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year 1 > GI - biochemistry > Flashcards

GI - biochemistry Flashcards

1
Q

what is glycogenesis

A

the synthesis of glycogen from glucose

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2
Q

what enzyme causes glycogenesis

A

glycogen synthase

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3
Q

what is glycogenolysis

A

the breakdown of glycogen to form glucose

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4
Q

what enzyme causes glycogenolysis

A

glycogen phosphorylase

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5
Q

what type of reaction is glycogenolysis

A

phosphorolysis

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6
Q

what does insulin do to glycogenesis

A

insulin stimulates glycogenesis

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7
Q

what does insulin do to glycogenolysis

A

insulin inhibits glycogenolysis

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8
Q

what does glucagon do to glycogenesis

A

glucagon inhibits glycogenesis

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9
Q

what does glucagon do to glycogenolysis

A

glucagon stimulates glycogenolysis

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10
Q

where is glycogen found

A

liver and muscle cells

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11
Q

what is glycogen used for in liver cells

A

stoked then released to maintain blood glucose concentration

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12
Q

what is glycogen used for in muscle cells

A

consumed within the muscle cell to produce ATP by glycolysis - not available for maintenance of blood glucose

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13
Q

how is glycogen released from liver to maintain BSL

A

liver dephosphorylates glucose-6-phosphate and releases it into blood as glucose

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14
Q

what maintains BSL immediately following meals

A

dietary CHO

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15
Q

what maintains BSL between meals

A

glycogenolysis

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16
Q

what maintains BSL when no dietary CHO is available and liver stores of glycogen are depleted and over night

A

gluconeogenesis

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17
Q

what bonds form long straight chains of glucose

A

alpha-1,4-glycosidic bonds

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18
Q

what bonds form branches in glycogen molecule

A

alpha-1,6-glycosidic bonds

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19
Q

true/false

the more branches a glycogen molecule has the greater the rate glucose can be added or cleaved off

A

true - more terminal ends

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20
Q

what is glycogenin

A

glycogen primer of 4 glucose molecules for glycogenesis

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21
Q

true/false

glycogen synthase starts glycogenesis from scratch

A

false

it adds extra glucose monomers to the existing glycogen formed by glycogenin primer

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22
Q

how often are branches introduced to the glycogen chain

A

every 10 glucose

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23
Q

what kind of bonds does glycogen synthase introduce to the glycogen polymer

A

alpha-1,4-glycosidic bonds

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24
Q

what enzyme introduces alpha-1,6-glycosidic bonds to glycogen

A

transglycosylase

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25
Q

what bonds does glycogen phosphorylase break

A

alpha-1,4-glycosidic bonds

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26
Q

what do adrenaline, cortisol and glucagon do to the rate of glycogenolysis

A

increase rate

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27
Q

what is the name of the transporter in liver cells that transports glucose into blood

A

GLUT2

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28
Q

what enzyme converts glucose into glucose-6-phosphate

A

hexokinase

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29
Q

what are the 2 options of fate of the glucose-6-phosphate

A

glycolysis

or converted to glucose-1-phosphate

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30
Q

what enzyme converts glucose-6-phosphate to glucose-1-phosphate

A

phosophglucomutase

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31
Q

what enzyme converts glucose-1-phosphate to UDP-glucose

A

UDP-glucose pyrophosphorylase

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32
Q

what enzyme converts UDP-glucose into glycogen by adding another glucose (1 at a time)

A

glycogen synthase

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33
Q

how is UTP regenerated in glycogenesis

A

UDP is produced as a bi-product at the end of the reaction when UDP-glucose forms glycogen by adding a glucose
the UDP is then phosphorylated to UTP by ATP

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34
Q

for each glucose added to glycogen how many ATP are used

A

1

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35
Q

what is the rate limiting step of glycogenolysis

A

glycogen phosphatase removing a glucose from glycogen by adding a phosphate

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36
Q

what enzyme converts glucose-1-phosphate into glucose-6-phosphate

A

phosphoglucomutase

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37
Q

what enzyme converts glucose-6-phosphate into glucose by phosphorylating

A

glucose-6-phosphatase

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38
Q

what is gluconeogenesis

A

synthesis of glucose from non-CHO precursors

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39
Q

what is the substrate of gluconeogenesis

A

pyruvate

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40
Q

what is the first stage in gluconeogenesis

A

pyruvate to oxaloacetate

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41
Q

where is energy for gluconeogenesis obtained

A

oxidation of fatty acids from adipose tissue

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42
Q

what are the 3 precursor molecules for gluconeogenesis

A

lactate
amino acids
glycerol

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43
Q

how many ATPs and how many pyruvate are needed to form 1 glucose molecule in gluconeogenesis

A

6 ATP

2 pyruvate

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44
Q

where does gluconeogenesis occur

A

liver

small amount in kidneys

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45
Q

where is lactate produced

A

anaerobically respiring skeletal muscle

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46
Q

how is lactate converted into pyruvate for gluconeogenesis

A

cori-cycle

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47
Q

what is the cori cycle

A

blood transports lactate to liver where it is converted into pyruvate and then into glucose which is transported back to the muscle cell/blood

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48
Q

could the cori cycle go on forever

A

no - consumes 6 ATP and produces 2

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49
Q

how are amino acids produced

A

proteolysis of muscle protein

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50
Q

how do amino acids enter gluconeogenesis

A

either converted to oxaloacetate from pyruvate

or enter TCA cycle through Acetyl-CoA which results in the eventual formation of oxaloacetate

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51
Q

what is the condition for amino acids to enter the TCA cycle

A

oxaloacetate must be present

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52
Q

what is the TCA intermediate needed for gluconeogenesis

A

oxaloacetate

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53
Q

how is glycerol formed for gluconeogenesis

A

lipolysis of triglycerides in adipose tissue

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54
Q

what is the effect of glucagon on glycolysis

A

glucagon inhibits glycolysis

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55
Q

what is the effect of glucagon on gluconeogenesis

A

glucagon stimulates gluconeogenesis

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56
Q

what is the effect of insulin on glycolysis

A

insulin stimulate glycolysis

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57
Q

what is the effect of insulin on gluconeogenesis

A

insulin inhibits gluconeogenesis

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58
Q

if [ADP] or [AMP] is high in a cell what happens to gluconeogenesis

A

inhibited - cell has low energy

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59
Q

if [ATP] is high in a cell what happens to gluconeogenesis

A

stimulated - cell has high energy

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60
Q

if molecules associated with the TCA cycle are high in a cell what happens to gluconeogenesis

A

gluconeogenesis is stimulated

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61
Q

if fructose-2,6-biphosphate (high in fed state) is high in a cell what happens to gluconeogenesis

A

gluconeogenesis is inhibited

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62
Q

what do citrate, alanine and acetyl-coA do to gluconeogenesis

A

simulate gluconeogenesis

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63
Q

how many liver enzymes are required to do the reverse of the 3 irreversible steps of glycolysis

A

4

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64
Q

what are the enzymes of 3 irreversible steps of glycolysis

A

hexokinase
phosphofructokinase
pyruvate kinase

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65
Q

what are the 3 irreversible steps of glycolysis

A

glucose –> glucose-6-phosphate
fructose-6-phosphate –> fructose-1,6-biphosphate
phosphoenolpyruvate –> pyruvate

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66
Q

true/false

lipids provide 2 times the energy of CHOs

A

true

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67
Q

do fatty acids tend to be cis or trans

A

cis

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68
Q

do essential fatty acids tend to be saturated, unsaturated or polyunsaturated

A

polyunsaturated

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69
Q

where does the synthesis of fatty acids occur and from what

A

cytoplasm

acetyl-CoA

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70
Q

what bonds join triglycerides

A

ester bonds

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71
Q

what happens when fatty acids and monoglycerides are absorbed by the intestinal mucosa

A

converted back into triglycerides and incorporated into chylomicrons which enter the lymph

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72
Q

what enzyme cleaves chylomicrons to release FAs and TGIs

A

lipoprotein lipase

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73
Q

what is the fate of the free fatty acids

A
  • converted to TGIs for storage in adipose tissue

- oxidised for energy in muscle cells

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74
Q

what is the effect of adrenaline on hormone sensitive lipases

A

fat broken down (lipolysis) for oxidation when needed

75
Q

what must happen in order for fatty acids to enter the mitochondria

A

must form a CoA derivative

76
Q

how is a coA derivative of FA formed and where

A

in cytoplasm

Co-A is added to form acyl-coA (requires 2 ATP)

77
Q

how does the acyl-coA enter the mitochondrion

A

carnitine shuttle

78
Q

what happens in the carnitine shuttle

A

acyl-group is transferred from Acyl-CoA to carnitine to form Acyl-carnitine which is transferred across the mitochondrial membrane into the matrix
in the matrix the acyl group is added to CoA forming Acyl-CoA and carnitine
carnitine then leaves through the mitochondrial membrane

79
Q

what is the transporter in the carnitine shuttle

A

translocase

80
Q

what is beta oxidation

A

oxidation of FAs in mitochondria into products that can be used in TCA cycle or oxidative phosphorylation

81
Q

what does one cycle of beta oxidation generate

A

1 acetyl coA
1 FADH2
1 NADH+H+
1 fatty acyl-CoA

82
Q

what happens to the acetyl-CoA produced from beta oxidation of fatty acids

A 
oxidised in TCA cycle to form
1 FADH2
2 CO2
1 GTP
3 NADH+3H+
83
Q

how do you work out how many BO cycles are needed for a fatty acid

A

C/2 - 1

84
Q

what happens in the last cycle of BO of an odd chain FA instead of yielding 2 acetyl-CoA

A

acetyl-CoA and propionyl-CoA are yielded

85
Q

what happens to propionyl-CoA formed from last BO of an odd chain FA

A

converted into succinyl-CoA which enters TCA directly

86
Q

what are ketone bodies formed from

A

from beta oxidation of acetyl-coA in liver mitochondrion as byproduct of glycerol digestion

87
Q

what happens to these ketones

A

diffuse into peripheral tissues where they are converted back to acetyl-coA which enter the TCA directly

88
Q

what is the name of a 4C ketone

A

oxaloacetate

89
Q

what is the name of the build up of Acetyl-CoA in diabetics/prolonged starvation and why does it occur

A

ketoacidosis

no oxaloacetate to deal with it

90
Q

when and where does fatty acid synthesis (lipogenesis) occur

A

excess energy intake - excess CHO causing excess citrate

liver

91
Q

what kind of process is lipogenesis

A

reductive

92
Q

what is the function of VLDL

A

carried TGIs to adipose tissue

93
Q

what is the function of albumin

A

carries free FA in plasma

94
Q

what is the function of Acetyl-CoA

A

precursor molecule for lipogenesis

95
Q

where does fatty acid breakdown to Acetyl-CoA occur

A

mitochondrial matrix

96
Q

where does fatty acid synthesis from Acetyl-CoA occur

A

cytoplasm

97
Q

what is the function of citrate

A

transports acetyl groups into the cytoplasm for lipogenesis

98
Q

when is citrate formed

A

1st step of TCA from oxaloacetate + Acetyl-CoA

99
Q

what is the regulatory enzyme for the 1st step of lipogenesis

A

Acetyl-CoA carboxylase

100
Q

what does Acetyl-CoA carboxylase do

A

activates Acetyl-CoA forming malonyl-CoA which donates an atom to the lipid

101
Q

what enzyme catalyses the synthesis of saturated long chain FAs from malonyl-CoA, Acetyl-CoA and NADPH

A

fatty acid synthase

102
Q

how many acyl-carrier proteins does fatty acid synthase carry per dimer

A

2

103
Q

what is the longest fatty acid that can be formed from fatty acid synthase

A

16C

104
Q

what is the function of the acyl-carrier protein

A

carries growing fatty acid chain until 16C chain is achieved

105
Q

what is the make up of palmitic acid

A

16:0

106
Q

what is the make up of stearic acid

A

18:0

107
Q

what is the make up of oleic acid

A

18:1

108
Q

what is the make up of linoleic acid

A

18:2

109
Q

what is the function of NADPH during lipogenesis

A

donates electrons to the growing FAC

110
Q

what does insulin do to the activity to acetyl-CoA carboxylase

A

stimulates

111
Q

what does glucagon do to the activity of acetyl-CoA carboxylase

A

inhibits

112
Q

what does adrenaline do to the activity of acetyl-CoA carboxylase

A

inhibits

113
Q

what is the name of the activated form of glycerol formed by liver and from glucose in adipose tissue that is required for TGI synthesis

A

glycerol-3-phosphate

114
Q

in a fatty acid what is the alpha carbon

A

adjacent to carboxyl group

115
Q

ina fatty acid what is the omega carbon

A

furthest away from carboxyl group

116
Q

how many carbons does a FA need to have to be solid at room temp

A

> 8C

117
Q

can amino acids be stored in the body

A

no

118
Q

what 2 phases of urea synthesis occur in the liver

A

deamination and urea cycle

119
Q

where does transamination occur and what does it involve

A

all cells - amino group transferred from alpha-amino acid to alpha-keto acid (usually alpha-ketoglutarate) forming glutamate

120
Q

what enzyme carried out transamination

A

aminotransferase

121
Q

what occurs in deamination

A

amino group from glutamate converted into ammonium ion (NADH also formed)

122
Q

what occurs in the urea cycle

A

conversion of ammonium to urea

123
Q

what is the equation of the urea cycle

A

ammonium ion + CO2 + aspartic acid –> urea + fumarate (byproduct used in TCA cycle

124
Q

what happens once an amino group has been removed from a ketogenic AA

A

either degraded to acetyl-CoA which can be oxidised in the TCA cycle
or give rise to ketone bodies

125
Q

what happens once an amino group has been removed from a glucogenic AA

A

either degraded to pyruvate or TCA cycle intermediates

or used in gluconeogenesis (converted into phosphoenolpyruvate)

126
Q

what are the 2 main transporter molecules of nitrogen to the liver

A

alanine - pyruvate + NH4

glutamine - glutamate + NH4

127
Q

what happens to alanine and glutamate once in liver

A

converted back to glutamic acid

128
Q

what is phenylketonuria

A

inherited disorder with failure to breakdown phenylamine which accumulates and causes mental retardation

129
Q

what is alcaptonuria

A

inherited disorder where the degradation of phenylalanine and tyrosine is blocked

130
Q

what is maple syrup urine disease

A

inherited disorder where degradation of valine, isoleucine and leucine is blocked

131
Q

what is the treatment of disorders of the urea cycle

A

low protein diet

drugs which remove nitrogen

132
Q

why are urea cycle disorders bad

A

accumulation of ammonia in blood

133
Q

how many strong phosphate bonds are broken in the urea cycle

A

4 - 3 ATP to 2 ADP + AMP

134
Q

where are alpha and beta globulins produced and what are they used for

A

liver

transport molecules

135
Q

what is caeruloplasmin

A

alpha globulin that transports copper

136
Q

what is retinol binding protein

A

alpha globulin that transports Vitamin A

137
Q

what is transferrin

A

beta globulin that transports iron in Fe3+ form

138
Q

what can transferrin be an indication for

A

iron deficiency

139
Q

what is the storage form of iron

A

ferritin (Fe2+ bound to ferritin)

140
Q

true/false

when you increase altitude there is a decrease in transferrin expression

A

false

when you increase in altitude there is an increase in transferrin expression

141
Q

how is fibrinogen activated

A

prothrombin

142
Q

what is fibrinogen

A

beta globulin produced by liver

inactive form of blood blotting agent fibrin

143
Q

what is the most abundant plasma protein in the blood

A

albumin

144
Q

what is the effect of insulin on albumin production

A

production stimulated by insulin

145
Q

what does albumin transport

A

FAs
bilirubin
thyroid hormones
aspirin

146
Q

what is the affinity/capacity of albumin for hydrophobic molecules

A

low affinity

high capacity

147
Q

is albumin positive negative or neutral

A

negative

148
Q

what is transthyretin and what does it reflect

A

pre albumin - reflects recent intake - useful for nutritional monitoring

149
Q

what happens to transthyretin levels in uraemia and dehydration

A

increased

150
Q

what happens to transthyretin levels in APR, fasting

A

decreased

151
Q

what is a good marker for muscle mass

A

urinary creatinine

152
Q

steroid hormones are hydrophilic/hydrophobic

A

hydrophobic

153
Q

where are steroid hormones produced

A

ovaries
testes
adrenal glands

154
Q

how is thyroxine (T4) transported in blood

A

bound to thyroid-binding globulin

155
Q

how is cortisol transported in blood

A

bound to cortisol-binding globulin

156
Q

order the following from heaviest to lightest

Gamma globulins
albumin
beta globulins
alpha globulins

A

gamma globulins (immunoglobulins)
beta globulins
alpha globulins
albumin

157
Q

how do plasma proteins buffer pH

A

donating / accepting a proton

158
Q

what is the function of lipoproteins

A

transfer fat in blood between organs and tissues

159
Q

order the following from most to least dense
Chylomicrons
LDL, HDL
VLDL, IDL

A

LDL, HDL
VLDL, IDL
Chylomicrons

160
Q

how do plasma proteins maintain osmotic pressure of blood

A

dont diffuse into interstitial fluid

161
Q

what is the function of chylomicrons

A

transport dietary fibre to liver

162
Q

what is the function of LDL

A

transports cholesterol from liver to peripheral tissue (bad)

163
Q

what is the function of HDL

A

transports cholesterol from peripheral tissue to liver (good)

164
Q

what is the main product of cholesterol metabolism

A

bile salts

165
Q

how are bile salts reabsorbed by the liver

A

enterohepatic recycling

166
Q

what do bile salt sequestrants do

A

block bile salt absorption in terminal ileum to lower cholesterol levels

167
Q

what is the only organ that can metabolise and excrete cholesterol

A

liver

168
Q

where are red blood cells broken down and what do they produce

A

spleen

haem + globulin

169
Q

what enzyme controls breaking down of haem

A

haemoxygenase

haem –> iron + porphyrin ring —> biliverdin

170
Q

what enzyme converts biliverdin to unconjugated bilirubin

A

biliverdin reductase

171
Q

how is bilirubin transported to liver

A

unconjugated bilirubin binds to albumin as it is lipid soluble

172
Q

what enzyme conjugates bilirubin in the liver by adding glucaronic acid

A

uridine glucuronyl transferase (UGT)

173
Q

conjugated bilirubin is then excreted into canaliculi and then to bile ducts and then to gall bladder where bile is stored and concentrated.
When bilirubin is secreted with bile into small intestine what is it converted to by intestinal bacteria

A

urobilinogen

stercobilinogen

174
Q

what is the fate of stercobillinogen

A

oxidised to stercobillrubin/stercobilin (brown colour of faeces)

175
Q

what is the fate of urobiliogen

A

reabsorbed into blood stream forming urobilin and either goes to liver or to kidneys where it is excreted giving urine its yellow colour

176
Q

what gives urine its yellow colour

A

urobillin

177
Q

what does cholesterol form an essential component of

A

cell membrane of animal cells

178
Q

how is cholesterol synthesised and by what

A

all cells

acetyl-CoA (18), NADPH (16) and ATP (36)

179
Q

what is the main site of cholesterol synthesis

A

liver

180
Q

what is the rate limiting enzyme of cholesterol synthesis

A

HMG-CoA reductase

181
Q

what does HMG-CoA reductase do

A

irreversibly catalyses the the formation of mevalonic acid

182
Q

what does starvation do to HMG CoA reductase synthesis and activity

A

stimulated

183
Q

what is the P/O ratio

A

measure of the number of ATP molecules formed per oxygen atom reduced

184
Q

what has a greater redox potential NADH+H or FADH2

A

NADH+H

year 1 (45 decks)

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