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bio year 2 booklet > topic 6 > Flashcards

topic 6 Flashcards

1
Q

Shoot tips and IAA

A
  1. Tip produces IAA;
  2. Mitosis/division occurs in shoot tips;
  3. Affects (shoot) length/growth/elongation;
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2
Q

Name the process by which IAA moves from the growing regions of a plant shoot to other tissues

A

Diffusion

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3
Q

When a young shoot is illuminated from one side, IAA stimulates growth on the shaded side. Explain why growth on the shaded side helps to maintain the leaves in a favourable environment

A
  1. Causes plant to bend / grow towards light / positive phototropism;
  2. (Light) required for photosynthesis
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4
Q

Give one similarity and one difference between a taxis and a tropism

A
  1. Similarity − directional response (to a stimulus) / movement towards / away from a stimulus;
  2. Difference − taxis (whole) organism moves and tropism a growth (response)
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5
Q

The movement of the woodlice in low relative humidity is an advantage to their survival. Explain how.

A

Low humidity results in more woodlice moving;
So increased movement increased chance of leaving dry / unfavourable environment so reduce water loss / reduce evaporation

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6
Q

Why is a reflex arc faster?

A

Only 3 neurones / nerve cells (in reflex arc)

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7
Q

Reflex arc advantages

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.
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8
Q

Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process

A
  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);
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9
Q

Sometimes myelin sheath damage causes heart rate irregularities.
Suggest and explain why

A
  1. Slower/fewer impulse(s) along sympathetic/parasympathetic (pathway/neurones);
    Accept action potentials for impulses.
  2. (Impulses) from cardiac centre
    OR
    (Impulses) from medulla;
  3. To SAN
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10
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 membranes.
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11
Q

Caffeine affects the autonomic nervous system and causes an increase in heart rate. Suggest how.

A
  1. More impulses/action potentials along sympathetic (nervous system pathway/branch);
  2. To SAN increasing the heart rate
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12
Q

Describe how a Pacinian corpuscle produces a generator potential when stimulated.

A
  1. (Increased pressure) deforms / changes stretch-mediated sodium (ion) channel;
  2. (Sodium channels open and) sodium ions flow in;
    Accept Na+
  3. Depolarisation (leading to generator potential).
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13
Q

The membrane potential is the same whether medium or heavy pressure was applied to a fingertip. Explain why.

A
  1. Threshold has been reached;
  2. (Threshold or above) causes maximal response / all or nothing principle
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14
Q

People with complete achromatopsia, where they have only rod cells and no functioning cone cells have difficulty in seeing detail.
Explain why.

A
  1. No (functional) cones
    OR
    Only rods;
  2. Cones are connected to a single neurone
    OR
    Several rods connected to a single neurone;
  3. (Cones) Separate (sets of) impulses to brain
    OR
    (Rods) Single (set of) impulse/s to brain;
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15
Q

People with red-green colour blindness are unable to distinguish between red and green, and also between other colours.
Explain why.

A
  1. Green sensitive pigment/cones non-functional
    OR
    Cones that detect green light non-functional;
  2. Three different types of pigment/cone;
  3. Other/different colours (‘seen’) due to stimulation of more than one cone/pigment
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16
Q

After a student had stared at a purple square, he saw a green afterimage.
Suggest why.

A
  1. (When staring at purple) red (sensitive) and blue (sensitive) cones are stimulated / green (sensitive) cones are not stimulated;
  2. Red and blue cone cells become exhausted / stop working;
  3. (Afterimage due to) green (sensitive) cone cells working
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17
Q

Cone cell and retinal convergence

A

1.High (visual)acuity;
2.(Each) cone is connected to a single neurone;
3.(Cones send) separate (sets of) impulses to brain;

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18
Q

Rod cells in dim light

A
  1. High (visual) sensitivity;
  2. Several rods connected to a single neurone;
  3. Enough (neuro)transmitter to reach/overcome threshold
    OR
    Spatial summation to reach/overcome threshold; more for ‘several’
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19
Q

Explain how the resting potential of -70 mV is maintained in a neurone

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.
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20
Q

Explain depolarisation

A

(Ion) channel proteins open, sodium in;
Changes membrane potential / makes inside of axon lessnegative / positive / depolarisation / reaches threshold;
More channels open / positive feedback;

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21
Q

Explain repolarisation

A

Potassium ion channels open;
Potassium ion out;
Sodium ion channels close;

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22
Q

Re-establishing resting potential

A

Pump / active transport / transport against concentration gradient;
sodium out / potassium in;
diffusion of K+ out of axon / little diffusion of Na+ into the axon;

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23
Q

Effect of myelination on an action potential

A

myelin insulates / prevents ion movement;
saltation / described leaping node to node;

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24
Q

Damage to the myelin sheath of neurones can cause muscular paralysis.
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
25
Q

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

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
26
Q

Synapse action

A

action potential arrives / depolarisation of pre-synaptic membrane occurs;
calcium channels open and calcium ions enter synaptic knob;
vesicles fuse with membrane and release acetylcholine;
acetylcholine diffuses (across synaptic cleft);
binds to receptors;
Sodium ions enter leading to depolarisation of post-synaptic neurone.

27
Q

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;
28
Q

Acetylcholine stimulates the production of nerve impulses in postsynaptic neurones.
Describe how

A
  1. (Acetylcholine) 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;
29
Q

Inhibitory response of chloride ions

A

inside becomes more negatively charged / hyperpolarised;
stimulation does not reach threshold level / action potential not produced;
depolarisation does not occur / reduces effect of sodium ions entering

30
Q

Cholinergic synapse & neuromuscular junction comparison

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;

31
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
32
Q

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.

A
  1. Releases relatively small amount of energy / little energy lost as heat;
    Key concept is that little danger of thermal death of cells
  2. Releases energy instantaneously;
    Key concept is that energy is readily available
  3. Phosphorylates other compounds, making them more reactive;
  4. Can be rapidly re-synthesised;
  5. Is not lost from / does not leave cells.
33
Q

Describe the roles of calcium ions and ATP in the contraction of a myofibril.

A
  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).
34
Q

Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force of muscle contraction.

A
  1. (Less/No) tropomyosin moved from binding site
    OR
    Shape of tropomyosin not changed so binding site not exposed/available;
    Reject active site only once.
  2. (Fewer/No) actinomyosin bridges formed;
  3. Myosin head does not move
    OR
    Myosin does not pull actin (filaments)
    OR
    (Less/No) ATP (hydrol)ase (activation)
35
Q

Explain the role of glycogen granules in skeletal muscle.

A
  1. As a store of glucose
    OR To be hydrolysed to glucose;
  2. For respiration / to provide ATP;
36
Q

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.

A
  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
    OR
    Fewer myosin heads can bind
37
Q

Mitochondrial disease (MD) often causes muscle weakness. Use your knowledge of respiration and muscle contraction to suggest explanations for this effect of MD

A
  1. Reduction in ATP production by aerobic respiration;
  2. Less force generated because fewer actin and myosin interactions in muscle;
  3. Fatigue caused by lactate from anaerobic respiration
38
Q

What is the role of ATP in myofibril contraction?

A
  1. (Reaction with ATP) breaks/allows binding of myosin to actin/ actinomyosin bridge;
  2. Provides energy to move myosin head;
39
Q

If myosin molecules are unable to bind to other myosin molecules, this prevents muscle contraction.Suggest why.

A
  1. Can’t form myosin / thick filaments;
    Neutral: prevents actin and myosin sliding filament action
  2. Can’t pull / can’t move actin / slide actin past / (myosin) have to be joined / fixed to pull actin;
    Accept: myosin can’t pull on each other
  3. Myosin moves / if attached doesn’t move;
  4. Can’t move actin towards each other / middle of sarcomere / between myosin / can’t shorten sarcomere / can’t pull Z lines together.
40
Q

Both slow and fast muscle fibres contain ATPase.
Explain why

A
  1. Splitting / breakdown / hydrolysis of ATP;
  2. (Muscle) contraction requires energy / ATP;
    Accept ‘uses energy’. Reject idea of ‘movement’ of muscles requiring energy.
    Reject suggestion that ‘energy is produced’.
  3. Use of ATP by myosin.
41
Q

Creatinine is a breakdown product of creatine found in muscle tissues that is filtered by out of the blood by the kidneys. Apart from age and gender, give two factors that could affect the concentration of creatinine in the blood.

A

Muscle / body mass
Ethnicity
Exercise
Kidney disease

42
Q

Describe what is meant by negative feedback.

A

where a change triggers a response which reduces the effect of a change;

43
Q

Give an example of negative feedback.

A

Maintaining body temperature, blood glucose levels, blood water levels

44
Q

In humans, when the stomach starts to become full of food, receptors in the wall of the stomach are stimulated. This leads to negative feedback on the desire to eat. Suggest why this negative feedback is important.

A
  1. (Negative feedback) stops desire / wish to eat / appetite;
  2. (This) limits amount eaten / stops eating;
  3. Prevents / reduces risk of obesity / too much energy intake;
45
Q

Describe the role of glucagon in gluconeogenesis.
Do not include in your answer details on the second messenger model of glucagon action.

A
  1. (Attaches to receptors on target cells and) activates/stimulates enzymes;
    Reject ‘produces enzymes’.
  2. Glycerol/amino acids/fatty acids into glucose;
46
Q

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

A
  1. (More) insulin binds to receptors;
  2. (Stimulates) uptake of glucose by channel/transport proteins
    OR
    Activates enzymes which convert glucose to glycogen;
47
Q

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.

A
  1. Less/no ATP is converted to cyclic AMP/cAMP;
  2. Less/no kinase is activated;
  3. Less/no glycogen is converted to glucose
    OR
    Less/no glycogenolysis;
48
Q

Binding of insulin leads to an increase in the rate of respiration in cells such as osteoblasts.
Explain how.

A
  1. (Insulin) leads to more transport proteins / channel (proteins) / carrier (proteins) for glucose;
  2. More glucose (for respiration / glycolysis) enters cell;
49
Q

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

A
  1. (Usually)Type II produce insulin;
  2. Cells / receptors less sensitive / responsive (to insulin)
    OR
    Faulty (insulin) receptors;
  3. (Treated / controlled by) diet / exercise;
50
Q

Give two ways in which people with type 1 diabetes control their blood glucose concentration.

A
  1. Treat with insulin (injection/infusion);
  2. (Control) diet/control sugar intake;
  3. Accept ‘(regular) exercise’
51
Q

Describe how ultrafiltration occurs in a glomerulus.

A
  1. High blood/hydrostatic pressure;
  2. Two named small substances pass out eg water, glucose, ions, urea;
  3. (Through small) gaps/pores/fenestrations in (capillary) endothelium;
  4. (And) through (capillary) basement membrane;
52
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.

A

Water is also reabsorbed

53
Q

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced

A
  1. Water potential of filtrate/tubule decreased;
  2. Less water (reabsorbed) by osmosis (from filtrate/tubule);
  3. Collecting duct (is where osmosis occurs);
54
Q

Give the location of osmoreceptors in the body of a mammal.

A

Hypothalamus.

55
Q

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

A
  1. Water potential of blood will decrease;
  2. Water moves from osmoreceptor into blood by osmosis.
56
Q

Describe and explain how the secretion of ADH affects urine produced by the kidneys.

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.
57
Q

glycogensis

A

glucose to glycogen

58
Q

glucogenolysis

A

glycogen to glucose

59
Q

gluconeogenesis

A

synthesis of glucose from non-carb molecules in the liver

bio year 2 booklet (8 decks)

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