Biochem HW 3 (CH 5)

Myoglobin is _____; hemoglobin is _____.

monomeric; tetrameric

The individual hemoglobin subunits and myoglobin share similar secondary structure but have rather different primary structure.

True

Which of the following fibers is correctly paired with the protein that forms the fiber?

 

all of the answers are correctly paired

The idea that binding of one molecule of oxygen to hemoglobin enhances further binding of oxygen to hemoglobin is called _____.

 

cooperativity

What is the most prevalent secondary structure observed in the proteins of intermediate filaments?

 

alpha helice

Which of the following statements about actin are true?

Both of them.

Which of the proteins below contain nucleotide (ATP, etc.)-binding sites?

Both actin and tubulin

Several oxygen dissociation curves are shown in the figure below.  Assuming that curve 3 corresponds to isolated hemoglobin placed in a solution containing physiologic concentrations of CO₂ and BPG at a pH of 7.0, indicate which of the curves reflects the following changes in conditions:

Terms:

Increased BPG concentration

Increased pH

Dissociation of hemoglobin into subunits.

Answer choices:

1,2,3,4

Increased BPG concentration: 4 Increased pH: 2 Dissociation of hemoglobin into subunits: 1

Match the feature of hemoglobin with the proper structural level.

Terms:

Amino acid sequence in each of the alpha and beta polypeptide chains:

8 alpha helices in each of the subunits:

Interaction of all of the side chains of all of the amino acids in each subunit:

Structure that describes the interactions between the 2 alpha and 2 beta polypeptide chains:

Definitions:

Primary Structure

Secondary Structure

Tertiary Structure

Quaternary Structure

Amino acid sequence in each of the alpha and beta polypeptide chains: Primary Structure

8 alpha helices in each of the subunits: Secondary Structure

Interaction of all of the side chains of all of the amino acids in each subunit: Tertiary Structure

Structure that describes the interactions between the 2 alpha and 2 beta polypeptide chains: Quaternary Structure

The presence of 2,3-BPG causes hemoglobin's affinity for oxygen to______.

decrease

Which amino acid is involved in heme coordination in both hemoglobin and myoglobin and is highly conserved?

 

Histidine

T/F: Conservative amino acid mutations (i.e. Val to Leu) are likely to affect stability or function of a protein.

False

Which of the following increases the affinity of hemoglobin for O₂?

Both

 

Match the protein with the appropriate description.

Terms:

Actin

Tubulin

 Kertain

Collagen

Definitions:

Dimer that forms a coiled-coil

Dimer that polymerizes to form microtubules

Monomer that polymerizes to form a microfilament 

A right handed triple helix formed from 3 left-handed helical strands

Actin: Monomer that polymerizes to form a microfilament, Tubulin: Dimer that polymerizes to form microtubules, Kertain: Dimer that forms a coiled-coil, Collagen: A right handed triple helix formed from 3 left-handed helical strands

Calculate the fractional saturation of myoglobin when pO₂ = 75 torr.  Let K = 2.8 torr.  Enter the answer exactly as you calculate it (don't convert to a percentage.). 

0.9635

At what pO₂ value is myoglobin 25% saturated? Let K = 2.8 torr.

Your answer should be in torr. 

0.93

The Bohr effect refers to…

 

the decrease in affinity of Hb for O2 when the pH goes down.

Which of the following is an example of a conservative amino acid substitution?

 

Asp with Glu

Growth of actin filaments is dynamic and continuous under normal cellular conditions.

True

Tropocollagen is a double helix of two left-handed polypeptide chains.

False

Which amino acid is critical for crosslinking of keratin fibers? 

Cys

Which of the following is an example of a conservative amino acid substitution?

 

Asp with Glu

Based on what you know about fibrous protein structure and sequence, what type of fibrous protein is this sequence most likely from (You can assume that the protein is longer than what is shown and is repeating as shown.)?

 

            Gly – Pro – Pro – Lys-  Gly – Pro – Pro - Gly – Lys– Pro – Pro -  Gly – Pro – Pro

Collagen

The Bohr effect refers to…

 

the decrease in affinity of Hb for O2 when the pH goes down.

In the graph below, A is representative of a myoglobin oxygen binding curve and B is representative of a hemoglobin binding curve.

Ans 1: A

Ans 2: B