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MICRB 106 - Exam 2 > Microbial Metabolism > Flashcards

Microbial Metabolism Flashcards

1
Q

Define metabolism

A

All chemical reactions in an organism

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2
Q

What is a metabolic ‘pathway’?

A

A sequence of enzyme-catalyzed reactions that lead to the conversion of a substance into a product

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3
Q

What are the 2 major classes of metabolism?

A
  • Catabolism
  • Anabolism
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4
Q

Describe catabolic reactions in terms of substrate size and products

A

The breakdown of larger molecules into smaller ones

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5
Q

Describe anabolic reactions in terms of substrate size and products

A

The synthesis of larger molecules from smaller products of catabolism

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6
Q

What is the major difference between catabolic and anabolic pathways in terms of energy dynamics?

A
  • Catabolic pathways = exergnoic
  • Anabolic pathways = endergonic
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7
Q

Differentiate between exergonic and endergonic reactions

A
  • Exergonic - release energy
  • Endergonic - require energy
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8
Q

How do cells temporarily store the energy released during catabolism?

A

In the bonds of ATP

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9
Q

Where does the energy required for anabolism come from?

A

From ATP molecules produced during catabolism

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10
Q

What is the difference between an electron donor and an electron acceptor?

A
  • Electron donor - a molecule that donates electrons
  • Electron acceptor - a molecule that accepts electrons
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11
Q

What ultimately occurs during ‘oxidation-reduction reactions’ (or ‘redox reactions’)

A

Electron transfers

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12
Q

Describe the term ‘reduced’ in the context of redox reactions

A

Gain in electrons reduces the electrical charge (negative charge)

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13
Q

Describe the term ‘oxidized’ in the context of redox reactions

A

Electrons are donated to oxygen atoms

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14
Q

What are the 2 ways by which an electron acceptor may become reduced?

A
  • Gaining a simple electron
  • Gaining an electron from a hydrogen atom
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15
Q

What are the 2 ways by which an electron acceptor may become oxidized?

A
  • Losing a simple electron
  • Losing a hydrogen atom
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16
Q

Name 2 important electron carriers derived from vitamins

A
  • Nicotinamide adenine dinucleotide (NAD+)
  • Flavin adenine dinucleotide (FAD)
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17
Q

Describe the oxidized and reduced forms of NAD+

A
  • NAD+ + 2 e- + 2 H+ (oxidized form)
  • NADH + H+ (reduced form)
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18
Q

Describe the oxidized and reduced forms of FAD

A
  • FAD + 2 e- + 2 H+ (oxidized form)
  • FADH₂ (reduced form)
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19
Q

Where is the energy stored in ATP?

A

In high-energy phosphate bonds

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20
Q

Differentiate among AMP, ADP, and ATP in terms of phosphate groups and charges

A
  • AMP - 1 phosphate group
  • ADP - 2 phosphate groups - uncharged
  • ATP - 3 phosphate groups - charged (phosphorylation)
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21
Q

Define substrate-level phosphorylation

A

The transfer of phosphate from a phosphorylated organic compound to form ATP from ADP

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22
Q

Describe oxidative phosphorylation

A

Use of an inorganic phosphate and a proton motive force to form ATP from ADP

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23
Q

In oxidative phosphorylation, how is the inorganic phosphate and proton motive force generated?

A

The electron transport chain

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24
Q

What is the function of a catalyst?

A

Increase reaction rates of chemical reactions

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25
Q

Catalysts are ______ in the process

A

Not permanently changed

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26
Q

What term is used to describe organic catalysts?

A

Enzymes

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27
Q

Describe the composition of enzymes (2)

A
  • Apoenzymes
  • One or more cofactors
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28
Q

What are apoenzymes?

A

Protein component

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29
Q

What are cofactors?

A

Nonprotein component

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30
Q

What are inorganic cofactors?

A

Ions

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31
Q

What are some examples of inorganic cofactors? (4)

A
  • Iron
  • Zinc
  • Copper
  • Magnesium
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32
Q

What are organic cofactors made from?

A

Vitamins - NAD+ and FAD

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33
Q

What are coenzymes?

A

Organic cofactors

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34
Q

Holoenzymes are a combination of …

A

Apoenzymes and cofactors

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35
Q

What is activation energy?

A

The amount of energy required to initiate a chemical reaction

36
Q

What effect do enzymes have upon activation energy?

A

Enzymes are required to lower the activation energy needed in a biological system

37
Q

What term is used to describe an enzyme’s functional site?

A

Active site

38
Q

What determines enzyme-substrate specificity?

A

The complementary shapes of active sites and their substrates

39
Q

What results in an enzyme-substrate complex?

A

An enzyme binds to a substrate (catabolism)

40
Q

How do competitive inhibitors prevent normal substrates from binding at an enzyme’s active site? (2)

A
  • Fit into the enzyme’s active site
  • Do not undergo chemical reactions to form products
41
Q

What are the consequences of a competitive inhibitor acting permanently?

A

Permanent loss of enzymatic activity

42
Q

What are the consequences of a competitive inhibitor acting reversibly?

A

Can be overcome by an increase in the concentration of substrate molecules

43
Q

How do noncompetitive inhibitors prevent normal substrates from binding at an enzyme’s active site?

A

They bind to an allosteric site

44
Q

What are allosteric sites?

A

Sites located somewhere else on the enzyme to prevent enzymatic activity

45
Q

What role do allosteric sites play in noncompetitive or ‘allosteric’ inhibition? (3)

A
  • Alters the shape of the active site
  • Substrates cannot be bound
  • Halts enzymatic activity
46
Q

Describe excitatory allosteric control

A

The change in the shape of the active site causes an inactive enzyme

47
Q

Describe the specific conditions under which ‘feedback inhibition’ occurs

A

When the final product is an allosteric inhibitor

48
Q

What are the 2 main processes by which glucose is catabolized in microbial cells?

A
  • Cellular respiration
  • Fermentation
49
Q

Which process results in the complete breakdown of glucose to carbon dioxide and water?

A

Cellular respiration

50
Q

Describe glycolysis

A

Catabolizes a single glucose molecule into 2 molecules of pyruvic acid (pyruvate)

51
Q

Glycolysis results in ______

A

A small amount of ATP production

52
Q

Respiration continues via ______

A

The Krebs cycle

53
Q

What does fermentation result in?

A

Organic waste products

54
Q

Fermentation results in ______ than cellular respiration

A

Less ATP production

55
Q

Of the 2 main processes by which glucose is catabolized in microbial cells, which one involves the Krebs cycle and an electron transport chain?

A

Cellular respiration

56
Q

Why does fermentation result in the production of much less ATP than respiration?

A

It does not use oxygen or the electron transport chain

57
Q

What is the name of the initial substrate in glycolysis, and how many carbon atoms does it possess?

A
  • Glucose
  • 6 carbon atoms
58
Q

What is the name of the final substrate in glycolysis, and how many carbon atoms does it possess?

A
  • Pyruvate
  • 2 separate intermediates of 3 carbon atoms
59
Q

How many ATP molecules are invested in the conversion of one molecule of glucose to one molecule of fructose 1,6-bisphosphate?

A

2 ATP

60
Q

How many NAD+ molecules are reduced to NADH in the oxidation of two molecules of glyceraldehyde 3-phosphate (G3P)?

A

2 NAD+

61
Q

Per initial glucose molecule, how many ATP molecules are ultimately generated via substrate-level phosphorylation along the pathway to the end products of glycolysis?

A

2 ATP

62
Q

What is the name of the end-product of glycolysis, how many of these molecules are generated per initial molecule of glucose, and how many carbon atoms does each contain?

A

2 molecules of pyruvate - each containing 3 carbon atoms

63
Q

What is the net amount of ATP generated via glycolysis per original molecule of glucose?

A

2 ATP

64
Q

In preparation for the Krebs cycle (the transition step), 2 pyruvate molecules per molecule of glucose are decarboxylated and oxidized to yield 2 molecules of acetyl-CoA.

  • How many carbon atoms does each acetyl-CoA molecule possess?
  • How many carbon dioxide molecules are liberated per initial molecule of glucose?
  • How many molecules of NAD+ are reduced to NADH per initial molecule of glucose?
A
  • Each acetyl-CoA molecule - 2 carbons
  • 2 CO₂ molecules liberated
  • A single molecule of NAD+
65
Q

In the Krebs cycle, what is the relationship among acetyl-CoA, oxaloacetic acid, and citric acid, and how many carbon atoms are found in each of these molecules?

A
  • Acetyl-coA enters the cycle by joining with oxaloacetic acid, forming citric acid
  • Acetyl-coA - 2 carbons
  • Oxaloacetic acid - 4 carbons
  • Citric acid - 6 carbons
66
Q

How many CO2 molecules are generated per acetyl-CoA molecule that enters the Krebs cycle?

A

2 CO2 molecules

67
Q

For every molecule of acetyl-CoA that passes through the Krebs cycle, how many molecules of NADH and FADH2 are formed?

A
  • 3 NADH
  • 1 FADH₂
68
Q

What is the fate of the NADH and FADH2 generated via the Krebs cycle? (2)

A
  • Regeneration of oxaloacetic acid
  • Large amount of ATP production
69
Q

______ is needed for the electron transport chain to function

A

An electron acceptor

70
Q

What would result in a lack of oxidative phosphorylation?

A

No electron acceptor

71
Q

What is a proton gradient?

A

An electrochemical gradient of protons that has potential energy

72
Q

What is the relationship between electron transport and the establishment of a proton gradient?

A

As electrons move down the transport chain, proton pumps use the electrons’ energy to actively transport protons (H+) across the membrane

73
Q

What is the final electron acceptor in aerobic respiration, and what molecule is formed as the final electron acceptor is reduced?

A
  • Final electron acceptor - oxygen
  • Forms H₂O molecule
74
Q

What is the difference between aerobic respiration and anaerobic respiration?

A
  • Aerobic respiration - requires oxygen
  • Anaerobic respiration - does not require oxygen
75
Q

Describe chemiosmosis

A

ATP is synthesized utilizing energy released by the flow of ions down their concentration gradient

76
Q

What is the term used to describe the potential energy in a proton gradient?

A

Proton motive force

77
Q

What is the relationship between a proton motive force and protein channels (ATPases)?

A

As proteins flow through a channel, the movement spins the protein

78
Q

Cellular respiration generates an estimated 34 molecules of ATP via oxidative phosphorylation. Indicate the number and kind of reducing power (and the equivalent ATP molecules) produced during:

  • Glycolysis
  • Synthesis of acetyl-Co-A
  • Krebs cycle
A
  • Glycolysis - 2 NADH (6 ATP)
  • Synthesis of acetyl-coA - 2 NADH (6 ATP)
  • Krebs cycle - 6 NADH (18 ATP) and 2 FADH₂ (4 ATP)
79
Q

Cellular respiration generates an estimated 4 molecules of ATP via substrate-level phosphorylation. Indicate from where these ATP molecules originate

A
  • Glycolysis - 2 ATP
  • Krebs cycle - 2 ATP
80
Q

What is the theoretical yield of ATP per molecule of glucose via aerobic respiration?

A

38 ATP

81
Q

What is the theoretical yield of ATP per molecule of glucose via fermentation?

A

2 ATP

82
Q

What are the functions of fermentation in terms of facilitating substrate-level phosphorylation during glycolysis? (2)

A
  • Regeneration of NAD+ for glycolysis
  • Ensures that ADP molecules can be phosphorylated to ATP
83
Q

Name 2 types of fermentation

A
  • Lactic acid fermentation
  • Alcoholic fermentation
84
Q

Describe lactic acid fermentation

A

NADH reduces pyruvic acid from glycolysis to form lactic acid

85
Q

Describe alcoholic fermentation

A

Pyruvic acid undergoes decarboxylation and reduction by NADH to form ethanol

86
Q

What is decarboxylation?

A

CO₂ is given off

MICRB 106 - Exam 2 (3 decks)

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