Henle, maximum 2 marks:
5.  Sodium / chloride ions absorbed from filtrate in ascending limb;
6.  Gradient established in medulla / concentration of ions increases down 
medulla;
For ADH, maximum 2 marks:
7.  Acts on collecting duct / distal convoluted tubule / second convoluted 
tubule;
8.  Makes cells more permeable / inserts aquaporins in plasma membranes

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36
Q

Glomerulosclerosis is a disease in which the glomeruli of the kidney are damaged. 
Explain why protein is not normally present in the urine of a healthy person but may be present in the urine of a person with glomerulosclerosis. (2)

A

Protein molecule too large (to cross filter in healthy person);
Protein can cross if filter is damaged / protein from damaged glomerulus 
enters filtrate;

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37
Q

What is negative feedback?

A

receptors detect when a level is too high/low and the info is communicated via the nervous system or hormonal system to effectors.

  1. effectors counteract the change
  2. mechanism that restores the change is called the negative feedback mechanism.
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38
Q

What is positive feedback?

A

Amplify a change from the normal level

continues to decrease unless action is taken

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39
Q

what do alpha and beta cells secrete?

A

a- insulin

b- glucagon

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40
Q

How does insulin lower blood glucose concentration?

A
  1. binds to specific receptors on CM of liver and muscle cells
  2. increases permeability of muscle cell membranes to glucose, so the cellls take up more glucose by increasing the amount of channel proteins.
  3. activates enzymes that convert glucose into glycogen.
  4. cells store glycogen in their cytoplasm.
  5. also increases the rate of respiration, in muscle cells
41
Q

How does glucagon raise blood glucose concentration?

A
  1. bind to specific receptors on liver cells
  2. activates enzyme that break down glycogen into glucose.
  3. from amina acid
  4. also decreases rate of respiration in cells
42
Q

Second messenger model

A
  1. Adrenaline and glucagon bind to their specific receptors
  2. activate enzyme called adenylate cyclase
  3. AC converts ATP into Cyclic AMP (the second messenger)
  4. CAMP activates protein kinase A
  5. protein kinase A activates a chain of reactions that bresk down glycogen into glucose.
43
Q

Suggest an explanation for the effect of temperature on the rate of carbon dioxide release. (insects)

A
  1. Enzymes / metabolism faster;
  2. Higher rate of respiration and carbon dioxide production / release;
  3. Spiracles open more often / remain open to excrete / get rid of carbon dioxide /
    get more oxygen;
44
Q

Explain the decrease in gross productivity as the woodland matures. (2)

A
  1. less light

2. reduced photosynthesis

45
Q

suggest one reason for conserving woodlands.

A
  1. Conserving / protecting habitats / niches;
  2. Conserving / protecting (endangered) species / maintains / increases
    (bio) diversity;
  3. Reduces global warming / greenhouse effect / climate change / remove /
    take up carbon dioxide;
  4. Source of medicines / chemicals / wood;
  5. Reduces erosion / eutrophication.
46
Q

Explain why the scientists measured the rate of production of oxygen in this
investigation.

A
  1. Oxygen produced in light-dependent reaction;

2. The faster (oxygen) is produced, the faster the light-dependent reaction.

47
Q

The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities.
Explain how these data support this suggestion (4)

A
  1. Have faster production of ATP and reduced NADP;
  2. (So) have faster / more light-independent reaction;
  3. (So) produce more sugars that can be used in respiration;
  4. (So) have more energy for growth;
  5. Have faster / more synthesis of new organic materials.
48
Q

NPP=GPP-R

49
Q

In photosynthesis, which chemicals are needed for the light-dependent reaction?

A

 NADP, ADP, Pi and water;

50
Q

Describe what happens during photoionisation in the light-dependent reaction. (2)

A
  1. Chlorophyll absorbs light/light excites electrons in chlorophyll
  2. Electrons are lost/chlorophyll becomes positively charged.
51
Q

Explain why the student marked the origin using a pencil rather than using ink.

A

ink and (leaf) pigments would mix
OR
(With ink) origin/line in different position
OR
(With pencil) origin/line in same position
OR
(With pencil) origin/line still visible;

52
Q

The pigments in leaves are different colours. Suggest and explain the advantage of having different coloured pigments in leaves.

A

Absorb) different/more wavelengths (of light) for photosynthesis;

53
Q

The photolysis of water is an important part of the process of photosynthesis. 
Describe what happens in the photolysis of water. (2)

A
  1. (Water) forms H+/ hydrogen ions and electrons / e–
  2. O2 / oxygen formed;
  3. (Light) excites electrons / raises energy level of electrons / electrons to chlorophyll / to photosystem;
54
Q

ATP and reduced NADP are two products of the light-dependent reactions. Describe
one function of each of these substances in the light-independent reactions. (2)

A

(ATP) Provides energy for GP → TP / provides P for RuP / TP → RuBP;

(Reduced NADP) Provides H / electrons for GP → TP / reduces GP to TP

55
Q

Describe the light-independent reactions of photosynthesis and explain how they 
allow the continued synthesis of hexose sugars.(6)

A

 1  5C / RuBP combines with CO2;
2  to form 3C compound / TP / GP;
3  using ATP;
4  and reduced NADP / eq;
5  2 molecules of 3C compound / TP / GP form hexose;
6  all RuBP is regenerated;
7  10 molecules of 3C / TP / GP form 6 molecules of 5C / RuBP;

56
Q

 Describe the role of electron transport chains in the light-dependent reactions of 
photosynthesis (6)

A 
1  electron transport chain accepts excited electrons;
2  from chlorophyll / photosystem;
3  electrons lose energy along chain;
4  ATP produced;
5  from ADP and Pi;
6  reduced NADP formed;
7  when electrons (from transport chain) and H+ combine with NADP;
8  H+
from photolysis
57
Q

Explain why the increase in the dry mass of a plant over twelve months is less than the mass of hexose produced over the same period. (4)

A

1  some hexose / biomass / eq. used in respiration;
growth cancels this point
2  CO2 produced (is lost to air);
3  some parts of the plant are eaten / some parts lost to decomposers
/ in leaf fall

58
Q

During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. (6)

A
  1. Carbon dioxide combines with ribulose bisphosphate / RuBP;
  2. Produces two glycerate (3-)phosphate / GP;
    Accept: any answer which indicates that 2 x as much GP
    produced from one RuBP.
  3. GP reduced to triose phosphate / TP;
    Must have idea of reduction. This may be conveyed by
    stating m.p. 4.
  4. Using reduced NADP;
    Reject: Any reference to reduced NAD for m.p.4 but allow
    reference to reduction for m.p. 3.
  5. Using energy from ATP;
    Must be in context of GP to TP.
  6. Triose phosphate converted to glucose / hexose / RuBP / ribulose 
    bisphosphate / named organic substance;
59
Q

Other than temperature and pH, give two factors which should be kept constant 
during this investigation. (2)

A

1.  Intensity of light;
Accept: distance from light
2.  Amount / number / mass / species of algae / photosynthesising cells;
3.  Carbon dioxide (concentration / partial pressure);
4.  Time.

60
Q

Crops use light energy to produce photosynthetic products.

Describe how crop plants use light energy during the light-dependent reaction. (5)

A

 1. Excites electrons / electrons removed (from chlorophyll);

  1. Electrons move along carriers/electron transfer chain releasing energy;
  2. Energy used to join ADP and Pi to 
  3. Photolysis of water produces protons, electrons and oxygen;
  4. NADP reduced by electrons / electrons and protons / hydrogen;
61
Q

(a)  Where precisely in a cell does the Calvin cycle take place?

A

Stroma (of chloroplasts);

62
Q

Where precisely is rubisco found in a cell?

A

stroma of chloroplast

63
Q

Heat stress decreases the light-dependent reaction of photosynthesis.
Explain why this leads to a decrease in the light-independent reaction.

A
  1. (Less/no) ATP;

2. (Less/no) reduced NADP

64
Q

Damage to the myelin sheath of neurones can cause muscular paralysis (lines 2–4).
Explain how.

A 
1. (Refers to) saltatory conduction
OR
(Nerve) impulses/depolarisation/ions pass to other neurones
OR
Depolarisation occurs along whole length (of axon);
2. (Nerve) impulses slowed/stopped;
3. (Refers to) neuromuscular junction
OR
(Refers to) sarcolemma
65
Q

Explain why the antibody binds to the transcription factor.

A

(Transcriptional factor/antibody) has a specific/tertiary structure/shape
Complementary (shape/structure);

66
Q

What is meant by a genome?

A

All) the DNA in a cell/organism;

67
Q

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. (3)

A
  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;
68
Q

Morphine is a drug that has a similar structure to endorphins and can provide pain
relief.
Explain how.(2)

A
  1. Morphine attaches to opioid receptors;

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

69
Q

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)

A
  1. (Inside of postsynaptic) neurone becomes more
    negative/hyperpolarisation/inhibitory postsynaptic potential;
  2. More sodium ions required (to reach threshold)
    OR
    Not enough sodium ions enter (to reach threshold);
  3. For depolarisation/action potential;
70
Q

When a nerve impulse arrives at a synapse, it causes the release of
neurotransmitter from vesicles in the presynaptic knob.
Describe how. (3)

A
  1. (Nerve impulse / depolarisation of membrane) causes Ca 2+ channel (proteins) to open;
  2. Ca 2+
    enter by (facilitated) diffusion;
  3. Causes (synaptic) vesicles to fuse with (presynaptic) membrane;
71
Q

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)

A
  1. Myosin head attaches to actin and bends / performs powerstroke;
  2. (This) pulls mitochondria past / along the actin;
  3. Other / next myosin head attaches to actin (and bends / performs powerstroke);
72
Q

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)

A
  1. (Mitochondria) supply (additional) ATP / energy;
  2. To move vesicles / for active transport of ions / for myosin to move past
    actin
    OR
    Re-synthesis / reabsorption of neurotransmitter / named
    neurotransmitter;
73
Q

The nerve pathway shown in the diagram may be regarded as a simple reflex arc.
Use the diagram to explain why.

A

Only 3 neurones / nerve cells (in reflex arc)

74
Q

Suggest two advantages of simple reflexes.

A
  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.
75
Q

In the nerve pathway in the diagram, synapses ensure that nerve impulses only travel towards the muscle fibre.
Explain how.

A
  1. Neurotransmitter only made in / stored in / released from pre-synaptic neurone;
  2. (Neuro)receptors only on the post-synaptic membrane;
76
Q

Axon P was found to conduct impulses much faster than other axons in the nerve
pathway shown in the diagram.
Describe and explain one feature of axon P that might cause this difference.

A
  1. Axon P is myelinated;
  2. So shows saltatory conduction / impulses jump between nodes of Ranvier
    OR
  3. Axon P has a larger diameter;
  4. So less resistance to flow of ions
77
Q

Explain how the resting potential of –70 mV is maintained in the sensory neurone
when no pressure is applied.

A
  1. Membrane more permeable to potassium ions and less permeable to sodium ions;
  2. Sodium ions actively transported / pumped out and potassium ions in.
78
Q

Explain how applying pressure to the Pacinian corpuscle produces the changes in
membrane potential recorded by microelectrode P.

A
  1. (Pressure causes) membrane / lamellae to become deformed /
    stretched;
  2. Sodium ion channels in membrane open and sodium ions move in;
  3. Greater pressure more channels open / sodium ions enter.
79
Q

The membrane potential at Q was the same whether medium or heavy pressure
was applied to the finger tip. Explain why.

A
  1. Threshold has been reached;

2. (Threshold or above) causes maximal response / all or nothing principle.

80
Q

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.

A
  1. Less / no saltatory conduction / action potential / impulse unable to
    ‘jump’ from node to node;
  2. More depolarisation over length / area of membrane
81
Q

The blink reflex is caused by stimulation of receptors in the eye or eyelid.
Suggest two types of stimuli to which these receptors might respond.

A 
light
• pressure
• touch
• temperature
• chemicals
• (loud) noise
• smell
82
Q

Some diseases cause changes in blink rate. Doctors do not often use blink rate to
diagnose these diseases. Suggest two reasons why.

A
  1. Would not know the patient’s / human’s normal blink
    rate so unable to make a comparison;
  2. Blink rate could be affected by stress of seeing a
    doctor;
  3. Many factors could affect blink rate so it would be
    difficult to tell if blink rate was due to illness
83
Q

The student did not carry out repeats. He was still able to carry out a statistical test.
Explain why.

A

Collected paired data;

84
Q

The blink reflex can be stopped by drugs which prevent the opening of sodium ion
channel proteins in the axons of motor neurones.
Suggest how these drugs affect the passage of nerve impulses along the axons.

A
  1. No / low influx of sodium ions;

2. So no depolarisation / action potential

85
Q

The blink reflex involves synapses. Channel proteins on presynaptic neurones are
involved in reflex responses.
Explain how

A
  1. Allows calcium ions in;
  2. At end of presynaptic neurone;
  3. Causing release of neurotransmitter;
86
Q

A myelinated axon conducts impulses faster than a non-myelinated axon.
Explain this difference.

A
  1. (In myelinated) action potential / depolarisation only at node(s);
  2. (In myelinated, nerve impulse) jumps from node to node / saltatory;
  3. (In myelinated) action potential / impulse does not travel along whole length;
87
Q

Serotonin diffuses across the synaptic gap and binds to a receptor on the postsynaptic membrane.
Describe how this causes depolarisation of the post-synaptic membrane.

A
  1. Causes sodium ion channels to open;

2. Sodium ions enter (cell and cause depolarisation)

88
Q

It is important that a neurotransmitter such as serotonin is transported back out of
synapses. Explain why.

A
  1. (If not removed) keeps binding (to receptors);

2. Keeps causing action potentials / depolarisation (in post-synaptic membrane);

89
Q

Describe the sequence of events which allows information to pass from one
neurone to the next neurone across a cholinergic synapse. (6)

A
  1. (impulse causes) calcium ions / Ca++ to enter axon;
  2. vesicles move to / fuse with (presynaptic) membrane;
  3. acetylcholine (released);
  4. (acetylcholine) diffuses across synaptic cleft / synapse;
  5. binds with receptors on (postsynaptic) membrane;
    (reject active sites, disqualify point)
  6. sodium ions / Na+
    enter (postsynaptic) neurone;
  7. depolarisation of (postsynaptic) membrane;
  8. if above threshold nerve impulse / action potential produced
90
Q

Give two differences between a cholinergic synapse and a neuromuscular
junction.

A

neurone to neurone and neurone to muscle;
action potential in neurone and no action potential in muscle / sarcolemma;
no summation in muscle;
muscle response always excitatory (never inhibitory);
some neuromuscular junctions have different neurotransmitters

91
Q

When a neurone transmits a series of impulses, its rate of oxygen consumption
increases. Explain why.

A

(More) respiration;

(More) energy supplied / (more) ATP supplied

92
Q

depolarisation

A

threshold around -55mv
more Na+ channels open
more Na+ diffuses into neurone rapidly

93
Q

Repolarisation

A

threshold around +30mV
Na+ ion channels close
K+ channels open
membrane more permeable to K so K can diffuse out down conc gradient. goes back to resting potential

94
Q

Hyperpolarisation

A

K+ ion channels are slow to close so theres slight overshoot, where too many K+ diffuse out of neurone.
potential diff becomes more negative than resting potential

95
Q

stimulus

A 
excites neurone cell membrane
causing Na+ channels to open 
becomes more permeable to Na
so Na+ ions diffuse into neurone down conc gradient 
inside of neurone less negative
96
Q

refractory period

A

Ap dont overlap but pass along as discrete impulses
limit to frequency AP can be transmitted
AP only travel in one direction

97
Q

excitatory neurotransmitter

A

depolarise postsynaptic membrane, making it fire an AP if threshold is reached

98
Q

Inhibatory neurotransmitter

A

hyperpolarise postsynaptic membrane, preventing it from firing an AP

Bio exam questions (3 decks)

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