Question

1) What is true of intermediate filaments?

1. They are only found in the cytoplasm
2. They are the most durable cytoskeleton element
3. All epithelial cells have the same keratin filaments
4. The ends of each tetramer are unique
5. They are found in almost every organism

2) Myosins are molecular motors that interact with actin filaments. Myosin-l ad myosin-ll have different structures and functions, such as all these are correct EXCEPT:

1. Myosin-l help pull the plasma membrane to new shapes.
2. Myosin-l is found in all cell types whereas myosin-ll is primarily found in muscles.
3. Myosin-ll is primarily used in cell division
4. Myosin-l moves vesicles along actin filaments.
5. Myosin-l has one globular head domain whereas myosin-ll has two globular head domains.

3) What is true about mutations in the Rb gene?

1. Rb mutations always lead to hereditary retinoblastoma
2. The cells with Rb mutations become malignant without acquiring any additional mutations
3. Mutations leading to hereditary retinoblastoma take longer to be acquired
4. Rb mutations behave like an autosomal dominant mutation when inherited

4) Apoptosis differs from necrosis in that necrosis

1. Causes cells to swell and burst, whereas apoptotic cells shrink and condense.
2. Causes DNA to fragment.
3. Requires the reception of an extracellular signal.
4. Induces inflammation.

Answer 1

1. Answer B

Cytoskeleton of intermediate filament is most durable because the tight association between protofilaments provide intermediate filaments with a high tensile strength.

2. Answer D

Myosin-VI moves endocytic vesicles from the plasma membrane

3. Answer B

Somatic mutation of the other allele of Rb gene coupled with oncogenic mutations in other genes leads to tumor malignancy

4. Answer B

In necrosis membrane disruption, respiratory poisons and hypoxia which cause ATP depletion, metabolic collapse, cell swelling and rupture leads to inflammation. In apoptosis DNA fragmentation takes place.