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MCAT Prep > Biochemical Energy Production > Flashcards

Biochemical Energy Production Flashcards

1
Q

Is glycolysis an aerobic process?

A

No

glycolysis does not require O2

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2
Q

Overall products of glycolysis

A

2 pyruvate
2 ATP
2 NADH

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3
Q

Does glycolysis require energy?

A

yes, during the energy investment phase requires 2 molecules of ATP

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4
Q

What is the first step in glycolysis?

A

glucose enters the cell and hexokinase converts glucose to glucose 6-phosphate

this prevents glucose from leaving the cell

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5
Q

Which steps of glycolysis require ATP?

A

steps 1 and 3

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6
Q

What is the second step of glycolysis?

A

glucose 6-phosphate is converted to fructose 6-phosphate by glucose 6-isomerase

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7
Q

What is the third step of glycolysis?

A

fructose 6-phosphate gets converted to fructose 1,6-bisphosphate by PFK1

uses ATP

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8
Q

what is the rate limiting step / commitment step of glycolysis?

A

fructose 6-phosphate to fructose 1,6-bisphosphate

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9
Q

What is the fourth step of glycolysis?

A

fructose 1,6-bisphosphate is cleaved to G3P and DHAP by aldolase

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10
Q

What is the last step of the energy investment phase of glycolysis?

A

DHAP is converted to G3P

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11
Q

What is the first step of the energy payment phase of glycolysis?

A

convert G3P to 1,3-bisphophate glycerate by G3P dehydrogenase

convert NAD+ to NADH

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12
Q

What is the second step of the energy payment phase of glycolysis?

A

PGK converts 1,3-bisphosphate glycerate to 3PG

one phosphate is pulled off

used to make ATP

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13
Q

In what steps of glycolysis is ATP created?

A

steps 7 and 10

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14
Q

What is the final step of glycolysis?

A

PEP converted to pryuvate by pyruvate kinase

form another molecule of ATP

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15
Q

Where do pyruvate and NADH go in aerobic conditions?

A

pyruvate enters the citric acid cycle

NADH goes to the ETC

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16
Q

Where do pyruvate and NADH go in anaerobic conditions?

A

into fermentation to reproduce NAD+ for glycolysis

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17
Q

What is the goal of fermentation?

A

to reproduce NAD+

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18
Q

What do high levels of citrate do to glycolysis?

A

inhibits PFK1 and downregulates glycolysis

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19
Q

What do high levels of NADH do to glycolysis?

A

downregulate it

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20
Q

insulin effects on the cell

A

insulin places more GLUT4 receptors on cell

allows for more glucose uptake and glycolysis

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21
Q

When blood sugar is low what molecule is high?

A

glucagon

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22
Q

glucagon effects on the cell

A

glucagon inhibits glycolysis and upregulates gluconeogenesis

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23
Q

how does glucose 6-phosphate regulate glycolysis?

A

it inhibits hexokinase

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24
Q

glucokinase

A

a form of hexokinase in the liver and pancreas

glucokinase has a lower affinity for glucose and is not affected by glucose 6-phosphate

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25
Q

Why is it beneficial for glucokinase to not be affected by glucose 6-phophate?

A

glucokinase can breakdown large amounts of glucose even when G6P is present

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26
Q

PFK1 regulators

A

downregulated by high levels of ATP and citrate

upregualted by ADP and fructose 2,6-bisphosphate

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27
Q

Fructose 2,6-bisphosphate works on …

A

PFK1 to activate it

fructose 1,6-bisphosphate to deactivate it

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28
Q

What makes fructose 2,6-bisphosphate?

A

PFK2

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29
Q

What breaks down fructose 2,6-bisphosphate?

A

fructose 2,6-bisphosphatase

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30
Q

How does glucagon affect fructose 2,6-bisphosphate?

A

it inhibits PFK2 and activates fructose 2,6-bisphosphatase

downregulates fructose 2,6-bisphosphate to increase gluconeogenesis and decrease glycolysis

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31
Q

How does insulin affect fructose 2,6-bisphosphate?

A

it activates PFK2 and inhibits fructose 2,6-bisphosphatase

upregulates fructose 2,6-bisphosphate to increase glycolysis and decrease gluconeogensis

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32
Q

What is the goal of glucagon?

A

to add more glucose to the blood

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33
Q

What is PK regulated by?

A

ATP inhibits

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34
Q

What reaction does PK catalyze?

A

the conversion of PEP to pyruvate

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35
Q

lactate dehydrogenase

A

reduces pyruvate and forms lactic acid

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36
Q

How many steps are in lactic fermentation?

A

1

simultaneous reduction of pyruvate and oxidation of NAD+

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37
Q

Ethanol fermentation

A

2 steps

first have a decarboxylation step

converts sugar to ethanol, while oxidizing NAD+

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38
Q

Where does gluconeogensis take place?

A

in the liver and to a lesser extent, the kidneys

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39
Q

Where in the cell does gluconeogenesis take place?

A

in the mitochondria and then moves to the cytosol

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40
Q

What is the starting molecule for gluconeogenesis?

A

pyruvate

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41
Q

Where does pyruvate for gluconeogenesis come from?

A

proteins, glycerol from fatty acids, or lactate

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42
Q

How does gluconeogenesis convert pyruvate to PEP?

A

takes 2 steps

first, pyruvate carboxylase makes oxaloacetate in the mitochondria

then PEP carboxylkinase converts oxaloacetate to PEP in cytosol

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43
Q

How does gluconeogenesis convert F16BP to F6P?

A

uses fructose 1,6-bisphosphatase

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44
Q

How does gluconeogenesis convert G6P to glucose?

A

glucose 6-phosphatase

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45
Q

How is fructose 1,6-bisphophatase regulated?

A

inhibited by AMP and fructose 2,6-bisphophate

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46
Q

Where does the citric acid cycle take place?

A

in the mitochondria

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47
Q

Where does pyruvate dehydrogenase take place?

A

on the inner-mitochondrial membrane

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48
Q

How does pyruvate enter the mitochondria?

A

by being converted to acetyl-CoA

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49
Q

How does the pyruvate dehydrogenase complex work?

A

oxidizes pyruvate to acetyl-CoA by removing CO2

simultaneously reduces NAD+ to NADH

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50
Q

What is the structure of acetal-CoA

A

a thioester connected to CoA group

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51
Q

What is the main goal of the citric acid cycle?

A

to reduce electron carriers

make FADH2 and NADH

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52
Q

What are other names for the citric acid cycle?

A

Krebs Cycle

TCA cycle

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53
Q

What is the first step of the citric acid cycle?

A

acetyl-CoA combines with oxaloacetate to produce citrate

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54
Q

What is the rate limiting step of the citric acid cycle?

A

step 3

the conversion of isocitrate to alpha-ketoglutarate

lose a carbon to CO2

1 NADH produced

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55
Q

What is step 4 of the citric acid cycle?

A

convert alpha-ketoglutarate to succinyl-CoA

lose CO2

1 NADH produced

56
Q

What is the final step of the citric acid cyle?

A

convert malate to oxaloacetate

produce NADH

57
Q

What drives the thermodynamically unstable final step of the citric acid cycle?

A

Le Chatlier’s principle

oxaloacetate is quickly combined with acetyl-CoA when it is formed, driving the final step of the cycle

58
Q

What does one pyruvate molecule produce?

A 
1 NADH (PDC)
1 GTP
3 NADH
1 FADH2
2 CO2
59
Q

How many pyruvates does one glucose produce?

A

2

60
Q

What step of the ETC has the highest reduction potential?

A

the final step

oxygen is reduced to water

61
Q

What happens to NADH in the ETC?

A

it is oxidized to NAD+ at complex I

ends up generating 2.5 ATP

62
Q

What happens to FADH2 in the ETC?

A

it is oxidized to FAD+ at complex II

ends up generating 1.5 ATP

63
Q

Which molecule generates more ATP, NADH or FADH2?

A

NADH

64
Q

How many net ATP molecules are produced from one glucose?

A

around 30

65
Q

What happens to the electrons in the ETC?

A

they keep moving to higher reduction potentials

66
Q

What comes first in the ETC, ubiquinone or cytochrome c?

A

ubiquinone

67
Q

Where does control of aerobic respiration start?

A

at the pyruvate dehydrogenase complex

68
Q

What do high levels of fatty acids do to aerobic respiration?

A

they downregulate PDC since fatty acids can also become acetyl-CoA

69
Q

Cyanide and the ETC

A

cyanide can bind to cytochrome C’s heme group and interrupt the ETC

70
Q

cytochrome c makeup

A

cytochrome c is made up of a heme group and can carry one electron on its Fe

Fe3+ to Fe2+

71
Q

When glucose levels are low how can a cell get energy?

A

1) use lipids and make ketone bodies for energy

2) glycogen breakdown to release glucose

72
Q

Why is glycogen stored in a branched structure?

A

branching creates large number of terminal residues for glycogen phosphorylase to act on

glycogen branching also increases its solubility

73
Q

What type of glycosidic links can be broken down?

A

alpha links (in glycogen and starch)

74
Q

What type of glycosidic links can not be broken down?

A

beta links (in cellulose)

75
Q

What type of glycosidic bonds are seen in glycogen?

A

alpha 1,4 in chains and alpha 1,6 at branching points

76
Q

Where is glycogen stored?

A

muscle and liver cells

77
Q

When does glycogenesis occur in muscle cells?

A

after exercise when glycogen levels are depleted

78
Q

What is the starting product for glycogenesis?

A

glucose 6-phosphate

79
Q

Steps of glycogenesis

A

glucose 6-phosphate to glucose 1-phosphate to UDP glucose to glycogen

80
Q

Glycogen synthase

A

makes alpha 1,4 linkages on pre-existing branches

81
Q

glycogen branching enzyme

A

allows us to make new branches at alpha 1,6 linkages

82
Q

glycogenin

A

central protein in glycogen that allows glycogen linkages to start growing

83
Q

glycogen phosphorylase

A

breaks down glycogen at alpha 1,4 bonds

84
Q

general steps of glycolysis

A

glycogen to glucose 1-phosphate to glucose 6-phosphate

85
Q

phosphoglucomutase

A

interconverts glucose 1-phosphate and glucose 6-phosphate

86
Q

epinephrine and blood glucose levels

A

epinephrine increases blood glucose levels by activating glycogen phosphorylase in muscle cells

87
Q

glucagon and glycogen

A

glucagon raises blood glucose levels by activating glycogen phosphorylase in liver cells

88
Q

Ca2+ and glycogen

A

Ca2+ is released when muscles are contracting and using energy

Ca2+ indicates that we need glucose and activates glycogen phosphorylase in skeletal muscles

89
Q

How does insulin activate glycogen synthase?

A

it inhibits its inhibitor

90
Q

What does the Pentose phosphate pathway do?

A

it converts NADP+ to NADPH and glucose to ribose 5-phosphate

91
Q

ribose 5-phosphate

A

building block for nucleotides

produced from the pentose phosphate pathway

92
Q

What does the non-oxidative phase of the PPP do?

A

recycles ribose 5-phosphate to get G6P again

93
Q

Where is the non-oxidative phase of the PP used?

A

in cells that need more NADPH than ribose 5-phosphate

cells like liver cells and adipocytes that do not need lots of nucleotides

94
Q

What cells is insulin produced by?

A

insulin is produced by pancreatic B-cells

95
Q

How is insulin released?

A

when blood glucose levels are high, glucose enters pancreatic cells and goes through glycolysis

the ratio of intracellular ATP increases, which triggers K+ concentration to increase and then Ca2+ concentration to increase

Ca2+ triggers the release of insulin

96
Q

Acetylcholine and insulin

A

acetylcholine is produced by the sympathetic nervous system, so it triggers the release of insulin after digestion

97
Q

Norepinephrine and insulin

A

norepinephrine is secreted by the parasympathetic nervous system and increases blood sugar levels

so, norepinephrine inhibits insulin release

98
Q

How does insulin trigger the uptake of glucose?

A

when insulin binds to its receptors it triggers the release of GLUT4 receptors

99
Q

How does glucose move into the cell?

A

through facilitated diffusion

100
Q

How does insulin affect lipids and proteins?

A

promotes lipid and protein anabolism

101
Q

Type I diabetes

A

can’t produce insulin

102
Q

Type II diabetes

A

cells do not respond to insulin

103
Q

What cells produce glucagon?

A

pancreatic alpha cells

104
Q

What does glucagon promote?

A

glycogenolysis, gluconeogenesis, and lipolysis

105
Q

Where does glycolysis take place?

A

in the cytoplasm

106
Q

What happens after glycolysis if no O2 is present?

A

fermentation

pyruvate is reduced to lactate and NADH is oxidized to NAD+

107
Q

What are the possible starting products for gluconeogenesis?

A

pyruvate, lactate, alpha-ketoglutarmate, oxaloacetate

108
Q

What is the main enzyme in glycogenlysis?

A

glycogen phosphorylase

109
Q

When is beta oxidation used?

A

can make acetyl-CoA for the citric acid cycle when glycolysis is not working

110
Q

How does beta oxidation work?

A

oxidize the beta carbon of a fatty acid

111
Q

What are possible uses for acetyl-CoA?

A

Can enter the citric acid cycle or be converted into ketone bodies for transport

112
Q

What are possible uses for oxaloacetate?

A

can be used in the citric acid cycle or as a starting product for gluconeogenesis

113
Q

What are possible uses for glucose 6-phosphate?

A

glycolysis, PPP, and glycogenesis

114
Q

What is the first half of the citric acid cycle?

A

1) acetyl-CoA and oxaloacetate are combined to form citrate
2) citrate becomes alpha ketoglutarate

*produces 1 CO2 and 1 NADH

115
Q

Is the first step of the citric acid cycle energetically favorable?

A

yes, it is highly favorable and irreversible

116
Q

What is the rate limiting step of the citric acid cycle?

A

step 3

117
Q

What is the second half of the citric acid cycle?

A

1) alpha ketoglutarate to succinyl coA
2) malate to oxaloacetate

*2 NADH, 1 FADH2, 1 CO2

118
Q

How to remember the intermediates of the citric acid cycle?

A

Our City Is Kept Safe and Sound From Mobsters

Oxaloactetate, citrate, isocitrate, alpha-Ketoglutarate, succinyl-CoA, succinate, fumarate, malate

119
Q

PFK2

A

phosphorylates fructose 2,6-bisphophate which activates glycolysis/PFK1

120
Q

glyceraldehyde 3-phosphate dehydrogenase

A

catalyzes the reaction of glyceraldehyde 3-phosphate to 1,3-bisphosphoglyerate

produces NADH

part of glycolysis

121
Q

Lactate dehydrogenase

A

oxidizes NADH to reproduce NAD+

also performs reverse reaction

122
Q

How does NADH allow its electrons to enter the inner mitochondrial membrane?

A

through the glycerol 3-phosphate shuttle or the malate-aspartate shuttle

123
Q

What three steps must be overcome in gluconeogenesis?

A

1) pyruvate kinase
2) PFK1
3) hexokinase

124
Q

How do you bypass pyruvate kinase in gluconeogenesis?

A

Pyruvate carboxylase and PEP carboxykinase

125
Q

How do you bypass PFK1?

A

fructose-1,6-bisphophatase

126
Q

How do you bypass hexokinase?

A

glucose-6-phosphatase

127
Q

What is the rate limiting enzyme of the PPP?

A

glucose-6-phosphate dehydrogenase

128
Q

What regulates glucose-6-phosphate dehydrogenase?

A

NADP+ activates and NADPH deactivates

129
Q

What is the key enzyme in cholesterol synthesis?

A

HMG-CoA reductase

130
Q

What fatty acid can humans synthesize?

A

palmitic acid

131
Q

What happens before B-oxidation of fatty acids?

A

carnitine shuttle

132
Q

What does B-oxidation of fatty acids produce?

A

ketone bodies that can be used for acetyl-CoA

133
Q

How does protein excretion occur?

A

amino groups are excreted as urea

134
Q

How many times does the citric acid cycle turn for one molecule of glucose?

A

two turns

135
Q

What are the products of the citric acid cycle?

A

per 1 turn (2 turns per glucose)

3 NADH, 1 FADH2, 1 GTP

136
Q

How many ATP molecules per NADH?

A

2.5

137
Q

How many ATP molecules per FADH2?

A

1.5

MCAT Prep (22 decks)

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