Question 1

Which of the following is NOT correct regarding the bands observed by electron microscopy of myofibrils?

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. 
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. A

Question 2

Which of the following features is a similarity between Rep helicase of E.coli and kinesin?

Accepted Answer

A) the capacity to move organelles 
B) ring-like structures that encircle the substrate 
C) 2 subunits,1 of which is always bound to the polymer at any moment 
D) tubulin binding heads that hydrolyze ATP 
A) the capacity to move organelles 
B) ring-like structures that encircle the substrate 
C) 2 subunits,1 of which is always bound to the polymer at any moment 
D) tubulin binding heads that hydrolyze ATP C

Question 3

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

Accepted Answer

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

Question 4

From which structure are microtubules formed?

Accepted Answer

A) myosin 
B) phospholipid 
C) membrane 
D) tubulin 
A) myosin 
B) phospholipid 
C) membrane 
D) tubulin

Question 5

Which of the following occurs during muscle contraction?

Accepted Answer

A) ATP is hydrolyzed. 
B) The length of the thick filament is reduced. 
C) The contraction produces an increased overlap of the actin and myosin filaments of the A band. 
D) The length of the thin filaments remains constant. 
A) ATP is hydrolyzed. 
B) The length of the thick filament is reduced. 
C) The contraction produces an increased overlap of the actin and myosin filaments of the A band. 
D) The length of the thin filaments remains constant.

Question 6

Which structural component houses a high concentration of Ca²⁺ and releases it to trigger muscle contraction?

Accepted Answer

A) sarcoplasmic reticulum 
B) sarcomere 
C) t-tubule 
D) sarcolemma 
A) sarcoplasmic reticulum 
B) sarcomere 
C) t-tubule 
D) sarcolemma

Question 7

Which protein component in the troponin complex shows 70% homology to calmodulin and is involved in Ca²⁺ binding?

Accepted Answer

A) TnT 
B) TnC 
C) TnI 
D) TnA 
A) TnT 
B) TnC 
C) TnI 
D) TnA

Question 8

What is the power stroke in muscle contraction associated with?

Accepted Answer

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

Question 9

Which of the following is NOT a part of the reaction sequence for the involvement of free actin,free myosin,and ATPase activity on each other?

Accepted Answer

A) Actin binds and activates ATPase activity by stimulating the formation of Camp. 
B) In the absence of actin,the addition of ATP to myosin produces a rapid release of H⁺. 
C) New ATP is bound to the actomyosin complex. 
D) Actomyosin dissociates into actin and myosin. 
A) Actin binds and activates ATPase activity by stimulating the formation of Camp. 
B) In the absence of actin,the addition of ATP to myosin produces a rapid release of H⁺. 
C) New ATP is bound to the actomyosin complex. 
D) Actomyosin dissociates into actin and myosin.

Question 10

Kinesins are proteins that exhibit ATPase activity.What are they involved with?

Accepted Answer

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

Question 11

Which of the following is NOT a function of microtubules?

Accepted Answer

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

Question 12

Which of these changes stimulates muscle contraction?

Accepted Answer

A) an increase in [Ca²⁺] in the vicinity of the muscle fibres 
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 
A) an increase in [Ca²⁺] in the vicinity of the muscle fibres 
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

Question 13

Which of the following is NOT a characteristic of molecular motors or motor proteins?

Accepted Answer

A) They must be able to associate irreversibly with a polymeric protein array,a surface,or substructure in the cell. 
B) They use chemical energy (e.g.,ATP)to orchestrate movement. 
C) They transfer ATP energy into mechanical energy. 
D) ATP hydrolysis is presumed to drive and control protein conformational changes that result in sliding or walking movement of one molecule relative to another. 
A) They must be able to associate irreversibly with a polymeric protein array,a surface,or substructure in the cell. 
B) They use chemical energy (e.g.,ATP)to orchestrate movement. 
C) They transfer ATP energy into mechanical energy. 
D) ATP hydrolysis is presumed to drive and control protein conformational changes that result in sliding or walking movement of one molecule relative to another.

Question 14

Which component(s)of the 6 polypeptides that make up the thick filament contain(s)the ATPase activity?

Accepted Answer

A) LC1 
B) LC2 
C) myosin heavy chains 
D) essential light chains 
A) LC1 
B) LC2 
C) myosin heavy chains 
D) essential light chains

Question 15

Which of the following is NOT a characteristic exhibited by troponin C (TnC)?

Accepted Answer

A) TnC has 2 binding sites that are always complexed to Ca²⁺. 
B) A conformational change in TnC occurs on Ca²⁺ binding. 
C) Ca²⁺ binding to TnC decreases interaction between TnI and actin. 
D) TnC has 4 equivalent Ca²⁺ binding sites 
A) TnC has 2 binding sites that are always complexed to Ca²⁺. 
B) A conformational change in TnC occurs on Ca²⁺ binding. 
C) Ca²⁺ binding to TnC decreases interaction between TnI and actin. 
D) TnC has 4 equivalent Ca²⁺ binding sites

Question 16

Which of these actions is treadmilling,as carried out by microtubules?

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 
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

Question 17

Which of the following troponin subunits is responsible for inhibiting actin-myosin binding?

Accepted Answer

A) troponin C 
B) troponin M 
C) troponin G 
D) troponin I 
A) troponin C 
B) troponin M 
C) troponin G 
D) troponin I

Question 18

Which of the following is NOT a characteristic of microtubules?

Accepted Answer

A) They are made up of 2 repeating subunits. 
B) They grow at one end and are degraded at the other end. 
C) They are static,helical structures. 
D) They are hollow,cylindrical structures. 
A) They are made up of 2 repeating subunits. 
B) They grow at one end and are degraded at the other end. 
C) They are static,helical structures. 
D) They are hollow,cylindrical structures.

Question 19

In E.coli,which action powers the rotation of the flagella?

Accepted Answer

A) the hydrolysis of GTP by the flagella 
B) phosphorylation of the motB protein by phosphoenolpyruvate 
C) the hydrolysis of ATP by the motB protein 
D) a proton gradient across the plasma membrane of the bacterium 
A) the hydrolysis of GTP by the flagella 
B) phosphorylation of the motB protein by phosphoenolpyruvate 
C) the hydrolysis of ATP by the motB protein 
D) a proton gradient across the plasma membrane of the bacterium

Question 20

In the b-sheet of the -α-β-α-segment of myosin,a particular sequence likely binds ATP and is found in other nucleotide-binding proteins.Which of the following represents that sequence?

Accepted Answer

A) Cys-X-X-Cys-X-His 
B) Arg-X-X-His-X-Gly 
C) Gly-X-X-Gly-X-Gly 
D) Lys-X-Gly-X-X-Ser 
A) Cys-X-X-Cys-X-His 
B) Arg-X-X-His-X-Gly 
C) Gly-X-X-Gly-X-Gly 
D) Lys-X-Gly-X-X-Ser

Exam 15: Molecular Motors

Which of the following is NOT correct regarding the bands observed by electron microscopy of myofibrils?

Which of the following features is a similarity between Rep helicase of E.coli and kinesin?

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

From which structure are microtubules formed?

Which of the following occurs during muscle contraction?

Which structural component houses a high concentration of Ca²⁺ and releases it to trigger muscle contraction?

Which protein component in the troponin complex shows 70% homology to calmodulin and is involved in Ca²⁺ binding?

What is the power stroke in muscle contraction associated with?

Which of the following is NOT a part of the reaction sequence for the involvement of free actin,free myosin,and ATPase activity on each other?

Kinesins are proteins that exhibit ATPase activity.What are they involved with?

Which of the following is NOT a function of microtubules?

Which of these changes stimulates muscle contraction?

Which of the following is NOT a characteristic of molecular motors or motor proteins?

Which component(s)of the 6 polypeptides that make up the thick filament contain(s)the ATPase activity?

Which of the following is NOT a characteristic exhibited by troponin C (TnC)?

Which of these actions is treadmilling,as carried out by microtubules?

Which of the following troponin subunits is responsible for inhibiting actin-myosin binding?

Which of the following is NOT a characteristic of microtubules?

In E.coli,which action powers the rotation of the flagella?

In the b-sheet of the -α-β-α-segment of myosin,a particular sequence likely binds ATP and is found in other nucleotide-binding proteins.Which of the following represents that sequence?

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

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Nutrition and the Organization of Metabolism

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

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

Metabolic Integration and Organ Specialization

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