Question 1

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

Accepted Answer

Bisphosphoglycerate (BPG), also known as 2,3-bisphosphoglycerate or 2,3-BPG, is a molecule that plays a crucial role in the regulation of oxygen binding to hemoglobin, the protein responsible for transporting oxygen in the blood. Hemoglobin can exist in two states: a high-affinity state (R state) where it binds oxygen tightly, and a low-affinity state (T state) where it releases oxygen more readily. The binding of BPG to hemoglobin decreases its affinity for oxygen, promoting oxygen release in tissues that need it.

Here's how BPG affects hemoglobin's oxygen affinity:

1. **Binding Site**: BPG binds to the central cavity between the beta subunits of hemoglobin in its T state. This cavity is present only when the hemoglobin is in the T state, which is the deoxygenated form.

2. **Stabilization of T State**: The binding of BPG stabilizes the T state of hemoglobin. BPG is negatively charged and forms salt bridges with positively charged amino acids in the hemoglobin beta subunits. This interaction locks hemoglobin in the T state, making it harder for oxygen to bind.

3. **Allosteric Effect**: Hemoglobin is an allosteric protein, meaning that the binding of a molecule at one site can affect the binding properties at another site. When BPG binds to hemoglobin, it induces a conformational change that reduces the affinity of the oxygen-binding sites on the hemoglobin molecule.

4. **Release of Oxygen**: By stabilizing the T state, BPG facilitates the release of oxygen from hemoglobin to the tissues. This is particularly important under conditions where tissues require more oxygen, such as during exercise or at high altitudes.

5. **Physiological Adaptation**: The concentration of BPG in the blood can change under different physiological conditions. For example, at high altitudes, the body produces more BPG to enhance the release of oxygen from hemoglobin to compensate for the lower oxygen availability.

In summary, BPG binding to hemoglobin decreases its affinity for oxygen by stabilizing the T state of the protein, which promotes the release of oxygen to the tissues where it is needed. This is a finely tuned regulatory mechanism that allows the body to adapt to varying oxygen demands and environmental conditions.

Question 2

Tropomyosin and troponin prevent muscle contractions in the absence of Ca2+ because they:

Accepted Answer

A)  block the myosin head binding sites on actin filaments. 
B)  prevent the hydrolysis of ATP by myosin. 
C)  degrade the actin filaments. 
D)  increase the release of Pi by myosin. 
E)  block the "power stroke" conformational change of actin filaments. 
A)  block the myosin head binding sites on actin filaments. 
B)  prevent the hydrolysis of ATP by myosin. 
C)  degrade the actin filaments. 
D)  increase the release of Pi by myosin. 
E)  block the "power stroke" conformational change of actin filaments. A

Question 3

If myosin head groups were unable to hydrolyze ATP due to an alteration in the protein structure but could still bind and release ADP and inorganic phosphate (Pi), which step in the actin-myosin cycle would NOT take place?

Accepted Answer

A)  dissociation of the myosin head group from the actin filament 
B)  repositioning of the myosin head group on the actin filament 
C)  attachment of the myosin head group to the actin filament 
D)  the "power stroke" conformational change in the myosin head group 
E)  the conformational change in the myosin head group in the presence of Ca2+ 
A)  dissociation of the myosin head group from the actin filament 
B)  repositioning of the myosin head group on the actin filament 
C)  attachment of the myosin head group to the actin filament 
D)  the "power stroke" conformational change in the myosin head group 
E)  the conformational change in the myosin head group in the presence of Ca2+ B

Question 4

Myosin moves relative to actin filaments by using energy derived from the hydrolysis of which molecule?

Accepted Answer

A)  GTP 
B)  ATP 
C)  NADH 
D)  coenzyme A 
E)  ADP 
A)  GTP 
B)  ATP 
C)  NADH 
D)  coenzyme A 
E)  ADP

Question 5

Patients with chronic hypoxia (low O2 levels) due to decreased lung function may adapt by increasing their circulating BPG levels. Predict which outcome will be TRUE for such a patient.

Accepted Answer

A)  p50 for O2 will be decreased. 
B)  p50 for O2 will be increased. 
C)  The R-state of hemoglobin will be favored. 
D)  O2 binding to hemoglobin will be hyperbolic. 
E)  None of the answers is correct. 
A)  p50 for O2 will be decreased. 
B)  p50 for O2 will be increased. 
C)  The R-state of hemoglobin will be favored. 
D)  O2 binding to hemoglobin will be hyperbolic. 
E)  None of the answers is correct.

Question 6

What is the concept of "induced fit" as it applies to antigen-antibody binding?

Accepted Answer

The concept of "induced fit" as it appli

Question 7

A prosthetic group of a protein is a nonprotein structure that is:

Accepted Answer

A)  a ligand of the protein. 
B)  a part of the secondary structure of the protein. 
C)  a substrate of the protein. 
D)  permanently associated with the protein. 
E)  transiently bound to the protein. 
A)  a ligand of the protein. 
B)  a part of the secondary structure of the protein. 
C)  a substrate of the protein. 
D)  permanently associated with the protein. 
E)  transiently bound to the protein.

Question 8

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.

Accepted Answer

A)  a and c 
B)  a and d 
C)  b and c 
D)  b and d 
E)  None of the statements is correct. 
A)  a and c 
B)  a and d 
C)  b and c 
D)  b and d 
E)  None of the statements is correct.

Question 9

You want to purify a specific soluble protein from a solution of lysed cells so that you can conduct biochemical tests of the protein's function. To best achieve this, which type of antibody would be MOST effective to use in your affinity purification?

Accepted Answer

A)  monoclonal IgE 
B)  polyclonal IgE 
C)  monoclonal IgG 
D)  polyclonal IgG 
E)  monoclonal IgM 
A)  monoclonal IgE 
B)  polyclonal IgE 
C)  monoclonal IgG 
D)  polyclonal IgG 
E)  monoclonal IgM

Question 10

Which type of antibody interacts with basophils and plays a role in the allergic response?

Accepted Answer

A)  IgA 
B)  IgD 
C)  IgE 
D)  IgG 
E)  IgM 
A)  IgA 
B)  IgD 
C)  IgE 
D)  IgG 
E)  IgM

Question 11

In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:

Accepted Answer

A)  hyperbolic. 
B)  linear with a negative slope. 
C)  linear with a positive slope. 
D)  random. 
E)  sigmoidal. 
A)  hyperbolic. 
B)  linear with a negative slope. 
C)  linear with a positive slope. 
D)  random. 
E)  sigmoidal.

Question 12

Explain why the structure of myoglobin makes it function well as an oxygen-storage protein, whereas the structure of hemoglobin makes it function well as an oxygen-transport protein.

Accepted Answer

Myoglobin and hemoglobin are both protei

Question 13

A significant contribution to the change in hemoglobin affinity for oxygen from pH 7.2 to pH 7.6 is due to a change in the protonation state of which amino acid side chain?

Accepted Answer

A)  Cys 
B)  His 
C)  Ser 
D)  Asp 
E)  Lys 
A)  Cys 
B)  His 
C)  Ser 
D)  Asp 
E)  Lys

Question 14

A person who is HIV-positive asks you why they have reduced immune system function. You tell them that the most likely reason is due to a deficiency of which cells that are targets of HIV viral infections?

Accepted Answer

A)  B cells 
B)  neutrophils 
C)  cytotoxic T cells 
D)  helper T cells 
E)  erythrocytes 
A)  B cells 
B)  neutrophils 
C)  cytotoxic T cells 
D)  helper T cells 
E)  erythrocytes

Question 15

You are attempting to crystallize the head group of a myosin-like muscle protein from a newly discovered vertebrate organism. Assuming that the protein structure is similar to other vertebrate myosins, which enzymes should you use to remove the myosin-like head group from the rest of the myosin-like protein?

Accepted Answer

A)  trypsin 
B)  myosinase 
C)  papain 
D)  both trypsin and myosinase 
E)  both trypsin and papain 
A)  trypsin 
B)  myosinase 
C)  papain 
D)  both trypsin and myosinase 
E)  both trypsin and papain

Question 16

CO binds more strongly to the heme iron than O2 does due to which reason?

Accepted Answer

A)  CO binds to the heme iron perpendicular to the porphyrin ring, allowing maximum electron orbital overlap between CO and Fe2+. 
B)  CO weighs less than O2, therefore binding to the heme iron more easily. 
C)  CO binds to the heme iron covalently, while O2 binds via ionic interactions. 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  CO binds to the heme iron perpendicular to the porphyrin ring, allowing maximum electron orbital overlap between CO and Fe2+. 
B)  CO weighs less than O2, therefore binding to the heme iron more easily. 
C)  CO binds to the heme iron covalently, while O2 binds via ionic interactions. 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 17

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

Accepted Answer

To find the fraction of ligand binding s

Question 18

Conversion of CO2 in the blood into the more soluble form of HCO3- is catalyzed by which enzyme?

Accepted Answer

A)  hemoglobinase 
B)  carbonic anhydrase 
C)  bicarbonase 
D)  carbondioxidease 
E)  carbon hydratase 
A)  hemoglobinase 
B)  carbonic anhydrase 
C)  bicarbonase 
D)  carbondioxidease 
E)  carbon hydratase

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

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

Accepted Answer

G-actin (globular actin) and F-actin (fi

Exam 5: Protein Function

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

Tropomyosin and troponin prevent muscle contractions in the absence of Ca2+ because they:

If myosin head groups were unable to hydrolyze ATP due to an alteration in the protein structure but could still bind and release ADP and inorganic phosphate (Pi), which step in the actin-myosin cycle would NOT take place?

Myosin moves relative to actin filaments by using energy derived from the hydrolysis of which molecule?

Patients with chronic hypoxia (low O2 levels) due to decreased lung function may adapt by increasing their circulating BPG levels. Predict which outcome will be TRUE for such a patient.

What is the concept of "induced fit" as it applies to antigen-antibody binding?

A prosthetic group of a protein is a nonprotein structure that is:

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.

You want to purify a specific soluble protein from a solution of lysed cells so that you can conduct biochemical tests of the protein's function. To best achieve this, which type of antibody would be MOST effective to use in your affinity purification?

Which type of antibody interacts with basophils and plays a role in the allergic response?

In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:

Explain why the structure of myoglobin makes it function well as an oxygen-storage protein, whereas the structure of hemoglobin makes it function well as an oxygen-transport protein.

A significant contribution to the change in hemoglobin affinity for oxygen from pH 7.2 to pH 7.6 is due to a change in the protonation state of which amino acid side chain?

A person who is HIV-positive asks you why they have reduced immune system function. You tell them that the most likely reason is due to a deficiency of which cells that are targets of HIV viral infections?

CO binds more strongly to the heme iron than O2 does due to which reason?

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

Conversion of CO2 in the blood into the more soluble form of HCO3- is catalyzed by which enzyme?

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

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

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

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

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

Tropomyosin and troponin prevent muscle contractions in the absence of Ca²⁺ because they:

If myosin head groups were unable to hydrolyze ATP due to an alteration in the protein structure but could still bind and release ADP and inorganic phosphate (P_i), which step in the actin-myosin cycle would NOT take place?

Patients with chronic hypoxia (low O₂ levels) due to decreased lung function may adapt by increasing their circulating BPG levels. Predict which outcome will be TRUE for such a patient.

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.

CO binds more strongly to the heme iron than O₂ does due to which reason?

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

Conversion of CO₂ in the blood into the more soluble form of HCO₃^- is catalyzed by which enzyme?

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