Exams 1-3 Together

Question 1

A solution is made of 0.5 M K_2 HPO_4 and 0.25 M KH_2 PO_4 (pK = 6.82). The pH of the solution would be __________.

a) 1.0
b) 3.0
c) 6.52
d) 7.12
e) 9.34

Answer 1

b) 7.12

Question 2

Which of the following DNA sequences is (are) palindromic in double stranded form?

a) AGCT
b) AAGCTT
c) AGGA
d) A and B
e) A, B, and C

Answer 2

d) A and B

Question 3

Which one of these characteristics is NOT true for the alpha helix?

a) It is represented in ribbon diagrams as a cylinder.
b) There is a requirement for glycine every third amino acid residue.
c) A hydrogen bond forms between the carbonyl oxygen of the nth amino acid residue and the NH group of the (n+4)th amino acid residue.
d) Proline is typically not found in the alpha helix.
e) All of the above are true of the alpha helix.

Answer 3

b) There is a requirement for glycine every third amino acid residue.

Question 4

A fast and common method for determining the concentration of protein in aqueous solution is:

a) tandem mass spectrometry
b) “salting in” with ammonium sulfate
c) drying a portion and weighing the solid
d) measuring light adsorption at 280 nm
e) Edman degradation

Answer 4

d) measuring light adsorption at 280 nm

Question 5

Amphiphilics molecules:

a) have both oxidizing and reducing groups
b) are micelles
c) have chromophores in two different wavelengths regions
d) have both acidic and basic groups
e) have both hydrophilic and hydrophobic groups

Answer 5

e) have both hydrophilic and hydrophobic groups

Question 6

Nucleotides contain phosphate groups bonded to the:

a) C3’ or C5’ atoms
b) C3 or C3’ atoms
c) C5 or N9 atoms
d) C3 or N9 atoms
e) none of the above

Answer 6

a) C3’ or C5’ atoms

Question 7

The disulfide bond between two cysteine molecules:

a) is a peptide bond
b) is an ionic bond that is stable at physiological pH
c) is a covalent bond formed by oxidation
d) is a hydrogen bond between the two sulfhydryl groups
e) is a weak ion-induced dipole attraction

Answer 7

c) is a covalent bond formed by oxidation

Question 8

Highly active muscle generates lactic acid by respiration so fast that the blood passing through the muscle experiences a drop in pH from about 7.4 to 7.2. Under these conditions, hemoglobin releases about 10% more O_2 than it does at pH 7.4. This is because of:

a) allostery
b) the Bohr effect
c) heme protonation
d) structural similarities with myoglobin
e) presence of carbon monoxide at higher acidity

Answer 8

b) the Bohr effect

Question 9

Either dansyl chloride or Edman’s reagent can be used to identify the __________ of a protein.

a) amino acid sequence
b) N-terminal amino acid
c) C-terminal amino acid
d) quaternary structure
e) none of the above

Answer 9

b) N-terminal amino acid

Question 10

The theory of evolution includes the following principles:

a) evolution is not directed towards a specific goal
b) evolution is ongoing, and is constrained by its past
c) evolution requires some sloppiness for adaptation to changes
d) A and B
e) A, B, and C

Answer 10

e) A, B, and C

Question 11

The most important intramolecular interaction involved in stabilizing protein structure is:

a) hydrogen bonds
b) disulfide bonds
c) hydrophobic interactions
d) electrostatic interactions
e) dipole-dipole interactions

Answer 11

c) hydrophobic interactions

Question 12

A(n) ______ has a rigid, planar structure consisting of about 40% double bond character.

a) amino acid
b) water molecule
c) purine base
d) peptide bond
e) pyrimidine base

Answer 12

d) peptide bond

Question 13

Nucleotides are linked together in nucleic acids by a __________ bond.

a) peptide
b) phosphodiester
c) glycosidic
d) ester
e) disulfide

Answer 13

b) phosphodiester

Question 14

Treatment of a protein with a reducing agent such as β-mercaptoethanol along with a detergent such as SDS (sodium dodecyl sulfate) disrupts all of the following interactions except:

a) ionic interactions
b) hydrogen bonds
c) disulfide bonds
d) peptide bonds
e) hydrophobic interactions

Answer 14

d) peptide bonds

Question 15

In the tetrapeptide: Serine-Lysine-Arginine Glutamate

a) Serine is the N-terminal amino acid, Glutamate is the C-terminal amino acid
b) Serine is the C-terminal amino acid, Glutamate is the N-terminal amino acid
c) Serine and Glutamate are both C-terminal amino acids
d) Serine and Glutamate are both N-terminal amino acids
e) Not enough information to tell

Answer 15

a) Serine is the N-terminal amino acid, Glutamate is the C-terminal amino acid

Question 16

Which of the following is true about membrane proteins?

a) Integral membrane proteins span the membrane as a random coil,
b) Lateral diffusion occurs unless other cellular components restrict their movement.
c) They readily undergo transverse (flip-flop) diffusion every few seconds.
d) They are never glycoproteins.
e) They contain entirely nonpolar amino acids in their primary structure.

Answer 16

b) Lateral diffusion occurs unless other cellular components restrict their movement.

Question 17

Which of the following statements describes integral membrane proteins?

a) They are easily removed by changes in pH or high salt.
b) The proteins tend to be water-soluble.
c) Amino acids that contact the fatty acid carbon chains of the membranes are hydrophobic.
d) They interact with the membrane via a lipid anchor.
e) None of the above.

Answer 17

c) Amino acids that contact the fatty acid carbon chains of the membranes are hydrophobic.

Question 18

What type of transport does NOT require the assistance of a membrane protein?

a) facilitated transport
b) simple diffusion
c) passive transport
d) none of the above

Answer 18

b) simple diffusion

Question 19

Which of the following is NOT true about enzymes?

a) Enzymes catalyze the reaction in only the forward direction.
b) Enzymes are often very specific for their substrates.
c) Enzymes typically catalyze reactions at much higher rates than chemical catalysts.
d) Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.
e) All of the statements given are true.

Answer 19

a) Enzymes catalyze the reaction in only the forward direction.

Question 20

How many stereoisomers are possible for aldopentose such as ribose?

a) 2
b) 4
c) 8
d) 16
e) 32

Answer 20

c) 8

Question 21

The protein that forms a Transmembrane pore that allows preproteins to pass through the ER membrane is called the

a) signal recognition particle
b) signal peptidase
c) docking protein
d) translocon
e) none of the above

Answer 21

d) translocon

Question 22

Which of the following amino acids would provide a side chain capable of increasing the hydrophobicity of a binding site?

a) aspartic acid
b) lysine
c) isoleucine
d) arginine
e) serine

Answer 22

c) isoleucine

Question 23

What is the velocity of a first order reaction when the reactant concentration is 610^(-2) M and the rate constant is 810^3 s^(-1)?

a) 1.3310^5 M^(-1) s^(-1)
b) 1.3310^5 M s^(-1)
c. ) 7.510^(-2) M s^(-1)
d. ) 4.810^2 M s^(-1)
e. ) not enough data are given here to make this calculation

Answer 23

d.) 4.8*10^2 M s^(-1)

Question 24

Which of the following is NOT a characteristic of the (Na^+-K^+)-ATPase?

a. ) Antiporter
b. ) It transports 3 Na^+ ions out of the cell and 2 K^+ ions into the cell.
c. ) Transport is coupled to the hydrolysis of ATP
d. ) Transport occurs against a concentration gradient
e. ) None of the above

Answer 24

e.) None of the above

Question 25

Chymotrypsin preferentially cleaves a peptide bond adjoining a bulky, nonpolar side chain because chymotrypsin’s “specificity pocket”

a) contains a sulfhydryl group that forms a disulfide bond with the substrate
b) is lined with small hydrophobic side chains, leaving considerable room in the pocket and making it nonpolar
c) contains a negative charge
d) is mostly filled with large side chains
e) is positively charged

Answer 25

b) is lined with small hydrophobic side chains, leaving considerable room in the pocket and making it nonpolar

Question 26

If you add an enzyme to a solution containing only the product (P) of the reaction R ↔ P, would you expect any R to form?

a. ) Yes, because the enzyme reduces the standard free energy change for the reaction
b. ) No, because the enzyme lowers the transition state energy barrier
c. ) No, because product inhibits the enzyme
d. ) No, because enzymes only catalyze the forward reaction
e. ) Yes, because the reaction proceeds backwards until reaching equilibrium

Answer 26

e.) Yes, because the reaction proceeds backwards until reaching equilibrium

Question 27

The rate of an enzyme-catalyzed reaction is determine by

a) the overall free energy change of the reaction
b) the equilibrium constant of the reaction
c) the activation energy
d) the number of subunits a single enzyme has
e) all of the above

Answer 27

c) the activation energy

Question 28

Which of the following amino acids do NOT comprise the catalytic triad of chymotrypsin?

a) histidine
b) glutamic acid
c) serine
d) aspartic acid

Answer 28

b) glutamic acid

Question 29

All of the following are components of membranes EXCEPT

a) cholesterol
b) triglycerides
c) glycerophospholipids
d) sphingolipids
e) cerebrosides

Answer 29

b) triglycerides

Question 30

Hexokinase and glucokinase both catalyze the phosphorylation of glucose to form glucose-6-phosphate. The values of K_m for the enzymes of 10 µM and 0.02 M, respectively. If blood glucose is 5 mM under fasting conditions and 20 mM after a high carbohydrate meal.

a. ) hexokinase will function at less than one half V_max after a high carbohydrate meal
b. ) glucokinase will function near its V_max under fasting conditions
c. ) hexokinase will function near its V_max under fasting conditions
d. ) glucokinase will function at less than one-half V_max after a high carbohydrate meal

Answer 30

c.) hexokinase will function near its V_max under fasting conditions

Question 31

The β cells of the pancreas secrete __________ in response to __________ glucose levels.

a) insulin, low
b) insulin, high
c) glucagon, low
d) glucagon, high
e) None of the above

Answer 31

b) insulin, high

Question 32

Which of the following is (are) associated with cAMP binding to protein kinase A?

a) cAMP binds to the regulatory subunits
b) regulatory subunits dissociate from catalytic subunits
c) catalytic subunits phosphorylate multiple targets
d) All of the above
e) None of the above

Answer 32

d) All of the above

Question 33

Consider the following metabolic reaction:
Succinyl-CoA + Acetoacetate → Acetoacetyl0CoA + Succinate ∆G^o’=-1.25 kJ/mol
This reaction is:
a.) Favorable under standard conditions
b.) Not favorable under standard conditions
c.) Always exergonic and can never proceed in the opposite direction
d.) Spontaneous as written when [succinate] and [acetoactyl-CoA] are high
e.) None of the above

Answer 33

a.) Favorable under standard conditions

Question 34

If you are running away from a bear,

a) your muscle cells will be running glycolysis, and your liver cells will be running gluconeogenesis
b) your muscle cells will be running gluconeogenesis, and your liver cells will be running glycolysis
c) both your muscle cells and liver cells will be running glycolysis
d) both your muscle cells and liver cells will be running gluconeogenesis

Answer 34

a) your muscle cells will be running glycolysis, and your liver cells will be running gluconeogenesis

Question 35

Increased levels of epinephrine in the blood will:

a) Activate cAMP production in liver and muscle cells
b) Stimulate glycogen synthesis
c) Inhibit glycolysis in the muscle cell
d) Stimulate gluconeogenesis in the muscle cell
e) Inhibit the formation of cAMP

Answer 35

a) Activate cAMP production in liver and muscle cells

Question 36

The K_eq is 0.503 at 25ºC for the following reaction. What is the ∆G^o’ for this reaction?
D-Glucose-6-phosphate → D-Fructose-6-phosphate
a.) -1,700 J/mol
b.) -2,870 J/mol
c.) +143 J/mol
d.) +1.70 kJ/mol
e.) none of the above

Answer 36

d.) +1.70 kJ/mol

Question 37

In skeletal muscle, the main purpose of fermentation of pyruvate to lactate is:

a) Remove toxic pyruvate from the cell
b) Regenerate NAD+ used during glycolysis
c) Provide a precursor for amino acid synthesis
d) Activate pyruvate for the citric acid cycle
e) prevent you from becoming intoxicated through ethanol fermentation

Answer 37

b) Regenerate NAD+ used during glycolysis

Question 38

Which of the following metabolic conversions is considered to be the major control point of glycolysis?

a. ) Fructose-1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde-3-phosphate
b. ) Glucose → glucose-6-phosphate
c. ) 2-phosphoglycerate → phosphoenolpyruvate
d. ) fructose-6-phosphate → fructose-1,6-bisphosphate
e. ) pyruvate → lactate

Answer 38

d.) fructose-6-phosphate → fructose-1,6-bisphosphate

Question 39

The metabolic fate(s) of glucose-6-phosphate include:

a) glycogen and glucose
b) Ribose-5-phosphate and acetyl-CoA
c) Both of the above
d) None of the above

Answer 39

c) Both of the above

Question 40

During glycolysis, the steps between glucose and the formation of the triose phophates:

a. ) Consumes two ATP and two NADH molecules
b. ) Consume two ATP molecules
c. ) Product two ADP and two NAD^+ molecules
d. ) Produce two ATP and two NADH molecules
e. ) Consume two NADH molecules

Answer 40

b.) Consume two ATP molecules

Question 41

In eukaryotes, the enzymes that catalyze the reactions of glycolysis are located in:

a) The cell nucleus
b) The endoplasmic reticulum
c) The mitochondria
d) The lysosomes
e) The cytosol

Answer 41

e) The cytosol

Question 42

The hormone secreted by the pancreas under low blood sugar conditions is

a) insulin
b) glucagon
c) epinephrine
d) neuropeptide Y
e) jurisisawesomine

Answer 42

b) glucagon

Question 43

Which of the following statements about glycogen and glucose metabolism in skeletal muscle is correct?

a) Glycogen is hydrolyzed to free glucose that can enter the glycolytic pathway
b) Glucose residues from glycogen yield a net of 3 ATP when converted to lactate in skeletal muscle
c) No nucleotide is required to convert glucose to glycogen
d) Phosphorylase is the only enzyme required to totally degrade glycogen to glucose-6-phosphate
e) ATP is directly required for the conversion of glycogen to glucose-1-phosphate

Answer 43

b) Glucose residues from glycogen yield a net of 3 ATP when converted to lactate in skeletal muscle

Question 44

The enzyme catalyzing the reaction fructose-6-phosphate → fructose-1,6-bisphosphate

a. ) is allosterically activated by AMP
b. ) is allosterically inhibited by ATP
c. ) is activated by fructose-2,6-bisphosphate
d. ) A, B, and C
e. ) A and C

Answer 44

d.) A, B, and C

Question 45

The carbons of galactose enter glycolysis at the level of

a) Glucose-6-phosphate
b) Fructose-6-phosphate
c) Dihydroxyacetone phosphate
d) 3-phosphoglycerate

Answer 45

a) Glucose-6-phosphate