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Biochemistry > Exam 3 Exam > Flashcards

Exam 3 Exam Flashcards

1
Q

The process of glycolysis occurs in _________.

A

virtually all organisms

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2
Q

In glycolysis, what type of enzyme catalyzes the interconversion of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate?

A

isomerase

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3
Q

In glycolysis, what type of enzyme catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate?

A

isomerase

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4
Q

Which statement below best describes ATP use/production for the series of reactions that convert one molecule of glucose to one molecule of glyceraldehyde-3-phosphate and one molecule of dihydroxyacetone phosphate?

A

2 ATP are used and 0 ATP are generated for a net yield of -2 ATP.

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5
Q

Glycolysis is the process of converting glucose to pyruvate. How many molecules of pyruvate are produced per glucose, and how many molecules of CO2 are released?

A

2 molecules pyruvate, 0 molecules CO2

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6
Q

Which glycolysis reaction(s) below requires ATP as a substrate?
(a) 3-phosphoglycerate → 2-phosphoglycerate
(b) glyceraldehyde-3-phosphate → dihydroxyacetone phosphate
Correct Answer
(c) glucose → glucose-6-phosphate

A

(c) glucose → glucose-6-phosphate

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7
Q

In glycolysis, the conversion of phosphoenolpyruvate to pyruvate is catalyzed by what type of enzyme?

A

kinase

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8
Q

What class of enzymes catalyzes the conversion of pyruvate to lactate?

A

dehydrogenase

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9
Q

The regeneration of ____ in the reduction of pyruvate to ethanol sustains glycolysis under anaerobic conditions.

A

NAD+

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10
Q

Gluconeogenesis utilizes a lot of the same reactions as glycolysis but in reverse. There are however a few unique steps in the gluconeogenesis pathway. Given reactions for GLYCOLYSIS below and their respective ΔG values under typical physiological conditions, which reaction would you expect would not be easily reversible in gluconeogenesis?

A

fructose-6-phosphate → fructose-1,6-bisphosphate ΔG = -22.2 kJ/mol

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11
Q

In gluconeogenesis, glucose-6-phosphate is converted into glucose by what type of enzyme?

A

phosphatase

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12
Q

How many nucleotide triphosphates (ATP and GTP) are required to convert two molecules of pyruvate into one molecule of glucose?

A

6

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13
Q

In actively respiring muscle tissue, lactate can be transported to the liver where it can be converted back to glucose and then transported back to the muscle tissue. What is this process called?

A

Cori cycle

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14
Q 
Pyruvate is converted to acetyl CoA by pyruvate dehydrogenase. Which of the following is not a cofactor/cosubstrate for pyruvate dehydrogenase?
thiamine pyrophosphate 
  lipoamide 
  NAD+
  FAD
A

all of the above are either cofactors or cosubstrates for pyruvate dehydrogenase

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15
Q

The condensation of acetyl CoA with oxaloacetate to form citrate is catalyzed by what type of enzyme?

A

synthase

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16
Q 
In which TCA cycle reaction below, is CO2 released as a product?
citrate → isocitrate 
  acetyl CoA + oxaloacetate → citrate 
  α-ketoglutarate → succinyl CoA 
  fumarate → malate
A

α-ketoglutarate → succinyl CoA

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17
Q

Which TCA cycle reaction below does NOT occur with reduction of NAD+ to NADH?

A

citrate → isocitrate

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18
Q

The yield from one mole of acetyl-CoA that completes the TCA cycle is (i) how many NADH, (ii) how many FADH2, and (iii) how many moles of GTP (or equivalents of ATP)? (Consider only the products of the TCA cycle reactions- do not include products from glycolysis or the pre-TCA cycle step.)

A

(i) 3 (ii) 1 (iii) 1

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19
Q

Why can plants invoke the net synthesis of glucose from the acetyl-CoA generated by the breakdown of fats, while animals cannot?

A

Both (a) and (b) are correct statements.
The glyoxylate cycle allows for bypass of the TCA cycle reactions that liberate carbon as CO2.
(b) The glyoxylate cycle allows for the net conversion of acetyl-CoA to oxaloacetate.

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20
Q

Where do the reactions of the TCA cycle take place in a eukaryotic cell?

A

mitochondrial matrix

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21
Q

Which enzyme catalyzes the reduction of O2?

A

Complex IV (cytochrome c oxidase)

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22
Q

The electrons from NADH enter the electron transport chain at which complex?

A

Complex I

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23
Q

Electrons from which complex(es) in the electron transport chain are transferred to Coenzyme Q?

A

(a) Complex I

(b) Complex II

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24
Q

The ATP synthase of the mitochondrial electron transport chain uses the energy contained in the H+ concentration gradient to __________.

A

release ATP bound to the complex after synthesis

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25
Q 
Which form of electromagnetic radiation would have the lowest amount of energy per photon?
 red visible light 
  violet visible light 
  ultraviolet light 
  blue visible light 
  green visible light
A

red visible light

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26
Q

In the photosynthetic light reactions, the direct electron donor to photosystem I is ______.

A

plastocyanin

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27
Q

Electrons from the chlorophyll special pair of Photosystem II are transferred most directly to which molecule below?

A

plastoquinone (Q)

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28
Q

In the light dependent reactions, which components below contribute to the development of the proton gradient in the thylakoid lumen?

A

(a) Photosystem II

(b) cytochrome b6f

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29
Q

If one mol of H2O was oxidized via the light reactions of photosynthesis, how many mol of NADPH could be produced?

A

1

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30
Q

How many molecules of ATP and NADPH are required to fix 3 molecules of CO2 via the Calvin cycle?

A

9 ATP, 6 NADPH

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31
Q

The step of the Calvin cycle that involves the addition of CO2 to ribulose 1,5-bisphosphate to produce 2 molecules of 3-phosphoglycerate is catalyzed by what enzyme?

A

Rubisco

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32
Q

In addition to glycogen phosphorylase, a debranching enzyme is required to cleave what type of glucosyl linkages in glycogen?

A

α 1,6

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33
Q

The products of the pentose phosphate pathway are required for _______.

A

(a) nucleotide biosynthesis
(b) fatty acid biosynthesis
(c) regeneration of reduced glutathione

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34
Q

Which of the following would best describe amylose?

A

glucose monomers linked by α 1,4 linkages; no branching

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35
Q

Which polymer of glucose serves as a nutritional reserve in animals?

A

(d) glycogen

36
Q

What is the storage form of lipids?

A

triacylglycerides

37
Q

Which of the following is a true statement regarding phospholipids and sphingolipids?

A

In phospholipids, fatty acids are attached to the backbone molecule through an ester linkage, while in sphingolipids fatty acids are attached to the backbone molecule through an amide linkage.

38
Q

Which of the following compounds would NOT be classified as an isoprenoid?

A

sphingolipid

39
Q

The development of “golden rice” involved the introduction of 3 genes required to synthesize which essential molecule required for the synthesis of vitamin A?

A

beta-carotene

40
Q

Which of the following is/are correct statement(s) regarding cholesterol?
Cholesterol is a component of cell membranes.
Cholesterol serves as a precursor to many biologically active steroid molecules.
Cholesterol is an isoprenoid.

A

All of the above are correct statements regarding cholesterol.

41
Q

Which of the following statements about cell membranes is NOT true?
Cell membranes consist mainly of lipids and proteins.
Cell membranes are held together by covalent interactions.
Cell membranes are fluid.
Cell membranes are asymmetric.

A

Cell membranes are held together by covalent interactions.

42
Q

A protein that spans the cell membrane is known as a(n) _________.

A

integral membrane protein

43
Q

What type of membrane protein uses the downhill flow of one species to drive the uphill flow of a different species in the same direction across a membrane?

A

symporter

44
Q

Which of the following processes is an example of active transport?

(a) A substance moves from high to low concentration across a cell membrane without the need of a transporter protein.
(b) A substance is moved from high to low concentration across a cell membrane through a protein channel.
(c) A substance is moved from low to high concentration across a cell membrane requiring both energy and the use of a transporter protein.

A

(c) A substance is moved from low to high concentration across a cell membrane requiring both energy and the use of a transporter protein.

45
Q

Which molecule will be able to most freely traverse a cell membrane via simple diffusion without the need for a transporter protein?

A

N2

46
Q

In the insulin signaling system, how is the signal terminated?

A

dephosphorylation of the tyrosine kinase domains on the receptor protein, and dephosphorylation of the target proteins

47
Q

In the G-protein signal transduction system, what is one way that the signal is terminated?

A

intrinsic GTPase activity of the receptor protein

48
Q

Which of the following types of enzymes functions to de-phosphorylate another protein?

A

phosphatase

49
Q

Caffeine would be expected to have what effect on the G-protein coupled receptor/adenylate cyclase signal transduction system?

A

inhibition of phosphodiesterase

50
Q 
The major purpose(s) for which organisms require energy is/are:
  (a) performance of mechanical work 
  (b) active transport 
  (c) synthesis of biomolecules 
  both (a) and (c)
A

all (a), (b), and (c)

51
Q

For an endergonic reaction at standard conditions, ___________.

A

ΔG°’ is positive, and Keq is less than 1.

52
Q

The following reaction, A ⇌ B, has a value of ΔG°’ of +18.0 kJ/mol (at 298 K). What is the value of the equilibrium constant (Keq) for this reaction?

A

7.00 x 10-4

53
Q

The reaction of A → B is found to be exergonic as shown. What is the maximum amount of D that can be produced (in mol) if the reactions are perfectly coupled?
A → B ΔG°’ = -1500 kJ/mol
C → D ΔG°’ = +75 kJ/mol

A

20 mol D

54
Q

Using the information below:
A + B ⇌ C + D ΔG°’ = -85.0 kJ/mol
B ⇌ C ΔG°’ = +42.0 kJ/mol

What is ΔG°’ for A ⇌ D?

A

-127 kJ/mol

55
Q

Using the information for the reaction below, what would be the value of ΔG’ at 298 K if [A] = 0.005 M and [B] = 0.0002 M?
A ⇌ B ΔG°’ = +32.0 kJ/mo

A

+24.0 kJ/mol

56
Q

Which activated carriers contain adenosine phosphate units?
Coenzyme A
NADH
FADH2

A

all of the above

57
Q

The conversion of methane (CH4) to methanol (CH3OH) is a ________.

A

2 electron oxidation

58
Q

The following reaction (which is purposely not balanced) is a _________.
NADH → NAD+

A

2 electron oxidation

59
Q

In a carbonyl group, which atom is capable of serving as a hydrogen bond acceptor?

A

oxygen

60
Q

A hydrogen bond would be expected to have an approximate length of ______.

A

2 Å

61
Q

The molecular geometry of water, which contributes to the overall polarity of the molecule, would best be described as __________.

A

bent

62
Q

Relative to water, a phospholipid would be considered ________.

A

amphipathic

63
Q

If the [H+] increases by a factor of 100, how does the pH of the solution change?

A

The pH decreases by 2.

64
Q

Benzoic acid is a weak acid with a pKa of 4.2. If benzoic acid is dissolved in water and the pH of the solution is adjusted to 5.2, what is the ratio of the acid to the conjugate base in the solution?

A

1 : 10

65
Q

Malonic acid is a weak acid with two carboxylic acid groups; one with a pKa of 2.3 and the other with a pKa of 5.7. What would be the charge on a malonic acid molecule where the pH is 8?

A

-2

66
Q

The phenomenon of nonpolar molecules spontaneously aggregating in water is known as the ___(i)___ and is driven largely by the ___(ii)___.

A

(i) hydrophobic effect (ii) entropy of water

67
Q 
Amino acids are often grouped based on the nature of their side chains (at pH 7). Which amino acid is classified INCORRECTLY below?
  valine = nonpolar 
  arginine = positively charged 
  glutamate = negatively charged 
  serine = polar, uncharged 
  isoleucine = polar
A

isoleucine = polar

68
Q

Which amino acid would you predict to MOST LIKELY find in the interior of a protein?

A

valine

69
Q

What would be the overall charge on the amino acid glutamate at pH = 7?

A

-1

70
Q

The partial double bond character of the peptide bond results from the movement of electrons from the ________ into the peptide bond.

A

non-bonding electrons from nitrogen

71
Q

What is the net charge on the tripeptide His-Val-Lys at pH = 5?

A

+2

72
Q

In the protein alpha helix, the -NH from the peptide bond participates in hydrogen bonding with the ___(i)___ on the amino acid approximately ___(ii)___ amino acids ahead in the chain.

A

(i) C=O of the peptide bond (ii) 4

73
Q

Protein denaturation can be caused by all of the following, EXCEPT:
heat
changes in pH
kinetic energy

A

All of the above can lead to protein denaturation.

74
Q

The Gibbs free energy of activation is:

A

the energy difference between the substrate and the transition state

75
Q

Which of the following statements about enzymes is true?

a) Enzymes force reactions to proceed in only one direction.
(b) Enzymes alter the equilibrium position for the reaction.
(c) Enzymes increase the reaction rate by stabilizing the transition state.
(d) Enzymes increase the reaction rate by lowering the activation energy.

A

(c) Enzymes increase the reaction rate by stabilizing the transition state.
(d) Enzymes increase the reaction rate by lowering the activation energy.

76
Q

Which of the following statements is correct regarding the active site of an enzyme and enzyme specificity?

A

(a) enzymes bind substrates via many weak interactions in the enzyme active site
(b) the active site of an enzyme is formed by specific amino acids involved in substrate interactions and catalysis

77
Q

When the substrate concentration is equal to Km, the rate of catalysis is equal to:

A

½ Vmax

78
Q

Addition of a noncompetitive inhibitor will result in what type of change for what kinetic parameter of an enzyme?

A

(d) Vmax will decrease

79
Q

Which of the following would be appropriate units for the Km of an enzyme catalyzed reaction?

A

mM

80
Q

For an enzyme catalyzed reaction, the Km is found to be 4.0 μM, and the Vmax is 18.0 μM product/s. At a substrate concentration of 1.5 μM, what would be the expected rate of reaction?

A

4.9 μM product/s

81
Q

Ibuprofen is an inhibitor that binds to the active site of cyclooxygenase (COX) via multiple weak interactions. This would be an example of what type of regulation?

A

noncovalent, reversible modification

82
Q

Which is the best example of allosteric control?

A

It means that the binding of a substrate to one subunit of a multiple subunit enzyme controls binding to other subunits of the same enzyme molecule.

83
Q

The difference between a deoxyribonucleotide and a ribonucleotide is that the deoxyribonucleotide has a H atom at which position on the sugar portion of the molecule?

A

2’

84
Q

In the formation of an oligonucleotide (like RNA or DNA), a phosphodiester bond is formed between the ___(i)___ carbon atoms on adjacent nucleotides and a molecule of ___(ii)___ is released in the process.

A

(i) 3’ and 5’ (ii) H2O

85
Q

Differences between the A, B and Z forms of double helical DNA include all of the following, EXCEPT:
the pitch of the helix
the diameter of the helix
the turn of the helix (ex. right handed vs left handed)
the types of base pairs that are allowed to form

A

the types of base pairs that are allowed to form

86
Q

Analysis of a genome reveals that it is a double stranded DNA molecule contains 35% adenine. What would be the percentage of cytosine in this molecule?

A

15%

87
Q

Histone proteins bind to DNA. What amino acids would you predict to find on the surface of histone proteins?

A

Arg, Lys

Biochemistry (7 decks)

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