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Biology 2 > Lecture 10- Pathways that harvest chemical energy > Flashcards

Lecture 10- Pathways that harvest chemical energy Flashcards

1
Q

What is the difference between slow twitch and fast twitch muscle fibers?

A

Slow twitch: lots of mitochondria to form ATP

Fast twitch: Fewer mitochondria, generate ATP in short bursts in absence of O2

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2
Q

What protein breaks down fat in fat tissues and leads to ‘marathon mouse’? (increase in slow twitch muscle fibers)

A

PPARδ

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3
Q

What are fuels?

A

Molecules whose stored energy can be released for use

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4
Q

How are molecules such as fats or proteins able to supply energy?

A

They are converted into glucose or intermediate compounds

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5
Q

Complex chemical transformations in the cell occur…

A

in a series of separate reactions that form metabolic pathways

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6
Q

Each reaction in a metabolic pathway is

A

catalyzed by a specific enzyme

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7
Q

Metabolic pathways are

A

similar in all organisms, from humans to bacteria

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8
Q

Metabolic pathways are comp_____

A

Compartmentalized in eukaryotes (certain reactions occur in specific organelles)

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9
Q

Each metabolic pathway is regulated by…

A

Key enzymes that can be inhibited or activated to determine how fast a reaction can go

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10
Q

C6H12O6 +6O2 —>

A

6CO2 + 6H20 + free energy

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11
Q

What is the function of the glucose metabolism pathway?

A

To trap stored energy of glucose into ATP molecules

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12
Q

What is the reaction that traps free energy into ATP molecules?

A

ADP + Pi + free energy –> ATP

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13
Q

What is the change in free energy from the complete conversion of glucose and oxygen into carbon dioxide and water?

A

-686 kcal/mol (exergonic)

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14
Q

What are the three metabolic processes that harvest energy from glucose?

A

Glycolysis
Cellular respiration
Fermentation

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15
Q

What is glycolysis?

A

The first step in glucose metabolism in all cells and produces two three carbon pyruvates

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16
Q

Does glycolysis use oxygen?

A

No

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17
Q

What is cellular respiration?

A

Aerobic
Converts each pyruvate molecule into three CO2 molecules
Energy stored in covalent bonds is transferred into ADP and Pi to form ATP

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18
Q

What is fermentation?

A

Anaerobic

Converts pyruvate into lactic acid or ethanol (energy rich molecules)

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19
Q

Why does fermentation not release as much energy as cellular respiration?

A

Lactic acid or ethanol is produced. Glucose break down is incomplete, less energy is released

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20
Q

What four pathways operate when oxygen is present as the final electron acceptor?

A

Glycolysis,
Pyruvate oxidation
Citric acid cycle
Electron transport chain

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21
Q

What 2 pathways operate in the absence of oxygen?

A

Glycolysis

Fermentation

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22
Q

What is a redox reaction?

A

A reaction in which one substance transfers one or more electrons to another substance

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23
Q

What type of reaction is the addition of phosphate to ADP to make ATP?

A

Endergonic

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24
Q

In redox reactions, what type of agent is glucose and what type of agent is oxygen?

A

Glucose is a reducing agent

Oxygen is a oxidizing agent

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25
Q

What are co-enzymes?

A

Small molecules that assist in enzyme-catalyzed reactions

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26
Q

How is ADP a coenzyme?

A

It picks up energy released in exergonic reactions and uses it to form ATP

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27
Q

Other than ADP, what molecule acts as a coenzyme in redox reactions?

A

NAD acts as an electron carrier

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28
Q

What does NAD stand for?

A

Nicotinamide adenine dinucleotide

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29
Q

What is the oxidized and reduced form of NAD?

A

Oxidized: NAD+
Reduced: NADH + H+

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30
Q

What is the equation for the reduction of NAD+?

A

NAD+ + 2H –> NADH + H+

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31
Q

What is transferred to NAD+ to form NADH?

A

A hydride ion, H-

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32
Q

Why does oxygen readily accept electrons from NADH?

A

It is highly electronegative

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33
Q

What is the equation for the oxidation of NADH?

A

NADH +H+ +1/202 –> NAD+ +H20

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34
Q

What is the delta G value for oxidation of NADH?

A

-52.4 kcal/mol

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35
Q

What type of reaction is the oxidation of NADH?

A

Exergonic

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36
Q

Other than NAD, name another electron carrier in cells.

A

FAD

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37
Q

What does FAD stand for?

A

Flavin adenine dinucleotide

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38
Q

Where does glycolysis and fermentation occur in eukaryotes?

A

external to mitochondria

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39
Q

Where does glycolysis occur in prokaryotes?

A

In the cytoplasm

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40
Q

Where does fermentation occur in prokaryotes?

A

In the cytoplasm

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41
Q

Where does the citric acid cycle occur in prokaryotes?

A

In the cytoplasm

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42
Q

Where does the electron transport chain occur in eukaryotes?

A

The inner membrane of the mitochondria

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43
Q

Where does the electron transport chain occur in prokaryotes?

A

Plasma membrane

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44
Q

Where does the citric acid cycle and pyruvate oxidation occur in eukaryotes?

A

The matrix of the mitochondria

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45
Q

Where does pyruvate oxidation occur in prokaryotes?

A

On the plasma membrane

46
Q

Does glycolysis generate CO2?

A

no

47
Q

How many enzyme catalysed reactions are there in glycolysis?

A

10

48
Q

What does glycolysis produce?

A

2 molecules of pyruvate
4 molecules of ATP
2 molecules of NADH

49
Q

What are the two stages of glycolysis?

A

Energy investment reactions

Energy harvesting reactions

50
Q

What are the first 5 energy investment reactions of glycolysis?

A

Endergonic

51
Q

In what two reactions in glycolysis is ATP invested?

A

1 and 3

52
Q

What happens during reaction 1 and 3 of glycolysis?

A

Two phosphate groups are attached to the glucose molecule using energy from ATP

53
Q

What is the result of investing 2 ATP molecules during glycolysis?

A

Fructose 1,6-bisphosphate

54
Q

What is the free energy of fructose 1,6 bisphosphate compared to that of glucose?

A

Higher

55
Q

What enzyme catalyzes reaction 1 of glycolysis?

A

hexokinase

56
Q

What is a kinase?

A

An enzyme that catalyzes the transfer of a phosphate group from ATP to another substrate

57
Q

What enzyme catalyzes reaction 3 of glycolysis?

A

Phosphofructokinase

58
Q

What does reaction 4 of glycolysis do?

A

Opens up the six-carbon ring structure and cleaves it into two different three carbon sugar phosphates

59
Q

In summary, what is the end product of the energy investing reactions of glycolysis?

A
  • Two molecules of ATP have been invested

- Two three carbon sugar phosphate molecules have been produced

60
Q

What is the name of the 3 carbon sugar phosphate produced by the energy investing glycolysis reactions?

A

Glyceraldehyde 2-phosphate (G3P)

61
Q

What is the drop in free energy for reaction 6 of glycolysis?

A

100kcal/mol

62
Q

What type of reaction is reaction 6 of glycolysis?

A

Oxidation

63
Q

How is the energy released in reaction 6 of glycolysis stored?

A

Reducing 2 molecules of NAD+ to NADH + H+

64
Q

What happens if NAD is not recycled?

A

Glycolysis comes to a stop because its is present only in small amounts

65
Q

What happens in reaction 7-10 of glycolysis?

A

2 phosphate groups are transferred to ADP

66
Q

What is the name of the enzyme-catalyzed transfer of phosphate groups from donor molecules to ADP molecules to form ATP?

A

Substrate-level phosphorylation

67
Q

What happens in reaction 7 of glycolysis?

A

Phosphoglycerate kinase catalyzes the transfer of a phosphate group from BPG to ADP

68
Q

How many ATP molecules are produced per glucose molecule in the energy harvesting reactions?

A

4 (2 net)

69
Q

At the end of glycolysis, each glucose molecule yields…

A

2 pyruvate
2 NADH +H+
2 ATP

70
Q

What does pyruvate oxidation link?

A

Glycolysis and the citric acid cycle

71
Q

What is Coenzyme A?

A

A complex molecule responsible for binding two-carbon acetate molecule

72
Q

Acetyl coenzyme A formation is a

A

multi step reaction

73
Q

What is acetyl coenzyme A formation catalysed by?

A

Pyruvate dehydrogenase complex

74
Q

What is pyruvate dehydrogenase complex?

A

A multi-enzyme complex attached to the inner mitochondrial membrane

75
Q

What happens after pyruvate diffuses into the mitochondrion?

A

Pyruvate is oxidised to a two carbon actyl group (acetate) and CO2 is released

76
Q

What happens after pyruvate is oxidised to become acetate?

A

Part of the energy from the oxidation is captured by reducing NAD+ to NADH + H+

77
Q

How is the rest of the energy from oxidation of pyruvate into acetate stored?

A

Temporarily, by combining the acetyl group with CoA to form acetyl CoA

78
Q

What is the overall reaction for the pyruvate oxidation reaction?

A

pyruvate + NAD+ CoA –> acetyl CoA + NADH +H+ +CO2

79
Q

What does the citric acid cycle do?

A

Completes the oxidation of glucose to CO2

80
Q

What is the starting molecule of the citric acid cycle?

A

Acetyl CoA

81
Q

How many reactions are there in the citric acid cycle?

A

8

82
Q

The citric acid cycle is maintained in a ________

A

steady state

83
Q

What does it mean that the citric acid cycle is maintained in a steady state?

A

The concentration of the intermediates does not change

84
Q

What is the first reaction of the citric acid cycle?

A

oxaloacetate and energy stored in Acetyl CoA forms citrate

85
Q

What is removed during the first reaction of the citric acid cycle?

A

Coenzyme A

86
Q

What is the second reaction of the citric acid cycle?

A

Citrate is rearranged to form isocitrate

87
Q

What is the third reaction of the citric acid cycle?

A

Isocitrate is converted to alpha-ketoglutarate
2 hydrogen atoms and 1 CO2 is removed
NADH + H+ forms

88
Q

What is the 4th reaction in the citric acid cycle?

A

alpha-ketoglutarate is oxidised to succinyl CoA

Catalysed by a multi-enzyme complex

89
Q

What is the 5th reaction in the citric acid cycle?

A

GDP +Pi–>GTP

Succinyl CoA releases CoA to become succinate

90
Q

What does GTP stand for?

A

Guanosine triphosphate

91
Q

What is the reaction of GDP +Pi –> GTP an example of?

A

Substrate level phosphorylation

92
Q

What is GTP used for?

A

To make ATP from ADP

93
Q

What is the 6th reaction of the citric acid cycle?

A

Succinate is oxidised to fumarate

FAD –> FADH2

94
Q

What is the 7th reaction of the citric acid cycle?

A

Fumarate and water react, malate is formed

95
Q

What is the final reaction of the citric acid cycle?

A

Malate is oxidised to oxaloacetate

NADH + H+

96
Q

How many times does the citric acid cycle operate for each molecule of glucose?

A

Twice

97
Q

What is the input for each citric acid cycle?

A

Acetate (actyl CoA)
Water
Oxidised electron carriers

98
Q

What is the output for each citric acid cycle?

A

CO2
reduced electron carriers
ATP

99
Q

How is the citric acid cycle regulated?

A

Electron carriers that were reduced must be oxidized

100
Q

What two chemical pathways oxidize electron carriers so that the citric acid cycle can proceed?

A

Fermentation

Oxidative phosphorylation

101
Q

At the end of the citric acid cycle, each molecule of glucose yields from all three stages:

A

6 CO2
10 NADH + H+
2 FADH2
4 ATP

102
Q

What does fermentation use to reduce pyruvate?

A

NADH +H+

103
Q

What are the two most understood fermentation pathways?

A

Lactic acid fermentation

Alcoholic fermentation

104
Q

What serves as the electron acceptor in lactic acid fermentation?

A

Pyruvate

105
Q

Why does lactic acid build up in muscles cause problems?

A

The acid ionizes
pH of the cell is lowered
Cellular activities reduce

106
Q

Where does alcoholic fermentation take place?

A

Certain yeasts

Some plant cells

107
Q

How does alcoholic fermentation metabolize pyruvate?

A

two enzymes

108
Q

What is the first step in alcoholic fermentation?

A

carbon dioxide is removed from pyruvate to make acetaldehyde

109
Q

What is the second step in alcoholic fermentation?

A

Acetaldehyde is reduced by NADH +H+ to produce ehtanol and NAD+

110
Q

What is net yield of ATP from fermentation?

A

two ATP’s

Biology 2 (14 decks)

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