Biochemistry COPY Flashcards
1
Q
what is glycogenesis?
A
the synthesis of glycogen from glucose
2
Q
what is glycogenolysis?
A
the breakdown of glycogen to form glucose
3
Q
when is liver glycogen broken down?
A
between meals
4
Q
from which organ can glycogen be converted back to glucose to maintain blood glucose levels?
A
liver
hepatic glycogen
5
Q
what is glycogen within muscles used for?
A
production of ATP
6
Q
during bursts of physical activity what pathway does glycogen go down to produce ATP?
A
glycolysis and the TCA cycle (citric acid cycle)
7
Q
what type of breakdown is glycogenolysis?
A
phosphorolysis
8
Q
what is the primary way of maintaining glucose concentrations overnight?
A
gluconeogenesis
9
Q
what is gluconeogenesis?
A
the synthesis of glucose from non-carbohydrate precursors
10
Q
what are the 3 sources of blood glucose within the body?
A
dietary glucose
glucose produced from glycogenolysis
glucose produced from gluconeogenesis
11
Q
what is glycogen?
A
a polymer consisting of glucose monomers
12
Q
what links join the straight chains of glucose monomers within glycogen?
A
a1-4 glycosidic bonds
13
Q
what links introduce branches into the glucose monomers within glycogen?
A
a1-6 glycosific bonds
14
Q
what does the extensive branching of glycogen allow?
A
increases speed at which glucose can be cleaved/added
as this happens at the ends of the polymers
15
Q
what is the protein at the centre of glycogen?
A
glycogenin
16
Q
what is the function of glycogenin?
A
can bind to up to 4 glucose molecules in order to create a primer for glycogenesis
17
Q
what is the enzyme which adds extra glucose monomers to the existing glycogen?
A
glycogen synthase
18
Q
why is a primer needed for glycogenesis?
A
because glycogen synthase can only add glucose molecules to existing glycogen so needs some way to start
19
Q
before glucose can be used for any metabolic pathway what must be done to it?
A
glucose first has to be phosphorylated
20
Q
what is the first step of glycogen synthesis from glucose?
A
phosphorylation of glucose to glucose-6-phosphate
21
Q
what enzyme catalyses the formation of glucose-6-phosphate from glucose?
A
hexokinase
22
Q
once glucose has been phosphorylated to glucose-6-phosphate, where does it become trapped?
A
in the cell
23
Q
if a cell requires energy, what happens to the glucose-6-phosphate?
A
glycolysis for ATP
24
Q
if a cell doesn’t require energy, what happens to the glucose-6-phosphate?
A
glycogenesis (conversion into glycogen)
25
if a cell doesn't require energy, and so goes through the glucogenesis route, what is the glucose-6-phosphate converted to?
glucose-1-phosphate
26
what enzyme converts glucose-6-phosphate to glucose-1-phosphate?
phosphoglucomutase
27
what type of reaction is the conversion of glucose-6-phosphate to glucose-1-phosphate?
reversible reaction
28
how does the glucose-1-phosphate become activated?
by forming UDP-glucose
29
what enzyme uses the substrates UDP-glucose and glycogen to make a longer chain of glycogen + UDP?
glycogen synthase
30
what happens to the UDP left over after the formation of a 1-monomer-longer-glycogen?
UDP gets phosphorlyated to UTP
| requires ATP
31
how many molecules of ATP net does glycogenesis require?
1 ATP molecule
32
what type of bonds does glycogen synthase introduce into the glycogen polymer?
a1-4 glycosidic bonds
33
what enzyme removes a glucose monomer from the glycogen in glycogenolysis?
glycogen phosphorylase
34
what does glycogen phosphorylase do to the glucose it has removed from glycogen?
phosphorlyates it to glucose-1-posphate
35
what enzyme converts glucose-1-phosphate to glucose-6-phosophate in the process of glycogenolysis?
phosphoglucomutase
36
what is the difference between glucose-6-phosphate in a liver cell and in a muscle cell?
glucose-6-phosphate in the liver can be dephosphorylated and then the free glucose released into the blood stream
glucose-6-phosphate in a muscle cell can't be dephosphorlyate and so it can only be used to produce ATP for itself through glycolysis
37
what type of bonds does glycogen phosphorlyase break in the glycogen polymer?
only straight chain a1-4 glucosidic bonds
38
what branching enzyme introduces a1-6 glycosidic branches into glycogen?
transglycosylase
39
what is the rate limiting step of glycogenolysis?
getting glucose-1-phosphate from glycogen by the action of glycogen phosphorlyase
40
what transporter allows glucose to leave the liver and enter the blood?
GLUT2
41
what 3 hormones up regulate glycogen phosphorylase?
| and so increase rate of glycogenolysis
glucagon
adrenaline
cortisol
(hormones of hungry state)
42
what hormone down regulates glycogen phosphrolase?
| and so decreases rate of glycogenolysis
insulin
| hormone of fed state
43
what 3 precursors can be used for gluconeogenesis?
lactate
amino acids
glycerol
44
when is lactate synthesised in the body?
by muscle under anaerobic conditions
45
how are amino acids produced?
proteolysis of muscle protein
46
how is glycerol produced?
lipolysis of triglycerides in adipose tissue
47
where does gluconeogenesis occur?
mainly in the liver
| small amounts in the kidneys
48
what does gluconeogenesis obtain its energy from?
from oxidation of fatty acids released from adipose tissue
49
what is gluconeogenesis essentially the reverse of?
glycolysis
50
what is the end product of glycolysis?
pyruvate
51
most of the reactions in glycolysis are reversible, what are the 3 irreversible reactions in glycolysis which need different enzymes for the reverse to occur? (for gluconeogenesis)
glucose to glucose-6-phosphate by hexokinase
fructose-6-phosphate to fructose-1-6-biphosphate by phosphofructokinase
phosphoenolpyruvate to pyruvate by pyruvate kinase
52
how many unique liver enzymes are needed to do the reverse of the 3 irreversible reactions within glycolysis?
(for gluconeogenesis)
4
53
in gluconeogenesis what is the substrate?
pyruvate
54
what is the first step within gluconeogenesis?
pyruvate to oxaloacetate
55
for each glucose formed by gluconeogenesis how many pyruvates and how many ATPs (or equivalents) are used?
```
2 pyruvates
6 ATP (or equivalents)
```
56
how many ATPs are generated for each glucose that is oxidised through glycolysis? (net)
2 ATP
57
how is lactate produced in muscle cells transported to the liver?
blood stream
58
why can the Cori cycle (the cycle of glucose-lactate in liver and muscle) not go on forever?
because it generates less ATP than it consumes
59
what are the 2 classes of amino acids?
ketogenic amino acids
| glucogenic amino acids
60
which class of amino acid can be used as a precursor for gluconeogenesis?
glucogenic amino acids
61
what are the 2 ways that glucogenic amino acids can form oxaloacetate? (The first step in gluconeogenesis)
1. conversion into pyruvate which gets converted into oxaloacetate
2. entering the TCA cycle by joining with an intermediate which results in the eventual formation of oxaloacetate
62
through what molecule do ketoamino acids enter the TCA cycle as?
acetyl CoA
63
what molecule needs to be present for acetyl CoA (made from ketogenic amino acits) to enter the TCA cycle?
oxaloacetate
64
oxaloacetate accepts acetyl CoA thus adding it into the TCA cycle, what is the product that is formed?
citric acid
65
what do AMP/ADP stimulate? (gluconeogenesis or glycolysis)
glycolysis
| inhibit gluconeogenesis
66
what does ATP stimulate? (gluconeogenesis or glycolysis)
gluconeogenesis
| inhibit glycolysis
67
what does fructose 2,6-biphosphate stimulate? (gluconeogenesis or glycolysis)
glycolysis
(inhibits gluconeogenesis)
[this is because fructose 2-6 biphosphate is high in the fed state, so no more blood glucose is needed]
68
what do citrate, alanine and acetyl-CoA stimulate? (gluconeogenesis or glycolysis)
gluconeogenesis
(inhibits glycolysis)
[these substances are high when intermediates or building blocks are abundant]
69
what are essential fatty acids?
fatty acids that can not be made in the body
70
what are the 4 major fat-soluble vitamins? (absorption of these is closely linked to that of fat and they are stored in body fat)
A, D, E, K
71
what is the main energy storage form in adipose tissue?
triglycerides
72
what do triglycerides consist of?
glycerol + 3 fatty acids
73
fats are aliphatic, what does this mean?
their structure contains no rings
74
what type of structures within fatty are rare?
branched chain fats
| odd numbers of carbons
75
what are the 3 types of fatty acids?
saturated
unsaturated
polyunsaturated
76
what is a saturated fatty acid?
there are no C=C double bonds within the chain
77
what is an unsaturated fatty acid?
there is 1 C=C double bond within the chain?
78
what is a polyunsaturated fatty acid?
there are several C=C double bonds within the chain
79
compare the cis formation of a C=C double bond to a trans formation?
cis C=C double bond: both R chains are on the same side
| trans C=C double bond: R chains are on dopposing sides
80
describe the structure of palmittic acid?
16:0
16 carbon chain, 0 C=C double bonds
-saturated
81
describe the structure of stearic acid?
18:0
18 carbon chain, 0 C=C double bonds
-saturated
82
describe the structure of oleic acid?
18:1
18 carbon chain, 1 C=C double bonds
-unsaturated
83
describe the structure of linoleic acid??
18:2
18 carbon chain, 2 C=C double bonds
-polyunsaturated
84
what is the difference between stearic, oleic and linoleic acid?
all have 18 carbons in the chain
stearic acid has 0 C=C double bonds
oleic acid has 1 C=C double bond
linoleic acid has 2 C=C double bonds
85
in a fatty acid, which carbon is C1?
the carbon of the carboxyl roup
86
in a fatty acid which carbon is a-carbon? (alpha carbon)
the carbon adjacent t the carboxyl group
87
in a fatty acid which carbon is a w-carbon? (omega carbon)
the furtherst away carbon from the carboxyl group
88
how long does a fatty acid chain have to be to be a solid at room temperature?
>8 carbons
89
what do C=C double bonds do to the melting point of the fatty acid?
lower the melting point
90
what type of fatty acids are contained within plant fats?
unsaturated fatty acids
| liquid at room temp
91
what type of fatty acids are contained within animal fats?
saturated fatty acids
| solid at room temp
92
what are the 3 main products of fat digestion?
glycerol
fatty acids
monoglycerides
93
what happens to short and medium length fatty acids once absorbed into the enterocytes of the intestine?
enter portal blood system
94
what happpens to the longer chain fatty acids and monoglycerides once absorbed into the enterogytes of the intestine?
re-sythensised into triglycerides, form chylomicrons and enter lymphatic system
95
where is fat stored in the body?
adipose tissue
96
what type of lipases cleave the fat into free fatty acids and glycerol?
(lipolysis)
hormone sensitive lipases
97
what has to happen before fatty acids can be oxidised to generate energy?
fatty acids must be converted to CoA derivatives
| acyl-CoA
98
where does the conversion of fatty acids into CoA deriviatives occur?
cytoplasm
99
how much ATP is required for the conversion of fatty acids to CoA derivatives?
2 ATP
100
where does oxidation of the fatty acid derived acyl-CoA occur?
mitochondrial matrix
101
how is the acyl CoA transferred from the cytoplasm to the mitochondrial matrix?
carnitine shuttle
102
describe the carnitine shuttle?
1. fatty acids are transferred from acyl-CoA to canitine: acyl carnitine
2. acyl-carnitine transporter facilitates the transport of acyl-carnitine into the mitochondrion
3. fatty acids are transferred from the acyl-carnitine to CoA: acyl-CoA
4. acyl-carnitine transporter facilitates the tranport of canitine out of the mitochondrion
[CoA itself doesn't get tranported across, 2 separate pools of CoA]
103
what is beta-oxidation?
the catabolism of fatty acids into products that can be used in the TCA cycle or oxidative phosphorylation
104
how many steps are in each cycle of beta-oxidation?
4
105
what are the products of 1 beta-oxidation cycle?
1 acetyl-CoA
1 FADH2
1 NADH + H+
1 fatty acyl-CoA (shortened by 2 carbon atoms)
106
how do you calculate the number of beta-oxidation cycles needed for a specific fatty acid?
(number of Carbons/2) -1
eg stearic aicd
(18/2) -1 = 8 cycles
107
what is acetyl-CoA (produced from beta-oxidation of fatty acids) oxidised in the TCA cycle to produce?
1 FADH2
3 NADH + 3H+
1 GTP
2 CO2
108
compare the yield of FADH2 in saturated fatty acids compared to unsatruated fatty acids?
unsaturated fatty acids yield less FADH2 than saturated fatty acids because they are already partially oxidise
109
in the last cycle of beta oxidation of an odd-chain fatty acid instead of yielding 2 acetyl Co-As what is yielded?
acetyl CoA (2 carbon)
+
propionyl-CoA (3 carbon)
110
how does propionyl-CoA enter the TCA cycle?
converted to succinyl-CoA which enters the TCA cycle directly
111
where are ketone bodies formed?
in the liver mitochondria
112
what are ketone bodies formed from?
acetyl CoA from beta oxidation
113
what is the function of ketone bodies?
diffuse into peripheral tissues and then can be converted back into acetyl CoA which enters the TCA cycle
114
how many carbons are in oxaloacetate?
4
115
in starvation or diabetes why can acetyl CoA from the ketone bodies not convert back into acetyl CoA and enter the TCA cycle?
because to enter the TCA cycle there needs to be oxaloacetate
in starvation nor diabetes, gluconeogenesis has used up the oxaloacetate and so acetyl-CoA can't enter the TCA cycle and accumulates in tissues instead
116
what blood gas result does starvation or diabetes cause due to the accumulation of ketone bodies?
```
metabolic acidosis
(diabetic ketoacidosis due to hypoglycaemia)
```
117
where does de novo synthesis of fatty acids mainly occur?
in the liver, kidney, mammary glands, adipose tissue and brain
118
lipoenesis is a reductive process, what does this mean?
electrons are required
119
what is the precursor molecule in the synthesis of fatty acids?
acetyl CoA
120
where does synthesis of fatty acids from acteyl-CoA occur?
cytoplasm
121
why can acetyl-CoA not easily transfer between mitochondrial matrix and cytoplasm?
inner mitochondrial membrane is impermeable to acetyl-CoA
122
what transports the acetyl made in the matrix (by beta oxidation) to the cytoplasm for lipogenesis?
citrate
123
how is citrate formed?
condensation of acetyl-CoA with oxaloacetate
| first step of TCA cycle
124
why would citrate leave the mitochondria to allow lipogenesis to take place instead of carrying on with the TCA cycle?
if the cirrate concentrations are very high
125
what is the first step in lipogenesis?
activation of acetyl-CoA to malonyl-CoA
126
what enzyme converts acetyl-CoA to malonyl-CoA
acetyl-CoA carboxylase
127
what is the function of fatty acid synthase?
catalyses synthesis of saturated long-chain fatty acids from malonyl-CoA, acetyl-CoA and NADPH
128
what is teh function of NADPH within lipogenesis?
donates electrons
129
how many acyl-carrier proteins does fatty acid synthase carry?
2 per dimer
130
what is the longest fatty acid that can be created by fatty acid synthase?
palmitic acid (16:0)
131
what does each lipogenesis cycle do to the growing acyl-CoA?
2 carbons are added to the acetyl-CoA on the first cycle from maloynyl-CoA
and this cycle continues until a 16 carbon molecule is made
132
what derivative of glycerol is needed for the synthesis of triglycerides?
glycerol-3-phosphate
133
what does the liver produce glycerol-3-phosphate from?
glycerol
134
what does adipose tissue produce glycerol-3-phosphate from?
glucose
135
when are fats synthesised de novo?
when there are times of excess carbohydrates
| causing excess citrate
136
where is the main site of amino acid degradation?
liver
137
what are the 4 major nitrogen-containing excretory molecules?
(remember nitrogen comes from amino acids)
urea
uric acid
creatinine
ammonium ion
138
where is urea produced?
liver
139
what are the 3 steps in the synthesis of urea?
transamination
de-amination
urea cycle
140
where does the transamination phase of urea synthesis occur?
all cells
141
what happens in the transamination phase of urea synthesis?
production of glutamic acid from the transfer of an amino group from amino acid to ketoglutarate
142
what enzyme catalyses the transmination phase of urea synthesis?
amino transferase
143
where does the de-amination phase of urea synthesis occur?
liver cells
144
what happens in the de-amination phase of urea synthesis?
amino group is removed from glutamatic acid
| and NADH + NH4+ is formed
145
what 2 amino acids are the main transporter molecules of nitrogen to the liver?
alanine
glutamate
(glutamic acid is converted to these for transport to the liver, once in the liver they are converted back)
146
what is the overall process of the urea cycle?
ammonium ion + CO2 + aspartic acid = urea
147
how many high energy phosphate bonds are used in the urea cycle?
4
| 3ATP to 2 ADP + AMP
148
what biproduct is made in the urea cycle?
fumerate
149
once the amino group has been removed, what are the 2 options for ketogenic amino acids?
1. degraded to acetyl-CoA which can be oxidised in the TCA cycle
2. give rise to ketone bodies
150
once the amino group has been removed, what are the 2 options for glucogenic amino acids?
1. degraded to pyruvate or TCA cycle intermediates
| 2. converted into phosphoenolpyruvate and then into glucose (gluconeogenesis)
151
what is alcaptonuria?
an inherited disorder where the degradation of phenylalanine and tyrosine is blocked
152
what is mable syrup urine disease?
an inherited disorder where degradation of valine, isoleucine and leucine is blocked
153
what is phenylketonuria?
an inherited disorder where phenylalanine cant be broken down
154
how do you treat urea cycle disorders?
low-protein diet
| drugs which remove nitrogen
155
why are urea cycle disorders so dangerous?
accumulation of ammonia in the blood (toxic)
156
what are the 6 principle roles of the liver?
1. destination of most nutrients and xenobiotics absorbed from the GI tract
2. bile production
3. elimination of unwanted molecules
4. secretion of plasma proteins
5. storage of important molecules
6. regulation of metabolism
157
what are the 6 main classes of liver-derived plasma protein?
```
albumin
alpha 1 globulins
alpha 2 globulins
beta 1 globulins
beta 2 globulins
gamma globulins
```
158
what are gamma globulins more commonly known as?
immunoglobulins
159
describe the relative concentrations of liver-derived plasma proteins?
albumins are present at high concentrations
| alpha, beta and gamma globulins are present at lower concentrations
160
list the liver-derived plasma proteins in terms of molecular weight?
(heaviest to lightest)
gamma globulins
beta 1 + 2 globulins
alpha 1 + 2 globulins
albumin
161
what are the 5 main function of plasma proteins?
1. maintenance of osmotic pressure in blood vessel
2. transport of hydrophobic substances
3. pH buffering
4. enzymatic
5. immunity
162
how do plasma protein buffer the pH?
by accepting or donating protons
163
what plasma protein binds copper?
ceruloplasmin
164
what type of liver-derived plasma protein is ceruloplasin?
alpha globulin
165
what type of liver-derived plasma protein is transferrin?
beta globulin
166
what type of liver-derived plasma protein is fibrinogen?
beta globulin
167
what can loss of transferrin indicate?
iron deficiency
168
what happens to transferrin expression when you increase altitude?
a rise in transferrin expression (because increasing altitude is an erythopoetic effect)
169
what is fibrinogen?
inactive form of fibrin
| activated by prothrombin
170
what is the plasma protein which is the determinant of plasma oncotic pressure?
albumin
171
what hormone stimulates the production of albumin in the liver?
insulin
172
what 3 things cause the decreased levels of albumin?
starvation
low protein diet
liver disease
173
albumin also has a transport function, describe affinity albumin has for hydrophobic molecules?
describe capacity albumin has for hydrophobic molecules?
```
low affinity
high capacity (due to high concentration)
```
174
what plasma protein carries bilirubin to the liver?
albumin
175
what is bilirubin the breakdown product of?
haem
176
what form is iron transported as?
ferric (Fe3+)
177
what protein is Fe3+ bound to for transport?
transferrin
178
what form is iron stored as?
ferrous (Fe2+)
179
when stored within cells, what is fFe2+ bound to?
ferritin
180
what metal plays the essential role of oxidising Fe2+ to Fe3+ for transport?
copper
| within ceruloplasmin
181
what is Wilsons disease?
an inherited disease where you are deficient in ceruloplasmin leading to the accumulation of copper in organs and tissue
182
how is thyroxine (T4) transported?
bound to thyroid-binding globulin
183
how is cortisol transported?
cortisol-binding globulin
184
what do binding globulins do to the hormone biological half life?
(how?)
extend it
| because without binding globulins the hormones would be eliminated rapidly by liver or kidney
185
why does malnutrition (because of vitamin deficiency) take a long time to come into effect?
because the liver has stored up many vitamins
186
what does the synthesis of cholesterol require?
18 mol of acetyl-CoA
16 mol of NADPH
36 mol of ATP
187
what is the rate limiting step in cholesterol synthesis?
the action of HMG-CoA reductase
188
what is the function of HMG-CoA reductase?
irreversibly catalyses the formation of mevalonic acid
189
what stimulates the synthesis and activity of HMG-CoA reductase?
starving
190
what 2 molecules does vitamin D have a key role in the regulation of their metabolism?
calcium
| phosphorus
191
what 3 organs are steroid hormones produced from?
ovaries
testis
adrenal glands
192
how many carbons are in a corticosteroid?
21 carbon atoms
193
how many carbons are in an androgen?
19 carbon atoms
194
how many carbons are in an estrogen?
18 carbon atoms
195
what is the main metabolic product of cholesterol?
bile salts
196
where does fatty acid synthesis take place?
cytoplasm
197
where does beta oxidation take place?
mitochondrial matrix
198
what is the donor molecule of carbons to a growing fatty acid?
malonyl-CoA
199
where does glycolysis occur?
cytoplasm
200
what is the P/O ratio?
a measure of the number of ATP molecules formed per oxygen atom reduced
201
which has a greater redox potential- NADH + H+ or FADH2?
| ie likes to give away electons more
NADH + H+
