Membranes & Neurons

Question 1

Ionic chemicals, such as Na + and phosphate PO43

Answer 1

prefer to be dissolved in aqueous solutions rather than lipid environments

Question 2

Comparing unsaturated and saturated hydrocarbon molecules, which of the following is incorrect?

a. Unsaturated hydrocarbons have double of triple bonds
b. Saturated hydrocarbons have a more rigid shape than unsaturated hydrocarbons
c. A double bond results in a kink in a hydrocarbon
d. Both types of hydrocarbons are lipophilic (likes being in fats) and hydrophobic (hates water)

Answer 2

b. Saturated hydrocarbons have a more rigid shape than unsaturated hydrocarbons

Question 3

Which statement about animal cell membranes is correct?

a. Unsaturated phosholipds cause increased viscosity of the membrane
b. Saturated phosphilds result in reduced membrane fluidity
c. At body temp, cholesterol increases the fluidity of membranes
d. Unsaturated phosphikips are less kinked than saturated lipids
e. Because of its ordered structure, cholestrerl always decreased the fluidity of the membrane

Answer 3

b. Saturated phosphilds result in reduced membrane fluidity

Question 4

Which of the following is incorrect about the structure of proteins?

a. A particular amino acid can only occur once in a protein
b. Proteins consist of amino acids joined by peptide bonds
c. The side chains on the amino acids in a protein vary in chemical properties
d. Some side chains like to associate with the lipid part of cell membranes

Answer 4

a. A particular amino acid can only occur once in a protein

Question 5

Which of the following amino acids would most likely be present in the transmembrane domain of an integral membrane protein

a. a charged amino acid like lysine
b. a polar amino acid like serine
c. a special amino acid like glycine or proline
d. a hydrophobic amino acid like valine
e. Any of the above , with no preference.

Answer 5

d. a hydrophobic amino acid like valine

Question 6

Compare the tonicities of each of the following with the contents of red blok cells: I water, II 150mM NaCl and III solution of 50 mM fructose + 250mM ethanol

Answer 6

a. 1 and 11 are hypotonic and 11 is isotonic
b. Because ethanol moves across easily by passive diffusion. Fructose stays as fructose, NaCL breaks down so 300, water is 0. Blood is 300mOmol

Question 7

Why did the red blood cells burst in water

Answer 7

a. The water was markedly hypotonic compared with the cell contents.

Question 8

Which of the following is not true about membrane phospholipids

a. They are the main component of cell membranes
b. They are amphipathic
c. They are mobile
d. They mediate movements of ions across membranes
e. They can be saturated or non-saturated

Answer 8

d. They mediate movements of ions across membranes

Question 9

Which of the following molecules will move most quickly across a lipid bilayer membrane by simple diffusion

a. K+
b. CO2
c. Fructose
d. HCO3-
e. H20

Answer 9

b. CO2

Question 10

Which of the following statements is correct regarding transport across cell membranes both facilitated diffusion and active transport

a. Use proteins to mediate transport across the cell membrane
b. Can be mediated by ion channels
c. Can generate electrical potentials across cells
d. Require the solute to dissolve in the phospholipids bilayer
e. Require energy from ATM

Answer 10

a. Use proteins to mediate transport across the cell membrane

Question 11

In the stages of cell signalling, the signalling molecule (e.g. hormone or neurotransmitter) is directly involved in:

a) Amplification of the signal in the cell
b) Producing the 2nd messenger in the cell
c) Transduction
d) Activation of the cellular response
e) Reception

Answer 11

e) Reception

Question 12

Adrenaline is secreted from the adrenal medulla near the kidney and acts on the heart to increase heart rate. This is an example of which type of signalling?

a) Paracrine signalling by adrenaline
b) Hormonal signalling by adrenaline carried in the blood
c) Synaptic signalling by adrenaline released from nerves
d) Local signalling by adrenaline in the heart
e) Long-distance signaling by nerves

Answer 12

b) Hormonal signalling by adrenaline carried in the blood

Question 13

Adrenaline is secreted from the adrenalal medulla near the kidney and acts on the heart to increase heart rate. The effect of adrenaline on the heart?

a) Affects the activity of th eenzyme cyclooxygenase
b) Requires adrenaline to go into the heart cells by active transport
c) Is mediated by a Gp protein coupled recpetor
d) Results in the production of the first messenger cyclic AMP
e) Requires a change in only one protein in the heart cells to mediate the response.

Answer 13

c) Is mediated by a Gp protein coupled recpetor

Question 14

The families of receptos that mediate the effects of neurotransmittes released from neurons are

a) Steroid receptors, after the neurotransmitter enters the cells
b) Ion channel receptors and GPCRs that produce a rapid response
c) Only receptor tyrosine kinases as phosphorylation is required
d) GPCRs because a second messengers is required in neurotransmission
e) Any type except steroid receptors, because neurotransmitters cannot diffuse across cell membranes

Answer 14

b) Ion channel receptors and GPCRs that produce a rapid response

Question 15

Which of the following Is not a function of membrane proteins in cells?

a) Signal transduction
b) Transport and enzymatic acticity
c) Attachment of the cytoskeleton and extracellur matrix
d) Cell to cell recognition by glycoproteins
e) Making membranes more fluid at temperatures

Answer 15

e) Making membranes more fluid at temperature

Question 16

Maintaining appropriate concentrations of ions across cell membranes is dependent on:

a) The low water solubility of ions
b) The pressure of ion channels in the cell membrane
c) Passive diffusion of ions across the membrane phospholipid bilayer
d) Active transport via ion channels (only allow things to go through by facilitated diffusion, so along the concentration gradient high to low, need transport of carriers)
e) Osmotic movement of water to the region of lower ion concentration (water moves to region where ion concentration is higher as need to dilute)

Answer 16

b) The pressure of ion channels in the cell membrane

Question 17

Which one of the following statements about Na+/K+-ATPase is incorrect?

a) Functions as an electrogenic pump
b) Allows active transport of cations
c) Uses energy from ATP breakdown
d) Transports Na+ ions does the concentration gradient
e) Works with the Na+ glucose cotransporter for active uptake of glucose

Answer 17

d) Transports Na+ ions does the concentration gradient

Question 18

G protein-coupled receptors (GPCRs)

a) Are not important for the action of chemicals released from neurons (neurotransmitters)
b) Have only 1 transmembrane spanning domain
c) Have the fastest action of the super families of receptors
d) Active the production of a cascade of 2nd messenger molecules

Answer 18

d) Active the production of a cascade of 2nd messenger molecules

Question 19

Which membrane proteins are important in establishing the resting membrane potential?

Answer 19

15,150 Na+ and 140,5 K+ - need to know

Question 20

Activation of Na+/K+-ATPase

a) Is required to generate an action potential
b) Decrease intracellular K+
c) Increases intracellular Cl-
d) Increases intracellular Ca2+
e) Decreases intracellular Na+

Answer 20

e) Decreases intracellular Na+

Question 21

Digoxin is used to inhibit Na+/K+-ATPase in a toad sciatic nerve preparation. Which of the following would you not expect to occur in neurons?

a) Na+ ion gradient gradually disappears
b) K+ ion gradient gradually disappears
c) Cl- ion gradient gradually disappears – (has nothing to do with it)
d) Resting membrane potential is reduced (difference between 0 and value, so a reduced potential is one that is closer to 0 which would occur)
e) Intracellular negative charge is decreased

Answer 21

c) Cl- ion gradient gradually disappears – (has nothing to do with it)

Question 22

How does water move across cell membranes?

Answer 22

Some simple passive diffusion but mostly through aquaporins which is example of channels so facilitated diffusion. Water will move to dilute the solute, so runs along concentration gradient

Question 23

what would happen to red blood cells if placed in the solution?
1. 100mM glucose

Answer 23

stays as glucose, so its 100mOsm/L – Hypotonic solution – cells gain water and expands and busts/lysis.

Question 24

what would happen to red blood cells if placed in the solution?
2. 100mM CaCl2

Answer 24

will split into 3 ions, so CaCl2 will dissociate into 3 ions, so 300mOsm/L – so equilibrium - Isotonic solution – no change to cell

Question 25

what would happen to red blood cells if placed in the solution?
3. 100mM fructose + 150mM NaCal

Answer 25

= 100x1 + 150 x2 = 400oMsm/L – Hypertonic solution – cell loses water and shrivels

Question 26

what would happen to red blood cells if placed in the solution?
4. 200mM of Drug X (small and non-polar) + 100 NaCl

Answer 26

= just the NaCl so 100x2 = 200mOsm/L – hypotonic solution – cell gains water. Drug x will move by simple diffusion

Question 27

You are training for endurance running. Explain why it is preferable to have a hypotonic glucose and salt drink rather than a hypotonic glucose drink

Answer 27

• Think about how salt (na) can help glucose get across the cell membrane. Primary active transport can use energy from ATP directly, knock of high energy phosphate and use the energy to transport the ions against the concentration gradient.
• Animal cells: Na+/K+‐ATPase working together with, for example, the Na+‐glucose cotransporter to drive glucose uptake against its concentration gradient, pumps potassium in and sodium out. So co transport pairs the primary active transporter with another transporter and works by secondary active transport
• High concentration of Na+ outside the cell, so the second co-transport can use the chemical energy by lettering Na+ go into the cell along with glucose go in against its concentration gradient.
• If add more sodium to the glucose, then more chemical energy which will allow more glucose into cell for endurance run.
• When running best to drink hypotonic so not trying to move water out into the intestinal cell.

Question 28

The concentrations of Na+ and K+ in the cytosol and extracelluar fluid (in mM) are:

Answer 28

Na - 15,150; K - 140,5

Question 29

The resting membrane potential of cells is not influenced by

a) The activity of the sodium potassium pump
b) The high membrane permeability of potassium ions
c) Energy derived from ATP
d) Voltage-gated sodium channels
e) The low membrane permeability of sodium ions

Answer 29

d) Voltage-gated sodium channels

Question 30

Activation of voltage-gated Na+ channels

a) Causes hyperpolarisation of neurons
b) Has no effect on membrane potential
c) Increases intracellular Cl-
d) Decreased intracellular Na+
e) Increases intracellular Na+

Answer 30

e) Increases intracellular Na+

Question 31

Voltage-gated Na+ and K+ channels

a) Are both activated by depolarisation in the neuron
b) Cause hyperpolarisation of neurons when they are activated
c) Both cycle through three conformations during their activity
d) Are both activated rapidly
e) Increase intracellular K+

Answer 31

a) Are both activated by depolarisation in the neuron

Question 32

Local anaesthetics

a) Activate Cl- channels to hyperpolarise neurons
b) Block voltage-gated Na+ channels
c) Block Na+/K+ ATPase
d) Inhibit the step of transition of Na+ channels from closed to open
e) Stimulate generation of action potentials in sensory neurons

Answer 32

b) Block voltage-gated Na+ channels

Question 33

The process for acetylchlorins from motor neurons involves

a) Opening of ligand-gated calcium channels
b) Acetylochloline-receptor mediated formation of clathrin-coated vesicles
c) Phagocytosis
d) Pinocyctosis
e) Exocytosis

Answer 33

e) Exocytosis

Question 34

What properties make something impermeable to the lipid membrane

Answer 34

Charged ions, hydrophilic molecules, large molecules

Question 35

What is the osmolarity of a red blood cell

Answer 35

300mOsm/L

Question 36

What happens if 200mM KCl outside cell

Answer 36

outside 400mOsm/L. therefore hypertonic. Blood cell becomes shrivelled

Question 37

What happens is 100nM NaCl and 40mM KCl and 20mOsm/l DNA

Answer 37

total oSmol/L = 300mOsm/L. therefore isotonic

Question 38

What are the 4 main receptors:

Answer 38

1. Ion channel receptors - fasters
2. Gpcr g protein coupled receptors
3. tyrosine kinase
4. intracellular receptors – slowest

Question 39

What receptors rely on hydrophilic signalling

Answer 39

1. Ion channel receptors - fasters
2. Gpcr g protein coupled receptors
3. tyrosine kinase

Question 40

What do you know about ion channel receptors. Can you think of any examples of how they work

Answer 40

• Ligand binds to receptors causing ion channels to
• Na+ or K+ channel to open (e.g. Na+ channels)
• Very fast response (nervous system)
• Nicotinic receptors

Question 41

What do you know about GPCRs. Can you explain the process through which they work?

Answer 41

• They have 7 transmembrane domains
• Lots of stimuli, can be targeted by many drugs
• Coupled step process binds to G protein
• Activates G protein which binds to an enzyme and activates second messenger which causes the cellular response

Question 42

What do you know about Tyrosine Kinase receptors. Can you explain the process they work?

Answer 42

• They’re dimers
• Kinase is an enzyme that add phosphates to things
• Phosphorylation cascade via kinases, so lots of phosphates being added on, which activates some things and de-activates other things
• Targeted by insulin
• Activate/inactivate proteins to mediate response

Question 43

What are the concentrations of K+ and Na+ either side of the membrane?

Answer 43

Na+: 15mM/L inside, 150mM/L outside
K+: 140mM/L inside, 5mM/L outside
(to remember, there is 155 on either side, then remember one nuber)

Question 44

How is membrane potential maintained?

Answer 44

Na+/K+ATPase pump – 3 Na out and 2K in and more K+ channels open that Na+ channels

Question 45

Why is it important to maintain concentration gradient?

Answer 45

To maintain membrane potential to allow action potentials to occur

Question 46

What is the process through which an action potential occurs?

Answer 46

Resting membrane potential, then a stimulus occurs and reaches threshold causing depolarisation
and then goes to repolarisation then undershoot

Question 47

Where does the Action Potential usually begin?

Answer 47

Axon Hillock

Question 48

How does the action potential make it all the way down the axon?

Answer 48

Regenerates itself

Question 49

Why does the action potential not go backwards?

Answer 49

Refractory period prevents depolarisation again so repolarisation is still occurring

Question 50

How can the action potential travel faster

Answer 50

Myelin sheaths (as it only needs to regenerate at the nodes of ranvier), larger diameter, temperature

Question 51

An EPSP occurred in a postsynaptic neuron in response to a release of glutamate from a presynaptic neuron. Which mechanism could explain this?

a) Activation of voltage-gated sodium channels
b) Actication of voltage-gated potassium channels
c) Activation of ligand-gated sodium channels
d) Activation of ligand-gated chloride channels
e) Inhibition of voltage-gated sodium channels

Answer 51

c) Activation of ligand-gated sodium channels

Question 52

Which states about calcium ions is incorrect?

a) Resting intracellular Ca2+ concentration is 0.1 um
b) The Ca2+ gradient across cell membranes is about 10,000 fold
c) Ca2+ enters neurons and stimulates exocytotic release of neurotransmitter
d) Ca2+ enters presynaptic neurons via ligand gated Ca2+ channels
e) Ca2+ is a second messenger in cells

Answer 52

d) Ca2+ enters presynaptic neurons via ligand gated Ca2+ channels

Question 53

Comparing postsynaptic potentials with action potentials, which statement is correct?

a) Both are all or nothing
b) Both are generated at the cell body
c) Both travel along the axon
d) Both can cause depolarisation of the neuronal membrane
e) Both are inhibitory and cause hyperpolarisation

Answer 53

d) Both can cause depolarisation of the neuronal membrane

Question 54

Which statements about 2nd messengers is incorrect? Second messengers

a) Are always present in cells at the same concentration
b) Mediate cell signalling when they are present
c) Act as amplifiers when they are synthesised or released
d) Have regulated mechanism for their destruction or removals
e) Include cyclic AMP and Ca2+

Answer 54

a) Are always present in cells at the same concentration

Question 55

The release of noradrenaline from a presynaptic neuron is the brain stimulated postsynaptic B-adrenoreceptors. This resulted in cyclic AMP synthesis and an inhibitory effect on the postsynaptic neuron. This is an example of?

a) Direct synaptic transmission
b) Depolarisation of the postsynaptic neuron
c) Cyclic AMP acting as a second messenger
d) A response mediated by ligand-gated ion channels
e) An amino acid acting as a neurotransmitter

Answer 55

c) Cyclic AMP acting as a second messenger

Question 56

Removal of noradrenaline from the synaptic cleft

a) Occurs rapidly by diffusion
b) Involves metabolism by the enzyme acetylocholinesterase
c) Requires rapid uptake by B-adrenoceptors
d) Occurs primarily by uptake into glial cells
e) Is mediated by reuptake into the presynaptic neuron by a transporter

Answer 56

e) Is mediated by reuptake into the presynaptic neuron by a transporter

Question 57

What happens to the membrane potential when there are a lot of open K+ channels in the membrane at rest. If there were other channels open, what potential would occur in the cell membrane at equilibrium

Answer 57

If only channels open are K+ and ATPase still working, charge would be -90mV (EK), as K would move out and would end up with a more negative charge inside cell. It will make the chemical energy across the membrane smaller as reducing the concentration gradient. The electrical energy is increasing as making the charge more negative. Produce an equilibrium EK which is -90mV

Question 58

What happens to the membrane potential if there are a lot of open sodium channels?

Answer 58

there is a large influx of Na+ ions, leading to depolarisation and an action potential

Question 59

Name types of chemical synaptic transmission

Answer 59

Direct synaptic transmision -
neuotransmitter opens ion channels on the postsynaptic membrane. action via ion channel linked receptors
Indirect
neurotranmsitter binds to g protein-coupled receptor on the postsynaptic membrane
activated a signal transduction pathway
involves a second messenger

Question 60

The Broca’s area is involved in _______ and Wernicke’s area is responsible for _______ in the brain, the grey matter is on the _____and is comprised of ______ However, white matter is on the inside and appears to be this colour due to _____.

Answer 60

The Broca’s area is involved in speech production and Wernicke’s area is responsible for speech comprehension in the brain, the grey matter is on the outside and is comprised of cell bodies and dendrites However, white matter is on the inside and appears to be this colour due to myelin.

Question 61

The amygdala, hippocampus, olfactory bulb, and the diencephalon make up the _____ that is responsible for _____.

Answer 61

The amygdala, hippocampus, olfactory bulb, and the diencephalon make up the limbic system that is responsible for emotion.

Question 62

What are the 3 components of the brainstem?

Answer 62

Midbrain
Pons
Medulla oblongata

Question 63

What is the role of the cerebellum?

Answer 63

Integrates complex sequence activities like riding bike, motor function and coordination and cognitive and perceptual function

Question 64

What constitutes as the diencephalon? Outline their roles
• Epithalamus
• Thalamus
• Hypothalamus

Answer 64

•	Epithalamus
o	Connects limbic system (“emotional center”) to the rest of the brain
o	Pineal gland: melatonin (sleep)
•	Thalamus
o	Input from sensory neurons
o	Output via motor neurons
•	Hypothalamus
o	Homeostatic regulation ‐ hormones
o	Biological clock
o	Temperature regulation
o	Survival ‐ hunger, thirst…

Question 65

Which of the following is INCORRECT?

a) Neurotransmitters can be taken up by the pre-synaptic neuron from the synaptic cleft.
b) Glycine is an inhibitory amino acid neurotransmitter. Glycine is inhibitory
c) Neurotransmitters can passively diffuse out of the synaptic cleft.
d) Neurotransmitters can be taken up by the post-synaptic neuron from the synaptic cleft.
e) Some neurotransmitters have specific enzymes that rapidly breakdown the neurotransmitter (for example acetylcholine and acetylcholinesterase).

Answer 65

d) Neurotransmitters can be taken up by the post-synaptic neuron from the synaptic cleft. (they don’t enter the post-synaptic neuron

Question 66

Which of the following is true regarding postsynaptic potentials?

a) they are always depolarisation
b) they are graded potentials
c) they are generated at the axon hillock
d) they are always excitatory

Answer 66

b) they are graded potentials

Question 67

In an action potential, voltage-gated Na+ and K+ channels…

a) both cause hyperpolarisation of neurons when activated
b) are both activated by depolarisation of the neuron
c) are both activated rapidly
d) both cycle through three conformations during their activity

Answer 67

b) are both activated by depolarisation of the neuron

Question 68

Which of the following statements about astrocytes is INCORRECT?

a) Astrocytes are found in the blood brain barrier.
b) Astrocytes form in the blood brain barrier.
c) Astrocytes form myelin sheaths around axons. Shwann cells do this
d) Astrocytes are involved in regulating the concentration of neurotransmitters and
e) ions in extracellular fluid.

Answer 68

c) Astrocytes form myelin sheaths around axons. Shwann cells do this

Question 69

Which of the following statements regarding the nervous system is FALSE?

a) Motor neurons leave the spinal cord via the ventral root.
b) Skeletal muscles are influenced by the somatic nervous system.
c) The central nervous system is only comprised of the brain and spinal cord.
d) Sensory neurons enter the spinal cord via the ventral root.
e) Ganglia are segmented clusters of neurons.

Answer 69

d) Sensory neurons enter the spinal cord via the ventral root.

Question 70

List the three stages of information processing.

Answer 70

• Sensory
• Motor input
• integration

Question 71

Obligodenrocytes

Answer 71

CNS
Form myelin sheaths around axons
Lipid membrane insulator

Question 72

Astrocytes

Answer 72

CNS
Structural support
Regulate extracellular concentration of ions
Formation of blood brain barrier

Question 73

Schwann Cells

Answer 73

PNS
Form myelin sheaths around axons
Lipid membrane insulator

Question 74

What are the 4 mechanisms of neurotransmitter removal from the synaptic cleft?

Answer 74

• Recycled by selective uptake transporters
• Lost by diffusion
• Taken up by astrocytes
• Broken down by enzymes

Question 75

Draw a graph showing the membrane potential during an action potential. Describe what is happening at each section of the graph. Label the absolute refractory period (ARP) and relative refractory period (RRP).

Answer 75

ARP – you cannot get another action potential in ARP as Na channels inactived
RRP – you can, but would need a very large voltage increase

Question 76

Number the following steps as they occur during the process of neurotransmitter release.

Action potential depolarises presynaptic membrane.
Elevated Ca2+ concentrations result in vesicle fusion (exocytosis)
Influx of Ca2+.
Neurotransmitter binds to ligand-gated ion channels.
Neurotransmitter released in synaptic cleft.
Voltage-gated ion channels open.

Answer 76

1 Action potential depolarises presynaptic membrane.
4 Elevated Ca2+ concentrations result in vesicle fusion (exocytosis)
3 Influx of Ca2+.
6 Neurotransmitter binds to ligand-gated ion channels.
5 Neurotransmitter released in synaptic cleft.
2 Voltage-gated ion channels open.

Question 77

What would increase the conduction speed of an action potential along an axon.

Answer 77

• An increase in temperature

* Increase in the degree of myelination

Question 78

Why is the resting membrane potential negative?

Answer 78

• At rest, there is more extracellular Na+ more intracellular K+
• The membrane is more permeable to the movement of K+ leaving the cell than Na+ entering the cell
• This is because there are more open K+ channels in the membrane than open Na+ and Cl- channels
• As the RMP is determined by the concentration of these ions, the RMP is driven to a negative states as more K+ leaves.

Question 79

Axon Hillock

Answer 79

The place where action potentials originate

Question 80

Nodes of Ranvier

Answer 80

The breaks in the fatty coat (these breaks result in Saltatory conduction)

Question 81

Dendrites

Answer 81

The parts of a neuron that receives signals from other neurons

Question 82

What are the 3 components of the brainstem?

Answer 82

Medulla oblongatta
Pons
midbrain

Question 83

What is the role of the cerebellum?

Answer 83

Coordination
Motor function
Cognitive and perceptual function

Question 84

How does local anaesthetic work?

Answer 84

It prevents Na+ channels transitioning from inactive state to closed state
Blocks repeated action potential generation since deploarisation is blocked

Question 85

Provide an example Figure Title

Answer 85

Figure 1. The effect of stimulus interval (ms) of two 1V pulses on the second peak CAP (mV) generated by the ulnar nerve of Rattus norvegicus. Data represents the mean of three replicates.

Question 86

What goes on the X and y axis

Answer 86

X axis – Stimulus interval (independent variable)

Y axis is CAP

Question 87

Briefly compare and contracts the properties of channels and transporters in membrane transport

Answer 87

Comparison
both are membrane proteins
both allow passage of hydrophilic substances across the membrane
both allow facilitated diffusion to occur
both allow movement of a solute along its concentration gradient
Contrast
transports, mediate active transport
transporters can mediate transport against a concentration gradient
some transporters are electrogenic
channels open and close to allow and prevent solute transport
transporters change their shape after a solute binds to shuttle the solute across the membrane

Question 88

The resting membrane potential in a neuron is approx. -70mV. Explain how Na+/K+-ATPase and other membrane proteins are involved in establishing and maintaining this membrane potential

Answer 88

Na/K-ATPase; 3 Na out and 2K in, using energy from ATP to break down to ADP + pi
A lot of constitutively open K channels. This allows a significant net outflow of K ions resulting in a negative charge inside the cell
very few open Na channels results in very little net diffusion of Na ions down its concentration gradient into the cell
The resting membrane potential of -70mV occurs when a steady state is reached - equal and opposite Na and K currents

Question 89

Which of the following factors would tend
to increase membrane fluidity?
A. a greater proportion of
unsaturated phospholipids
B. a greater proportion of saturated
phospholipids
C. a lower temperature
D. a relatively high protein content
in the membrane
E. a greater proportion of relatively
large glycolipids compared to
lipids having smaller molecular
masses

Answer 89

A. a greater proportion of

unsaturated phospholipids

Question 90

In which one of the following solutions would
red blood cells be most likely to burst?
A. 150 mM NaCl
B. 80 mM CaCl2
C. 100 mM NaCl + 200 mM glucose
D. 50 mM NaCl + 200 mM Drug X
(X = a small non‐polar molecule)
E. 300 mM NaCl

Answer 90

D. 50 mM NaCl + 200 mM Drug X

X = a small non‐polar molecule

Question 91

Which of the following is NOT a characteristic
of G protein‐coupled receptors? They
A. bind and activate heterotrimeric
G proteins
B. are the most abundant type of
receptor in our genome
C. are membrane proteins that are
found only in the periphery
D. are major targets for the actions
of clinically used drugs
E. generate amplified intracellular
signals (e.g. cAMP and Ca2+)

Answer 91

C. are membrane proteins that are

found only in the periphery

Question 92

Insulin and glucagon have opposing effects on blood
glucose levels. Which of the following is CORRECT
regarding the receptors for insulin and glucagon?
A. Receptors for both insulin and glucagon
have 7 transmembrane domains
B. Receptors for both insulin and glucagon
stimulate a cascade of phosphorylation
C. Insulin receptor stimulation results in
reduced glucose transport into cells
D. Glucagon acts on a G‐protein coupled
receptor and results in c‐AMP production
E. The timescale for stimulation of both
receptor types is minutes to hours

Answer 92

D. Glucagon acts on a G‐protein coupled

receptor and results in c‐AMP production

Question 93

Passive diffusion
A. allows rapid passage of nutrients
such as glucose across distances
of centimetres
B. avoids the necessity to have a
circulatory system
C. requires energy generated from
ATP
D. allows the transfer of gases
across epithelial cell membranes
E. is not an important mechanism
in cells of mammalian systems

Answer 93

D. allows the transfer of gases

across epithelial cell membranes

Question 94

What is the osmolarity of a 250 mM
aqueous KCl solution?
A. 250 ml
B. 250 mosmol l‐1
C. 500 mosmol l‐1
D. 750 mosmol l‐1
E. Isotonic

Answer 94

C. 500 mosmol l‐1