QUESTION 1 (15 marks) Why are membranes \"semi-permeable\"? Briefly describe the

Question

QUESTION 1 (15 marks)

Why are membranes "semi-permeable"? Briefly describe the structure of integral proteins that allow them to act as channels, and relate this to the types of amino acids that must form the transmembrane segments. How could an integral protein act as a voltage-sensor?

QUESTION 2 (15 marks)

Describe the ionic basis of the resting membrane potential and show, with evidence, how changes in membrane permeability are responsible for changes in membrane potential during the action potential in a nerve cell membrane.

QUESTION 3 (15 marks)

Describe the processes that occur at the neuromuscular junction. How does the permeability of the post-junctional membrane change during synaptic transmission to produce an EPP? How does an EPP at the neuromuscular junction differ from an EPSP?

QUESTION 4 (15 marks)

Calcium is central to skeletal muscle contraction!

Critically evaluate the above statement by describing the role and regulation of intracellular calcium during skeletal muscle contraction.

QUESTION 5 (15 marks)

You are conducting typical force-voltage, force-frequency and length-tension experiments on the toad sciatic nerve/gastrocnemius muscle preparation. Draw and explain the twitch characteristics, recruitment and length-tension results obtained during these experiments. How might the results differ if SR density was increased?

QUESTION 6 (15 marks)

Describe the metabolic changes which accompany high rate (fatiguing) and low rate (steady state) contraction regimes

QUESTION 7 (15 marks)

Skeletal muscle fatigue has been ascribed to a number of different processes!

Explain and support with evidence one potential cause of skeletal muscle fatigue.

QUESTION 8 (15 marks)

Draw the force-velocity relationship of skeletal muscle.

Describe how the shape of the force-velocity relationship can be explained by the properties of the S2 region and number of cross bridges formed. What else might influence this relationship?

QUESTION 9 (15 marks)

Describe the contractile, neural and calcium regulation of cardiac muscles

QUESTION 10 (15 marks)

Too much of a good thing is bad for you!

Critically evaluate the above statement by discussing the role of elevated calcium in muscle damage and degeneration. Discuss the pathological changes in Duchenne’s muscular dystrophy as a result of repeated damage and repair cycles.

QUESTION 11 (15 marks)

Skeletal muscle fibres are considered to be "plastic" as they can respond to various stimuli. Describe in detail the properties of the three basic types of skeletal muscle fibres and describe the major pathways that cause hypertrophy.

Explanation / Answer

1. Plasma membrane is semi-permeable as it allows only certain molecules to enter the cell and prevent the rest from entry. This helps in maintaining the integrity of the cell.

Integral membrane proteins are strongly bounded to the membrane. They can only be removed by some strong detergents. Integral proteins have one or more segment which is embedded in phospholipid bilayer from both the sides. They have hydrophobic amino acid residues that allow then to get inserted in the membrane and allow the interaction with fatty acyl groups of the membrane phospholipids.

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