Biochemistry

Biochemistry Practice Problems II

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Question 1

Increasing concentrations of either 2,3-bisphosphoglycerate (BPG) or protons (H+) cause a (rightward OR leftward) shift of the hemoglobin/oxygen binding curve. However, the mechanisms by which these two substances mediate this effect are distinct. Compare & contrast the way by which BPG and protons interact with hemoglobin and thereby influence its structure and function.

Question 2

Which of the following statements is true?  Select any/all answers that apply.

  • Both Mb and Hb bind O2 cooperatively.
  • Mb and Hb have similar affinities for BPG (2,3-bisphosphoglycerate).
  • Both Mb and Hb transport oxygen within the blood.
  • A single Mb molecule and a single Hb subunit have similar tertiary structures.
  • Both Mb and Hb contain multiple oxygen-binding sites.

Question 3

At a pO2 of ~100 torr, hemoglobin in whole blood is about 90% saturated with oxygen. This corresponds to ____ pressure, where the _____ of hemoglobin is favored.

  • venous; tense state
  • venous; relaxed state
  • arterial; tense state
  • arterial; relaxed state

Question 4

Consider a chemical reaction wherein the ΔGreactants is 27.5 kJ/mol and the ΔGproducts is 44.0 kJ/mol. Calculate ΔGrxn (show work and/or explain your answer). Would this reaction be spontaneous in the forward or reverse direction? Why?

Question 5

Questions #5-13 refer to the trisaccharide drawn below. All sugar residues are in their D-isomeric forms.

2

The first (left-most) monosaccharide residue is _____  (simply name the sugar).

Question 6

The second (middle) monosaccharide residue is ______  (simply name the sugar).

Question 7

The third (right-most) monosaccharide residue is ______ (simply name the sugar).

Question 8

The first sugar residue is a(n):  (select any/all answers that apply)

  • hexose.
  • pentose.
  • furanose.
  • pyranose.
  • aldehyde when drawn in its linear form.
  • ketone when drawn in its linear form

Question 9

The second sugar residue is an epimer of:

  • altrose at C2.
  • glucose at C3.
  • altrose at C4.
  • glucose at C4.
  • talose at C4.

 Question 10

As drawn, there are _____ chiral carbons in this trisaccharide.

Question 11

Which of the following best describes the glycosidic linkage between the first and second residues?

  • 5 <–> 4
  • 5 <–> α1
  • 2β<–> 4
  • 2α<–> 4
  • 2β<–> α1

Question 12

Which of the following best describes the glycosidic linkage between the second and third residues?

  • 1β <–> α2
  • 1β<–> β2
  • 1α<–> α2
  • 1α<–> β2
  • 1β<–> 5

Question 13

Is this trisaccharide a reducing sugar?

Question 14

α-linolenic acid has a lower melting point than ___________ because, although they have the same number of carbons, the former is an unsaturated fatty acid whereas the latter is a saturated fatty acid.

  • palmitic acid
  • stearic acid
  • oleic acid
  • linoleic acid
  • arachidonic acid

Question 15

Arachidic acid has a lower melting point than ___________ because the former has a shorter hydrocarbon chain than the latter.

  • lignoceric acid
  • stearic acid
  • palmitic acid
  • palmitoleic acid
  • arachidonic acid

Question 16

Phosphatidylinositol 4,5-bisphosphate (PIP2) is a ____ that carries a net ___ charge.

  • glycerophospholipid;  -1
  • glycerophospholipid;  -2
  • glycerophospholipid;  -3
  • sphingolipid;  -2
  • sphingolipid;  -3

Question 17

Some cytosolic proteins are anchored to the cell membrane via covalent bonds between cysteine or serine residues and _____ within the inner leaflet of the plasma membrane.

  • GPI anchors
  • cholesterol molecules
  • lauric acid groups
  • myristic acid groups
  • palmitic acid groups

Question 18

Lysozyme catalyzes a “bi-bi” reaction, which means there are (____) reactants and (___) products. List, in order, the reactants that bind and the products that are released during a lysozyme-catalyzed reaction cycle — be succinct but be specific.
1. First reactant =
2. First product =

 

Following questions are based on the Lineweaver-Burke plot shown below. Kinetic data were generated in the (1) absence of any inhibitor, (2) presence of 15 µM of a reversible inhibitor, or (3) presence of 20 µM of a second (distinct) reversible inhibitor. Purified enzyme concentration was 5 µM. The y-intercept of Lines (A) and (B) is 0.9 sec/uM; the y-intercept of Line (C) is 0.3 sec/uM. The slope of Line (A) is 1.8 sec; the slope of Lines (B) and (C) is 0.6 sec.

Question 19

Line (A) represents ____________.

A. an enzyme-catalyzed reaction in the absence of any inhibitor.

B. an enzyme-catalyzed reaction in the presence of a competitive inhibitor.

C. an enzyme-catalyzed reaction in the presence of an uncompetitive inhibitor.

D. an enzyme-catalyzed reaction in the presence of a noncompetitive, or mixed, inhibitor.

Question 20
Line (B) represents ____________.

A. an enzyme-catalyzed reaction in the absence of any inhibitor.

B. an enzyme-catalyzed reaction in the presence of a competitive inhibitor.

C. an enzyme-catalyzed reaction in the presence of an uncompetitive inhibitor.

D. an enzyme-catalyzed reaction in the presence of a noncompetitive, or mixed, inhibitor.

Question 21
Line (C) represents ____________.

A. an enzyme-catalyzed reaction in the absence of any inhibitor.

B. an enzyme-catalyzed reaction in the presence of a competitive inhibitor.

C. an enzyme-catalyzed reaction in the presence of an uncompetitive inhibitor.

D. an enzyme-catalyzed reaction in the presence of a noncompetitive, or mixed, inhibitor.

Question 22
Calculate the Vmax of the reaction represented by Line (C). Show all mathematical work and indicate proper units.

Question 23
Calculate the Km of the reaction represented by Line (B). Show all mathematical work and indicate proper units.

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Categories: Biochemistry, Biology