Question 1

Describe the cycle of actin-myosin association and disassociation that leads to muscle contraction.

Accepted Answer

First,ATP binds to myosin and a cleft in the myosin molecule opens,disrupting the actin-myosin interaction so that the bound actin is released.Second,ATP is hydrolyzed,causing a conformational change in the protein to a "high-energy" state that moves the myosin head and changes its orientation in relation to the actin thin filament.Myosin then binds weakly to an F-actin subunit closer to the Z disk than the one just released.Third,as the phosphate product of ATP hydrolysis is released from myosin,another conformational change occurs in which the myosin cleft closes,strengthening the myosin-actin binding.Fourth,this is followed quickly by a "power stroke" during which the conformation of the myosin head returns to the original resting state,its orientation relative to the bound actin changing so as to pull the tail of the myosin toward the Z disk.ADP is then released to complete the cycle.

Question 2

For the binding of a ligand to a protein,what is the relationship between the Ka (association constant),the Kd (dissociation constant),and the affinity of the protein for the ligand?

Accepted Answer

K_a = 1/K_d.The larger the K_a (and hence the smaller the K_d),the higher the affinity of the protein for the ligand.

Question 3

How does BPG binding to hemoglobin decrease its affinity for oxygen?

Accepted Answer

BPG binds to a cavity between the $\beta$ subunits.It binds preferentially to molecules in the low-affinity T state,thereby stabilizing that conformation.

Question 4

The fundamental cause of sickle-cell disease is a change in the structure of:

Accepted Answer

A) blood. 
B) capillaries. 
C) hemoglobin. 
D) red cells. 
E) the heart. 
A) blood. 
B) capillaries. 
C) hemoglobin. 
D) red cells. 
E) the heart.

Question 5

During muscle contraction,hydrolysis of ATP results in a change in the:

Accepted Answer

A) conformation of actin. 
B) conformation of myosin. 
C) structure of the myofibrils. 
D) structure of the sarcoplasmic reticulum. 
E) structure of the Z disk. 
A) conformation of actin. 
B) conformation of myosin. 
C) structure of the myofibrils. 
D) structure of the sarcoplasmic reticulum. 
E) structure of the Z disk.

Question 6

The energy that is released by the hydrolysis of ATP by actin is used for:

Accepted Answer

A) actin filament assembly. 
B) actin filament disassembly. 
C) actin-myosin assembly. 
D) actin-myosin disassembly. 
E) muscle contraction. 
A) actin filament assembly. 
B) actin filament disassembly. 
C) actin-myosin assembly. 
D) actin-myosin disassembly. 
E) muscle contraction.

Question 7

Describe briefly the two principal models for the cooperative binding of ligands to proteins with multiple binding sites.

Accepted Answer

In the concerted model,binding of a liga

Question 8

Why is carbon monoxide (CO)toxic to aerobic organisms?

Accepted Answer

It binds to heme with a higher

Question 9

A monoclonal antibody differs from a polyclonal antibody in that monoclonal antibodies:

Accepted Answer

A) are labeled with chemicals that can be visualized. 
B) are produced by cells from the same organism that produced the antigen. 
C) are synthesized by a population of identical,or "cloned," cells. 
D) are synthesized only in living organisms. 
E) have only a single polypeptide chain that can recognize an antigen. 
A) are labeled with chemicals that can be visualized. 
B) are produced by cells from the same organism that produced the antigen. 
C) are synthesized by a population of identical,or "cloned," cells. 
D) are synthesized only in living organisms. 
E) have only a single polypeptide chain that can recognize an antigen.

Question 10

(a)What is the effect of pH on the binding of oxygen to hemoglobin (the Bohr Effect)? 
(b)Briefly describe the mechanism of this effect.

Accepted Answer

(a)The affinity decreases with decreasin

Question 11

An allosteric interaction between a ligand and a protein is one in which:

Accepted Answer

A) binding of a molecule to a binding site affects binding of additional molecules to the same site. 
B) binding of a molecule to a binding site affects binding properties of another site on the protein. 
C) binding of the ligand to the protein is covalent. 
D) multiple molecules of the same ligand can bind to the same binding site. 
E) two different ligands can bind to the same binding site. 
A) binding of a molecule to a binding site affects binding of additional molecules to the same site. 
B) binding of a molecule to a binding site affects binding properties of another site on the protein. 
C) binding of the ligand to the protein is covalent. 
D) multiple molecules of the same ligand can bind to the same binding site. 
E) two different ligands can bind to the same binding site.

Question 12

Describe briefly the structure of myosin.

Accepted Answer

Myosin contains two copies of a large po

Question 13

What is the relationship between G-actin and F-actin?

Accepted Answer

G-actin is a monomeric protein

Question 14

Which of the following parts of the IgG molecule are not involved in binding to an antigen?

Accepted Answer

A) Fab 
B) Fc 
C) Heavy chain 
D) Light chain 
E) Variable domain 
A) Fab 
B) Fc 
C) Heavy chain 
D) Light chain 
E) Variable domain

Question 15

Which of the following generalizations concerning motor proteins is correct?

Accepted Answer

A) They convert chemical energy into kinetic energy. 
B) They convert chemical energy into potential energy. 
C) They convert kinetic energy into chemical energy. 
D) They convert kinetic energy into rotational energy. 
E) They convert potential energy into chemical energy. 
A) They convert chemical energy into kinetic energy. 
B) They convert chemical energy into potential energy. 
C) They convert kinetic energy into chemical energy. 
D) They convert kinetic energy into rotational energy. 
E) They convert potential energy into chemical energy.

Question 16

Neuroglobin is a member of the globin family found in neurons.It is a monomeric protein that helps protect the brain from hypoxia (low O2).Identify the correct statement(s)about neuroglobin below.
a-It binds O2 with a hyperbolic binding curve.
b-It binds O2 with a sigmoidal binding curve.
c-It binds O2 with higher affinity than hemoglobin.
d-It binds O2 with lower affinity than hemoglobin.

Accepted Answer

A) a and c 
B) a and d 
C) b and c 
D) b and d 
E) None of the above 
A) a and c 
B) a and d 
C) b and c 
D) b and d 
E) None of the above

Question 17

What properties of antibodies make them useful biochemical reagents? Describe one biochemical application of antibodies (with more than just the name of the technique).

Accepted Answer

The important properties are the high sp

Question 18

What fraction of ligand binding sites are occupied ($\theta$ )when [ligand] = Kd? Show your work.

Accepted Answer

The answer of What fraction of ligand binding sites are...

Question 19

When oxygen binds to a heme-containing protein,the two open coordination bonds of Fe2+ are occupied by:

Accepted Answer

A) one O atom and one amino acid atom. 
B) one O2 molecule and one amino acid atom. 
C) one O2 molecule and one heme atom. 
D) two O atoms. 
E) two O2 molecules. 
A) one O atom and one amino acid atom. 
B) one O2 molecule and one amino acid atom. 
C) one O2 molecule and one heme atom. 
D) two O atoms. 
E) two O2 molecules.

Question 20

Explain why most multicellular organisms use an iron-containing protein for oxygen binding rather than free Fe2+.Your answer should include an explanation of (a)the role of heme and (b)the role of the protein itself.

Accepted Answer

(a)Binding of free Fe²⁺ to oxygen would re

Exam 5: Protein Function

Describe the cycle of actin-myosin association and disassociation that leads to muscle contraction.

For the binding of a ligand to a protein,what is the relationship between the Ka (association constant),the Kd (dissociation constant),and the affinity of the protein for the ligand?

How does BPG binding to hemoglobin decrease its affinity for oxygen?

The fundamental cause of sickle-cell disease is a change in the structure of:

During muscle contraction,hydrolysis of ATP results in a change in the:

The energy that is released by the hydrolysis of ATP by actin is used for:

Describe briefly the two principal models for the cooperative binding of ligands to proteins with multiple binding sites.

Why is carbon monoxide (CO)toxic to aerobic organisms?

A monoclonal antibody differs from a polyclonal antibody in that monoclonal antibodies:

(a)What is the effect of pH on the binding of oxygen to hemoglobin (the Bohr Effect)? (b)Briefly describe the mechanism of this effect.

An allosteric interaction between a ligand and a protein is one in which:

Describe briefly the structure of myosin.

What is the relationship between G-actin and F-actin?

Which of the following parts of the IgG molecule are not involved in binding to an antigen?

Which of the following generalizations concerning motor proteins is correct?

What properties of antibodies make them useful biochemical reagents? Describe one biochemical application of antibodies (with more than just the name of the technique).

What fraction of ligand binding sites are occupied ( θ\thetaθ )when [ligand] = Kd? Show your work.

When oxygen binds to a heme-containing protein,the two open coordination bonds of Fe2+ are occupied by:

Explain why most multicellular organisms use an iron-containing protein for oxygen binding rather than free Fe2+.Your answer should include an explanation of (a)the role of heme and (b)the role of the protein itself.

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

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For the binding of a ligand to a protein,what is the relationship between the K_a (association constant),the K_d (dissociation constant),and the affinity of the protein for the ligand?

What fraction of ligand binding sites are occupied ( $\theta$ )when [ligand] = K_d? Show your work.

When oxygen binds to a heme-containing protein,the two open coordination bonds of Fe²⁺ are occupied by:

Explain why most multicellular organisms use an iron-containing protein for oxygen binding rather than free Fe²⁺.Your answer should include an explanation of (a)the role of heme and (b)the role of the protein itself.