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MCAT > MCAT BIOCHEM Part 2 > Flashcards

MCAT BIOCHEM Part 2 Flashcards

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1
Q

__ is the substrate concentration at which the reaction velocity is half its maximum

A

Michaelis constant Km

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2
Q

If an enzyme-substrate pair has a low Km ___

A

it means that not very much substrate is required to get the reaction rate to half the maximum rate, the enzyme has high affinity for the substrate

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3
Q

An enzyme inhibitor that competes with substrate for binding at the active site of the enzyme. When the inhibitor is bound no product can be made

A

Competitive inhibitor

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4
Q

An enzyme inhibitor that can bind to the enzyme either in its free form or as enzyme-substrate complex

A

Mixed-type inhibition

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5
Q

An enzyme inhibitor that binds at a site other than the active site of an enzyme (binds to the allosteric site). This changes the three-dimensional shape of the enzyme such that it can no longer catalyze the reaction

A

Noncompetitive inhibitor

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6
Q

An enzyme inhibitor that can bind to the enzyme only after its substrate has bound. __appear to increase the affinity an enzyme has for its substrate because it effectively locks the two together

A

Uncompetitive inhibition

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7
Q

How can competitive inhibition be overcome?

A

Adding more substrate!!

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8
Q

How does adding more substrate overcome competitive inhibitors?

A

If the substrate concentration is high enough, the substrate can outcompete the inhibitor

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9
Q

Is Vmax affected by competitive inhibitor?

A

No the reaction just needs alot more substrate to get there

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10
Q

___ bind at an allosteric site, not the active site

A

Noncompetitive inhibitors

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11
Q

If the enzyme is only able to bind to the enzyme-substrate complex, it is referred to as an __

A

uncompetitive inhibitor

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12
Q

For competitive inhibitirion Vmax___ and Km____

A

Vmax is NOT CHANGED

Km increases

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13
Q

For noncompetitive inhibition Vmax___ and Km___

A

Vmax DECREASES

Km NO CHANGE

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14
Q

For uncompetitive inhibition Vmax___ and Km__

A

Vmax DECREASES

Km DECREASES

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15
Q

For mixed-type inhibition Vmax__ and Km__

A

Vmax DECREASES

Km varies in its change

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16
Q

The slope of a graph using lineweaver burk plot =

A

Km/Vmax

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17
Q

The y-intercept of a graph using lineweaver burk plot is

A

1/Vmax

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18
Q

The x-intercept using lineweaver burk plot is_

A

-1/Km

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19
Q

The first substrate in the Krebs cycle is__

A

Acetyl-CoA

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20
Q

___ is produced primarily from the oxidation of pyruvate by the pyruvate dehydrogenas complex

A

Acetyl-Coa

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21
Q

__ is produced during fatty acid oxidation and protein catabolism along with the Krebs cycle

A

Acetyl-Coa

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22
Q

A protein complex found in the inner membrane of the mitochondria that is essentially a channel that allows H+ ions to flow down from the intermembrane space to the matrix; as this occurs ATP is synthesized from ADP and Pi

A

ATP synthase

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23
Q

A small non-protein electron carrier in the electron transport chain

A

Coenzyme Q (ubiquinone)

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24
Q

The folds of the inner membrane of the mitochondrion

A

Cristae

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25
Q

A small iron-containing protein in the electron transport chain

A

Cytochrome C

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26
Q

A series of enzyme complexes found along the inner mitochondrial membrane. NADH and FADH2 are oxidized by these enzymes; the electrons are shuttled down the chain and are ultimately passed to oxygen to produce water. The electron energy is used to pump H+ out of the mitochondrial matrix; the resulting H+ gradient is subsequently used to drive the production of ATP

A

Electron transport chain

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27
Q

The reduction of pyruvate to either ethanol or lactate in order to regenerate NAD+ from NADH. ___ occurs in the absence of oxygen and allows glycolysis to continue under these conditions

A

Fermentation

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28
Q

A protein associated with FAD that is commonly involved in redox reactions

A

Flavoproteins

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29
Q

___ dephosphorylates fru-1,6-bisP in gluconeogenesis

A

fructose- 1,6- bisphosphatase

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30
Q

The simultaneous activation of metabolic pathways with opposing roles e.g. running glycolysis and gluconeogenesis at the same time. The tight regulation of metabolic pathways exists to prevent ___

A

futile cycling

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31
Q

A peptide hormone produced and secreted by the alpha cells of the pancreas__

A

glucagon

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32
Q

___ targets primarily the liver, stimulating the breakdown of glycogen, thus increasing blood glucose levels

A

Glucagon

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33
Q

A metabolic pathway that synthesizes glucose from non-carbohydrate precursors.

A

Gluconeogenesis

34
Q

__occurs in the liver when dietary stores of glucose are unavailable and the liver has depleted its stores of glycogen and glucose

A

Gluconeogenesis

35
Q

The enzyme that catalyzes the first step in the oxidative phase of the pentose phosphate pathway

A

glucose-6-phosphate dehydrogenase (G6PDH)

36
Q

____ decarboxylates glucose-6-P to form ribulose-5-P and forms NADPH in the process

A

Glucose-6-phosphate dehydrogenase

37
Q

The enzyme that decarboxylates glu-6-P in gluconeogenesis. This step is important so that glucose can exit the liver cell and enter the bloodstream

A

Glucose-6-phosphatase

38
Q

The enzyme that catalyzes the phosphorylation and subsequent removal of one glucose monomer at the end of a glycogen polymer

A

Glycogen phosphorylase

39
Q

The enzyme that catalyzes the addition of glucose monomers to the glycogen polymer

A

Glycogen synthase

40
Q

The anaerobic splitting of a glucose molecule into 2 pyruvic acid molecules, producing two net ATP molecules and two NADH molecules.

A

Glycolysis

41
Q

This is the first step in cellular respiration

A

Glycolysis

42
Q

The bond holding two monosaccharides together

A

Glycosidic linkage

43
Q

The enzyme that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis

A

Hexokinase

44
Q

___ is feedback inhibited by glucose-6-P

A

Hexokinase

45
Q

A peptide hormone produced and secreted by the B-cells of the pancreas

A

Insulin

46
Q

__targets all cells in the body,especially the liver and muscle, and allows them to take glucose out of the blood (lowering blood glucose levels)

A

Insulin

47
Q

The third stage of cellular respiration, in which acetyl-CoA is combined with oxaloacetate to form citric acid.

A

Krebs Cycle

48
Q

What are the byproducts of Krebs cycle?

A

3 molceuls of NADH, 1 molecule of FADH2, and 1 molecule of GTP

49
Q

The interior of a mitochondrion (the region bounded by the inner membrane).

A

Matrix

50
Q

The __ is the site of action of the pyruvate dehydrogenase complex and the Krebs cycle

A

Matrix

51
Q

This is the most common electron carrier in cellular respiration

A

NADH

52
Q

A four-carbon molecule that binds with the two-carbon acetyl unit of acetyl-CoA to form citric acid in the first step of the Krebs cycle

A

Oxaloacetate

53
Q

The oxidation of high energy electron carriers (NADH and FADH2) coupled to the phosphorylation of ADP, producing ATP. In eukaryotes this occurs in the mitochondria

A

Oxidative phosphorylation

54
Q

A metabolic pathway that diverts glucose-6-P from glycolysis in order to form ribose-5-P, which can be used to synthesize nucleotides. It also produces NADPH, which can be used as reducing power in fatty acid synthesis

A

Pentose phosphate pathway

55
Q

Decarboxylates and phosphorylates oxaloacetate to form phosphoenolpyruvate in the second step of gluconeogenesis

A

PEPCK Phosphpoenolpyruvate carboxykinase

56
Q

The enzyme that catalyzes the phosphorylation of fructose-6 phosphate to form fructose-1-6-bisphosphate in the third step of glycolysis. This is the main regulatory step of glycolysis.

A

Phosphofructokinas (PFK)

57
Q

Phosphofructokinase (PFK) is feedback-inhibited by __

A

ATP

58
Q

A non-protein, but organic molecule (such as a vitamin) that is covalently bound to an enzyme as part of the active site

A

Prosthetic group

59
Q

A group of three enzymes that decarboxylates pyruvate, creating an acetyl group and carbon dioxide

A

Pyruvate dehydrogenase complex

60
Q

The ___is the second stage of cellular respiration

A

Pyruvate dehydrogenase complex

61
Q

Catalyzes the final step in glycolysis, the conversion of PEP into pyruvate

A

`Pyruvate kinase

62
Q

The product of glycolysis 2 of these are produced from a single glucose molecule

A

Pyruvic acid

63
Q

Inb the absence of oxygen __ undergoes fermentation and is reduced to either lactic acid or ethanol

A

Pyruvic acid

64
Q

In the presence of oxygen, ___ is oxidized to produce acetyl-CoA, which can enter the Krebs cycle

A

Pyruvic acid

65
Q

The tight regulatory control exerted over opposing metabolic pathways in order to avoid futile cycling

A

Reciprocal control

66
Q

The four steps in order for glucose oxidation to produce CO2 and ATP

A
  1. Glycolysis
  2. Pyruvate dehydrogenase complex (PDC)
  3. the Krebs cycle
  4. Electron trasport/oxidative phosphorylation
67
Q

Glycolysis occurs in the __ and does NOT require oxygen

A

Cytoplasm

68
Q

During this stage pyruvate produced in glycolysis is decarbozylated to form an acetyl group that is then attached to coenzyme A (Acetyl-CoA)

A

Pyruvate dehydrogenase complex

69
Q

During pyruvate dehydrogenase a small amount of __ is produced

A

NADH

70
Q

During ___ and____ can only occur when oxygen is available, but neither use OXYGEN directly

A

Krebs cucle or PDC

71
Q

KRebs cycle and PDC occur in the __

A

innermost compartment of the mitochondria: the matrix

72
Q

During this stage the high energy electrons carried by NADH and FADH2 are oxidized to produce ATP

A

Electron transport/oxidative phosphorylation

73
Q

The ETC is in the __

A

inner mitochondrial membrane

74
Q

The final stage in ETC is the __

A

reduction of oxygen to H20

75
Q

__is the universal first step in glucose metabolism

A

Glycolysis

76
Q

All cells from ALL DOMAINS possess the enzymes of this pathway

A

Glycolysis

77
Q

What are the products of glycolysis?

A 
2 Pyruvate
2ATP
2NADH
2H20
2 H+
78
Q

___ is the key biochemical valve controlling the flow of substrate to product in glycolysis

A

Phosphofructokinase becasue its catalysis in the third step of glycolsis is very thermodynamically favorable

79
Q

In oxidartive decarboxylation, pyruvate is changed from a 3-carbon molecule to a ___ while____is given off and ___ is produced

A

pyruvate is converted to a 2-carbon molecule, CO2 is given off, and NADH is made from NAD+

80
Q

Citric acid is the first intermediate in the Krebs cycle formed from ___ and ___

A

Oxaloacetate (4 carbons)

Acetyl-CoA (2 carbons)

MCAT (45 decks)

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