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Biochemistry Flashcards

1
Q

What is glycogen?

A

Storage molecule for carbohydrates

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2
Q

What is glycogenesis?

A

Synthesis of glycogen from glucose

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3
Q

What is glycogenolysis?

A

Breakdown of glycogen to glucose

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4
Q

What enzyme controls glycogenesis?

A

Glycogen synthase

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5
Q

What enzyme controls glycogenolysis?

A

Glycogen phosphorylase

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6
Q

Where is glycogen the main storage molecule of glucose?

A

Liver and muscle cells

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7
Q

What is the same and what is the difference between glycogen in liver and muscle cells?

A

Same molecule- different function

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8
Q

When is glycogen broken down to glucose in the liver?

A

In between meals to maintain blood glucose levels for cells

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9
Q

When is glycogen from muscle cells used and how is glucose formed here?

A

During bursts of physical activity- through glycolysis and TCA cycle

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10
Q

What is gluconeogenesis?

A

Formation of glucose from non-carbohydrate precursors

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11
Q

When does gluconeogenesis occur?

A

When liver cannot produce glucose- prolonged starvation

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12
Q

What binds glucose molecules together to form glycogen?

A

Alpha 1,4 linkages

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13
Q

What are the branches of glycogen formed by?

A

Alpha 1, 6 linkages

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14
Q

What do alpha 1, 4 linkages form between?

A

1C carbon of a glucose and a 4C carbon of another

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15
Q

What do alpha 1, 6 linkages form between?

A

1C carbon of a glucose and a 6C carbon of another

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16
Q

What increases how fast glucose can be synthesised or broken down?

A

The more ends the molecule has

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17
Q

What is the protein at the centre of glycogen known as?

A

Glycogenin

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18
Q

What does glycogenin do?

A

Binds 4 glucose molecules to itself

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19
Q

What does glycogenin with glucose attached act as?

A

A precursor for glycogen production

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20
Q

What has to happen to glucose to make glycogen?

A

Phosphorylated

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21
Q

What is formed from the phosphorylation of glucose?

A

Glucose-6-phosphate

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22
Q

What enzyme catalyses the phosphorylation of glucose?

A

Hexokinase

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23
Q

What must happen to glucose-6-phosphate in order for it to form either glucose or glycogen?

A

Transformed to glucose-1-phosphate

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24
Q

What enzyme moves the phosphate in from C6 to C1?

A

Phosphoglucomutase

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25
Q

What is the substrate for glycogen synthase?

A

UDP-glucose

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26
Q

What happens in terms of ATP for every added glucose molecule to form glycogen?

A

1 ATP is consumed

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27
Q

Where is glucose attached to UDP?

A

2nd phosphate group

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28
Q

What is the glucose phosphate bond in terms of energy?

A

High energy

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29
Q

What does the enzyme transglycosylase do?

A

Introduces alpha 1, 6 glycosidic branches into glycogen

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30
Q

What is the product of glycogen breakdown?

A

Glucose-1-phosphate

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31
Q

After glucose-1-phosphate has formed glucose-6-phosphate in glycogenolysis, what can this do?

A

Be dephosphorylated in the liver to release glucose into the bloodstream or not be dephosphorylated in muscle

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32
Q

How is glucose formed in the liver transported into the bloodstream?

A

GLUT2

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33
Q

What does insulin stimulate?

A

Glycogen synthase

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34
Q

What does insulin inhibit?

A

Glycogen phosphorylase

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35
Q

What does glucagon stimulate?

A

Glycogen phosphorylase

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36
Q

What does glucagon inhibit?

A

Glycogen synthase

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37
Q

What do adrenaline and cortisol stimulate?

A

Glycogen phosphorylase

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38
Q

What happens in glycogen storage disease?

A

Increased glycogen deposits in the liver, muscle, both

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39
Q

What are some precursors for gluconeogenesis?

A

Lactic acid, amino acids, glycerol

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40
Q

When is lactic acid synthesised?

A

By skeletal muscle under anaerobic conditions

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41
Q

Where are amino acids derived from?

A

Muscle protein by proteolysis

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42
Q

Where is glycerol derived from?

A

Triglycerides by lipolysis in adipose tissue

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43
Q

What is gluconeogenesis in terms of energy?

A

Energy consuming

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44
Q

Where does gluconeogenesis occur?

A

Liver or small amounts in the kidneys

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45
Q

Is gluconeogenesis the opposite of glycolysis?

A

Almost, but not

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46
Q

What does gluconeogenesis require?

A

4 unique liver enzymes

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47
Q

What does gluconeogenesis proceed via the synthesis of?

A

Oxaloacetate in the mitochondria

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48
Q

What energy does gluconeogenesis use?

A

4 ATP and 2 GTP

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49
Q

What type of amino acids cannot be used for gluconeogenesis?

A

Hetogenic

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50
Q

What type of amino acids can be used for gluconeogenesis?

A

Glucogenic

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51
Q

What does glucagon show?

A

A need for glucose- stimulates gluconeogenesis/inhibits glycolysis

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52
Q

What does insulin show?

A

Too much glucose- stimulates glycolysis/inhibits gluconeogenesis

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53
Q

What does a high AMP or ADP signal?

A

need for energy- breakdown glucose

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54
Q

What does high ATP signal?

A

Gluconeogenesis

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55
Q

What do high concentrations of fructose 2, 6 biphosphate, citrate, alanine and acetyl CoA signal?

A

Gluconeogenesis

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56
Q

What does increased aft intake with no energy expenditure result in?

A

Increased adipocytes and increased fat in adipocytes

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57
Q

What can fat deficiency lead to?

A

Membrane disorders, increased skin permeability and mitochondrial damage

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58
Q

What are fat soluble vitamins?

A

ADEK

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59
Q

Where are fat soluble vitamins stored?

A

In body fat

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60
Q

What can fats otherwise be known as?

A

Lipids

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61
Q

What are simple lipids?

A

Fatty acids and triglycerides

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62
Q

What are compound lipids?

A

Phospho or glycolipids

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63
Q

What is cholesterol and example of?

A

A steroid

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64
Q

What part of lipid structure makes them insoluble in water?

A

Long chain fatty acids

65
Q

What is the main energy form in adipose tissue and dietary fat?

A

Triglycerides

66
Q

What do triglycerides consist of?

A

3 fatty acids and glycerol

67
Q

Describe saturated fatty acids?

A

No double bonds

68
Q

Describe unsaturated fatty acids?

A

Single double bond

69
Q

Describe polyunsaturated fatty acids?

A

Many double bonds

70
Q

What formation are the double bonds of fatty acids usually in?

A

Cis isomer

71
Q

What type of fatty acids have their double bond 3 carbons from the end of the chain?

A

Omega 3 fatty acids

72
Q

What are the main products of fat digestion?

A

Glycerol, fatty acids and monoglycerides

73
Q

Where is glycerol absorbed?

A

Intestinal epithelial cells

74
Q

Short/medium chain fatty acids enter the portal system straight away. What must long chain fatty acids become first?

A

Triglycerides

75
Q

How do triglycerides enter the blood?

A

Combine with other lipids and proteins to form chylomicrons which enter the lymph system and then blood

76
Q

What can happen to free fatty acids when they arrive at tissues?

A

Resynthesised to triglycerides for storage or oxidised to produce energy on muscle cells

77
Q

What is lipolysis?

A

Breakdown of lipids

78
Q

What do fatty acids have to be converted to before they can be oxidised to form energy? Where does this happen and what does it require?

A

CoA derivatives- in the cytoplasm and requires 2 ATP

79
Q

Where does further oxidation take place?

A

Mitochondrial matrix

80
Q

What facilitates transport of fats converted to CoA derivatives from the cytoplasm to matrix?

A

Carnitine shuttle- acyl CoA in matrix

81
Q

Where is the beta oxidation cycle of reactions?

A

Mitochondrial matrix

82
Q

What is the substrate for beta oxidation?

A

Acyl CoA

83
Q

What is formed when Acyl CoA is shortened by 2 carbons?

A

1 Acetyl CoA and a shortened acyl CoA, 1 FADH2 and 1 NADH + H+

84
Q

What is formed at the end of the beta oxidation pathway?

A

2 Acetyl CoAs

85
Q

What types of fats require additional enzymes to be oxidised?

A

Unsaturated, odd chain and branched chain

86
Q

What enzyme activates glycerol to glycerol 3 phosphate?

A

Glycerol kinase

87
Q

What is glycerol 3 phosphate dehydrogenated to?

A

Dyhydroxyacetone phosphate

88
Q

What are ketone bodies associated with?

A

Oxidation of fats

89
Q

Where are ketone bodies formed and from what?

A

Liver mitochondria from Acetyl CoA

90
Q

What makes ketone bodies be generated?

A

Lots of acetyl CoA

91
Q

What problem to ketone bodies cause?

A

Oxaloacetate is consumed for gluconeogenesis

92
Q

What does increased ketone bodies in the blood cause?

A

Acidosis, loss of function, acidic coma, death

93
Q

Ultimately fat is broken down to form what?

A

ATP

94
Q

What is lipgenesis?

A

Fatty acid synthesis

95
Q

Where does lipogenesis mainly take place?

A

Liver

96
Q

What type of redox process is lipogenesis and so what is required?

A

Reductive process- electrons are required

97
Q

What is the substrate for lipogenesis?

A

Acetyl CoA

98
Q

Where specifically in liver cells does lipogenesis take place?

A

Cytoplasm of cells

99
Q

What facilitates the transport of acetyl CoA from the mitochondrial matrix to the cytoplasm?

A

Citrate

100
Q

What is Acetyl CoA converted to before fatty acids are synthesised?

A

Malonyl-CoA

101
Q

What is Malonyl CoA responsible for?

A

Giving carbon to fatty acids

102
Q

What enzyme converts acetyl CoA to malonyl CoA?

A

Acetyl CoA carboxylase

103
Q

What is the only type of fatty acid synthesised through fatty acid synthase?

A

Long chain saturated

104
Q

What is the source of electrons for lipogenesis?

A

NADPH

105
Q

What is the function of acyl carrier protein contained in fatty acid synthase?

A

The growing chain is attached to it

106
Q

When does fatty acid synthase stop having an effect?

A

Once the chain is 16C in length

107
Q

In lipogenesis, further enzymes are required to do what?

A

Elongate the chains or add to double bonds

108
Q

When are levels of Palmitoyl CoA high?

A

Excess fatty acids

109
Q

What has to be present for synthesis of triglycerides?

A

Glycerol 3 phosphate

110
Q

What produces glycerol 3 phosphate and from what?

A

Liver from glucose

111
Q

Are all amino acids converted to Acetyl CoA?

A

No

112
Q

Can all amino acids be oxidised in the TCA cycle?

A

Yes

113
Q

What happens to amino acids if they are not used?

A

They are degraded in the liver

114
Q

What does amino acid breakdown produce which has to be removed?

A

Nitrogen (originally ammonia and ammonium ions)

115
Q

What is the major nitrogen containing excretory molecule?

A

Urea

116
Q

Where is urea formed?

A

Liver

117
Q

How many nitrogens does urea have?

A

2

118
Q

In all tissues, the first stage of amino acid catabolism is what?

A

Amino group is transferred onto a heto acid- usually forms glutamic acid

119
Q

The second stage of amino acid catabolism which occurs in the liver is what?

A

Removal of amino group from glutamic acid to form free ammonia

120
Q

How is an amino acid transported to the liver?

A

Glutamate is transferred to pyruvate to give alanine

121
Q

Where are the main transporters of nitrogen?

A

Blood

122
Q

What is the carbon found in urea derived from?

A

CO2

123
Q

What are the products of urea production?

A

Urea and a by product which can enter the TCA cycle

124
Q

After the removal of the alpha amino group, what are the remaining carbons converted to?

A

Major metabolic intermediates

125
Q

What are ketogenic amino acids degraded to?

A

Acetyl CoA- can give rise to ketone bodies and fatty acids

126
Q

What are glucogenic amino acids degraded to?

A

Pyruvate/TCA cycle intermediates- can give rise to glucose

127
Q

Glucose is our primary energy source which is oxidised to?

A

CO2 and H2o

128
Q

What 3 pathways can glucose take?

A
  • Pentose Phosphate pathway (oxidation)
  • Fermentation by anaerobic glycolysis
  • Oxidation through aerobic glycolysis
129
Q

What is formed from glucose through the pentose phosphate pathway and what does this do?

A

Ribose-5-phosphate: precursor for nucleotide synthesis and DNA repair, essential for growth

130
Q

What is formed from glucose through anaerobic glycolysis and what does this do?

A

Lactate- rapid, inefficient production of ATP

131
Q

What is formed from glucose through aerobic glycolysis and what does this do?

A

Pyruvate- efficient ATP production

132
Q

What two ways can glucose be transported into cells?

A

Glucose/Na+ co-transporters or passive facilitated diffusions

133
Q

Which GLUT transporters are found in the brain and have a low Km?

A

GLUT1 and GLUT3

134
Q

Describe GLUT2?

A

Found in liver and beta cells, high Km and is insulin dependent

135
Q

Describe GLUT4?

A

Found in muscle and adipose tissue and is insulin dependent

136
Q

Describe GLUT5?

A

Fructose transport in the gut

137
Q

What is formed in glycolysis?

A

2 pyruvate, 4ATP, 2H2O, 2NADH, 2H+

138
Q

What enzyme controls substrate entry in glycolysis?

A

Hexokinase

139
Q

What enzyme controls rate of flow in glycolysis?

A

Phosphofructokinase

140
Q

What enzyme controls product exit in glycolysis?

A

Pyruvate kinase

141
Q

What are 3 inhibitors of glycolysis?

A

ATP, citrate, H+

142
Q

What is used to ferment pyruvate to lactate in anaerobic conditions?

A

NADH

143
Q

When is NADH regenerated in glycolysis?

A

Beginning of stage 3

144
Q

Catabolism of pyruvate must cause reduction of what to what?

A

NAD+ to NADH + H+

145
Q

How is NAD+ regenerated?

A

Oxidative metabolism of pyruvate

146
Q

Where does the TCA cycle occur?

A

Mitochondrial matrix

147
Q

How does pyruvate enter the mitochondrial matrix?

A

By an H+ gradient from the cytosol

148
Q

What does pyruvate dehydrogenase complex catalyse?

A

Oxidation of pyruvate to acetyl CoA

149
Q

Is pyruvate oxidation to acetyl CoA reversible?

A

No

150
Q

How many reactions are there in the TCA cycle?

A

8

151
Q

2C acetyl CoA combines with 4C ? to form citrate?

A

Oxaloacetate

152
Q

What happens to 6C citrate in the TCA cycle?

A

It is decarboxylated twice to form CO2

153
Q

What does the TCA cycle yield in terms of electron donors and energy?

A

1 GTP, NADH+H+, FADH2

154
Q

All enzymes of the TCA cycle are located in the mitochondrial matrix except 1. What is this and where is it found?

A

Succinate dehydrogenase- inner mitochondrial membrane

155
Q

In oxidative phosphorylation, NADH and FADH2 are used to form what and how?

A

Reduction of O2 to H2O

156
Q

The energy created in the reduction reaction of O2-H2O is used to do what in oxidative phosphorylation?

A

Pump proteins from the matrix to the intermembrane spaces

157
Q

What is used to phosphorylate ADP to ATP in oxidative phosphorylation?

A

Energy of proton flow

158
Q

What are used to help NADH across the mitochondrial membrane?

A

Malate aspartate shuttle and glycerol-3-phosphate

159
Q

What are cytochromes?

A

Proteins with a haem group as a co-factor which can take up and release electrons

GI (17 decks)

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