BIOCHEM Exam II Study Guide

During the formation of microfilaments, which of the following occurs?

ATP binds to F-actin

F-actin polymerizes, becoming G-actin

ATP hydrolysis is catalyzed by F-actin

polymerization proceeds quickly at first, then slows after about ten actin monomers have polymerized

none of the above

ATP hydrolysis is catalyzed by F-actin

How does CO₂ affect hemoglobin-oxygen binding?

CO₂ is converted to bicarbonate and H⁺ which promotes the deoxy state

When a cell moves along a surface, actin _____ occurs at the leading edge while _____ occurs at the trailing edge

polymerization;  depolymerization

Which of the following explains how cell division is blocked by drugs that prevent proper microtubule function?

the condensation of chromatin requires a microtubule skeleton

production of new membranes for organelles and nucleus requires microtubules

chromosomes separate along a microtubule spindle

division of organelles between daughter cells requires organelle movement along microtubules 

none of the above

chromosomes separate along a microtubule spindle

Which of the following explains the conversion of hemoglobin subunits from deoxy to oxy state?

all four subunits switch simultaneously

each subunit switches only upon oxygen binding to the particular subunit

both a subunits simultaneously switch first followed by both b subunits

both b subunits simultaneously switch first followed by both a subunits

none of the above

all four subunits switch simultaneously

Which of the following occurs in hemoglobin upon oxygen binding?

the heme Fe²⁺ is pulled out of the plane of the heme group

the His coordinated to the heme Fe²⁺ is pushed away from the heme group

the central cavity between the four subunits is decreased in size

hemoglobin changes from the R state to the T state

all of the above occur

the central cavity between the four subunits is decreased in size

A plot of the binding of oxygen to myoglobin as a function of pO2 gives a _____ shape;  a similar plot for hemoglobin gives a _____ shape.

hyperbolic;  sigmoidal

Hemoglobin S, the variant responsible for the misshapen red blood cells characteristic of the disease sickle-cell anemia, is potentially advantageous to heterozygotes because it confers some level of resistance to the disease _____.

malaria 

en oxygen is bound to the heme group of myoglobin, it is coordinated between _____ and _____.

E7 His; Fe²⁺ of heme

Proteins such as hemoglobin are known as _____ proteins since binding of a molecule to one site alter binding to other sites.

allosteric

Which of the following amino acids contains a side chain that is polar and uncharged from pH 1-13?

Phe

Tyr

Asp

Gln

Ile

Phe

A technique for determining protein structure where the protein is in solution is ___.

NMR spectroscopy

What level of protein structure is characterized by the amino acid sequence?

primary

A technique for determining protein structure that requires crystals of the protein is ___.

NMR spectroscopy

X-ray crystallography

electron crystallography

mass spectrometry

none of these choices

X-ray crystallography

What is the net charge of the pentapeptide Ala-Cys-Ser-Glu-Asn at pH 7?

-2

-3

0

+1

none of these choices

none of these choices

The predominant non-covalent interaction seen in a-helices and b-sheets is ___.

hydrogen bonds

Which of the following interactions would be involved in quaternary structure?

hydrogen bonds

hydrophobic interactions

disulfide bonds

salt bridges

all of these choices

all of these choices

At physiological pH, all amino acids have at least ___ charged groups.

2

Which amino acid does not have a primary a-amino group?

glutamine

arginine

lysine

proline

glutamate

proline

Which of the following is the most effective way to increase the rate of a biochemical reaction?

increase the temperature

increase the concentrations of the reactants

increase or decrease the pH

add a catalyst

none of the above

add a catalyst

The ability for an enzyme to pick out one particular substrate from the myriad of molecules floating around its environment is an example of _____.

 specificity

Different enzymes that catalyze the same reaction are known as _____.

isozymes

An organic molecule that is tightly bound to an enzyme and participates in an enzyme catalyzed reaction is specifically referred to as a _____.

prosthetic group

During the first half of the chymotrypsin mechanism where the acyl-enzyme intermediate is formed, what role does His play?

general base then general acid

An enzyme that forms a covalent bond with its substrate during the course of a reaction is considered to undergo _____.

covalent catalysis

The highest point in a reaction coordinate diagram represents _____.

the transition state

The enzyme hexokinase catalyzes a reaction where its substrates are completely sequestered from the aqueous environment allowing for interactions to occur between enzyme and substrates that would not normally occur in an aqueous environment.  What term describes this type of catalysis?

electrostatic catalysis

Of the following ions, which would be most likely to participate in metal ion catalysis?

Na⁺

Zn²⁺

Ag⁺

K⁺

Ba²⁺

Zn²⁺