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MCAT Biology > Metabolism Overview > Flashcards

Metabolism Overview Flashcards

1
Q

4 characteristics of GLUT 2?

A

found in liver and pancreas
high Km
not responsive to insulin
cannot be saturated under normal conditions

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2
Q

3 characteristics of GLUT 4?

A

found in adipose tissue and muscles
low Km
stimulated by insulin (mvt of GLUT 4 to the membrane by exocytosis)

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3
Q

What is the normal glucose concentration in peripheral blood?

A

4-6 mM

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4
Q

Where does glycolysis take place?

A

cytoplasm

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5
Q

Does glycolysis require O2?

A

No

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6
Q

What are the products of glycolysis?

A

Pyruvate + 2 ATP + 2 NADH

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7
Q

Where is pyruvate converted to acetyl-CoA?

A

Mitochondria

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8
Q

What are the products of pyruvate conversion to acetyl-CoA?

A

1 Acetyl-CoA + 1 CO2 + 1 NADH`

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9
Q

Does pyruvate conversion require O2?

A

No

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10
Q

In what organs does glycogenesis and glycogenolysis occur? For what purpose?

A

Liver: maintain constant levels of glucose
Muscles: provide glucose to the muscle during exercise

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11
Q

Where do glycogenesis and glycogenolysis occur in the cell?

A

Cytoplasm

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12
Q

Do glycogenesis and glycogenolysis require O2?

A

No

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13
Q

Where does gluconeogenesis occur in the cell?

A

First step takes place in the mitochondria (pyruvate to oxaloacetate)
The rest of the reactions take place in the cytosol

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14
Q

In what organs does gluconeogenesis occur? For what purpose?

A

Liver and kidneys

To maintain blood glucose levels during fasting

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15
Q

Does gluconeogenesis require O2?

A

No

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16
Q

What is the energy source for glycogenesis?

A

UTP

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17
Q

What is the energy source for gluconeogenesis?

A

1 ATP + 1 GTP

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18
Q

What happens to acetyl-CoA once it is synthesized from pyruvate? 2 options

A
  1. If ATP is needed: entry into TCA

2. If there is enough ATP: fatty acid synthesis

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19
Q

What happens to pyruvate after glycolysis? 2 options

A
  1. If there isn’t enough acetyl-CoA: converted to acetyl-CoA

2. If there is enough acetyl-CoA: converted to oxoloacetate to enter gluconeogenesis

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20
Q

What happens to the 2 NADH produced by glycolysis? 2 options

A
  1. If O2/mitochondria are present: oxidized by ETC

2. If O2/mitochondria aren’t present: oxidized by fermentation

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21
Q

Where does the pentose phosphate pathway occur?

A

Cytoplasm

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22
Q

What does the PPP generate?

A

NADPH and sugars

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23
Q

What happens to NADPH after PPP? 3 options

A
  1. used for fatty acid synthesis
  2. bactericidal bleach in white blood cells
  3. acts as a reducing agent to maintain glutathione stores to protect against reactive O species
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24
Q

What happens to the sugars after PPP?

A

Nucleotide synthesis

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25
Q

What metabolic processes does insulin stimulate?

A
  1. PPP
  2. Glycolysis
  3. Fatty acid synthesis
  4. Glycogenesis
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26
Q

What are the 3 pathways to generate acetyl-CoA?

A
  1. Glycolysis and generation from pyruvate
  2. Fatty acid oxidation = beta oxidation
  3. From C skeletons of ketogenic amino acids, ketone bodies, and alcohol
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27
Q

Does the citric acid cycle require O2?

A

No, but it cannot occur without O2 being present, since it will be used by the ETC, which is the next step –> the citric acid cycle is an aerobic process!

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28
Q

Does the ETC require O2?

A

Yes

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29
Q

What are the products of the citric acid cycle?

A

3 NADH + 1 FADH2 + GTP + 2 CO2 + CoA-SH

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30
Q

What is another name for glycolysis?

A

Aerobic respiration

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31
Q

How much ATP does 1 NADH generate?

A

1.5 or 2.5 ATP

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32
Q

How much ATP does 1 FADH generate?

A

1.5 ATP

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33
Q

How much ATP does 1 GTP generate?

A

1 ATP

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34
Q

Is the electron transport of the ETC spontaneous or nonspontaneous?

A

Spontaneous = exergonic

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35
Q

What are the 2 transport mechanisms to bring NADH into the mitochondrial intermembrane space? How much ATP does each generate?

A
  1. Glycerol-3-phosphate shuttle: 1.5 ATP/1 NADH

2. Malate aspartate shuttle: 2.5 ATP/1 NADH

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36
Q

How do I know which NADH shuttle a cell uses?

A

More aerobic organs will use the most efficient one: malate-aspartate shuttle

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37
Q

Where does oxidative phosphorylation occur?

A

Mitochondrial inner membrane, generating ATP into the matrix

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38
Q

How does low O2 affect oxidative phosphorylation?

A

Inhibits it

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39
Q

How does low O2 affect the concentration of NADH and FADH2?

A

Increases! They accumulate because they cannot enter the ETC

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40
Q

How does low O2 affect the citric acid cycle?

A

Inhibits it to stop producing NADH and FADH2, which are already abundant

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41
Q

How do high levels of ADP affect the citric acid cycle?

A

Stimulates it

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42
Q

How does citric acid cycle activation affect the concentration of NADH and FADH2?

A

Increases them

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43
Q

What metabolic processes does glucagon stimulate?

A
  1. Gluconeogenesis
  2. Fatty acid beta-oxidation
  3. Ketolysis
  4. Glycogenolysis
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44
Q

Where does fatty acid synthesis occur in the cell?

A

Cytoplasm

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45
Q

Where does fatty acid beta-oxidation occur?

A

Mitochondria (and a little in the peroxisome)

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46
Q

Where does conversion from pyruvate to acetyl-CoA occur?

A

Mitochondria

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47
Q

Where does ketogenesis occur?

A

Mitochondria

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48
Q

When does ketogenesis occur?

A

When acetyl-CoA accumulates in the fasting state

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49
Q

Where does ketolysis occur?

A

Mitochondria

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50
Q

What does ketolysis generate?

A

Acetyl-CoA

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51
Q

What does ketogenesis generate?

A

Ketone bodies for energy source

52
Q

When does protein catabolism occur?

A

Extreme energy deprivation

53
Q

In which organs does protein catabolism occur?

A

Muscle and liver

54
Q

What is the purpose of fermentation?

A

Utilizing the excess NADH when there isn’t oxygen or mitochondria and regenerates NAD+

55
Q

When does excess fermentation occur?

A

When there isn’t enough O2 for the NADH to go to the ETC

56
Q

When does fatty acid synthesis occur?

A

When there is excess carbohydrates and protein from diet

57
Q

In what organ does fatty acid synthesis occur?

58
Q

In what compound are fatty acids stored? In which organ is this synthesized?

A

Tryacylglycerol

Liver (and a little in adipose tissue)

59
Q

Which metabolic processes do cortisol and cortisone stimulate?

A
  1. Fatty acid beta-oxidation

2. Inhibition of glucose uptake

60
Q

Which metabolic processes do catecholamines stimulate?

A
  1. Glycogenolysis

2. Fatty acid beta-oxidation

61
Q

What are ketone bodies made from?

A

Acetyl-CoA

62
Q

Where does the citric acid cycle occur?

A

Mitochondria

63
Q

What is the first step to start the citric acid cycle?

A

Citrate is formed from acetyl-CoA

64
Q

What is oxidative stress?

A

Low NADPH level –> low glutathione –> reactive oxygen species from aerobic metabolism are not reduced –> oxidize lipid membranes (lysis) OR DNA damage (cancer)

65
Q

What are flavoproteins?

A

A subclass of electron carriers derived from vitamin B2

66
Q

When does the postprandial/well-fed state occur?

A

3-5 hours after a meal

67
Q

What are the two types of cells that are insensitive to insulin?

A

Nervous tissue and red blood cells

68
Q

When does the postabsorptive/fasting state occur?

A

12 hours after a meal

69
Q

When does the prolonged fasting/starvation state occur?

A

24 hours after a meal

70
Q

What is the impact of T3 and T4 on metabolic processes?

A

Increase the basal metabolic rate: increase O2 consumption

71
Q

Which hormone is stronger: T3 or T4?

72
Q

What are the cells of the liver called?

A

Hepatocytes

73
Q

What energy source does a resting muscle use?

A

Glucose and free fatty acids from the blood

74
Q

What energy source does an active muscle use? 3 steps

A

First: creatine phosphate (ADP to ATP)
Second: Glycogen stores and fatty acids
Third: fatty acids

75
Q

What energy source does the heart use?

A

Always fatty acid oxidation

76
Q

What energy source does the brain and NS use?

A

Glucose and up to 2/3 ketone bodies during starvation

77
Q

What is the respiratory quotient equal to?

A

RQ = CO2 produced / O2 consumed

78
Q

Why are glucocorticoids related to stress-related weight gain?

A

They inhibit glucose uptake, so the excess glucose promotes fat storage

79
Q

RQ of 0.7 indicates which fuel is being metabolized?

80
Q

RQ of 1 indicates which fuel is being metabolized?

A

Carbohydrates

81
Q

RQ of 0.8-0.9 indicates which fuel is being metabolized?

A

Amino acids

82
Q

Delta G of cAMP?

83
Q

Delta G of ATP?

84
Q

Delta G of creatine phosphate?

85
Q

Delta G of ADP?

86
Q

Delta G of AMP?

87
Q

Delta G of glucose-6-phosphate?

88
Q

How is mitochondrial acetyl-CoA carried to the cytoplasm?

A

Citrate shuttle

89
Q

What are the reactants of cholesterol synthesis?

A

1 ATP + 1 NADPH + acetyl-CoA

90
Q

Which anabolic process is referred to as nontemplate synthesis?

A

Fatty acid synthesis

91
Q

How is cytoplasmic acetyl-CoA carries to the mitochondria?

A

Carnitine shuttle

92
Q

Which amino acids are glucogenic?

A

All but leucine and lysine

93
Q

Which amino acids are ketogenic?

A 
FITTT + leucine and lysine:
Phe
Isole
threonine
trypto
tyrosine
94
Q

How does the body get rid of excess nitrogen?

A

Urea cycle

95
Q

What is the the only fatty acid that can be synthesized by humans de novo?

A

palmitic acid: 16:0 (16 Cs and 0 double bonds)

96
Q

What are the electron donor and acceptor in Complex I of the ETC? Through?

A 
NADH and CoQ
Flavin mononucleotide (FMN) and an iron-sulfer cluster
97
Q

How many H+ are pumped in Complex III of the ETC?

98
Q

What are the electron donor and acceptor in Complex II of the ETC? Through?

A

Succinate –> CoQ

Through FADH2 and iron-sulfur cluster

99
Q

How many H+ are pumped in Complex II of the ETC?

100
Q

How many H+ are pumped in Complex I of the ETC?

101
Q

How many H+ are pumped in Complex IV of the ETC?

102
Q

What are the electron donor and acceptor in Complex IV of the ETC? Through?

A

Cytochrome c –> O2

Through cytochrome ala3

103
Q

What are the electron donor and acceptor in Complex III of the ETC?

A

CoQH2 –> cytochrome c

104
Q

What are the two other carbohydrates that can be broken down to enter glycolysis?

A

Fructose and galactose

105
Q

What are the 5 steps of fatty acid synthesis?

A
  1. Activation
  2. Bond formation
  3. Reduction
  4. Dehydration
  5. Reduction
106
Q

Structure of acetyl-CoA?

A

CH3-C=O-S-CoA

107
Q

Structure of pyruvate?

A

CH3-C=O-COOH

108
Q

What are the 4 steps of fatty acid beta-oxidation?

A
  1. Oxidation
  2. Hydration
  3. Oxidation
  4. Cleavage
109
Q

How do I know how many cycles of beta-oxidation occur?

A 
# cycles = n/2 - 1 
n = # of Cs in chain
110
Q

How many NADH and FADH2 are produced per cycle of beta oxidation?

111
Q

What is the energy source for fatty acid beta oxidation?

112
Q

How many ATP molecules are generated per acetyl-CoA?

113
Q

Steps to find out the number of ATP molecules per fatty acid?

A
  1. Calculate the number of cycles of beta-oxidation necessary
  2. Calculate the number of NADH and FADH2 from those cycles (1 each per cycle) and how much ATP they generate
  3. Divide number of Cs by 2 = number of acetyl-CoA molecules produced –> 10 ATP per molecule
  4. Substract 1 ATP needed to activate the beta-oxidation
114
Q

How many kcal/gram from proteins?

115
Q

How many kcal/gram from carbs?

116
Q

How many kcal/gram from fats?

117
Q

What are the 3 roles of the peroxisome? What do they contain?

A
  1. Breakdown of very long chain fatty acids through beta-oxidation
  2. Phospholipid synthesis participation
  3. Involved in pentose phosphate pathway

They contain hydrogen peroxide: H2O2

118
Q

What are the 2 important unsaturated fatty acids that humans can synthesize?

A

alpha linolenic acid and linoleic acid

119
Q

In what organs does fatty acid synthesis take place?

120
Q

Where are fatty acids stored?

A

In adipose tissue

121
Q

What are the 2 important ketone bodies?

A
  1. Acetoacetate

2. 3-hydroxybutyrate

122
Q

Which metabolic processes does growth hormone affect?

A
  1. Stimulates fatty acid beta oxidation

2. Inhibits glycogenesis

123
Q

What would cause the lowest ATP production: problem at complex I or IV?

124
Q

What are the reactants and products of fermentation in humans?

A

Glucose —> 2 Pyruvate + 2 NADH + 2 ATP

2 Pyruvate + 2 NADH —> 2 lactate

125
Q

What can other types of fermentation produce?

A

In yeast: alcohol

MCAT Biology (18 decks)

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