Modules 1-3 Revision

Question 1

What would happen if you transplanted a leg mesenchyme of a developing chick embryo beneath the wing apical ectodermal ridge?

Answer 1

Distal hindlimb structures will also develop at the end of the forelimb

Question 2

Cell membranes have been described as ‘fluid mosaics of lipids and proteins’. Which one of the following is NOT a property of cell membranes that fits with this description?

a) The presence of unsaturated hydrocarbons increases the fluidity of cell membranes.
b) Phospoholipids in cell membranes move rapidly in a lateral direction, but not often in a flip-flop direction to the other side of the membrane.
c) Amphipathic phospholipids include a hydrophilic head in contact with extracellular fluid and a hydrophobic tail in contact with intracellular fluid.
d) Membrane-embedded glycoproteins are involved in cell-cell recognition.
e) Fused rat and human cell membranes show mixing of marker proteins from the two species within a short time of the fusion, such as after 1 hour.

Answer 2

Option c; Amphipathic phospholipids include a hydrophilic head in contact with extracellular fluid and a hydrophobic tail in contact with intracellular fluid.

Question 3

In the pancreas, insulin is released by beta cells in response to high plasma glucose levels and glucagon is released by alpha cells in response to low plasma glucose levels.

Glucagon acts on G-protein coupled glucagon receptors to produce cyclic AMP in its target cells.

Which of the following statements about insulin receptors and glucagon receptors is INCORRECT?

a) Glucagon receptors mediate a cascade of activation of adenylate cyclase to produce the second messenger cyclic AMP
b) Insulin receptors mediate a faster response in cells than glucagon receptors
c) Glucagon receptors bind to intracellular heterotrimeric G-proteins when they are activated
d) Insulin receptors mediate a cascade of phosphorylation of proteins in cells
e) Insulin receptors are tyrosine kinase linked receptors

Answer 3

Option b; Insulin receptors mediate a faster response in cells than glucagon receptors

Question 4

Menstruation begins because…

Answer 4

progesterone and oestrogen levels decline

Question 5

Which area of the brain is most intimately associated with unconscious homeostatic control of such functions as respiration and circulation?

Answer 5

medulla oblongata

Question 6

An egg is ovulated from a…

Answer 6

Graafian follicle

Question 7

Following ovulation, a ruptured follicle…

Answer 7

differentiates into the corpus luteum

Question 8

After the depolarisation phase of an action potential, the membrane potential decreases due to…

Answer 8

the opening of voltage-gated K+ ion channels and the inactivation of voltage-gated Na+ ion channels.

Question 9

If the release of luteinising hormone (LH) were inhibited in a human female, which of the following events would NOT occur?

a) release of follicle stimulating hormone (FSH) from the pituitary
b) development and maturation of a primary follicle and oocyte
c) release of gonadotrophin-releasing hormone (GnRH) from the hypothalamus
d) spermatogenesis
e) ovulation of a secondary oocyte

Answer 9

Option b; development and maturation of a primary follicle and oocyte

Question 10

Following fertilisation, the placenta eventually forms from the…

Answer 10

trophoblast and endometrium

Question 11

Which of the following statements regarding transport of molecules across cell membranes is CORRECT?

a) Transporters in cell membranes are involved in facilitated diffusion, but not active transport
b) Small, charged and polar molecules cross cell membranes readily by passive diffusion
c) Water crosses cell membranes mainly via recently discovered channels called aquaporins
d) There is a specific protein transporter for oxygen molecules in all cells in the body
e) Ion channels are required for active transport of Na+ ions and K+ ions across cell membranes

Answer 11

Option c; Water crosses cell membranes mainly via recently discovered channels called aquaporins

Question 12

Dopamine is an example of a neurotransmitter that acts via indirect synaptic transmission when it is released from dopaminergic neurons in the brain. When dopamine is released from presynaptic neurons in different areas of the brain, it acts on postsynaptic D1-receptors which are linked to activation of adenylate cyclase, or on postsynaptic D2-receptors which are linked to inhibition of adenylate cyclase. Use this information and your knowledge of related areas to answer this question and the next question.

Based on the background information, which of the following is a CORRECT statement regarding transmission by these neurons?

a) Dopamine activates ligand-gated sodium channels on the postsynaptic membrane.
b) Dopamine is lipid soluble and diffuses into the cell membrane to act on the intracellular D1- and D2-receptors.
c) The events at this synapse are an example of electrical transmission.
d) D2-receptors mediate their effects by decreasing the levels of cyclic AMP in the postsynaptic neuron.
e) The postsynaptic D1-receptors are voltage-gated calcium channels.

Answer 12

Option d; D2-receptors mediate their effects by decreasing the levels of cyclic AMP in the postsynaptic neuron.

Question 13

Dopamine is an example of a neurotransmitter that acts via indirect synaptic transmission when it is released from dopaminergic neurons in the brain. When dopamine is released from presynaptic neurons in different areas of the brain, it acts on postsynaptic D1-receptors which are linked to activation of adenylate cyclase, or on postsynaptic D2-receptors which are linked to inhibition of adenylate cyclase.

Additional information: Stimulating the D1-receptors results in depolarisation and stimulating the D2-receptors results in hyperpolarisation.

Based on the background information and also the additional information, which one of the following statements is CORRECT?

a) Dopamine acting on either D1-receptors or D2-receptors has its effects amplifiied in the cell by G-protein-mediated effects on the activity of adenylate cyclase.
b) Dopamine is rapidly removed from the synaptic terminal by metabolism to inactive products.
c) Dopamine, glutamate and GABA all act on ligand-gated ion channels to cause very fast responses at neuronal synapses.
d) The cell signalling mechanism activated by dopamine on D1-receptors is the same as that for glutamate acting on NMDA receptors in that it involves a G-protein.
e) The cell signalling mechanism activated by the D2-receptors is like that for GABAA receptors in that it involves the opening of ligand-gated chloride channels.

Answer 13

Option a; Dopamine acting on either D1-receptors or D2-receptors has its effects amplifiied in the cell by G-protein-mediated effects on the activity of adenylate cyclase.

Question 14

John, aged 32 years old, has had debilitating symptoms for several months, and has undergone a range of diagnostic tests to determine the cause. He is diagnosed with multiple sclerosis, after detection of progressive demyelination of neurons in several parts of his nervous system over several months.

Considering the effects of the demyelination of some neurons in John’s nervous system, you would expect actional potentials in the damaged neurons…

Answer 14

not to be propagated effectively because of loss of the electrical insulating properties of the oligodendrocytes

Question 15

Oestrogen and progesterone provide feedback control on the…

Answer 15

pituitary

Question 16

The acrosome functions to…

Answer 16

contain enzymes that help a sperm head to ‘digest’ its way into the egg

Question 17

Assume that a single EPSP has a positive magnitude of +1.5 mV at the axon hillock, and that a single IPSP has a negative magnitude of -1.0 mV. For a neuron with an initial membrane potential of -70 mV, the net effect of the simultaneous arrival of 6 EPSPs and 8 IPSPs would be to ___________ the membrane by moving its potential to ________ .

Answer 17

slightly depolarise; -69 mV

Question 18

The operation of the sodium-potassium “pump”, also known as Na+/K+-ATPase, moves…

Answer 18

sodium ions out of the cell and potassium ions into the cell against their concentration gradients.

Question 19

Consider a patient who requires urgent treatment and you are contemplating injecting one of the following solutions intravenously. Which of the solutions would you recommend NOT to use because it would be the MOST likely to result in the patient’s red blood cells bursting?

a) 100 mM NaCl + 100 mM Drug Y (which is a small lipophilic molecule)
b) 100 mM NaCl + 40 mM of XCl2 where X is a divalent ion
c) 100 mM NaCl + 75 mM glucose
d) 150 mM NaCl
e) 300 mM glucose

Answer 19

Option a; 100 mM NaCl + 100 mM Drug Y (which is a small lipophilic molecule)

Question 20

The main difference between cleavage and the somatic cell cycle is…

Answer 20

cleavage results in smaller daughter cells due to the lack of a growth phase

Question 21

Organisms that are haploid and reproduce by asexual means may have…

Answer 21

a disadvantage, because they lack half of the chromosomes of diploid individuals, causing reduced genetic diversity

Question 22

For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of the cytoplasm of the neuron would result in…

Answer 22

hyperpolarisation of the neuron.

Question 23

Which of the following activities would be associated with the parasympathetic division of the nervous system?

a) increased digestion in the gastrointestinal tract
b) opening of the airways to allow increased O2 intake
c) increased heart rate
d) increased metabolic rate and blood glucose levels
e) release of adrenaline from the adrenal medulla

Answer 23

Option a; increased digestion in the gastrointestinal tract

Question 24

Which of the following is a characteristic feature of a transporter protein in a plasma membrane?

a) It exhibits specificity for a particular type of molecule.
b) It requires the expenditure of cellular energy to function.
c) It is a peripheral membrane protein.
d) It has few, if any, hydrophobic amino acids.
e) It works against diffusion.

Answer 24

Option a; It exhibits specificity for a particular type of molecule.

Question 25

Which of the following statements BEST defines the ‘determination’ of a developing embryo?

a) The cell cannot respond to differentiation signals
b) A phase where inductive signals trigger cell differentiation
c) Cells have made a commitment to a differentiation program
d) A phase where specific biochemical actions occur in embryonic cells
e) The cells have different structure and function specialisation

Answer 25

Option c; Cells have made a commitment to a differentiation program

Question 26

In vertebrate animals, spermatogenesis and oogenesis differ in that…

Answer 26

oogenesis produces one functional ovum, whereas spermatogenesis produces four functional spermatozoa

Question 27

John, aged 32 years old, has had debilitating symptoms for several months, and has undergone a range of diagnostic tests to determine the cause. He is diagnosed with multiple sclerosis, after detection of progressive demyelination of neurons in several parts of his nervous system over several months.

Considering John’s case in the background material, you start to think about how neuronal conduction occurs normally. Which of the following statements about myelination and conduction of action potentials in neurons is INCORRECT?

a) Voltage-gated sodium channels that are required for conduction of an action potential are restricted to the nodes of Ranvier in a myelinated neuron
b) Action potentials are propagated along a myelinated neuron by saltatory conduction
c) Conduction of action potentials in myelinated neurons occurs much faster than in unmyelinated neurons of the same diameter
d) Conduction of action potentials only occurs at the nodes of Ranvier between the myelin sheaths
e) Action potentials are generated across the neuronal membrane in the myelinated region, despite the electrical insulation provided by the Schwann cells

Answer 27

Option e; Action potentials are generated across the neuronal membrane in the myelinated region, despite the electrical insulation provided by the Schwann cells

Question 28

In the pancreas, insulin is released by beta cells in response to high plasma glucose levels and glucagon is released by alpha cells in response to low plasma glucose levels. Insulin and glucagon…

Answer 28

are hormones that are carried in the blood and act on cells distant from where they are released

Question 29

After being produced in the testes, sperm mature further in a structure called the…

Answer 29

epididymis

Question 30

The central nervous system integration of simple responses to stimuli, such as the patellar reflex, is accomplished by which of the following?

a) hypothalamus which is part of the diencephalon
b) corpus callosum connecting the left and right cerebral hemispheres
c) medulla oblongata in the brainstem
d) grey matter in the cerebellum
e) neurons in the spinal cord

Answer 30

Option e; neurons in the spinal cord