Deck 13: The Cytoskeleton

Question 1

During evaluation of a couple for infertility, it turns out that the male partner has a normal sperm count, but his sperm cells are totally immotile.He also has a history of recurrent bronchitis and sinusitis, and when he was a child, the pediatrician had told his mother that his heart was not on the left but on the right side.Abnormalities in which protein could possibly account for these problems?

A)Vinculin.
B)Dynein.
C)Connexin.
D)Cadherin.
E)β-Catenin.

Answer 1

Dynein.

Question 2

A boy showed extensive skin blistering shortly after birth, with large areas of epidermis detaching from the dermis.Treatment with high doses of morphine was started to alleviate the seemingly excruciating pain suffered by the infant.Histological analysis shows that the basement membrane appeared intact in fresh blisters, but the stratum germinativum was destroyed.This type of disease is most likely caused by defects in which protein?

A)Desmin.
B)Tubulin.
C)Elastin.
D)Keratin.
E)Dystrophin.

Answer 2

Keratin.

Question 3

A 4-year-old boy is seen by the pediatrician for clumsiness and difficulty climbing stairs.Physical examination shows poorly developed muscles, and a blood test shows that the level of the muscle enzyme creatine kinase is 40 times the upper limit of normal.This disease is most likely caused by a deficiency of the muscle protein:

A)Troponin.
B)Tropomyosin.
C)-Actinin.
D)Dystrophin.
E)Titin.

Answer 3

Dystrophin.

Question 4

A bound guanosine triphosphate (GTP) is involved in the reversible assembly of:

A)Thick filaments in skeletal muscle.
B)Keratin filaments in the skin.
C)Actin microfilaments in the cytoplasm of most cells.
D)Microtubules during mitosis.
E)Lamins in the nucleus.

Question 5

Cells can exchange inorganic ions and small metabolites with neighboring cells in the tissue.This process requires the protein:

A)Vinculin.
B)Dynein.
C)Connexin.
D)Cadherin.
E)β-Catenin.

Question 6

A 42-year-old man of European ancestry is found to have a blood hemoglobin concentration of 36% (normal, 40% to 54%).Blood analysis shows the presence of abnormally rounded and elliptical erythrocytes, and these cells are more easily destroyed than normal cells by exposure to hypotonic saline solution.The structural protein that is most likely reduced in the blood cells of this patient is:

A)Actin.
B)Spectrin.
C)-Actinin.
D)Tubulin.
E)Keratin.