Question

1. Place the following statements in the correct order to represent the events occurring at a synapse upon the arrival of an action potential. (1, 2, 3, 4, 5 or 6)

Opening of ligand-gated ion channels to allow Na+ or cations to flow into the dendritic spines__

Depolarization of the postsynaptic membrane and generation of action potential__

Ca2+ channels in the presynaptic membrane open and to allow calcium to flow in___

propagation of action potential through the opening of voltage gated channels____

the increase in the concentration of cytosolic Ca2+ in the terminal knob triggers the fusion of synaptic vesicles with the presynaptic membrane___

diffusion of the released neurotransmitter across the synaptic cleft and binding to ion-channel receptors on the postsynaptic membrane___

2. FILL IN THE BLANKS. Plasma membranes are said to be asymmetric because of the unequal distribution of different types of phospholipids in the outer leaflet and the inner leaflet.

1. Which phospholipids are more abundant in the outer leaflet of animal membranes?

Blank 1________

2. Which phospholipids more abundant in the inner leaflet?

Blank 2_________

3. Some lipids termed as Blank 3 ______carry oligosaccharide head-groups and are enriched in the Blank 4 ________ leaflet of the plasma membrane.

4. In animal cells, Blank 5_________is equally distributed between the outer and inner leaflets of the plasma membrane and it modifies membrane fluidity and permeability. Membrane fluidity is also increased by increasing the degree of Blank 6_______ of fatty acid chains

3 .Briefly describe the structure and possible applications of liposomes.

4.Briefly explain the mechanism of function of a ligand gated Na+ channel.

5. Briefly summarize the mechanism of function of a voltage-gated K+ channel.

6. Which of the following proteins or structures are responsible for maintaining resting potential in nerve cells?

A. K+ leak channels

B. Na+/K+ ATPase

C. Na+ leak channels

D. Glucose transporters

7. The class of molecule that mediates most functions in biological membranes is______

A. carbohydrates

B. triglycerides

C. phospholipids

D. proteins

8. The class molecule that is most responsible for the structure of biological membranes is________

A. carbohydrates

B. triglycerides

C. phospholipids

D. proteins

9. Which of the following molecules is likely to be transported by diffusion across a biological membrane?

A. glucose

B. water

C. k+

D. oxygen

10. The difference between active and passive transport is that____

A. ATP is expended during active transport

B. ATP is expended during passive transport

C. Non-polar substances are transported by active transport

D. Non-polar substances are transported by passive transport

11. Cholesterol in biological membranes___

A. increases fluidity

B. decreases fluidity

C. increases freezing temperature

D. has no effect

12. Active transport is achieved by___

A. integral membrane proteins

B. peripheral membrane proteins

C. phospholipids

D. glycolipids