Cytoskeleton And Muscle Biochemistry

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| By Kar

Kar, Assistant Professor (Biochemistry)

Karthikeyan Pethusamy is an assistant professor in the Department of Biochemistry at the All India Institute of Medical Sciences in New Delhi

Quizzes Created: 33 | Total Attempts: 47,457

Questions: 18 | Attempts: 243 | Updated: Mar 21, 2023

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Questions and Answers

1.

Which is a microfilament?
- A.
  
  Actin
- B.
  
  Vimentin
- C.
  
  Keratin
- D.
  
  Desmin
Correct Answer
A. Actin

Explanation
others are intermediate filaments.

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2.

Which is NOT a molecular motor ?
- A.
  
  Dynein
- B.
  
  Actin
- C.
  
  Myosin
- D.
  
  Dynamin
Correct Answer
B. Actin

Explanation
Myosin is the motor, actin filaments are the tracks along which myosin moves, and ATP is the fuel that powers movement.

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3.

Hutchinson-Gilford progeria syndrome is due to mutation of
- A.
  
  Keratin A
- B.
  
  Keratin B
- C.
  
  Lamin A
- D.
  
  Lamin B
Correct Answer
C. Lamin A

Explanation
Lamin A & C mutation --> accumulation of farnesylated Lamin A --> disrupted nuclear scaffolding

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4.

Which component of cytoskeleton is defective in kartageners syndrome ?
- A.
  
  Dynein
- B.
  
  Actin
- C.
  
  Myosin
- D.
  
  Dynamin
Correct Answer
A. Dynein

Explanation
Kartagener's syndrome is a genetic disorder that affects the cilia, which are hair-like structures involved in cell movement. Dynein is a motor protein that plays a crucial role in the movement of cilia. In Kartagener's syndrome, there is a defect in the dynein protein, leading to impaired ciliary movement. This results in various symptoms, including chronic respiratory infections and infertility. Therefore, the defective component in Kartagener's syndrome is dynein.

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5.

Griseofulvin is a tubulin inhibitor
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Griseofulvin is a medication used to treat fungal infections. It works by inhibiting the function of tubulin, a protein involved in cell division. By inhibiting tubulin, griseofulvin prevents the formation of the mitotic spindle, which is necessary for cell division to occur. This inhibitory action ultimately leads to the death of the fungal cells, making the statement "Griseofulvin is a tubulin inhibitor" true.

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6.

Which component of cytoskeleton is defective in epidermolysis bullosa ?
- A.
  
  Desmin
- B.
  
  Vimentin
- C.
  
  Keratin
- D.
  
  Dynamin
Correct Answer
C. Keratin

Explanation
Epidermolysis bullosa is a genetic disorder that affects the skin, causing it to be extremely fragile and prone to blistering. Keratin is a structural protein that plays a crucial role in maintaining the integrity and strength of the skin. Mutations in the genes encoding keratin proteins can lead to a defective cytoskeleton in the skin cells, resulting in the characteristic symptoms of epidermolysis bullosa. Therefore, the correct answer is Keratin.

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7.

Microfilaments are dynamic structures which undergo rapid assembly and disassembly.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Microfilaments are a type of cytoskeletal filament found in cells, composed of actin protein subunits. These filaments are highly dynamic and can rapidly assemble and disassemble, allowing cells to quickly change their shape and move. This dynamic behavior is essential for various cellular processes such as cell division, cell migration, and intracellular transport. Therefore, the statement that microfilaments are dynamic structures that undergo rapid assembly and disassembly is true.

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8.

TRUE about positive end of actin filament
- A.
  
  Addition and dissociation of actin monomers are slow at +Ve end
- B.
  
  ATP binding promotes the addition of actin monomers
- C.
  
  ADP binding promotes the addition of actin monomers
- D.
  
  None
Correct Answer
B. ATP binding promotes the addition of actin monomers

Explanation
ATP binding promotes the addition of actin monomers because ATP-bound actin monomers have a higher affinity for the filament compared to ADP-bound actin monomers. When ATP is hydrolyzed to ADP, the affinity of actin monomers for the filament decreases, leading to dissociation. Therefore, the addition of actin monomers is favored when ATP is bound to actin. The statement that addition and dissociation of actin monomers are slow at the positive end is not supported by the given information.

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9.

Sarcomere is a segment between
- A.
  
  H and I bands
- B.
  
  Two I bands
- C.
  
  Two Z disk
- D.
  
  None
Correct Answer
C. Two Z disk

Explanation
A sarcomere is a segment of a muscle fiber that is defined by the presence of two Z disks. These Z disks act as anchors for the thin filaments of the sarcomere and help to maintain the structural integrity of the muscle fiber. Therefore, the correct answer is two Z disks.

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10.

TRUE about A band
- A.
  
  Consists only of thin filaments
- B.
  
  Contains the entire length of a single thick filament
- C.
  
  I band is a component of A band
- D.
  
  None
Correct Answer
B. Contains the entire length of a single thick filament

Explanation
The correct answer is "contains the entire length of a single thick filament." This means that the A band, which is a region in a sarcomere, includes the full length of a thick filament. The A band is made up of both thick and thin filaments, but only the thick filament runs the entire length of the A band. The I band, on the other hand, consists only of thin filaments.

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11.

Myosin binding sites on actin are blocked by Troponin
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
Myosin binding sites on actin are blocked by Tropomyosin.

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12.

Calcium binding motif present in calmodulin is known as
- A.
  
  Rossman fold
- B.
  
  EF hand
- C.
  
  Zinc finger
- D.
  
  Actin fold
Correct Answer
B. EF hand

Explanation
EF hand is a helix-loop-helix . E and F are the 2 helices oriented with an angle of 90 degree to each other. Loop binds to calcium.

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13.

Calcium binding results in a conformational change in troponin complex that pulls tropomyosin from the actin binding sites of myosin.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
The statement is false because calcium binding actually causes a conformational change in troponin complex that exposes the actin binding sites of myosin, allowing for muscle contraction to occur.

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14.

Kinesin is involved in retrograde trasport. Dynein is involved in anterograde transport.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
It is the vice versa.

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15.

Flagella is not found in humans.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
Spermatocyte is the only flagellated cells in humans.

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16.

Length of actin and myosin doesn't change during muscle contraction
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
During muscle contraction, the length of actin and myosin filaments does not change. Instead, the filaments slide past each other, resulting in the shortening of the sarcomere, which is the functional unit of a muscle. This sliding filament theory explains that the actin and myosin filaments overlap more, causing the muscle to contract. Therefore, the statement that the length of actin and myosin doesn't change during muscle contraction is true.

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17.

Troponin C binds to
- A.
  
  2 calcium
- B.
  
  3 calcium
- C.
  
  4 calcium
- D.
  
  5 calcium
Correct Answer
C. 4 calcium

Explanation
EGF hand binds to 4 calcium

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18.

Malignant hyperthermia is due to mutation of
- A.
  
  RYR1
- B.
  
  ATPase 7A
- C.
  
  ATPase 7B
- D.
  
  None
Correct Answer
A. RYR1

Explanation
Ryanodine receptor calcium release channel mutations are the common one. Other mutations are also involved.

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Current Version
Mar 21, 2023

Quiz Edited by
ProProfs Editorial Team
Jan 07, 2015

Quiz Created by
Kar

Cytoskeleton And Muscle Biochemistry

Which is a microfilament?

Which is NOT a molecular motor ?

Hutchinson-Gilford progeria syndrome is due to mutation of

Which component of cytoskeleton is defective in kartageners syndrome ?

Griseofulvin is a tubulin inhibitor

Which component of cytoskeleton is defective in epidermolysis bullosa ?

Microfilaments are dynamic structures which undergo rapid assembly and disassembly.

TRUE about positive end of actin filament

Sarcomere is a segment between

TRUE about A band

Myosin binding sites on actin are blocked by Troponin

Calcium binding motif present in calmodulin is known as

Calcium binding results in a conformational change in troponin complex that pulls tropomyosin from the actin binding sites of myosin.

Kinesin is involved in retrograde trasport. Dynein is involved in anterograde transport.

Flagella is not found in humans.

Length of actin and myosin doesn't change during muscle contraction

Troponin C binds to

Malignant hyperthermia is due to mutation of