Metabolism Flashcards
1
Q
What is the simplest amino acid?
A
Glycine
2
Q
What amino acid is formed if the R group is CH3?
A
Alanine
3
Q
If an amino acid has non-polar side chains what does this make the amino acid?
A
Hydrophobic
4
Q
If an amino acid has polar side chains what does this make the amino acid?
A
Hydrophillic
5
Q
What ability gives amino acids buffering capability?
A
The ability to take up and release protons
6
Q
What are enantiomers of amino acids?
A
Mirror images of an amino acid
7
Q
in what form are amino acids in the body?
A
L-form
8
Q
What reaction forms amino acid peptides?
A
Condensation reaction
9
Q
What is steric hindrance?
A
Where side chains in a protein do not clash with the main chain
10
Q
What bond is present in disulphide bridges?
A
Covalent bonds
11
Q
What are Van der Waals forces?
A
Transient, weak electrostatic attraction between atoms. Requires closeness
12
Q
Where does an alpha helix bond form?
A
The C=O of one amino acid bonds to the N-H four amino acids along bonds to stabilise the structure
13
Q
What amino acid causes kinks in the alpha helix chain?
A
Proline
14
Q
What is a primary protein structure?
A
The linear structure- the amino acid sequence
15
Q
What is a secondary protein structure?
A
The alpha-helices and beta-pleated sheets
16
Q
What is a tertiary protein structure?
A
Arrangement of secondary structures into compact globular structures called domains
17
Q
What is quaternary protein structure?
A
The 3D structure of a multimeric protein that has multiple polypeptide chains eg haemiglobin
18
Q
Where are γ-carboxyglutamate residues formed in proteins?
A
In clotting factors in the blood clotting cascade
19
Q
What is the function of γ-carboxyglutamate residues?
A
They are critical for normal clotting function by increasing calcium binding capabilities
20
Q
How does Warfarin work?
A
Warfarin inhibits the carboxylation reaction of γ-carboxyglutamate residues, reducing the coagulative properties of the clotting factors
21
Q
What is free energy?
A
The amount of energy within a molecule that could perform useful work at a constant temperature
22
Q
A reaction can only occur if △G is what?
A
Negative
23
Q
What is the high energy bond in ATP?
A
Phosphoanhydride bonds
24
Q
What do enzymes do to the rate of reaction and the activation energy?
A
The increase the rate of reaction and lower the activation energy
25
What do enzymes do to △G?
Nothing
26
What does lysozyme do?
Catalyses the hydrolysis of sugar molecules N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM within bacterial cell walls that are necessary for their structure.
27
What are the three stages of metabolism?
1) Digestion: Enzymes mediated, liberates small molecules, takes place in the GI tract
2) Cellular metabolism I: Oxidation of small molecules within the cytosol of individual cells generating ATP and NADH
3) Cellular metabolism II: oxidation of small molecules generated by the first stage of cellular metabolism within the mitochondria, generating ATP and waste
28
What does a deficiency in thiamine (vitamin B1) cause?
Beri-Beri
| Symptoms include: damage to the peripheral nervous system, weakness of muscles and decreased cardiac output
29
Where is pyruvate converted into Acetyl-CoA
In mitochondria
30
Where does glycolysis take place?
In the cytoplasm of cells
31
Is glycolysis aerobic or anaerobic?
Anaerobic
32
What is the net ATP gain from glycolysis?
2 ATP molecules
33
What is the net ATP gain from aerobic respiration?
38 ATP molecules
34
What is the high energy bond in Acetyl-CoA?
A thioester bond (C-S)
| Allows Acetyl-CoA to donate 2C to a molecule (CO-CH3)
35
How does palmitic acid make Acetyl-CoA?
β-oxidation
36
What are the products of one β-oxidation cycle?
1 FADH2
1 NADH
1 Acetyl CoA
37
What is transamination?
A reaction in which an amine group is transferred from one amino acid to a keto acid thereby forming a new pair of amino and keto acids
38
Persistently high levels of alanine aminotransferase are diagnostic of what?
Hepatic disorders such as Hepatitis C
39
Where does the Kreb's cycle occur?
In the mitochondrial matrix
40
Is the Kreb's cycle aerobic or anaerobic?
Aerobic
41
How does NADH + electrons cross from the cytosol to the mitochondrial matrix in skeletal muscle and the brain?
Glycerol phosphate shuttle
42
How does NADH + electrons cross from the cytosol to the mitochondrial matrix in the liver, kidney and heart?
Malate-aspartate shuttle
43
The result of the malate-aspartate shuttle leave NAD+ and NADH where?
NAD+ is cytoplasmic
| NADH is mitochondrial
44
How many ATP molecules so you get from oxidative phosphorylation of 1 NADH?
3 ATP molecules
45
How many ATP molecules so you get from oxidative phosphorylation of 1 FADH2?
2 ATP molecules
| Because the electrons enter at ubiquinone with FADH2
46
How many ATP molecules do you get from glycolysis?
8 ATP molecules
47
How many ATP molecules do you get from one Acetyl-CoA in the Kreb's cycle?
12 ATP molecules
48
How many ATP molecules do you get from palmitate metabolism?
129 ATP molecules
49
Where does oxidative phosphorylation occur?
In the inner mitochondrial membrane
50
What is oxidative phosphorylation?
The process in mitochondria in which ATP formation is driven by the transfer of electrons from food molecules to molecular oxygen. Involves the intermediate generation of a pH gradient across a membrane and chemiosmotic coupling
51
Which subunit and disc of ATP synthase rotates when a proton moved from intermembrane space to the matrix?
Disc of subunit c and the attached γ subunit rotate
52
How much ATP does the average human body synthesis per day?
70kg
53
How long is the average ATP lifespan?
Between 1 and 5 minutes
54
What is the most common cause of a failure in the process of oxidative phosphorylation?
Hypoxia (diminished) and Anoxia (Total)
55
How does cyanide affect the electron transport chain?
It binds with very high affinity to ferric iron in haem group in the cytochrome oxidase complex. This blocks the flow of electrons through the respiratory chain and consequently, the production of ATP
56
How does carbon monoxide affect the electron transport chain?
It binds to the ferrous iron in haem group, blocking the flow of electrons.
57
How does malonate affect the electron transport chain?
It closely resembles succinate and acts as a competitive inhibitor of succinate dehydrogenase. It effectively slows down the flow of electrons from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate
58
How does oligomycin affect the electron transport chain?
It is an antibiotic produced by streptomyces that inhibits oxidative phosphorylation by binding with the stalk of ATP synthetase. This blocks the flow of protons through the enzyme. As a result, ATP synthesis is inhibited and a backlog of protons will build up in the intermembrane space. This will eventually inhibit the flow of electrons through the electron transport chain as the outside of the mitochondrion will build up to a saturation point at which no more protons can be pumped out against this proton gradient
59
What is needed to digest and emulsify fats?
Bile salts
60
What is steatorrhea?
Fatty stools resultant from lack of bile salts
61
β-oxidation is the metabolism of what?
Fatty acids
62
Where does β-oxidation occur?
In the mitochondrial matrix
63
Fatty acid synthesis uses which two enzymes?
Acetyl CoA Carboxylase
| Fatty Acid Synthase
64
What are the two molecules needed for lipogensis
Acetyl CoA
| Malonyl CoA
65
Where does fatty acid synthesis take place?
In the cytoplasm
66
What are the 3 types of intracellular transport?
1) Gates transport (eg nuclear import)
2) Transmembrane transport (eg import of newly synthesised proteins into ER)
3) Vesicular transport (eg inter-organellar transport)
67
What post translational modifications does the endoplasmic reticulum make?
```
Folding
Formation of disulphide bonds
Initial glycosylation (addition of sugars)
Specific proteolytic cleavages
Assembly of multimeric proteins
```
68
Where are unassembled or misfolded proteins retained and exported back to the cytosol to be degraded?
The endoplasmic reticulum
69
What is constitutive secretion?
Where proteins are secreted from a cell continuously, regardless of external factors or signals
70
What is regulated secretion?
Where proteins are stored and secreted on demand in response to a signal eg insulin
71
Describe the process of the receptor-mediated endocytosis of LDL in the liver?
LDL binds to LDL receptors and endocytosis occurs into a clathrin-coated vesicle
Uncoating of the vesicle occurs
Fusion with the endosome
Budding off of transport vesicle of LDL receptor
Return of LDL receptor to plasma membrane
72
What does CFTR stand for?
Cystic fibrosis transmembrane conductance regulator
73
What is the most common mutation to cause cystic fibrosis and what does it cause?
Mutation at △F508 causes a loss of phenylalanine at the 508th position causing the protein to misfold
74
A mutation of what causes familial hypercholesterolaemia?
LDL receptor
75
What is from progestagens?
Glucocorticoids
Mineralocorticoids
Androgens- Estrogens
76
How are progestagens formed from cholesterol?
Cholesterol→Pregnenolone→Progestagens
77
What enzyme converts cholesterol to pregnenolone?
Desmolase
78
What is the process of synthesis of vitamin D from cholesterol?
7-Dehydrocholesterol→Previtamin D3→Vitamin D3→Calcitriol
79
What is required to convert 7-Dehydrocholesterol to Previtamin D3?
Ultraviolet light
80
What bile salts are produced from cholesterol?
Glycocholate and taurocholate
81
What is the main breakdown product of cholesterol?
Bile salts
82
How big are high-density lipoproteins?
8-10nm
83
How big are low-density lipoproteins?
20-25nm
84
What is the function of high-density lipoproteins?
Take cholesterol from peripheral tissues back to the liver for use of disposal
85
What is the function of low-density lipoproteins?
Take cholesterol synthesised in the liver to peripheral tissues
86
What cholesterol is "good cholesterol"?
High-density lipoprotein
87
What cholesterol is "bad cholesterol"?
Low-density lipoprotein
88
With a single copy of the familial hypercholesterolaemia gene, how much higher is your cholesterol?
2-3 times higher
89
With a two copies of the familial hypercholesterolaemia gene, how much higher is your cholesterol?
5 times
90
What drug aims to lower cholesterol by targeting the intestines?
Resins
91
What drug aims to lower cholesterol by targeting the liver?
HMG-CoA Reductase Inhibitors (a.k.a Statins)
92
Where does aerobic respiration take place?
In mitochondria
93
Where does anaerobic respiration take place?
In the cytoplasm
94
Where does skeletal muscle get it's ATP during light contractions?
Oxidative phosphorylation
95
Where does skeletal muscle get it's ATP during vigorous contractions?
Glycolysis and pyruvate is converted to lactate
96
What does the brain use as a source of energy?
Glucose
97
What is the only other partial substitute for glucose the brain uses?
Ketone bodies
98
What type of respiration does the heart use?
Aerobic (completely)
99
What is the normal blood glucose range?
4.0-5.5mM
100
What does the liver store?
Glycogen
101
When is insulin secreted?
When glucose levels rise
102
What does insulin cause?
Uptake and use of glucose and storage as glycogen and fat
103
When is glucagon secreted?
When glucose levels fall
104
What does glucagon cause?
Production of glucose by gluconeogenesis and breakdown of glycogen and fat
105
Where are insulin and glucagon secreted?
The islets of the pancreas
106
What is the role of adrenaline?
Strong and fast metabolic effects to mobilise glucose for "fight or flight"
107
What is epinephrine?
Adrenaline
108
What is the role of glucocorticoids?
Steroid hormones which increase synthesis of metabolic enzymes concerned with glucose availability
109
Where are adrenaline and glucocorticoids secreted?
The adrenal glands
110
Where is insulin made?
In β-cells in islets of Langerhans
111
When you eat what processes occur?
Increased blood glucose
Insulin secretion
Increased glucose uptake by the liver for glycogen synthesis and glycolysis
Increased glucose uptake and glycogen synthesis in muscle
Increased triglyceride synthesis in adipose tissue
Increased use of metabolic intermediates throughout the body
112
What happens after a meal when glucose levels begin to fall?
Increased glucagon secretion as insulin levels fall
Glucose production from the liver from glycogen breakdown and gluconeogenesis
Fatty acid breakdown as alternative substrate for ATP production
113
What happens after prolonged fasting when glycogen stores are depleted?
Glucagon/insulin ratio increases further
Adipose tissue begins to hydrolyse triglyceride to provide fatty acids for metabolism
TCA cycle intermediates are reduced in amount to provide substrate for gluconeogenesis
Protein breakdown provides amino acid substrates for gluconeogenesis
Ketone bodies are produced from fatty acids and amino acids in liver to substitute partially the brain's requirement for glucose
