Metabolism Flashcards
(123 cards)
1
Q
What is the Gibbs free energy equation?
A
ΔG = ΔH - T ΔS
2
Q
What is ΔH
A
Enthalpy
Because it has a H!!
3
Q
What is ΔS
A
Entropy
4
Q
Why is ATP broken down into ADP?
A
- Motion
- Active transport
- Biosynthesis
etc
5
Q
When is ADP converted back into ATP?
A
- Oxidation of fuel molecules
- Photosynthesis
6
Q
What are the 2 ATP production pathways?
A
- Substrate level phosphorylation
- Oxidative phosphorylation
7
Q
How is metabolism regulated?
A
- Levels and accessibility of substrate
- Amount of metabolic enzymes
- Modulation of enzyme activity
8
Q
How can enzyme activity be modulated?
A
- Allosteric interactions
- Covalent modification
- Association with regulatory proteins
9
Q
What is feedback inhibition?
A
Where the end product of an enzymatic reaction inhibits an enzyme earlier in the pathway
10
Q
What is the adenylate charge?
A
The ratio of ATP, ADP, and AMP in a cell
11
Q
What methods of covalent modification are there?
A
- Adenylation
- Methylation
- Phosphorylation
(method of modifying enzyme activity to regulate metabolism)
12
Q
What is glucose turned into in glycolysis? What enzyme does this? Anything else that needs to be known about this step?
A
- Glucose-6-phosphate (G6P)
- Enzyme = hexokinase
- ATP is dephosphorylated here
ATP is dephosphorylated, G6P is phosphorylated
13
Q
What is G6P turned into in glycolysis? What enzyme does this?
A
- Fructose-6-phosphate
- Enzyme = phosphohexose isomerase
14
Q
What is F6P turned into in glycolysis? What enzyme does this? Anything else to know about this step?
A
- Fructose-1,6-bisphosphate
- Enzyme = phosphofructokinase
- An ATP is used here
ATP provides the phosphate group
15
Q
What is Fructose-1,6-bisposphate turned into in glycolysis? What enzyme does this?
A
- Glycerol-3-phosphate AND DHAP
- Enzyme = Aldolase
DHAP isn’t fucntional here so we need to turn it into something else
16
Q
What is DHAP turned into in glycolysis? What enzyme does this?
A
- Another G3P (there are now 2x G3P)
- Triose phosphate isomerase (TIM)
17
Q
What is G3P turned into in glycolysis? What enzyme does this? Is there anything else important about this step?
A
- 1,3 - bisphosphoglycerate
- Enzyme = Glyceraldehyde-3-phosphate dehydrogenase
- Produces 2x NADH, 2x H+
18
Q
What is 1,3-bisphosphoglycerate turned into in glycolysis? What enzyme does this? Anything else you need to know about this step?
A
- 3-phosphoglycerate
- Enzyme = Phosphoglycerate kinase
- 2x ATP produced (one by each molecule)
This is the first ATP ‘payoff’
19
Q
What is 3-phosphoglycerate turned into in glycolysis? What enzyme does this?
A
- 2-Phosphoglycerate
- Enzyme = Phosphoglycerate mutase
20
Q
What does 2-phosphoglycerate get turned into in glycolysis? What enzyme does this? Is there anything else to knwo about this step?
A
- Phosphoenol pyruvate
- Enzyme = Enolase
- Produces 2x H2O (each molecule makes one H2O)
21
Q
What does phosphoenol pyruvate get turned into in glycolysis? What enzyme does this? Is there anything else to be aware of with this step?
A
- Pyruvate
- Enzyme = pyruvate kinase
- This step makes 2x ATP
This makes up the 4x ATP produced in glycolysis
22
Q
Why do animals store energy as glycogen?
A
- Maintains blood glucose levels
- Essential for the brain
- Rapidly mobilised for sudden energy demands
- Provides energy under anaerobic conditions
23
Q
What is the synthesis of glycogen called?
A
Glycogenesis
24
Q
How is glucose uptake from the blood facilitated in glycogenesis?
A
Transport proteins:
- GLUT2
- GLUT4
25
Where are GLUT2 transporters? When does this uptake glucose?
- liver and pancreas β-cells
- GLUT2 uptakes glucose after meals when levels are high
26
Where are the GLUT4 transporters? What is special abiout these receptors
- Muscle and fat cells
- The more you exercise, the more they are expressed in muscle cells
27
What is glucose converted into in glycogensis? What enzyme(s) does this? Where?
- Glucose --> glucose-6-phosphate
- Enzymes = hexokinase in the muscles, and glucokinase in the liver
28
What Enzyme does G6P produced in gycogenesis have a negative feedback loop with?
Hexokinase
29
What does G6P get turned into in glycogenesis? What enzyme does this?
- Glucose-1-phosphate
- Enzyme = phosphoglucomutase
30
What does G1P get turned into in glycogenesis? What enzyme does this?
- UDP-Glucose
- Enzyme = UDP-glucose phosphorylase
31
What does UDP glucose do in glycogenesis? What enzyme facilitates this?
- Glucose is added to a glycogen polymer, elongating the chain
- UDP is then left as its own molecule
- Enzyme = glycogen synthase
32
What is needed to facilitate the initiation of the glycogen chain in glycogenesis?
Glycogenin primer needed to start the chain formation
## Footnote
UDP-glucose then brings along the glucose monomers to bid to this
33
How is glycogen synthase regulated?
Protein kinase A phosphorylates the glycogen synthase, making it inactive (see below)
- A = active form of glycogen synthase - UNPHOSPHORYLATED
- B = inactive form of glycogen synthase - PHOSPHORYLATED
| A for active!!
34
What things promote the A form of glycogen synthase?
- Protein phosphatase 1
- Insulin
35
What things promote the B form of glycogen synthase?
- Protein kinase A
- High levels of G6P
36
What effect do high G6P levels have on glycogen synthase?
High G6P allosterically activates the inactive B form of glcogen synthase
37
What opposes the action of protein kinase A? What does it therefore do?
- Insulin - it counteracts phosphorylation, ensuring glycogen synthase is in its A form, therefore telling the body to synthesise glycogen
- Protein phosphatase 1 activates it by removing phosphates, turning it into the A form
38
What creates the branched shape of glycogen? How? What does this shape provide?
- Branching enzyme
- It moves a 7-glucsose unit from an 11+ chain to a new location, creating a new α-1,6 bond
- This increases solubility, and the number of non-reducing ends from which the chain can grow further / be readily mobilised
39
What is the opposite process to glycogenesis?
Glycogenolysis
40
What enzyme breaks down glycogen in glycogenolysis? Where does it stop?
- Enzyme = Glycogen phosphorylase
- It stops 4 glucoses before a branching point
41
What happens to the 4-glucose branch during glycogenolysis?
- Transferase moves 3 glucoses to another point in the chain, leaving 1
- This bond is cleaved by α-1,6-glucosidase, generating 1 glucose molecule
42
What molecule does glycogen phosphorylase break down the ends of glycogen chains into?
G1P
| This stops 4 glucoses before a branching point remember!!
43
What does G1P turn into in glycogenolysis? What enzyme does this?
- G6P
- Enzyme = Phosphoglucomutase
44
What is G6P broken down into in glycogenolysis? What enzyme does this and where?
- In the liver: glucose-6-phosphatase breaks G6P into glucose for release into the blood
- In the muscles: G6P is used in glycolysis instead (muscles dont have glucose-6-phosphatase)
45
What things promote glycogenolysis?
- Glucagon
- Adrenaline
- AMP (indicates low energy levels)
46
What things inhibit glycogenolysis?
- Insulin
- G6P
- ATP (indicates high energy levels)
47
Why is glycogenolysis different from glycogenesis?
| As in why do they not use the same pathway?
Breakdown and synthesis don't use the same pathway to allow separate regulation
48
What is Von Gierke's disease?
- Deficiency in **glucose-6-phosphatase**
- Liver can't pump glucose into the blood
- Causes hypoglycaemia (requires constant glucose intake, even when asleep)
49
What is Cori's disease?
- Deficiency in the transferase / debracnching enzyme
- Glycogen accumulates with shorter side chains that can't be broken down
| Less severe than Von Gierke's disease
50
What is McArdle's disease?
- Deficiency in **muscle glycagon phosphorylase** - muscle therefore can't break down glycogen
- Leads to exercise-induced cramps and no increase in lacatate upon exercise
- Prolonged exercise can lead to muscle rupture
51
What are the major precursors for gluconeogenesis?
1. Lactate - skeletal muscle and RBC
2. Amino acids (AAs) - dietary protein or muscle breakdown in starvation
3. Glycerol - hydrolysis of triglycerides in adipose tissue
52
What amino acids can't be used in gluconeogenesis? Why not?
Leucine and lysine, as they are purely ketogenic
| They are used in ketone body production instead!!
53
Name the 8 enzymes used in the TCA cycle in order
1. Citrate synthase
2. Aconitase
3. Isocitrate dehydrogenase
4. a-Ketoglutanate dehydrogenase
5. Succinyl-CoA synthetase
6. Succinate dehydrogenase
7. Fumerase
8. Malate dehydrogenase
54
Between which 2 intermediates in the TCA cycle is GTP formed from GDP and Pi?
Succinyl CoA and Succinate
55
Between which 2 intermediates in the TCA cycle does FAD become FADH2?
Succinate and Fumerase
56
What compound is joined with Acetyl-CoA to make citrate in the TCA cycle?
Oxaloacetate
57
In the TCA cycle, what is fumerate hydrated to become?
Malate
58
What 8 molecules are created during the citric acid cycle? In order
1. Citrate
2. Isocitrate
3. a-Ketoglutarate
4. Succinyl CoA
5. Succinate
6. Fumerate
7. Malate
8. Oxaloacetate
59
How many key regulatory points are there in the Krebs cycle? Where are they?
2
Isocitrate dehydrogenase
a-Ketoglutarate dehydrogenase
60
What is the standard reduction potential?
A measure of a compounds affinity for electrons
61
What is the final electron acceptor in the ETC? What is the reduction potential compared to the other complexes?
Oxygen, has the highest potential
62
What are the 2 methods of transporting NADH into the mitochondria?
Glycerol 3-phosphate shuttle
Malate-aspartate shuttle
63
What is the name of complex I in the electron transport chain?
NADH coenzyme Q oxidoreductase
64
What is the name of complex III in the ETC?
CoQ-Cytochrome c Oxidoreductase
65
What is the name of complex IV in the ETC?
Cytochrome c oxidase
66
What is the important enzyme in the link reaction?
Pyruvate dehydrogenase (this is a huge complex that uses vitamins like B1 = thiamine)
67
What is a stoichiometric cofactor?
A cofactor that is used up or chemically changed during the reaction
68
Name 2 stoichiometric cofactors part of the pyruvate dehydrogenase complex
Thiamine pyrophopshate (TPP)
Lipoic acid
69
What is step 1 of the link reaction?
Decarboxylation
Pyruvate enters → loses CO₂ → gets caught by TPP
70
What is step 2 of the link reaction?
Oxidation
The 2-carbon piece gets moved to lipoic acid, and while moving, it loses electrons
71
What is step 3 of the link reaction?
Formation of acetyl-CoA
The acetyl group jumps onto CoA, making Acetyl-CoA (the golden ticket into the TCA cycle)
72
What is step 4 of the link reaction?
Oxidation of lipoic acid back to the original state
Lipoic acid gets "cleaned up" using FAD and NAD⁺, and we make NADH
73
What does a single molecule of pyruvate form in the link reaction?
1 Acetyl-CoA formed.
1 NADH formed.
1 CO₂ released
74
What does pantothenic acid deficiency cause?
Hypertension
75
What does a B1/thiamine deficiency cause?
Beriberi
Neurological and cardiovascular symptoms
Raised blood pyruvate levels
Nervous system relies on glucose for energy
76
What kind of enzyme completes the oxidation steps of the TCA cycle?
Dehydrogenases
77
What are the 3 enzyme steps used by ubiquitin?
Ubiquitin activating enzyme (E1)
Ubiquitin conjugating enzyme (E2)
Ubiquitin protein ligase (E3)
78
What do the 2 parts of a proteasome do?
19S part recognizes the tagged protein.
20S part chops it up into amino acids
79
Where are amino groups removed mostly?
Liver
80
What kinds of amino acids can muscles break down?
Branched e.g. leucine, lysine
81
What tags proteins for degradation?
Ubiquitin (small protein tag).
82
What are the 3 enzymes involved in ubiquitination?
E1 = Ubiquitin activating enzyme; E2 = Ubiquitin conjugating enzyme; E3 = Ubiquitin ligase.
83
What structure destroys ubiquitin-tagged proteins?
26S Proteasome (19S = recognition, 20S = protease).
84
Where is amino group removal mainly happening?
In the liver (muscles degrade branched-chain amino acids).
85
What happens to amino groups and carbon skeletons?
Amino group → Urea; Carbon skeleton → TCA/Krebs Cycle.
86
What is an aminotransferase?
Enzyme that transfers an amino group to α-ketoglutarate, forming glutamate.
87
Name two important aminotransferases.
Alanine transaminase (ALT) and Aspartate transaminase (AST).
88
What cofactor do aminotransferases need?
Pyridoxal phosphate (Vitamin B6 derivative).
89
What enzyme removes ammonia from glutamate?
Glutamate dehydrogenase.
90
What happens to ammonia after deamination?
Converted into Urea via the Urea Cycle.
91
What are the steps of the Urea Cycle?
1. Carbamoyl phosphate synthetase
2. Ornithine transcarbamoylase
3. Argininosuccinate synthetase
4. Argininosuccinase
5. Arginase.
92
What powers urea production?
4 ATP equivalents are used per urea molecule.
93
What happens to fumarate made in the Urea Cycle?
Hydrated to malate → Oxidized to oxaloacetate → Used in gluconeogenesis or aspartate production.
94
What is nitrogen fixation?
Conversion of atmospheric N₂ into NH₄⁺ (ammonia) by bacteria using nitrogenase enzyme.
95
How many ATP are used in nitrogen fixation?
16 ATP per N₂ molecule.
96
What enzyme assimilates ammonium (NH₄⁺) into glutamate?
Glutamate dehydrogenase and Glutamine synthetase (uses ATP).
97
What is 'protein quality'?
High-quality protein contains all essential amino acids in correct proportions; Animal proteins usually higher quality than plant proteins.
98
What is a limiting amino acid?
The essential amino acid present in the lowest amount relative to the body's need; it limits new protein synthesis.
99
How many NADH molecules are produced per Krebs cycle and per glucose molecule?
3 per cycle, 6 per molecule
100
How many FADH molecules are produced per Krebs cycle and per glucose molecule?
1 per cycle, 2 per molecule
101
How many CO2 molecules are produced per Krebs cycle and per glucose molecule?
2 per cycle, 4 per molecule
102
How many GTP molecules are produced per Krebs cycle and per glucose molecule?
1 per cycle, 2 per molecule
103
Between which intermediates is NADH produced in the Krebs cycle? Alternatively, with which enzymes?
1. Isocitrate -> a-ketoglutarate, with isocitrate dehydrogenase
2. a-ketoglutarate -> succinyl-CoA with a-ketoglutarate dehydrogenase
3. Malate -> oxaloacetate with malate dehydrogenase
104
Which dehydrogenase enzyme in the Krebs cycle does NOT produced NADH in its reaction?
Succinate dehydrogenase
105
Between which intermediates and with which enzyme is FADH2 produced in the Krebs cycle?
Succinate -> fumerate
Succinate dehydrogenase
106
Between which 2 intermediates and with which enzyme is GTP produced in the Krebs cycle?
Succinyl-CoA -> Succinate
Succinyl-CoA synthetase
107
Which enzyme reactions in glycolysis use ATP?
Step 1, hexokinase
Step 3, phosphofructokinase-1
108
What are the 10 intermediates in glycolysis in order?
1. Glucose
2. G6P
3. F6P
4. F1,6BP
5. G3P and DHAP
6. 1,3BPG
7. 3PG
8. 2PG
9. PEP
10. Pyruvate
109
What are the 10 enzymes of glycolysis in order?
1. Hexokinase
2. Phosphoglucose isomerase
3. Phosphofructokinase-1
4. Aldolase
5. Triose phosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase
6. Phosphoglycerate kinase
7. Phosphoglycerate mutase
8. Enolase
9. Pyruvate kinase
110
What enzyme turns G3P into 1,3BPG in glycolysis?
Glyceraldehyde 3-phosphate dehydrogenase
111
What are the net products of glycolysis?
2 pyruvate
2 ATP
2 NADH
2 H2O
2 H+
112
Which 2 steps of glycolysis create ATP?
3PG -> 2PG with phosphoglycerate mutase
PEP -> pyruvate with pyruvate kinase
113
Which step in glycolysis creates NADH?
G3P -> 1,3BPG with glyceraldehyde 3-phosphate dehydrogenase
114
What are the 4 steps of glycogenesis?
1. Glucose -> G6P
2. -> G1P
3. + UTP -> UDP-glucose + PPi
4. UDP-glucose + glycogen
115
What are the 4 enzymes of glycogenesis in order?
1. Hexokinase
2. Phosphoglucomutase
3. UDP-glucose pyrophosphorylase
4. Glycogen synthase
116
What step in glycogenesis is helped by a serine residue?
G6P->G1P
Phosphoglucomutase
117
What are the 4 steps of glycogenolysis in order?
1. Glycogen
2. G1P
3. G6P, debranching enzymes involved
4. Glucose
118
What are the enzymes of glycogenolysis in order?
1. Glycogen phosphorylase
2. Phosphoglucomutase
3. Glucose-6-phosphatase, transferase, a-1,6-glycosidase
119
What hormone cascade activates glycogen synthase? How?
Insulin
Insulin activates protein phosphatases
These inhibit PKA
PKA inhibits glycogen synthase, so without it synthase can take place
120
What signalling cascade inhibits glycogen synthesis? How?
Adrenaline activates GPCR
This activates adenylyl cyclase
Creates cAMP
Activates PKA
PKA inhibits glycogen synthase and activates phosphorylase kinase
Therefore activates glycogen phosphorylase
121
What does glucagon do?
When glucose levels are low, Glucagon is
released which counteracts the Insulin
122
Which form of glycogen synthase is active?
A form
123
What inhibits glycogen synthase? What turns it to its b form?
PKA
