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Uni 6 Flashcards

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1
Q

Suggest two advantages of simple reflexes (2)

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

Use your knowledge of indoleacetic acid (IAA) to explain the curved growth of a shoot (3)

A
  1. Tip produces IAA
  2. IAA diffuses into the shoot
  3. More elongation of cells on one side than the other
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3
Q

Explain how the uneven distribution of IAA causes a root to bend (2)

A
  1. IAA at bottom of root inhibits elongation
  2. IAA at top of the root leads to low elongation
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4
Q

Describe the role of receptors and of the nervous system in the increasing of heart rate (4)

A
  1. Chemoreceptors detect rise in CO2
  2. Send impulses to cardiac centre
  3. More impulses to the SAN
  4. By sympathetic nervous system
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5
Q

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.

A
  1. Electrical activity only through the Bundle of His
  2. Wave of electrical activity passes over both ventricles at the same time
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6
Q

Describe how a heartbeat is initiated and coordinated (5)

A
  1. SAN sends wave of electrical impulse causing atrial contraction
  2. Non-conducting tissue prevents immediate contraction of ventricles
  3. AVN delays impulse whilst blood leaves atria
  4. AVN sends wave of electrical impulses down Bundle of His
  5. Causing ventricles to contract from base up
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7
Q

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how? (6)

A
  1. SAN to AVN to Bundle of His
  2. Impulses over the atria
  3. The atria then contract
  4. Non-conducting tissue between atria and ventricles
  5. Delay at AVN ensures atria is empty
  6. Ventricles contract from apex upwards
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8
Q

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how? (5)

A
  1. SAN initiates the heartbeat
  2. SAN sends wave if electrical impulses causing atrial contraction
  3. Allows atria to empty before ventricles contract
  4. AVN sends wave of electrical impulses down Bundle of His
  5. Causing ventricles to contract
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9
Q

Explain how a resting potential is maintained across the axon membrane in a neurone (3)

A
  1. Higher concentration of potassium ions inside and higher concentration of sodium ions outside
  2. Membrane becomes more permeable to potassium ions
  3. So sodium ions are actively transported out and potassium ions in
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10
Q

Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon. (3)

A
  1. Myelination provides electrical insulation
  2. In myelinated sheath, Saltatory Conduction occurs
  3. In non-myelinated, depolarisation occurs along whole length
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11
Q

Describe the sequence of events involved in transmission across a cholinergic synapse (6)

A
  1. Depolarisation of presynaptic membrane
  2. Calcium channels open and calcium ions enter
  3. Synaptic vesicles fuse with presynaptic membrane and release acetylcholine
  4. Acetylcholine diffuses across synaptic cleft
  5. Attaches to receptors on the postsynaptic membrane
  6. Sodium ions enter postsynaptic neurone leading to depolarisation
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12
Q

Describe how the influx negatively charged ions can inhibit postsynaptic neurones. (3)

A
  1. Inside of postsynaptic neurone becomes more negative
  2. More sodium ions required
  3. For depolarisation to occur
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13
Q

Explain how blocking the calcium ion channels
at some synapses can reduce impulses at the
post synaptic membrane.

A
  1. No calcium ions enter synaptic knob
  2. No synaptic vesicles fuse with presynaptic membrane
  3. No neurotransmitters diffuse across the synaptic cleft
  4. No neurotransmitter attaches to receptor on the postsynaptic membrane
  5. No sodium ions enter, so fewer impulses sent to the brain
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14
Q

Suggest and explain how the interaction between the circular and radial muscles could cause the pupil to constrict (narrow) (2)

A
  1. Circular muscle contracts
  2. Radial muscle relaxes
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15
Q

Explain how a fovea allows an organism to see in detail (3)

A
  1. High Visual Acuity
  2. Each cone is connected to a single neurone
  3. Cones send separate impulses to brain
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16
Q

Explain how a high density of rod cells allows
an organism to have good night vision. (3)

A
  1. High Visual Sensitivity
  2. Several rods connected to a single neurone
  3. Enough neurotransmitters to overcome threshold
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17
Q

Describe how stimulation of a Pacinian corpuscle produces a generator potential (5)

A
  1. Stretch-mediated sodium ion channels
  2. Increased pressure deforms the sensory neurone
  3. Sodium ion channels open
  4. Sodium ions diffuse in
  5. Depolarisation
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18
Q

Describe the role of ATP in muscle contraction (4)

A
  1. To break actinomyosin
  2. To move the myosin head
  3. So actin filaments are moved
  4. For active transport of calcium ions
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19
Q

Explain how a decrease in the concentration of
calcium ions within muscle tissues could cause a
decrease in the force of muscle contraction. (3)

A
  1. Less tropomyosin moved from binding site
  2. Fewer actinomyosin bridges formed
  3. Myosin head does not move
20
Q

Describe the role of glucagon in gluconeogenesis. (2)

A
  1. Attaches to receptors on target cells and stimulates enzymes
  2. Glycerol into glucose
21
Q

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

A
  1. Less ATP is converted to cyclic AMP
  2. Less kinase is activated
  3. Less glycogen is converted to glucose
22
Q

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes. (3)

A
  1. High concentration of glucose in blood
  2. Not all the glucose is reabsorbed at the proximal convoluted tubule
  3. Carrier proteins are working at maximum rate
23
Q

Explain why a pancreas transplant would not be a suitable treatment for type 2 diabetes. (3)

A
  1. Type 2 produces insulin
  2. Cells are less sensitive to insulin
  3. So they need to be controlled by diet
24
Q

Adrenaline binds to receptors in the plasma
membranes of liver cells. Explain how this
causes the blood glucose concentration to
increase. (2)

A
  1. Adenylate cyclase is activated
  2. It activates the enzymes so glycogenolysis occurs
25
Q

Describe and explain how three features of the cells in the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood. (6)

A
  1. Microvilli provides a large surface area
  2. Many channel/carrier proteins for facilitated diffusion
  3. Many carrier proteins for active transport
  4. Many channel/carrier proteins for co-transport
  5. Many mitochondria to produce ATP for active transport
  6. Many ribosomes to produce carrier/channel proteins
26
Q

Describe the effect of ADH on the collecting
ducts in kidneys. (3)

A
  1. Stimulates the addition of channel proteins into membrane
  2. Increases permeability to water
  3. By osmosis
27
Q

Describe how ultrafiltration occurs in a
glomerulus. (4)

A
  1. High hydrostatic pressure
  2. Forces small substances out, such as water or ions
  3. Through small pores
  4. Through the capillary basement membrane
28
Q

How does the inhibition of the absorption of
sodium and chloride ions from the filtrate cause
an increase in the volume of urine produced. (3)

A
  1. Water potential of the filtrate decreased
  2. So less water is reabsorbed by osmosis
  3. Collecting duct is where osmosis occurs
29
Q

Describe the mode of action on insulin (6)

A
  1. Binds to receptors on liver and muscle cells
  2. Increases the permeability of muscle cell membranes to glucose by increasing the number of channel proteins
  3. Insulin also activates enzymes in the liver that convert glucose to glycogen. GLYCOGENESIS
  4. Lipid formation is stimulated
  5. Cells store more glycogen as an energy store
  6. Insulin also increases the rate o respiration of glucose
30
Q

Give two reasons why transmission across a cholinergic synapse is unidirectional (2)

A
  1. Vesicles of neurotransmitters are only found in pre-synaptic knob
  2. Receptors for neurotransmitters only in post-synaptic membrane
31
Q

Define Spatial Summation

A
  1. Several impulses from different presynaptic neurons arrive together, each release some neurotransmitters causing enough sodium ions to enter and reach threshold.
32
Q

Define Temporal Summation

A
  1. ACh breaks down in a few milliseconds so several impulses in quick succession ensures enough neurotransmitter builds up in the cleft to bind to the post synaptic membrane and cause it to reach threshold potential
33
Q

How do Adrenaline and Glucagon act as a secondary messenger? (5)

A
  1. Glucagon/Adrenaline bind to complementary receptors on cell membrane
  2. Activates adenylate cyclase
  3. Adenylate cyclase converts ATP into cAMP
  4. cAMP activates the enzyme protein kinase A
  5. Protein kinase A activates a chain of reactions to break down glycogen to glucose
34
Q

Explain the importance of reflex actions (3)

A
  1. Role in homeostasis
  2. Finding food/mate/suitable conditions
  3. Escape from predators
35
Q

Suggest two advantages of simple reflexes (5)

A
  1. Quicker
  2. Protect against damage to body
  3. Doesn’t have to be learnt
  4. Help escape from predators
  5. Enable homeostasis control
36
Q

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how (6)

A
  1. SAN to AVN to Bundle of His
  2. Electrical Impulses over atria
  3. Atria contract
  4. Non-conducting tissue
  5. Causes delay at AVN to ensure the atria is empty
  6. Before ventricles contract from apex upwards
37
Q

A woman takes moderate exercise. Explain what causes her heart rate to increase while she exercises (6)

A
  1. Respiration increases
  2. CO2 concentration increases
  3. In blood plasma
  4. Chemoreceptors
  5. In aortic bodies
  6. Impulses are then sent to the medulla
  7. Increased frequency of impulses
  8. Along sympathetic pathway
  9. To SAN
38
Q

Function of the sensory neurone (1)

A

Carry impulses from a receptor to the central nervous system

39
Q

Function of the motor neurone (1)

A

Transmit impulses from the CNS to an effector

40
Q

Describe the sequence of events involved in transmission across a cholinergic synapse (6)

A
  1. Calcium ions enter axon
  2. Vesicles fuse with presynaptic membrane
  3. Acetylcholine
  4. Diffuses across synaptic cleft
  5. Binds with receptors on postsynaptic membrane
  6. Sodium ions enter neurone
  7. Depolarisation of membrane
  8. If above threshold action potential produced
41
Q

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

A
  1. ATP won’t be converted into cAMP
  2. So no protein kinesis would be activated
  3. So no glycogen would be hydrolysed into glucose
  4. Therefore lowers the blood concentration glucose level
42
Q

Describe the role of glucagon in gluconeogenesis

A

It attaches to receptors on the target cells and stimulate the enzymes which convert fatty acids to glucose

43
Q

Name the stages of the reflex arc in order

A
  1. Stimulus
  2. Receptor
  3. Sensory Neurone
  4. Relay Neurone
  5. Motor Neurone
  6. Effector
  7. Response
44
Q

Neurone body contain large amounts of rough endoplasmic reticulum, ribosomes and mitochondria.
Explain why? (4)

A
  1. Neurones produce proteins called neurotransmitters to transmit impulses
  2. Large amounts of mitochondria to produce ATP needed for protein synthesis
  3. Large amounts of ribosomes to produce the proteins
  4. Large amounts of Rough Endoplasmic Reticulum for transport of proteins
45
Q

The axon of many neurones are coated in a myelin sheath.
Describe the structure of this sheath and explain how the function is achieved by this structure (4)

A
  1. Made of lipids
  2. Acts as an electrical insulator
  3. Prevents generation of the impulse except at Node of Ranvier
  4. Speeds up transmission of the impulse
46
Q

Describe how you could compare the IAA concentration in shoot tips from two different plant species (5)

A
  1. Size of shoot/tip
  2. Number of shoot tips
  3. Size/type of agar
  4. Shoots at same stage of growth/development
  5. Time tips kept on agar
  6. Temperature
  7. Repeat several times and calculate a mean
  8. Compare/read degree of curvature to determine IAA concentration

Biology Flash Cards (8 decks)

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