Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A2 AQA Biology - Burnley College (2023-24) > Organisms Respond to their Environment (3.6) > Flashcards

Organisms Respond to their Environment (3.6) Flashcards

1
Q

Survival & Response (AO1)

Organisms [1] their chance of survival by responding to [2] in their environment.

A

[1] increase

[2] changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Survival & Response (AO1)

List two simple responses by small organisms such as insects

A

Taxis

Kinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Survival & Response (AO1)

Function of taxis and kinesis for mobile organisms?

A

1. Keep organisms in a favourable environment.
(e.g. more food, more mates, less predators, less desiccation)

2. Increase chances of survival

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Survival & Response (AO1)

Define taxis

A

Directional movement in response to a stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Survival & Response (AO1)

Positive taxis

A

Directional response with movement towards the stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Survival & Response (AO1)

Negative taxis

A

Directional response with movement away from the stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Survival & Response (AO1)

Define kinesis

A

Random OR non-directional movements in response to the stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Survival & Response (AO2)

A

Behaviour:
(Positive photo) taxis;

Advantage:
Avoid competition / to find a mate / increase dispersal / to avoid predators;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Survival & Response (AO2)

A

1. Kinesis;

2. Movement is random / non-directional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Survival & Response (AO2)

A

Taxis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Survival & Response (AO1)

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

A

Similarity − directional response to a stimulus / movement towards OR away from a stimulus;

Difference − in taxis whole organism moves whereas tropism a growth response in part of the plant (e.g. shoot or root tips).

OR

Difference - taxis occurs in animals whereas tropisms occurs in plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Survival & Response (Maths)

A

11.1%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Survival & Response (AO2)

A

Taxis

B moves towards stimulus / light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Survival & Response (AO2)

A

kinesis;

random / non-directional movements;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Survival & Response (AO1)

In flowering plants, specific [1] factors move from growing regions to other tissues, where they regulate growth in response to directional [2].

A

[1] growth

[2] stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Survival & Response (AO1)

Which organisms demonstrate tropisms?

A

Plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Survival & Response (AO1)

Define tropism

A

Response of a plant to a directional stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Survival & Response (AO1)

Stimuli that cause tropisms

A

Light
Gravity
Water
Salinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Survival & Response (AO1)

Positive phototropism

A

Directional response of shoot tips towards light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Survival & Response (AO1)

Directional response of root tips away from light

A

negative phototropism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Survival & Response (AO1)

Positive gravitotropism

A

Directional response of root tips towards gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Survival & Response (AO1)

Auxis are a family of growth factors that cause tropisms. Which specific auxin must you know.

A

IAA

Full name: Indoleacetic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Survival & Response (AO1)

Where is IAA synthesised?

A

Shoot tips &
root tips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Survival & Response (AO1)

How does IAA move into the growing region of the shoot or root tip?

A

Diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Survival & Response (AO1)

Where does IAA build up in the shoot tips in response to light?

A

On the shaded side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Survival & Response (AO1)

Effect of IAA in the shoot tips

A
  1. Stimulates elongagation of cells on the shaded side;
  2. Causes shoot to bend towards the light;
    (this is a positive phototropism)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Survival & Response (AO1)

Where does IAA build up in the root tips in response to gravity?

A

On the side closest to gravity / on the underside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Survival & Response (AO1)

Effect of IAA in the root tips

A
  1. Inhibits elongagation of cells on the underside;
  2. Cells on opposite side (away from gravitiy) can elongate and cause the root tip to bend towards gravity;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Survival & Response (AO2)

A

1. Tip produces/synthesises IAA;

2. IAA diffuses (into growing region of shoot);

3. Stimulates elongation of cells on one side (than other);

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Survival & Response (AO2)

A

1. Tip produces IAA;

2. Affects concentration of IAA

OR Affects (shoot) length/growth/elongation;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Survival & Response (Maths)

A

0.4cm^3 stock IAA + 39.6cm^3 water

Step by step working:
C1 x V1 = C2 x V2
C1 = stock concentration
V1 = volume of stock
C2 = desired concentration
V2 = desired volume
1 x V1 = 0.01 x 40
V1 = 0.4cm^3 of IAA stock + 39.6cm^3 of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Survival & Response (AO2)

A

1. Grow in direction of / towards (pull of) gravity;

Accept: tropism for growth

Accept: positively geotropic / gravitropic

2. Grow away from salt;

3. Salt has more effect than gravity;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Survival & Response (AO2)

A

1. Seedlings / root tips respond to light;

2. Only measuring the effect of gravity;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Survival & Response (AO2)

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 (2 marks).

A

1. Causes plant to bend / grow towards light / positive phototropism;

2. Light energy required for photosynthesis;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Survival & Response (AO1)

TRUE or FALSE:

IAA is only produced in the light

A

FALSE

IAA is produced in the light AND dark

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Survival & Response (AO1)

Draw out a simple reflex arc
(include the neurons and an effector)

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Survival & Response (AO1)

Which neuron in the simple reflex arc contains receptors to the stimulus?

A

Sensory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Survival & Response (AO1)

Suggest two advantages of simple reflexes

A
  1. Rapid;
  2. Protect against damage to body tissues;
  3. Do not have to be learnt / innate behaviour / involuntary;
  4. Help escape from predators;
  5. Enable homeostatic control;
  6. Finding suitable conditions / keep organism in favourable environment;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Survival & Response (AO1)

Give two types of cell that act as effectors.

A

Muscles

Glands
(which produce hormones)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Survival & Response (AO1)

A

Only 3 neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Survival & Response (AO1)

What is found between the sensory neuron and relay neuron

A

Synapse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Nerve impulses (AO1)

Draw out and annotate a myelinated motor neuron

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Nerve impulses (AO1)

What is found on the cell surface membrane of the dendrites?

A

Receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Nerve impulses (AO1)

Organelles in the cell body of a neuron

A

Nucleus
Golgi apparatus / body
Ribosomes / Rough ER
Mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Nerve impulses (AO1)

Specialised cell that produces the myelin sheath

A

Schwann cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Nerve impulses (AO1)

Biological molecule found in myelin sheath

A

phospholipids

Myelin also contains cholesterol, so similar to cell surface membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Nerve impulses (AO1)

Released by axon terminals

A

neurotransmitters

e.g. acetylcholine, dopamine, serotonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Nerve impulses (AO1)

Process at nodes of ranvier

A

saltatory conduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Nerve impulses (AO1)

Stages of an action potential

A
  • Resting potential,
  • (Threshold potential),
  • Depolarisation,
  • Repolarisation,
  • Hyperpolarisation,
  • Re-establish resting potential.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Nerve impulses (AO1)

Resting potential in mV

A

-70mV

This means inside of axon is LESS positive than outside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Nerve impulses (AO1)

Channel proteins found in axon cell surface membrane

A

Voltage-gated sodium ion channels

Voltage-gated potassium ion channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Nerve impulses (AO1)

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

A

1. Sodium ions actively transported OUT and potassium ions IN;

2. LESS permeable to sodium ions as voltage-gated channels closed OR membrane MORE permeable to potassium ions;

3. Higher concentration of potassium ions inside AND higher concentration of sodium ions outside the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Nerve impulses (AO1)

The sodium potassium ion pump establishes an ________________ gradient.

A

electrochemical gradient

i.e., higher sodium ion concentration outside the axon, lower inside.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Nerve impulses (AO1)

Threshold potential in mV

A

-55mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Nerve impulses (AO1)

Channel open at -55mV

A

Voltaged-gated sodium ion channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Nerve impulses (AO1)

The all-or-nothing principle

A

An action potential is only generated/produced when threshold stimulus is reached (-55mv)

OR

An action potential is not generated/produced until/unless threshold stimules is reached (-55mv);

If stimulus reached, voltage-gated sodium ion channels open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Nerve impulses (AO1)

Sodium and potassium ions can only cross the axon membrane through channel proteins. Explain why (2 marks).

A

1. Cannot pass through phospholipid bilayer (via simple diffusion)

2. because they are NOT lipid soluble

OR because they are charged;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Nerve impulses (AO2)

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 marks).

A

1. No/less ATP produced;

2. No/less active transport
OR fewer sodium ions moved out.
OR Sodium/potassium pump inhibited;

3. Electrochemical gradient not maintained

OR same concentration of sodium and potassium ions either side of axon membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Nerve impulses (AO1)

A

C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Nerve impulses (AO2)

A

1. Voltage-gated sodium ion channels open, so sodium diffuses in;

2. Makes inside of more positive OR leads to depolarisation / reaches threshold;

3. More channels open;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Nerve impulses (AO1)

Sodium ions diffusing into the axon via open voltage-gated channels leads to___________________.

A

depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Nerve impulses (AO1)

Why does the graph increase from -55mV to +40mV?

A

1. Voltage-gated sodium ion channels are open

2. Sodium ions diffuse into the axon via faciliated diffusion (DOWN an electrochemical gradient)

3. Inside of the axon MORE positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Nerve impulses (AO1)

What happens at +40mV?

A

Voltage-gated sodium ion channels CLOSE

AND

Voltage-gated potassium ion channels OPEN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Nerve impulses (AO1)

Why does the graph decrease after +40mV during repolarisation?

A

1. Voltage-gated potassium ion channels are open (& voltage-gated sodium ion channels are closed).

2. Potassium ions rapidly diffuse OUT of the axon via faciliated diffusion (DOWN an electrochemical gradient)

3. Inside of the axon LESS positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Nerve impulses (AO1)

Hyperpolarisation in mV

A

-90mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Nerve impulses (AO1)

What causes hyperpolarisation?

A

1. Voltage-gated potassium ion channels stay open;

2. Potassium ions diffuse out of axon;

3. Inside of axon becomes even LESS positive (decreasing from -70mV to -90mV).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Nerve impulses (AO1)

Channels closed at -90mV

A

Voltage-gated potassium ion channels (close at -90mV)

Voltage-gated sodium ion channels (already closed during repolarisation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Nerve impulses (AO1)

Explain how the resting potential is re-established (2 marks).

A

1. Sodium potassium pump uses energy from ATP hydrolysis;

2. Sodium ions actively transported OUT and potassium ions IN.

Both ions move AGAINST their concentraton gradient from low to high.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Nerve impulses (AO1)

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

A

1. Myelination provides insulation;

2. In myelinated axon saltatory conduction occurs

OR In myelinated axon depolarisation only occurs at nodes of Ranvier;

3. In non-myelinated axon, depolarisation occurs along whole length of axon;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Nerve impulses (AO1)

Refractory period

A

1. Time during which a new action potential cannot be generated;

2. It lasts from the threshold potential until the resting potential has been re-established;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Nerve impulses (AO1)

Importance of the refractory period

A

1. Action potentials occur in one direction

2. Each impulse / action potential is discrete

3. Number of action potential is limited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

Nerve impulses (AO1)

Factors affecting speed of impulse conductance along an axon

A

Myelination

Temperature

Axon diameter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

Nerve impulses (AO1)

Explain how myelination affects conductance of an impulse

A

Insulates axon;

Depolarisation only occurs at nodes of Ranvier;

Leads to salatory conduction (action potential ‘jumps’ between nodes of Ranvier);

Impulse / action potential moves FASTER along axon;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

Nerve impulses (AO1)

Explain how increasing temperature affects conductance of an impulse

A

More kinetic energy;

Faster rate of diffusion of sodium and potassium ions DOWN electronchemical gradient;

Faster rate of diffusion of sodium ions within axon;

Impulse / action potential moves FASTER along axon;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

Nerve impulses (AO1)

Explain how increasing axon diameter affects conductance of an impulse

A

1. Larger surface area so more cell-surface membrane for voltage-gated sodium/potassium ion channel proteins;

2. Less resistance to flow ions within the axon;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Nerve impulses (AO2)

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 marks).

A

1. Less / no saltatory conduction / action potential / impulse unable to ‘jump’ from node to node;

2. More depolarisation over length of membranes;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

Nerve impulses (AO1)

A

D

B

C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Receptors (AO1)

Receptor to detect change in pressure

A

Pacinian corpuscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Receptors (AO1)

A

P = capsule/lamella(e)

Q = Axon (membrane) / (sensory) neurone

R = Schwann cell(s) / Myelin sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Receptors (AO1)

Channel proteins in Pacinian corpuscle

A

Stretch-mediated sodium ion channel proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Receptors (AO1)

Describe how stimulation of a Pacinian corpuscle produces a generator potential (3 marks).

A

1. Increased pressure deforms/changes membrane/lamella(e)

2. This opens the stretch-mediated sodium ion channels (in the membrane);

OR (Increased pressure) deforms/changes sodium ion channels;

3. Sodium ion channels open;

4. Sodium ions diffuse in;

5. Depolarisation (leading to generator potential);

Accept inside becomes positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

Receptors (AO1)

TRUE or FALSE:

The generator potential must exceed the threshold stimulus to trigger an action potential in the sensory neuron

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

Receptors (AO1)

[1] pressure leads to more stretch-mediated sodium [2] channels opening. This leads to [3] and makes it more likely the generator potential produced exceeds the [4] stimulus for an action potential.

This is an example of the [5] principle.

A

[1] Increased
[2] ion
[3] depolarisation
[4] threshold
[5] all or nothing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

Receptors (AO1)

TRUE or FALSE:

A new generator potential in the axon of the Pacinian corpuscle can be produced during the refractory period.

A

FALSE

The resting potential inside the axon must be re-established

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

Receptors (AO1)

Example of photoreceptors

A

Rods & cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

Receptors (AO1)

Photoreceptors location

A

Macula
(middle of retina)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

Receptors (AO1)

Cone location

A

Fovea
(the centre of the macula)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

Receptors (AO1)

Rod location

A

Edges of the macula
(not present in the fovea)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

Receptors (AO1)

Rods and cones convert [1] energy into electrical energy in the form of [2].

A

[1] light

[2] action potentials / nerve impulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

Receptors (AO1)

Sensivity of rods

A

High sensivity to low light intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

Receptors (AO1)

In rods, light breaks down the pigment [1] and this leads to the release of [2]. This leads to a [3] potential in the [4] neurone.

A

[1] rhodopsin
[2] neurotransmitter
[3] generator
[4] bipolar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

Receptors (AO1)

Retinal convergence

A

Several rod cells connected to a single bipolar neurone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Receptors (AO1)

Spatial summation

A

Release of neurotransmitter from one rod cell leads to generator potential below threshold stimulus in the bipolar neurone

Neurotransmitter released from several/additional rods cells connected to same bipolar neurone helps exceed the threhold and trigger an action potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

Receptors (AO1)

Photoreceptor with low visual acuity

A

Rods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

Receptors (AO1)

Acuity

A

How clear / detailed the image is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

Receptors (AO1)

Photoreceptor with high visual acuity

A

cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

Receptors (AO1)

Types of cone cells

A

3 cone cells specific to different wavelengths of light: red, blue & green.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

Receptors (AO1)

Sensivity of cones

A

Low sensitivity to low light intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

Receptors (AO1)

In cones, high intensity light breaks down the pigment [1] and this leads to the release of [2]. This leads to a [3] potential in the [4] neurone.

A

[1] iodopsin
[2] neurotransmitter
[3] generator
[4] bipolar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

Receptors (AO1)

Each [1] cell is connected to a single [2] neurone. This sends [3] impulses to the visual cortex via the optic nerve.

A

[1] cone
[2] bipolar
[3] separate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

Receptors (AO2)

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 marks).

A

1. Each cone cell is connected to a single bipolar neurone

OR no retinal convergence;

2. Cones send separate (sets of) impulses to brain / optic nerve;

3. Produces high visual acuity;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

Receptors (AO2)

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 marks).

A

1. High sensitivity to low light intensity

2. Retinal converage OR several rods connected to a single bipolar neurone;

3. Enough neurotransmitter released to reach/overcome threshold

OR spatial summation to reach/overcome threshold;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

Receptors (AO2)

A

no photoreceptor cells at Y
OR no rods and cones;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

Control of heart rate (AO1)

Cardiac muscle is ____________

A

myogenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

Control of heart rate (AO1)

Define myogenic

A

Contraction is initiated from within the muscle itself;

due to the action of the sinoatrial node (SAN)

(which acts as a ‘pacemaker’)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

Control of heart rate (AO1)

Nodes required for initiation and coordination of a heartbeat / cardiac cycle.

A

Sinoatrial node (SAN)

Atrioventricular node (AVN)

Note: you only need to recall ‘SAN’ and ‘AVN’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

Control of heart rate (AO1)

SAN location

A

Upper wall of right atrium

108
Q

Control of heart rate (AO1)

AVN location

A

Base of right atrium

109
Q

Control of heart rate (AO1)

bundle of his location

A

(ventricular) septum

The septum separates the L & R atria and ventricles

110
Q

Control of heart rate (AO1)

The sinoatrial node (SAN) is in the right atrium of the heart. Describe the role of the sinoatrial node (2 marks).

A

Sends out waves of electrical activity / impulses;

Which stimulates the contraction of atria OR acts as a ‘pacemaker’;

111
Q

Control of heart rate (AO1)

Describe how a heartbeat is initiated and coordinated (5 marks).

A

1. SAN sends wave of electrical activity / impulses across atria causing atrial contraction;

2. Non-conducting tissue prevents impluse spreading to the ventricles

3. AVN delays impulse whilst blood leaves atria and the ventricles fill;

4. AVN sends wave of electrical activity / impulses down the Purkinje fibres / bundle of His;

5. Causing ventricles to contract from base up;

112
Q

Control of heart rate (AO1)

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 marks).

A

1 Electrical activity only through AVN / purkinje fibres / bundle of His;

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

113
Q

Control of heart rate (Maths)

Cardiac output equation

A

Cardiac output (CO) = stroke volume (SV) x heart rate (HR)

114
Q

Control of heart rate (Maths)

TRUE or FALSE:

Heart rate is the length of one cardiac cycle in seconds

A

FALSE

Heart rate is the number of cardiac cycles / heart beats per minute

115
Q

Control of heart rate (Maths)

One cardiac cycle is 0.85s, what is the heart rate?

A

60 / 0.85 = 70.588 or 71 bpm

116
Q

Control of heart rate (Maths)

Heart rate of 62 bpm and a cardiac output of 4785cm^3 min^-1 - what is the stroke volume?

117
Q

Control of heart rate (Maths)

Convert 620 milliseconds (ms) into seconds (s)

A

620 / 1000 = 0.62s

118
Q

Mass Transport in Animals (Maths)

Convert 4.27 seconds (s) into milliseconds (ms)

A

4.27 x 1000 = 4270ms

119
Q

Control of heart rate (Maths)

A

8 beats in 800 ms
1 beat = 100 ms / 0.1s
Heart rate = 60 / 0.1 = 600bpm

CO = SV x HR
CO = 0.03 x 600 = 18cm^3 min^-1

120
Q

Control of heart rate (Maths)

Use the below graph to determine the length of one cardiac cycle.

A

Peak to peak OR trough to trough
e.g.1.24 - 0.48 = 0.76s

121
Q

Control of heart rate (Maths)

Use the below graph to determine stroke volume.

A

120 - 40 = 80cm^3

122
Q

Control of heart rate (Maths)

A

60 / 0.9 =
66.7 or 67 bpm

One cardiac cycle or heart beat = 0.9 seconds

123
Q

Control of heart rate (AO1)

Branches of the autonomic nervous system

A

sympathetic

parasympathetic

124
Q

Control of heart rate (AO1)

Increased activity of the ____________ nervous system increases heart rate

A

sympathetic

125
Q

Control of heart rate (AO1)

Increased activity of the ____________ nervous system decreases heart rate

A

parasympathetic

126
Q

Control of heart rate (AO1)

Receptors for blood pressure

A

baroreceptors

127
Q

Control of heart rate (AO1)

Baroreceptor location

A

aorta

carotid artey*

*supply blood to brain

128
Q

Control of heart rate (AO1)

Cardiac centres location

A

Medulla oblongata

129
Q

Control of heart rate (AO1)

Neurotransmitter released by parasympathetic nervous system

A

acetylcholine

130
Q

Control of heart rate (AO1)

Explain how a rise in blood pressure results in a decrease in heart rate (6 marks).

A

1. Baroreceptors in the aorta / carotid arteries

2. Send impulses to cardiac centres / medulla oblongata;

3. Increased frequency of impulses sent via parasympathetic nerves;

4. to SAN;

5. Release of acetylcholine inhibits SAN so decreases impulses;

6. So decreased implules to AVN;

131
Q

Control of heart rate (AO1)

Neurotransmitter released by sympathetic nervous system

A

noradrenaline

132
Q

Control of heart rate (AO2)

Suggest how caffeine increases heart rate (2 marks)

A

1. More impulses/action potentials along sympathetic nervous system;

2. To SAN

133
Q

Control of heart rate (AO1)

Receptors for carbon dioxide concentration in blood

A

chemoreceptors

134
Q

Control of heart rate (AO1)

Chemoreceptor location

A

aorta

carotid artey*

*supply blood to brain

135
Q

Control of heart rate (AO1)

Exercise causes an increase in heart rate.

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

A

1. Chemoreceptors detect rise in carbon dioxide in blood

2. Send impulses to cardiac centres / medulla oblongata;

3. More / increases frequency of impulses to SAN;

4. via sympathetic nervous system;

136
Q

Control of heart rate (AO2)

Some drugs inhibit the transmission of nerve impulses to the heart. Explain how these drugs reduce blood pressure (2 marks).

A

1. Inhibit impulses along sympathetic nervous system;

2. SAN not stimulated so less waves of electrical activity / impulses spread across atria;

137
Q

Synapses (AO1)

Neurotransmitter released by cholinergic synapse

A

acetylcholine

138
Q

Synapses (AO1)

Contains vesicles with neurotransmitter

A

Pre-synaptic neurone

139
Q

Synapses (AO1)

Contains receptors on cell-surface membrane for neurotransmitter

A

Post-synaptic neurone

140
Q

Synapses (AO1)

A

A - Vesicle

B - Neurotransmitter

C - Synaptic cleft

141
Q

Synapses (AO1)

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

Describe how (3 marks).

A

1. Depolarisation of membrane causes calcium ion channel proteins to open;

2. Calcium ions enter by (facilitated) diffusion;

3. Causes vesicles to fuse with presynaptic membrane;

142
Q

Synapses (AO1)

Describe the sequence of events involved in transmission across a cholinergic synapse (5 marks).

A

1. Depolarisation of / action potential moves into presynaptic membrane;

2. Calcium ion channels open AND calcium ions enter pre-synaptic terminal;

3. (cause) synaptic vesicles move to/fuse with presynaptic membrane and release acetylcholine/neurotransmitter;

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

5. Acetylcholine binds to receptors on the postsynaptic membrane;

6. Sodium ions enter (postsynaptic neurone) leading to depolarisation;

143
Q

Synapses (AO1)

TRUE or FALSE:

Acetylcholinesterase breaks down acetylcholine after it has binded to its receptor to prevet further depolarisation of the post synaptic neurone

144
Q

Synapses (AO2)

Synaptophysin is a protein involved in the production of synaptic vesicles.

Scientists can use the presence or absence of synaptophysin to identify presynaptic and postsynaptic membranes in synapses.

Explain why they are able to use synaptophysin for this purpose (1 mark).

A

(Synaptic) vesicles only found in presynaptic neurone

145
Q

Synapses (AO2)

Dopamine is a neurotransmitter. Production of too much dopamine is associated with schizophrenia. A drug used to treat schizophrenia binds to dopamine receptors in synapses. This binding does not lead to the formation of an action potential.

Suggest why the drug used to treat schizophrenia is able to bind to the same receptor as dopamine (1 mark).

A

Has similar tertiary structure / shape to dopamine

OR

Complementary (to binding site on receptor);

146
Q

Synapses (AO2)

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

Explain why (2 marks).

A

1. If not removed keeps binding to receptors;

2. Keeps causing action potentials / depolarisation of post-synaptic membrane;

147
Q

Synapses (AO2)

Glutamate is a neurotransmitter involved in the transmission of nerve impulses from pain receptors to the brain. Ziconotide is a drug that can reduce severe, constant pain. Ziconotide blocks the calcium ion channels at some of the synapses which use glutamate.

The transmission of glutamate at synapses is similar to that of acetylcholine.

Explain how ziconotide reduces severe, constant pain (5 marks).

A

1. No/less calcium ions enter presynpatic neurone via calcium ion channels;

2. No/fewer synaptic vesicles move to/fuse with presynaptic membrane and no/less glutamate is released;

3. No/less glutamate diffuses across synaptic cleft;

4. No/less glutamate binds to receptors on the postsynaptic membrane;

5. No/fewer sodium ions enter (postsynaptic neurone) so no/ fewer impulses (sent to brain);

148
Q

Synapses (AO2)

Ziconotide is a polypeptide and acts on synapses in the spinal cord. Scientists investigated the effectiveness of ziconotide in reducing severe, constant pain.

Ziconotide was injected into each patient’s cerebrospinal fluid that bathes the brain and spinal cord.

Suggest two reasons why the patients had ziconotide injected into their cerebrospinal fluid rather than taking a pill containing the drug (2 marks).

A

1. Rapidly/quickly/directly reaches synapses / spinal cord;

2. Is broken down by enzymes / proteases

OR is broken down by stomach acid

OR is too large to be absorbed;

149
Q

Synapses (AO2)

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 marks).

A

1. Dopamine diffuses across synapse;

2. Binds to receptors on postsynaptic membrane;

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

150
Q

Synapses (AO2)

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 marks).

A

1. Inside of postsynaptic neurone becomes more negative/hyperpolarisation;

2. More sodium ions required (to reach threshold)

OR Not enough sodium ions enter (to reach threshold);

3. For depolarisation/action potential;

151
Q

Synapses (AO1)

Describe how synapses are unidirectional (2 marks)

A

1. Neurotransmitters are only made in and released from the presynaptic neurone

2. Receptors for the neurotransmitter are only found on the membrane postsynaptic neurone

152
Q

Synapses (AO1)

Explain spatial summation involving synapses (3 marks)

A

Several presynaptic neurones connect to a single postsynaptic neurone;

Low amounts of neurotransmitter are released from each presynaptic neurone;

Having several presynaptic neurones increases the likelihood of the threshold potential being reached in the postsynaptic neurone;

153
Q

Synapses (AO1)

Explain temporal summation involving synapses (2 marks)

A

A single presynaptic neurone releases neurotransmitter many times over a short period;

Over time this can accumulate and the threshold potential is reached in the postsynaptic neurone;

154
Q

Synapses (AO1)

A neuromuscular junction is a specific synapse of a _____________ neurone and a muscle cell.

155
Q

Synapses (AO1)

Neurotransmitter involved at the neuromuscular junction

A

acetylcholine

156
Q

Synapses (AO1)

TRUE or FALSE:

Following events at the neuromuscular junction, the muscle is depolarised.

157
Q

Synapses (AO1)

Compare the cholinergic synapse and neuromuscular junction

A

1. Action potential arrives at pre-synaptic bulb / knob;

2. Calcium ions enter pre-synaptic bulb and are needed for release of acetylcholine;

3. Acetylcholine receptors;

4. Neurotransmitter binds to receptor causing depolarisation;

5. Acetylcholinesterase needed
to hydrolyse neurotransmitter

158
Q

Synapses (AO1)

Contrast the cholinergic synapse and neuromuscular junction

A

1. Cells of muscle fibre is depolarised rather than a post-synaptic neurone

2. Muscle cell surface membrane has folds that form clefts, so larger surface area

3. So more receptors and acetylcholinesterase

4. Motor neuron firing an action potential always triggers a response in a muscle, not always the case in the brain (i.e. requires spatial summation)

159
Q

Synapses (AO2)

Myasthenia gravis (MG) is an autoimmune disease caused when antibodies bind to the sarcolemma postsynaptic membrane of neuromuscular junctions. This can weaken contraction of muscles.

Suggest and explain how MG can weaken contraction of muscles (2 marks).

Do not include details of myofibril or muscle contraction in your answer

A

1. Less/no acetylcholine/neurotransmitter binds to receptors;

2. Less/no depolarisation

OR Fewer/no action potential(s)

OR Fewer/no sodium ions enter to reach threshold;

160
Q

Synapses (AO2)

The black mamba’s toxin kills prey by preventing their breathing. It does this by inhibiting the enzyme acetylcholinesterase at neuromuscular junctions.

Explain how this prevents breathing (2 marks).

A

1. Acetylcholine not broken down / stays bound to receptor;

2. Sodium ions continue to enter / continued depolarisation / Na+ channels (kept) open / action potentials / impulses fired (continuously);

3. Intercostal muscles / diaphragm stay contracted / cannot relax;

161
Q

Skeletal muscle (AO1)

Muscles act in ______________ pairs against an incompressible skeleton

A

antagonistic

e.g., when biceps contract, the triceps relax

162
Q

Skeletal muscle (AO2)

A
  1. Circular muscle contracts;
  2. Radial muscle relaxes;
163
Q

Skeletal muscle (AO1)

Individual muscles are made up of many fibres - the specialised cell of the muscle. These cells are very long, [1] and surrounded by a cell surface membrane called the [2].

A

[1] multinucleated

[2] sarcolemma

164
Q

Skeletal muscle (AO1)

Within each muscle fibre there are many [1] which contain the contractile proteins [2] and myosin. There are also many [3] to produce ATP.

A

[1] myofibrils

[2] actin

[3] mitochondria

165
Q

Skeletal muscle (AO1)

Which organelle surrounds the myofibrils and stores and releases calcium ions.

A

Sacroplasmic reticulum

166
Q

Skeletal muscle (AO1)

Label the below ultrastructure of a myofibril

167
Q

Skeletal muscle (AO1)

A

C - M-line / myosin

D - Mitochondrion

E - Myofibril

168
Q

Skeletal muscle (AO1)

Name the structure between A to B in the below image

169
Q

Skeletal muscle (AO1)

A

1. Light/I band only actin;

2. H zone/band only myosin;

3. Darkest/overlapping region actin and myosin;

170
Q

Skeletal muscle (AO1)

A
  1. Actin;
  2. ATP hydrolase
  3. Tropomyosin
171
Q

Skeletal muscle (AO1)

A

i) decreases

ii) stays the same length

172
Q

Skeletal muscle (AO1)

A

H band not visible / reduced OR no myosin only region OR actin close together;

I band not visible / reduced OR little / no thin filament / actin only region;

A band occupies nearly all sarcomere / thick filament / myosin close to Z line;

Large zone of thick-thin overlap;

173
Q

Skeletal muscle (AO1)

Protein that blocks myosin head binding sites on actin

A

Tropomyosin

174
Q

Skeletal muscle (AO1)

Describe the role of calcium ions in the contraction of a myofibril (3 marks).

A

1. Calcium ions diffuse into myofibrils from sarcoplasmic reticulum;

2. Cause movement of tropomyosin (on actin);

3. This movement exposes binding sites on actin;

4. Myosin heads attach to binding sites on actin;

175
Q

Skeletal muscle (AO1)

When myosin heads bind to actin, this is called a ____________ bridge.

A

actinomyosin

176
Q

Skeletal muscle (AO1)

Describe the roles of ATP in muscle contraction (3 marks).

A

(Hydrolysis of ATP releases energy which…)

1. Moves/bends the myosin head;
.
2. So actin filaments are moved/pulled inwards (towards the centre of the sarcomere);

3. A new ATP binds to myosin heads and breaks actinomyosin bridges;

4. For active transport of calcium ions (into the sarcoplasmic reticulum);

177
Q

Skeletal muscle (AO2)

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

A

1. Less / no tropomyosin moved from myosin head bind sites on actin

2. Fewer / no actinomyosin bridges formed

3. Myosin head does not move

OR myosin head does not pull action

178
Q

Skeletal muscle (AO2)

A

1. Can’t form myosin / thick filaments;

2. Can’t pull / can’t move actin / slide actin past;

3. Myosin if attached doesn’t move;

4. Can’t move actin towards each other / middle of sarcomere / can’t shorten sarcomere / can’t pull Z lines together;

179
Q

Skeletal muscle (AO1)

Creatine + phosphate =

A

Phosphocreatine

180
Q

Skeletal muscle (AO1)

What is the role of phosphocreatine in providing energy during muscle contraction? (2 marks)

A
  1. Provides phosphate
  2. Which is required to produce ATP
181
Q

Skeletal muscle (AO2)

Some studies have suggested that taking creatine supplements can improve muscle performance during intense short-term exercise.

Describe and explain how taking creatine supplements can improve performance of different types of muscle fibres during different types of exercise (2 marks).

A

1. Fast skeletal muscle fibres used during short-term/intense exercise;

2. Creatine used to form phosphocreatine;

3. Phosphocreatine combines with ADP to form ATP;

182
Q

Skeletal muscle (AO1)

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.

A

1. Regenerates/produces NAD

OR oxidises reduced NAD;

2. So glycolysis continues;

183
Q

Skeletal muscle (AO1)

Properties of slow-twitch muscle fibres

A

Contract more slowly

Produce less force

Fatigue less quickly (due to less lactate production)

Suited to endurance activities like walking and perching

Ideal for animals that migrate or engage in long-distance activities (e.g., wings of migrating geese, legs of wolves)

184
Q

Skeletal muscle (AO1)

Structure of slow-twitch muscle fibres

A

Rely on aerobic respiration for ATP production

Many large mitochondria

Myoglobin dissociates from oxygen at very low partial pressures (provides an emergency supply of oxygen and also gives these fibres their red colour)

Denser network of capillaries for increase blood supply so efficient oxygen and glucose supply

185
Q

Skeletal muscle (AO1)

Properties of fast-twitch muscle fibres

A

Contract faster

Produce more force

Fatigue quickly (due to lactate production)

Suited to short bursts of high-intensity activity e.g sprinting and weight lifting

Common in animals’ limbs used for escaping predators or hunting prey (e.g., robin’s wings, cheetah’s legs).

186
Q

Skeletal muscle (AO1)

Structure of fast-twitch muscle fibres

A

Rely on anaerobic respiration for ATP production

Higher concentrations of glycogen

Larger stores of phosphocreatine

Fewer capillaries

187
Q

Skeletal muscle (AO2)

Describe and explain how eating more carbohydrate, known as ‘carbohydrate loading’, for a few days before exercise can improve muscle performance of different muscle fibres when exercising for a long time (3 marks).

A

1. Fast (skeletal muscle) fibres used during short-term/intense exercise;

2. Slow (skeletal muscle) fibres used during long(er)-term exercise;

3. (Carbohydrate/glucose) stored as glycogen

OR Glycogenesis;

4. Glycogen hydrolysed to glucose

OR Glycogenolysis;

5. Glucose for respiration;

188
Q

Skeletal muscle (Maths)

A

Answer = 84 to 84.2 um

Step by step working below

189
Q

Skeletal muscle (AO1)

Explain the role of glycogen granules present in skeletal muscle (2 marks).

A

1. As a store of glucose

OR To be hydrolysed to glucose;

2. For respiration / to provide ATP;

190
Q

Homeostasis (AO1)

Homeostasis in mammals involves physiological control systems that [1] the internal [2] within restricted limits.

A

[1] maintain

[2] environment

191
Q

Homeostasis (AO1)

What internal factors should be kept stable to avoid negatively affecting enzyme activity.

A

core temperature

blood pH

192
Q

Homeostasis (AO1)

Explain the importance of maintaining a stable core temperature in relation to enzyme activity

A

To maintain optimum temperature for enzyme activity;

If too high enzymes may dentature = permanent change to tertiary structure;

Active site no longer complementary to substrate / no enzyme substrate complexes form;

193
Q

Homeostasis (AO1)

Explain the importance of maintaining a stable blood pH in relation to enzyme activity

A

To maintain optimum pH for enzyme activity;

If too low OR too high enzymes may dentature = permanent change to tertiary structure;

Active site no longer complementary to substrate / no enzyme substrate complexes form;

194
Q

Homeostasis (AO1)

Explain the importance of maintaining a stable blood glucose concentration

A
  1. Glucose is a key respiratory substrate;
  2. Required for both aerobic and anaerobic respiration to produce ATP;

OR

  1. Increased levels of glucose also lowers the water potential of blood;
  2. This increases volume of urine produced and leads to symptoms such as dehydration / thirst
195
Q

Homeostasis (AO1)

Explain the importance of maintaining a stable water potential of blood

A

To maintain blood pressure;

Avoids osmostic damage to cells e.g. swelling / lysis OR loss of water from cells;

196
Q

Homeostasis (AO1)

______________ feedback restores systems to their original level.

197
Q

Homeostasis (AO1)

During [1] feedback, the response involves producing more of the [2].

A

[1] positive

[2] stimululs

198
Q

Homeostasis (AO1)

A

(Insulin stimulates release of osteocalcin – no mark)

1. Osteocalcin causes more release of insulin;

2. (More) insulin causes more inactive osteocalcin to be released;

199
Q

Blood glucose homeostasis (AO1)

The control of blood glucose concentrations involves which type of feedback.

200
Q

Blood glucose homeostasis (AO1)

What increases blood glucose concentration?

A

Consumption of carbohydrate-rich foods;

e.g. fruits which contain monosaccharides AND/OR
foods such as potatoes, pasta and rice which contain high concentrations of the polysaccharide starch;

201
Q

Blood glucose homeostasis (AO1)

What decreases blood glucose concentration?

A

Exercise;

by increasing cellular uptake of glucose for aerobic and anaerobic respiration;

202
Q

Blood glucose homeostasis (AO1)

Hormone produced in response to increases in blood glucose concentration

203
Q

Blood glucose homeostasis (AO1)

Specialised cells of pancreas that synthesise and secrete insulin

A

Beta cells

204
Q

Blood glucose homeostasis (AO1)

Insulin is a small modified protein with a specific [1] structure that is [2] to its receptor.

A

[1] tertiary

[2] complementary

205
Q

Blood glucose homeostasis (AO1)

Location of insulin receptors

A

Cell surface membrane of liver and muscle cells

206
Q

Blood glucose homeostasis (AO1)

Hormone that causes glycogenesis

207
Q

Blood glucose homeostasis (AO1)

Glycogenesis

A

Conversion of (alpha) glucose into glycogen

208
Q

Blood glucose homeostasis (AO1)

Decribe how insulin reduces blood glucose concentration

A

1. Binds to receptors with a specific and complementary shape

2. Increases uptake of glucose by increasing the number of glucose channel proteins in the cell-surface membrane

3. Activates enzymes involved in the conversion of glucose to glycogen
(glycogenesis)

209
Q

Blood glucose homeostasis (AO1)

A

Tick in box 4

210
Q

Blood glucose homeostasis (AO1)

When insulin binds to receptors on liver cells, it leads to the formation of glycogen from glucose. This lowers the concentration of glucose in liver cells.

Explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration (2 marks).

A

1. Glucose concentration in liver cells falls below that in blood (plasma) which creates / maintains glucose concentration / diffusion gradient;

2. Glucose enters cell / leaves blood by facilitated diffusion via channel protein;

211
Q

Blood glucose homeostasis (AO2)

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 marks).

A

1. Changes tertiary structure;

2. No longer complementary to receptor;

212
Q

Blood glucose homeostasis (AO2)

A

1. Less/no AKT activated;

2. Fewer/no vesicles move to membrane

OR Fewer/no (channel) proteins in membrane;

3. Less/no glucose diffuses into cell (so high blood glucose);

213
Q

Blood glucose homeostasis (AO2)

Binding of insulin to its receptors leads to an increase in the rate of respiration in target cells.

Explain how (2 marks).

A

1. Leads to more glucose channel proteins in cell surface membrane

2. More glucose enters the cell for respiration / glycolysis;

214
Q

Blood glucose homeostasis (AO1)

Hormone produced in response to decreases in blood glucose concentration

215
Q

Blood glucose homeostasis (AO1)

Specialised cells of pancreas that synthesise and secrete glucagon

A

alpha cells

216
Q

Blood glucose homeostasis (AO1)

Glucagon is a small modified protein with a specific [1] structure that is [2] to its receptor.

A

[1] tertiary

[2] complementary

217
Q

Blood glucose homeostasis (AO1)

Location of glucagon receptors

A

Cell surface membrane of liver and muscle cells

218
Q

Blood glucose homeostasis (AO1)

Hormones that causes glycogenolysis

A

glucagon

adrenaline

219
Q

Blood glucose homeostasis (AO1)

Define glycogenolysis

A

Glycogen is broken down / hydrolysed into (alpha) glucose

220
Q

Blood glucose homeostasis (AO1)

Hormone that causes gluconeogenesis

221
Q

Blood glucose homeostasis (AO1)

Define gluconeogenesis

A

Amino acids / fatty acids / glycerol converted into glucose

222
Q

Blood glucose homeostasis (AO1)

Decribe how glucagon increases blood glucose concentration

A

1. Binds to receptors on the cell-surface membrane;

2. Activates enzymes involved in the conversion of glycogen to glucose (glycogenolysis);

3. Activates enzymes involved in the conversion of glycerol / fatty acids / amino acids into glucose (gluconeogenesis);

223
Q

Blood glucose homeostasis (AO1)

Describe the role of glucagon in gluconeogenesis (2 marks)

A

1. Binds to receptors on target cells

2. Activates enzymes that convert;

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

224
Q

Blood glucose homeostasis (AO2)

Scientists investigated the control of blood glucose concentration in mice. They kept a group of normal mice without food for 48 hours. After 48 hours, the blood glucose concentrations of the mice were the same as at the start of the experiment.

Explain how the normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours (2 marks).

A

1. Release of glucagon;

(Binds to receptors on liver cells)

2. Activates enzymes;

3. Which convert glycerol / fatty acids / amino acids into glucose (gluconeogenesis)

225
Q

Blood glucose homeostasis (AO1)

Adenylate cyclase converts ATP into ___________

226
Q

Blood glucose homeostasis (AO1)

Describe the second messanger model for glucagon / adrenaline (3 marks)

A

1. Adrenaline OR glucagon (“1st messenger”) bind to receptors

2. Activates adenylate cyclase

3) Adenylate cyclase converts ATP into cAMP = “2nd messenger”

4. cAMP activates protein kinase which leads to conversion of glycogen into glucose (glycogenolysis)

Note: 2nd messengers lead to an increase in enzyme controlled reactions, amplifying the effect of the 1st messanger binding to its receptor

227
Q

Blood glucose homeostasis (AO1)

Cause of type 1 diabetes

A

No / less production of insulin by beta cells

228
Q

Blood glucose homeostasis (AO1)

Treatment(s) for type 1 diabetes

A

Insulin pump / injections;

Constant monitoring of blood glucose levels

Improve diet e.g. less carbohydrates / high GI foods

Increased exercise

Transplants involving beta cells
(whole pancreas OR specific tissues with beta cells)

229
Q

Blood glucose homeostasis (AO1)

Cause of type 2 diabetes

A

Insulin insensitivity i.e. till produce insulin but target cells become ‘resistant’ or ‘insensitive’

unable to lower blood glucose concentration.

230
Q

Blood glucose homeostasis (AO1)

Treatment(s) for type 2 diabetes

A

Improve diet e.g. less carbohydrates / high GI foods

Increased exercise

Drugs that improve insulin sensitivity OR replace action of insulin

231
Q

Blood glucose homeostasis (AO2)

Metformin is a drug commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a mechanism that increases a cell’s sensitivity to insulin.

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

A

1. (More) insulin binds to receptors;

2. (Stimulates) uptake of glucose by channel/transport proteins

OR Activates enzymes which convert glucose to glycogen;

232
Q

Blood glucose homeostasis (AO2)

Metformin is a drug commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a mechanism that inhibits adenylate cyclase.

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration (2 marks).

A

1. Less/no ATP is converted to cAMP;

2. Less/no protein kinase activated;

3. Less/no glycogen is converted to glucose

OR Less/no glycogenolysis;

233
Q

Blood glucose homeostasis (AO2)

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 marks).

A

1. Type II produce insulin;

2. Cells / receptors less sensitive (to insulin)

OR faulty (insulin) receptors;

3. Treated / controlled by diet / exercise;

234
Q

Osmoregulation (AO1)

A [1] is the structural and functional unit of the kidney responsible for filtering blood and producing [2].

A

[1] nephron

[2] urine

235
Q

Osmoregulation (AO1)

Each __________ contains millions of nephrons.

236
Q

Osmoregulation (AO1)

Draw out and label a nephron

A

You do NOT need to know the name of the blood vessels

237
Q

Osmoregulation (AO1)

TRUE or FALSE:

Nephrons span the cortex and medulla of the kidney

238
Q

Osmoregulation (AO1)

Filtering of blood, reabsorption of key molecules back into blood and formation of urine takes place via which steps?

A

1. Formation of glomerular filtrate

2. Selective reabsorption of glucose and water by the proximal convoluted tubule

3. Maintaining a gradient of sodium ions in the medulla by the loop of Henle

4. Reabsorption of water by the distal convoluted tubule and collecting ducts - osmoregulation via ADH

239
Q

Osmoregulation (AO1)

Blood vessel found in glomerulus

A

capillaries

240
Q

Osmoregulation (AO1)

Structure that surrounds the glomerulus

A

Bowman’s capsule

*aka renal capsule

241
Q

Osmoregulation (AO1)

Describe how ultrafiltration occurs in a glomerulus (4 marks)

A

1. High blood/hydrostatic pressure;

2. Two named small substances pass out eg water, glucose, ions, urea, amino acids;

3. Through small gaps/pores/fenestrations in capillary endothelium;

4. (And) through basement membrane;

242
Q

Osmoregulation (AO2)

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of protein in their urine).

Suggest how AS could cause proteinuria (2 marks).

A

1. Affects/damages basement membrane

OR More protein channels/carriers in basement membrane;

2. Proteins can pass into the (glomerular) filtrate/tubule;

243
Q

Osmoregulation (AO1)

Part of nephron where majority of glucose and water is selectively reabsorbed

A

proximal convoluted tubule

244
Q

Osmoregulation (AO1)

Water is reabsorbed via [1] and moves from the [2] cells lining the proximal convoluted tubule into the capillaries [3] a water potential gradient.

A

[1] osmosis

[2] epithelial

[3] down

245
Q

Osmoregulation (AO1)

Describe selective reabsorption of glucose by epithelial cells lining the proximal convoluted tubule (3 marks).

A

1. Sodium ions are actively transported out of epithelial cells into the surrounding capillaries;

2. Creates a concentration gradient for sodium ions;

3. Sodium ions and glucose enter the epithelial cell by facilitated diffusion using co-transporter proteins;

4. Glucose moves into the capillaries by facilitated diffusion;

246
Q

Osmoregulation (AO1)

A

Glucose by facilitated diffusion and active transport and water down a water potential gradient

247
Q

Osmoregulation (AO1)

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

A

1. Microvilli provide a large surface area

2. Many channel/carrier proteins for facilitated diffusion;

3. Many carrier proteins / sodium-potassium pumps for active transport;

4. Many cotransport proteins for co-transport;

5. Many mitochondria produce ATP
OR Many mitochondria for active transport;

6. Many ribosomes to produce carrier/channel proteins;

248
Q

Osmoregulation (AO2)

A

Water is also reabsorbed

249
Q

Osmoregulation (AO1)

The [1] limb of the loop of Henle [2] transports sodium and chloride out of the loop into the interstitial space immediately surrounding the loop of Henle.

This [3] the water potential and leads to water leaving the descending limb via osmosis. Only the descending limb is [4] to water. The ascending limb is impermeable to water.

A

[1] ascending

[2] actively

[3] lowers

[4] permeable

250
Q

Osmoregulation (AO1)

The active transport of sodium and chloride ions out of the loop maintains a [1] gradient for longer along the entire length of the loop of Henle, which leads to more reabsorption of water via [2] from the descending limb into the capillaries that surround the loop of Henle.

A

[1] concentration

[2] osmosis

251
Q

Osmoregulation (AO1)

TRUE or FALSE:

As the filtrate approaches the distal convoluted tubule, it is increasingly concentrated in urea and now starts to resemble urine.

252
Q

Osmoregulation (AO2)

A

1. Thicker medulla means a longer loop of Henle;

2. Longer loop of Henle means sodium ion gradient maintained for longer (in medulla)

OR (The longer the loop of Henle means) more sodium ions are moved out (into medulla);

3. TTherefore water potential gradient maintained for longer, so more water (re)absorbed

OR More water is (re)absorbed from the loop of Henle by osmosis;

253
Q

Osmoregulation (AO2)

TRUE or FALSE:

Camels have a shorter loop of Henle

A

FALSE

Longer loop of Henle, more Na+ actively transported out, more osmosis

254
Q

Osmoregulation (AO2)

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 (3 marks).

A

1. Water potential of filtrate/tubule decreased;

2. Less water reabsorbed by osmosis (from filtrate/tubule);

3. From proximal convoluted tubule OR descending loop of Henle OR collecting duct;

255
Q

Osmoregulation (AO1)

Define osmoregulation

A

control of blood water potential

256
Q

Osmoregulation (AO1)

Osmoregulation is an example of ____________ feedback

257
Q

Osmoregulation (AO1)

Where does ADH act on the nephron

A

distal convoluted tubule
AND
collecting duct

258
Q

Osmoregulation (AO1)

Osmoreceptor location

A

hypothalamus

259
Q

Osmoregulation (AO1)

Role of osmoreceptors

A

Detect changes in blood water potential

260
Q

Osmoregulation (AO1)

Releases ADH

A

posterior pituitary gland

261
Q

Osmoregulation (AO1)

ADH binds to specific and ____________ shaped receptors on the distal convoluted tubule and collecting duct.

A

complementary

262
Q

Osmoregulation (AO1)

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

A

1. Stimulates addition of channel proteins / aquaporins into cell-surface membrane;

2. Increases permeability to water

OR More water reabsorbed;

3. By osmosis;

263
Q

Osmoregulation (AO2)

Alcohol decreases the release of ADH into the blood.

Suggest two signs or symptoms which may result from a decrease in ADH (2 marks).

A

1. Dehydration/thirst;

2. Frequent urination
OR Increase in volume of urine;

3. Less concentrated urine
OR dilute urine

264
Q

Osmoregulation (AO2)

A decrease in blood pressure stimulates the release of ADH.

Explain how the release of ADH will affect blood pressure (2 marks).

A

1. ADH increases reabsorption of water;

2. Increases volume of blood and pressure increases

265
Q

Osmoregulation (AO2)

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

A

1. High concentration of glucose in blood/filtrate;

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

3. Carrier/co-transport proteins are working at maximum rate

OR Carrier/co-transport proteins/ are saturated;

266
Q

Osmoregulation (AO1)

Explain how urea is concentrated in the filtrate (3 marks).

A

1. Reabsorption of water / by osmosis;

2. At the proximal convoluted tubule / descending loop of Henle;

3. At the distal convoluted tubule / collecting ducts;

4. Active transport of Na+ and Cl- ions creates gradient;

A2 AQA Biology - Burnley College (2023-24) (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions