Question 1

Rep helicase of E. coli and kinesin are alike in that they both have:

Accepted Answer

A)  binding sites for the DNA lattice. 
B)  ring-like structures that encircle the substrate. 
C)  two subunits, one of which is always bound to the polymer at any moment. 
D)  tubulin binding heads that hydrolyze ATP. 
E)  the capacity to move organelles. 
A)  binding sites for the DNA lattice. 
B)  ring-like structures that encircle the substrate. 
C)  two subunits, one of which is always bound to the polymer at any moment. 
D)  tubulin binding heads that hydrolyze ATP. 
E)  the capacity to move organelles.

Question 2

Which of the following muscle protein components is responsible for ATP hydrolysis?

Accepted Answer

A)  tropomyosin 
B)  myosin 
C)  troponin C 
D)  actin 
E)  troponin M 
A)  tropomyosin 
B)  myosin 
C)  troponin C 
D)  actin 
E)  troponin M

Question 3

Discuss the structure of flagellar rotors and the gradients that power them.​

Accepted Answer

Gradients of protons and Na⁺ ions exist a

Question 4

All of the statements about the bands observed by electron microscopy of myofibrils are true EXCEPT:

Accepted Answer

A)  I bands show a hexagonal array of thick filaments. 
B)  thin filaments are composed mainly of actin, troponin, and tropomyosin. 
C)  H zones contain an array of thick filaments that are composed mainly of myosin. 
D)  thick filaments are joined by cross-bridges. 
E)  Z lines lie in the middle of the I bands, marking the ends of the sarcomere. 
A)  I bands show a hexagonal array of thick filaments. 
B)  thin filaments are composed mainly of actin, troponin, and tropomyosin. 
C)  H zones contain an array of thick filaments that are composed mainly of myosin. 
D)  thick filaments are joined by cross-bridges. 
E)  Z lines lie in the middle of the I bands, marking the ends of the sarcomere.

Question 5

Negative cooperativity of Rep helicase from E. coli means that:

Accepted Answer

A)  when one subunit binds DNA, the other releases from the DNA. 
B)  when both subunits are bound to DNA, ATP hydrolysis promotes release of both subunits. 
C)  ATP hydrolysis promotes DNA binding of both subunits simultaneously. 
D)  once it binds ssDNA, binding dsDNA is prohibited. 
E)  none of the above. 
A)  when one subunit binds DNA, the other releases from the DNA. 
B)  when both subunits are bound to DNA, ATP hydrolysis promotes release of both subunits. 
C)  ATP hydrolysis promotes DNA binding of both subunits simultaneously. 
D)  once it binds ssDNA, binding dsDNA is prohibited. 
E)  none of the above.

Question 6

Muscle contraction is stimulated by:

Accepted Answer

A)  an increase in [Ca2+] in the vicinity of the muscle fibers. 
B)  a decrease in the [Ca2+] in the mitochondria. 
C)  an increase in [Ca2+] in the sarcolemma. 
D)  a decrease in the [Ca2+] in the Golgi. 
E)  an increase in [Ca2+] in the sarcoplasmic reticulum. 
A)  an increase in [Ca2+] in the vicinity of the muscle fibers. 
B)  a decrease in the [Ca2+] in the mitochondria. 
C)  an increase in [Ca2+] in the sarcolemma. 
D)  a decrease in the [Ca2+] in the Golgi. 
E)  an increase in [Ca2+] in the sarcoplasmic reticulum.

Question 7

The power stroke in muscle contraction is associated with:

Accepted Answer

A)  the binding of ATP to ATPase. 
B)  the dissociation of ADP and Pi from the ATPase. 
C)  binding of myosin to actin. 
D)  addition of water for ATP hydrolysis. 
E)  the hydrolysis of ATP. 
A)  the binding of ATP to ATPase. 
B)  the dissociation of ADP and Pi from the ATPase. 
C)  binding of myosin to actin. 
D)  addition of water for ATP hydrolysis. 
E)  the hydrolysis of ATP.

Question 8

Kinesins are proteins that exhibit ATPase activity and are involved with:

Accepted Answer

A)  movement of flagella. 
B)  movement of cilia. 
C)  movement of muscles. 
D)  intracellular movement of organelles and vesicles from the minus end to plus end of microtubules. 
E)  A-tubule and B-tubule movement within an axoneme. 
A)  movement of flagella. 
B)  movement of cilia. 
C)  movement of muscles. 
D)  intracellular movement of organelles and vesicles from the minus end to plus end of microtubules. 
E)  A-tubule and B-tubule movement within an axoneme.

Question 9

Troponin C (TnC) exhibits all of the following characteristics EXCEPT:

Accepted Answer

A)  TnC has two binding sites that are always complexed to Ca2+. 
B)  the Ca2+ binding increases the interaction of TnC and TnI. 
C)  TnC has four equivalent Ca2+ binding sites. 
D)  Ca2+ binding to TnC decreases interaction between TnI and actin. 
E)  a conformational change in TnC occurs on Ca2+ binding. 
A)  TnC has two binding sites that are always complexed to Ca2+. 
B)  the Ca2+ binding increases the interaction of TnC and TnI. 
C)  TnC has four equivalent Ca2+ binding sites. 
D)  Ca2+ binding to TnC decreases interaction between TnI and actin. 
E)  a conformational change in TnC occurs on Ca2+ binding.

Question 10

If the non-hydrolyzable ATP analog β,γ-methylene-ATP were given to muscle cells, where would inhibition occur?

Accepted Answer

A)  during formation of the cross bridge between actin and myosin when Pi is released 
B)  during the conformational change in the myosin head that moves actin and myosin relative to each other 
C)  during the ATP binding step where actin and myosin dissociate 
D)  during the conformational change in the myosin head when ATP hydrolysis occurs 
E)  at steps c and d above 
A)  during formation of the cross bridge between actin and myosin when Pi is released 
B)  during the conformational change in the myosin head that moves actin and myosin relative to each other 
C)  during the ATP binding step where actin and myosin dissociate 
D)  during the conformational change in the myosin head when ATP hydrolysis occurs 
E)  at steps c and d above

Question 11

All are functions of microtubules EXCEPT:

Accepted Answer

A)  providing variations and maintenance of cell shape. 
B)  formation of the mitotic spindle during cell division. 
C)  unwinding DNA to single-stranded DNA (ssDN
A) . 
D)  movement of organelles. 
E)  forming intracellular scaffolds. 
A)  providing variations and maintenance of cell shape. 
B)  formation of the mitotic spindle during cell division. 
C)  unwinding DNA to single-stranded DNA (ssDN
A) . 
D)  movement of organelles. 
E)  forming intracellular scaffolds.

Question 12

The component that houses a high concentration of Ca2+ and releases it to trigger muscle contraction is:

Accepted Answer

A)  sarcoplasmic reticulum. 
B)  sarcomere. 
C)  t-tubules. 
D)  sarcolemma. 
E)  troponin. 
A)  sarcoplasmic reticulum. 
B)  sarcomere. 
C)  t-tubules. 
D)  sarcolemma. 
E)  troponin.

Question 13

Which of the following is the first event following ATP binding in the movement of actin and myosin?

Accepted Answer

A)  binding of actin and myosin 
B)  the power stroke 
C)  dissociation of actin and myosin 
D)  the up-lever state 
E)  the down-lever state 
A)  binding of actin and myosin 
B)  the power stroke 
C)  dissociation of actin and myosin 
D)  the up-lever state 
E)  the down-lever state

Question 14

Which of the following loops are present in the myosin head to give rise to the ATP-binding site?

Accepted Answer

A)  switch 1 
B)  switch 2 
C)  relay helix 
D)  converter domain 
E)  both A and B are correct 
A)  switch 1 
B)  switch 2 
C)  relay helix 
D)  converter domain 
E)  both A and B are correct

Question 15

Treadmilling as carried out by microtubules means:

Accepted Answer

A)  ATP-hydrolysis-dependent movement over a plane. 
B)  ATP-dependent addition of dimmers to the plus end. 
C)  GTP-hydrolysis-dependent movement of α-tubulin over β-tubulin. 
D)  GTP-dependent addition to the plus end and removal at the minus end. 
E)  ATP-dependent "walking" along a surface in one place. 
A)  ATP-hydrolysis-dependent movement over a plane. 
B)  ATP-dependent addition of dimmers to the plus end. 
C)  GTP-hydrolysis-dependent movement of α-tubulin over β-tubulin. 
D)  GTP-dependent addition to the plus end and removal at the minus end. 
E)  ATP-dependent "walking" along a surface in one place.

Exam 16: Molecular Motors

Rep helicase of E. coli and kinesin are alike in that they both have:

Which of the following muscle protein components is responsible for ATP hydrolysis?

Discuss the structure of flagellar rotors and the gradients that power them.​

All of the statements about the bands observed by electron microscopy of myofibrils are true EXCEPT:

Negative cooperativity of Rep helicase from E. coli means that:

Muscle contraction is stimulated by:

The power stroke in muscle contraction is associated with:

Kinesins are proteins that exhibit ATPase activity and are involved with:

Troponin C (TnC) exhibits all of the following characteristics EXCEPT:

If the non-hydrolyzable ATP analog β,γ-methylene-ATP were given to muscle cells, where would inhibition occur?

All are functions of microtubules EXCEPT:

The component that houses a high concentration of Ca2+ and releases it to trigger muscle contraction is:

Which of the following is the first event following ATP binding in the movement of actin and myosin?

Which of the following loops are present in the myosin head to give rise to the ATP-binding site?

Treadmilling as carried out by microtubules means:

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids and the Peptide Bond

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, Tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Membranes and Membrane Transport

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Recombinant Dna, Cloning, Chimeric Genes, and Synthetic Biology

Enzymeskinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Metabolism: an Overview

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Lipid Biosynthesis

Nitrogen Acquisition and Amino Acid Metabolism

Synthesis and Degradation of Nucleotides

Metabolic Integration and Organ Specialization

Dna Metabolism: Replication, Recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Completing the Protein Life Cycle: Folding, Processing, and Degradation

The Reception and Transmission of Extracellular Information

Filters

Discuss the structure of flagellar rotors and the gradients that power them.

The component that houses a high concentration of Ca²⁺ and releases it to trigger muscle contraction is: