02.07 - The Cytoskeleton, Cell Motility and the Extracellular Matrix

Question 1

Which of the following is not a function of the cytoskeleton?

a. Cell motility
b. Structural support
c. Cytokinesis
d. None of the above.

Answer 1

d. None of the above.

Question 2

Which is the first step in the assembly of microtubules?

a. Formation of protofilaments
b. Dimerization of alpha and beta tubulin units
c. Assembly of the microtubule cylinder
d. None of the above

Answer 2

b. Dimerization of alpha and beta tubulin units

Question 3

Which statement does not describe microtubules?

a. Microtubules have polarity and are always in the state of dynamic instability.
b. Intracellular trafficking of vesicles depend on microtubules.
c. Microtubules are involved in the axoplasmic flow of material along neuronal processes.
d. Microtubules are made up of polypeptide chains arranged in a right-handed supercoil.

Answer 3

d. Microtubules are made up of polypeptide chains arranged in a right-handed supercoil.

Question 4

Cilia is characterised by __________ movement; flagella is characterised by __________ movement.

Answer 4

Rotatory, undulatory

Question 5

Which of the following statements is incorrect?

a. A flagella has a 9+2 arrangement of microfilaments.
b. The bending of cilia is driven by the motor protein dynein.
c. Cilia and flagella have the same ultrastructure.
d. Respiratory cells are lined with cilia.

Answer 5

a. A flagella has a 9+2 arrangement of microfilaments.

Question 6

What is the principle behind the use of colchicine against gout?

a. Colchicine disassembles microtubules, facilitating the rearrangement of the cytoskeleton and thereby the movement of WBCs.
b. Colchicine inhibits the mitosis of the fungus causing gout.
c. Colchicine inhibits cellular division of WBCs.
d. Colchicine prevents microtubules from facilitating the movement of cells involved in the inflammatory response.

Answer 6

d. Colchicine prevents microtubules from facilitating the movement of cells involved in the inflammatory response.

Question 7

This anti-fungal drug prevents fungal mitosis by inhibiting microtubules.

Answer 7

Griseofulvin

Question 8

What syndrome results from the lack of the motor protein dyne in?

Answer 8

Kartagener Syndrome/Primary ciliary dyskinesia/Siewert’s Syndrome

Question 9

Which does not occur in an individual with primary ciliary dyskinesia?

a. Inability of cilia to move debris out of the respiratory system
b. Improper migration of organs
c. Accelerated cellular ageing
d. Recurrent infections

Answer 9

c. Accelerated cellular aging

Question 10

Which of the following statements is correct?

a. F-actin, a monomeric and globular protein, polymerizes to form a double helical filament.
b. G-actin polymerizes covalently to form the F-actin filament.
c. Localized contraction of actin-myosin aggregates drives amoeboid movement.
d. During contraction, actin molecules walk along the myosin filament, pulling stacks of myosin fiber together.

Answer 10

c. Localized contraction of actin-myosin aggregates drives amoeboid movement.

Question 11

What triskelion-shaped protein facilitates receptor-mediated endocytosis during the internalization of LDL?

Answer 11

Clathrin

Question 12

Which of the following does not apply to intermediate filaments?

a. Intermediate filaments have a diameter of 8-10 nm.
b. Intermediate filaments are more permanent and stable compared to microfilaments.
c. Intermediate filaments are rather deformable; they can be stretched several times their initial length.
d. Lamins are cytoplasmic intermediate filaments that is lacking in Hutchinson-Gilford progeria.

Answer 12

d. Lamins are cytoplasmic intermediate filaments that is lacking in Hutchinson-Gilford progeria. (Lamins are nuclear.)

Question 13

Which of the following intermediate proteins is incorrectly paired with its distribution?

a. Lamins - nuclear lamina
b. Keratins - epithelial cells
c. Desmin - Glial cells
d. Peripherin - Neurons

Answer 13

c. Desmin - Glial cells (Desmin are found in muscle cells.)

Question 14

What disease results from the mutations in the gene encoding lamin A and lamin C and is characterised by alopecia, prominent scalp veins, and accelerated ageing?

Answer 14

Hutchinson-Gilford Progeria

Question 15

Mutations in genes encoding keratin results in a deficiency in the holding tension of the skin. This results into what disease?

Answer 15

Epidermolysis Bullosa Simplex

Question 16

Which of the following statements is incorrect?

a. The extracellular matrix helps the cytoskeleton resist tension from mechanical forces outside the cell.
b. The extracellular matrix is a cellular component present in all tissues and organs.
c. Th extracellular matrix provides essential physical scaffolding for cellular constituents.
d. The extracellular matrix helps in cell-to-cell signalling.

Answer 16

b. The extracellular matrix is a cellular component present in all tissues and organs. (The ECM is noncellular!)

Question 17

It is a structural protein that is major component of most connective tissues and is the most abundant protein in metazoans.

Answer 17

Collagen

Question 18

Which is not true about collagen?

a. It has a double helix structure, with two alpha polypeptide chains arranged in a right-handed supercoil.
b. It is usually composed of glycine, proline, and hydroxyproline.
c. Fibril-forming collagens are continuous and include Types I, II, and III.
d. Type VIII collagen forms a network in the Descemet’s membrane in the cornea.

Answer 18

a. It has a double helix structure, with two alpha polypeptide chains arranged in a right-handed supercoil. (Collagen is a triple-helix!)

Question 19

What type of network-forming collagen forms a mesh in the basement membrane in the lungs and kidneys?

Answer 19

Type IV

Question 20

These are short collagens with interruptions, often linked to collagen II, and carries a glycosaminoglycan chain.

Answer 20

Fibril-associated collagens with interrupted triple helices (FACITs)

Question 21

What type of collagen maintains functional integrity by connecting the epithelium to the stroma?

Answer 21

Type VII

Question 22

What type of collagen forms beaded filaments that provides structural links to cells?

Answer 22

Type VI

Question 23

Which is incorrectly paired?

a. Type I - bone
b. Type III - cartilage
c. Type IV - basement membrane
d. None of the above

Answer 23

b. Type III - cartilage

Question 24

Which does not occur during collagen synthesis ?

a. Vitamin C assists the hydroxylation of selected prolines and lysines.
b. Preprocollagen is synthesised in ribosomes.
c. Posttranslation modification occurs prior to transport into the extracellular environment.
d. None of the above

Answer 24

d. None of the above

Question 25

What disease results from excessive collagen deposition causing prolonged injury to the liver?

Answer 25

Hepatic cirrhosis

Question 26

Known as the brittle bone disease, this is caused by reduction or abnormality in type I collagen.

Answer 26

Osteogenesis imperfecta

Question 27

This disease results from a mutation in the COL1A1 or COL1A2 gene, and is characterised by weak muscles, brittle teeth, curved spine and blue sclerae.

Answer 27

Osteogenesis imperfecta

Question 28

What specific part of collagen synthesis is inhibited in scurvy?

Answer 28

Hydroxylation of prolines and lysines

Question 29

Which is not sign or symptom of scurvy? a. Liver spots on skin b. Spongy gums c. Irrational/unexplained cheerfulness d. Bleeding from mucous membranes

Answer 29

c. Irrational/unexplained cheerfulness

Question 30

This protein is involved in the extensibility of lung tissue and large arterial blood vessels.

Answer 30

Elastin

Question 31

Which statement incorrectly describes elastin? a. It is relatively absent in the circulatory system. b. It has no organised pattern or structure. c. Coil conformations are usually random to permit stretch and recoil. d. None of the above

Answer 31

a. It is relatively absent in the circulatory system.

Question 32

Which is not true about fibrillins? a. It is a large, rodlike glycoprotein. b. It controls the elasticity of elastin. c. It is a structural component of microfibrils. d. None of the above

Answer 32

d. None of the above

Question 33

What disease is caused by fibrillin-1 mutations, resulting in deficiency of elastin-associated microfibrils?

Answer 33

Marfan syndrome

Question 34

A patient with emphysema has: a. Loss of lung elasticity b. Decreased alveolar size c. Overproduction of elastic fibers d. All of the above

Answer 34

a. Loss of lung elasticity

Question 35

In the complex process of elastic fiber biogenesis, what cross links tropoelastins with each other?

Answer 35

Lysyl oxidase

Question 36

What are the three primary proteins that make up the basal lamina?

Answer 36

Laminin Entactin Type IV collagen

Question 37

Desmosomes are __________ while hemidesmosomes are ___________.

Answer 37

Cell-cell adhesion, cell-matrix adhesion

Question 38

Which of the following statements does not apply to laminins? a. Laminins interact with collagen and integrins to anchor the lamina to the cells. b. Laminins are formed by the linkage of three polypeptide chains, forming an elongated cruciform shape. c. Laminin trimers polymerize in the endoplasmic reticulum. d. Full-sized laminin trimers can self-polymerise through short arm-short arm interactions.

Answer 38

All of the above statements apply to laminins.