GI - biochemistry Flashcards
(184 cards)
1
Q
what is glycogenesis
A
the synthesis of glycogen from glucose
2
Q
what enzyme causes glycogenesis
A
glycogen synthase
3
Q
what is glycogenolysis
A
the breakdown of glycogen to form glucose
4
Q
what enzyme causes glycogenolysis
A
glycogen phosphorylase
5
Q
what type of reaction is glycogenolysis
A
phosphorolysis
6
Q
what does insulin do to glycogenesis
A
insulin stimulates glycogenesis
7
Q
what does insulin do to glycogenolysis
A
insulin inhibits glycogenolysis
8
Q
what does glucagon do to glycogenesis
A
glucagon inhibits glycogenesis
9
Q
what does glucagon do to glycogenolysis
A
glucagon stimulates glycogenolysis
10
Q
where is glycogen found
A
liver and muscle cells
11
Q
what is glycogen used for in liver cells
A
stoked then released to maintain blood glucose concentration
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
13
Q
how is glycogen released from liver to maintain BSL
A
liver dephosphorylates glucose-6-phosphate and releases it into blood as glucose
14
Q
what maintains BSL immediately following meals
A
dietary CHO
15
Q
what maintains BSL between meals
A
glycogenolysis
16
Q
what maintains BSL when no dietary CHO is available and liver stores of glycogen are depleted and over night
A
gluconeogenesis
17
Q
what bonds form long straight chains of glucose
A
alpha-1,4-glycosidic bonds
18
Q
what bonds form branches in glycogen molecule
A
alpha-1,6-glycosidic bonds
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
20
Q
what is glycogenin
A
glycogen primer of 4 glucose molecules for glycogenesis
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
22
Q
how often are branches introduced to the glycogen chain
A
every 10 glucose
23
Q
what kind of bonds does glycogen synthase introduce to the glycogen polymer
A
alpha-1,4-glycosidic bonds
24
Q
what enzyme introduces alpha-1,6-glycosidic bonds to glycogen
A
transglycosylase
25
what bonds does glycogen phosphorylase break
alpha-1,4-glycosidic bonds
26
what do adrenaline, cortisol and glucagon do to the rate of glycogenolysis
increase rate
27
what is the name of the transporter in liver cells that transports glucose into blood
GLUT2
28
what enzyme converts glucose into glucose-6-phosphate
hexokinase
29
what are the 2 options of fate of the glucose-6-phosphate
glycolysis
| or converted to glucose-1-phosphate
30
what enzyme converts glucose-6-phosphate to glucose-1-phosphate
phosophglucomutase
31
what enzyme converts glucose-1-phosphate to UDP-glucose
UDP-glucose pyrophosphorylase
32
what enzyme converts UDP-glucose into glycogen by adding another glucose (1 at a time)
glycogen synthase
33
how is UTP regenerated in glycogenesis
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
34
for each glucose added to glycogen how many ATP are used
1
35
what is the rate limiting step of glycogenolysis
glycogen phosphatase removing a glucose from glycogen by adding a phosphate
36
what enzyme converts glucose-1-phosphate into glucose-6-phosphate
phosphoglucomutase
37
what enzyme converts glucose-6-phosphate into glucose by phosphorylating
glucose-6-phosphatase
38
what is gluconeogenesis
synthesis of glucose from non-CHO precursors
39
what is the substrate of gluconeogenesis
pyruvate
40
what is the first stage in gluconeogenesis
pyruvate to oxaloacetate
41
where is energy for gluconeogenesis obtained
oxidation of fatty acids from adipose tissue
42
what are the 3 precursor molecules for gluconeogenesis
lactate
amino acids
glycerol
43
how many ATPs and how many pyruvate are needed to form 1 glucose molecule in gluconeogenesis
6 ATP
| 2 pyruvate
44
where does gluconeogenesis occur
liver
| small amount in kidneys
45
where is lactate produced
anaerobically respiring skeletal muscle
46
how is lactate converted into pyruvate for gluconeogenesis
cori-cycle
47
what is the cori cycle
blood transports lactate to liver where it is converted into pyruvate and then into glucose which is transported back to the muscle cell/blood
48
could the cori cycle go on forever
no - consumes 6 ATP and produces 2
49
how are amino acids produced
proteolysis of muscle protein
50
how do amino acids enter gluconeogenesis
either converted to oxaloacetate from pyruvate
| or enter TCA cycle through Acetyl-CoA which results in the eventual formation of oxaloacetate
51
what is the condition for amino acids to enter the TCA cycle
oxaloacetate must be present
52
what is the TCA intermediate needed for gluconeogenesis
oxaloacetate
53
how is glycerol formed for gluconeogenesis
lipolysis of triglycerides in adipose tissue
54
what is the effect of glucagon on glycolysis
glucagon inhibits glycolysis
55
what is the effect of glucagon on gluconeogenesis
glucagon stimulates gluconeogenesis
56
what is the effect of insulin on glycolysis
insulin stimulate glycolysis
57
what is the effect of insulin on gluconeogenesis
insulin inhibits gluconeogenesis
58
if [ADP] or [AMP] is high in a cell what happens to gluconeogenesis
inhibited - cell has low energy
59
if [ATP] is high in a cell what happens to gluconeogenesis
stimulated - cell has high energy
60
if molecules associated with the TCA cycle are high in a cell what happens to gluconeogenesis
gluconeogenesis is stimulated
61
if fructose-2,6-biphosphate (high in fed state) is high in a cell what happens to gluconeogenesis
gluconeogenesis is inhibited
62
what do citrate, alanine and acetyl-coA do to gluconeogenesis
simulate gluconeogenesis
63
how many liver enzymes are required to do the reverse of the 3 irreversible steps of glycolysis
4
64
what are the enzymes of 3 irreversible steps of glycolysis
hexokinase
phosphofructokinase
pyruvate kinase
65
what are the 3 irreversible steps of glycolysis
glucose --> glucose-6-phosphate
fructose-6-phosphate --> fructose-1,6-biphosphate
phosphoenolpyruvate --> pyruvate
66
true/false
| lipids provide 2 times the energy of CHOs
true
67
do fatty acids tend to be cis or trans
cis
68
do essential fatty acids tend to be saturated, unsaturated or polyunsaturated
polyunsaturated
69
where does the synthesis of fatty acids occur and from what
cytoplasm
| acetyl-CoA
70
what bonds join triglycerides
ester bonds
71
what happens when fatty acids and monoglycerides are absorbed by the intestinal mucosa
converted back into triglycerides and incorporated into chylomicrons which enter the lymph
72
what enzyme cleaves chylomicrons to release FAs and TGIs
lipoprotein lipase
73
what is the fate of the free fatty acids
- converted to TGIs for storage in adipose tissue
| - oxidised for energy in muscle cells
74
what is the effect of adrenaline on hormone sensitive lipases
fat broken down (lipolysis) for oxidation when needed
75
what must happen in order for fatty acids to enter the mitochondria
must form a CoA derivative
76
how is a coA derivative of FA formed and where
in cytoplasm
| Co-A is added to form acyl-coA (requires 2 ATP)
77
how does the acyl-coA enter the mitochondrion
carnitine shuttle
78
what happens in the carnitine shuttle
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
what is the transporter in the carnitine shuttle
translocase
80
what is beta oxidation
oxidation of FAs in mitochondria into products that can be used in TCA cycle or oxidative phosphorylation
81
what does one cycle of beta oxidation generate
1 acetyl coA
1 FADH2
1 NADH+H+
1 fatty acyl-CoA
82
what happens to the acetyl-CoA produced from beta oxidation of fatty acids
```
oxidised in TCA cycle to form
1 FADH2
2 CO2
1 GTP
3 NADH+3H+
```
83
how do you work out how many BO cycles are needed for a fatty acid
C/2 - 1
84
what happens in the last cycle of BO of an odd chain FA instead of yielding 2 acetyl-CoA
acetyl-CoA and propionyl-CoA are yielded
85
what happens to propionyl-CoA formed from last BO of an odd chain FA
converted into succinyl-CoA which enters TCA directly
86
what are ketone bodies formed from
from beta oxidation of acetyl-coA in liver mitochondrion as byproduct of glycerol digestion
87
what happens to these ketones
diffuse into peripheral tissues where they are converted back to acetyl-coA which enter the TCA directly
88
what is the name of a 4C ketone
oxaloacetate
89
what is the name of the build up of Acetyl-CoA in diabetics/prolonged starvation and why does it occur
ketoacidosis
| no oxaloacetate to deal with it
90
when and where does fatty acid synthesis (lipogenesis) occur
excess energy intake - excess CHO causing excess citrate
| liver
91
what kind of process is lipogenesis
reductive
92
what is the function of VLDL
carried TGIs to adipose tissue
93
what is the function of albumin
carries free FA in plasma
94
what is the function of Acetyl-CoA
precursor molecule for lipogenesis
95
where does fatty acid breakdown to Acetyl-CoA occur
mitochondrial matrix
96
where does fatty acid synthesis from Acetyl-CoA occur
cytoplasm
97
what is the function of citrate
transports acetyl groups into the cytoplasm for lipogenesis
98
when is citrate formed
1st step of TCA from oxaloacetate + Acetyl-CoA
99
what is the regulatory enzyme for the 1st step of lipogenesis
Acetyl-CoA carboxylase
100
what does Acetyl-CoA carboxylase do
activates Acetyl-CoA forming malonyl-CoA which donates an atom to the lipid
101
what enzyme catalyses the synthesis of saturated long chain FAs from malonyl-CoA, Acetyl-CoA and NADPH
fatty acid synthase
102
how many acyl-carrier proteins does fatty acid synthase carry per dimer
2
103
what is the longest fatty acid that can be formed from fatty acid synthase
16C
104
what is the function of the acyl-carrier protein
carries growing fatty acid chain until 16C chain is achieved
105
what is the make up of palmitic acid
16:0
106
what is the make up of stearic acid
18:0
107
what is the make up of oleic acid
18:1
108
what is the make up of linoleic acid
18:2
109
what is the function of NADPH during lipogenesis
donates electrons to the growing FAC
110
what does insulin do to the activity to acetyl-CoA carboxylase
stimulates
111
what does glucagon do to the activity of acetyl-CoA carboxylase
inhibits
112
what does adrenaline do to the activity of acetyl-CoA carboxylase
inhibits
113
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
glycerol-3-phosphate
114
in a fatty acid what is the alpha carbon
adjacent to carboxyl group
115
ina fatty acid what is the omega carbon
furthest away from carboxyl group
116
how many carbons does a FA need to have to be solid at room temp
> 8C
117
can amino acids be stored in the body
no
118
what 2 phases of urea synthesis occur in the liver
deamination and urea cycle
119
where does transamination occur and what does it involve
all cells - amino group transferred from alpha-amino acid to alpha-keto acid (usually alpha-ketoglutarate) forming glutamate
120
what enzyme carried out transamination
aminotransferase
121
what occurs in deamination
amino group from glutamate converted into ammonium ion (NADH also formed)
122
what occurs in the urea cycle
conversion of ammonium to urea
123
what is the equation of the urea cycle
ammonium ion + CO2 + aspartic acid --> urea + fumarate (byproduct used in TCA cycle
124
what happens once an amino group has been removed from a ketogenic AA
either degraded to acetyl-CoA which can be oxidised in the TCA cycle
or give rise to ketone bodies
125
what happens once an amino group has been removed from a glucogenic AA
either degraded to pyruvate or TCA cycle intermediates
| or used in gluconeogenesis (converted into phosphoenolpyruvate)
126
what are the 2 main transporter molecules of nitrogen to the liver
alanine - pyruvate + NH4
| glutamine - glutamate + NH4
127
what happens to alanine and glutamate once in liver
converted back to glutamic acid
128
what is phenylketonuria
inherited disorder with failure to breakdown phenylamine which accumulates and causes mental retardation
129
what is alcaptonuria
inherited disorder where the degradation of phenylalanine and tyrosine is blocked
130
what is maple syrup urine disease
inherited disorder where degradation of valine, isoleucine and leucine is blocked
131
what is the treatment of disorders of the urea cycle
low protein diet
| drugs which remove nitrogen
132
why are urea cycle disorders bad
accumulation of ammonia in blood
133
how many strong phosphate bonds are broken in the urea cycle
4 - 3 ATP to 2 ADP + AMP
134
where are alpha and beta globulins produced and what are they used for
liver
| transport molecules
135
what is caeruloplasmin
alpha globulin that transports copper
136
what is retinol binding protein
alpha globulin that transports Vitamin A
137
what is transferrin
beta globulin that transports iron in Fe3+ form
138
what can transferrin be an indication for
iron deficiency
139
what is the storage form of iron
ferritin (Fe2+ bound to ferritin)
140
true/false
| when you increase altitude there is a decrease in transferrin expression
false
| when you increase in altitude there is an increase in transferrin expression
141
how is fibrinogen activated
prothrombin
142
what is fibrinogen
beta globulin produced by liver
| inactive form of blood blotting agent fibrin
143
what is the most abundant plasma protein in the blood
albumin
144
what is the effect of insulin on albumin production
production stimulated by insulin
145
what does albumin transport
FAs
bilirubin
thyroid hormones
aspirin
146
what is the affinity/capacity of albumin for hydrophobic molecules
low affinity
| high capacity
147
is albumin positive negative or neutral
negative
148
what is transthyretin and what does it reflect
pre albumin - reflects recent intake - useful for nutritional monitoring
149
what happens to transthyretin levels in uraemia and dehydration
increased
150
what happens to transthyretin levels in APR, fasting
decreased
151
what is a good marker for muscle mass
urinary creatinine
152
steroid hormones are hydrophilic/hydrophobic
hydrophobic
153
where are steroid hormones produced
ovaries
testes
adrenal glands
154
how is thyroxine (T4) transported in blood
bound to thyroid-binding globulin
155
how is cortisol transported in blood
bound to cortisol-binding globulin
156
order the following from heaviest to lightest
Gamma globulins
albumin
beta globulins
alpha globulins
gamma globulins (immunoglobulins)
beta globulins
alpha globulins
albumin
157
how do plasma proteins buffer pH
donating / accepting a proton
158
what is the function of lipoproteins
transfer fat in blood between organs and tissues
159
order the following from most to least dense
Chylomicrons
LDL, HDL
VLDL, IDL
LDL, HDL
VLDL, IDL
Chylomicrons
160
how do plasma proteins maintain osmotic pressure of blood
dont diffuse into interstitial fluid
161
what is the function of chylomicrons
transport dietary fibre to liver
162
what is the function of LDL
transports cholesterol from liver to peripheral tissue (bad)
163
what is the function of HDL
transports cholesterol from peripheral tissue to liver (good)
164
what is the main product of cholesterol metabolism
bile salts
165
how are bile salts reabsorbed by the liver
enterohepatic recycling
166
what do bile salt sequestrants do
block bile salt absorption in terminal ileum to lower cholesterol levels
167
what is the only organ that can metabolise and excrete cholesterol
liver
168
where are red blood cells broken down and what do they produce
spleen
| haem + globulin
169
what enzyme controls breaking down of haem
haemoxygenase
| haem --> iron + porphyrin ring ---> biliverdin
170
what enzyme converts biliverdin to unconjugated bilirubin
biliverdin reductase
171
how is bilirubin transported to liver
unconjugated bilirubin binds to albumin as it is lipid soluble
172
what enzyme conjugates bilirubin in the liver by adding glucaronic acid
uridine glucuronyl transferase (UGT)
173
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
urobilinogen
| stercobilinogen
174
what is the fate of stercobillinogen
oxidised to stercobillrubin/stercobilin (brown colour of faeces)
175
what is the fate of urobiliogen
reabsorbed into blood stream forming urobilin and either goes to liver or to kidneys where it is excreted giving urine its yellow colour
176
what gives urine its yellow colour
urobillin
177
what does cholesterol form an essential component of
cell membrane of animal cells
178
how is cholesterol synthesised and by what
all cells
| acetyl-CoA (18), NADPH (16) and ATP (36)
179
what is the main site of cholesterol synthesis
liver
180
what is the rate limiting enzyme of cholesterol synthesis
HMG-CoA reductase
181
what does HMG-CoA reductase do
irreversibly catalyses the the formation of mevalonic acid
182
what does starvation do to HMG CoA reductase synthesis and activity
stimulated
183
what is the P/O ratio
measure of the number of ATP molecules formed per oxygen atom reduced
184
what has a greater redox potential NADH+H or FADH2
NADH+H
