Question

1. The energy required for tubular polymerization is provided by the hydrolysis of GTP.

A) True

B) False

2. Which of the following statements is correct with respect to flagella and cilia?

A) cilia generate a force parallel to the cell surface

B) cilia have a helical pattern of movement

C)There are usually fewer cilia than flagella

D)flagella display an oarlike pattern of beating

E) cilia are generally longer than flagella

3. Muscle contraction occurs in a cyclic process. Which of the following sequences is in the correct order?

A) power stroke, cross bridge formation, cross bridge dissociation, cocking of myosin

B)cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin

C) cross bridge formation, cross bridge dissociation, cocking of myosin, power stroke

D) cross bridge formation, power stroke, cross bridge dissociation, power stroke, cocking of myosin

E) cross bridge formation, cocking of myosin, power stroke, cross bridge dissociation.

4. Choose all the statements below that are true for tight junctions

A) site of membrane fusion that are limited to abutting ridges of adjacent membranes

B) allow the exchange of metabolites between the cytosols of two adjacent cells

C) seal membranes of two adjacent cells tightly together

D) require connexons

Answer 1

Answer=

1. The energy required for tubular polymerization is provided by the hydrolysis of GTP.

A) True

Explanation - The basic subunit of microtubule is the tubulin heterodimer,consisting of an alpha tubulin and beta -tubulin monomer,which are firmly associated with each other.both binds to one molecule of GTP.and acts as GTPases.In presence of GTP and Mg2+ ions,polymerization is favoured and the tubules extend from the plus end of the tubule,forming a GTP cap.GTP is progressively hydrolysed by the tubulin.hydrolysis of GTP provides energy for polymerization.

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2. Which of the following statements is correct with respect to flagella and cilia?

A) cilia generate a force parallel to the cell surface-

INCORRECT OPTIONS

B) cilia have a helical pattern of movement -flagella have helical pattern of movement

C)There are usually fewer cilia than flagella - there are very few number of flagella are present generally one -2.number of cilia are many.

E) cilia are generally longer than flagella flagella are longer than cilia.

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3. Muscle contraction occurs in a cyclic process. the following sequences is in the correct order

B)cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin

Explanation - muscle contraction is cyclic process in which first step is

1.Cross bridge formation - the myosin head forms cross bridge with actin

2. power stroke -during power stroke the myosin head bends and ADP and phosphate are released.

3.cross bridge dissociation -A new molecule of ATP attaches to myosin head,causing the cross bridge to detached.

4.cocking of myosin - ATP hydrolysis to ADP and phosphate ,which returns the myosin to the 'cocked"position