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BIOC192 > Metabolic Pathways > Flashcards

Metabolic Pathways Flashcards

1
Q

What does amylase hydrolyse

A

𝛼-1,4 glycosidic bonds

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2
Q

What active transporter enables absorption of glucose in the GI tract

A

SGLT1 (sodium-glucose linked transporter 1)

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3
Q

What active transporter enables absorption of glucose in general

A

SGLT (sodium-glucose linked transporter)

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4
Q

What facilitative transporter enables passive absorption of glucose in general

A

GLUT

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5
Q

What facilitative transporter enables passive absorption of glucose in the GI tract

A

GLUT2

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6
Q

Describe the action of SGLT

A

Symport of sodium and glucose into a cell, sodium moves down its concentration gradient, glucose moves up. Energy is required

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7
Q

What is the concentration of sodium in the cell

A

Low (Loner)

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8
Q

Describe the action of an Na+/K+ ATPase

A

Na+ moved up concentration gradient into interstitial fluid, K+ moved into epithelial cell, then returns to interstitium down concentration gradient

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9
Q

Describe the action of a GLUT transporter

A

Glucose moves down its concentration gradient into the interstitial fluid

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10
Q

Which cells preferentially use glucose

A

Red blood cells, neurons, cells in the eye, white muscle

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11
Q

Why do red blood cells preferentially use glucose

A

They lack mitochondria so have no machinery for other pathways, rely entirely on glucose and glycolysis

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12
Q

Why do neurons preferentially use glucose

A

Thought fatty acids couldn’t cross the blood-brain barrier, now think glucose provides a quick source of ATP without risk of damage

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13
Q

Why is glucose the favoured fuel in the eye

A

Blood vessels and mitochondria would refract light in the optical path: we want as much light travelling in a straight line onto the retina as possible

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14
Q

Why does white muscle prefer glucose as a fuel source

A

Faster way to make ATP, not relying on oxygen

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15
Q

What is the difference between white and red muscle

A

White: sprinting, glucose
Red: endurance, other fuel sources such as fat (more mitochondria)

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16
Q

How do NAD and FAD differ in terms of association with enzyme

A

NAD: associates with enzyme when required
FAD: associates with enzyme for long periods of time

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17
Q

What are the two phases of glycolysis and what reaction is in between the two

A

Energy investment (glucose activation) and energy payoff (net gain ATP). Splitting reaction is in between the two (6C -> 3C)

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18
Q

What is the total ATP yield and net gain of glycolysis

A

4ATP yield, 2ATP net gain per glucose molecule

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19
Q

What must be known about the first reaction of glycolysis,
glucose -> G-6-P

A

Coupled with hydrolysis of ATP to make energetically favourable, both steps facilitated by hexokinase (forms transient enzyme-bound intermediate)

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20
Q

What must be known about the second reaction of glycolysis,
G-6-P -> F-6-P

A

Unfavourable, driven forward by non standard conditions in pathway (equilibrium but product is used as substrate in next reaction)

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21
Q

What must be known about the third reaction of glycolysis,
F-6-P -> F-1,6-BP

A

Analogous to first reaction, driven forward by hydrolysis of ATP

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22
Q

What must be known about the reaction of glycolysis,
G-3-P -> 1,3-BPG

A

This is an oxidation by NAD+ of an aldehyde to an organic acid. Product is capable of providing sufficient energy to synthesise ATP

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23
Q

What must be known about the substrate level phosphorylations of glycolysis

A

These directly use the energy of the substrates to synthesise ATP

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24
Q

What is the overall equation of glycolysis

A

glucose + 2ADP + 2Pi + 2NAD+ -> 2 pyruvate + 2ATP + 2NADH + 2H+

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25
How does arsenic poison glycolysis
The phosphate group of G-3-P is replaced with an arsenate group. The arsenate reacts with the glyceraldehyde-3-phosphate to form 1-arseno-3-phosphoglycerate, bypassing the first ATP generating substrate level phosphorylation step. This means ATP will only be synthesised in the second substrate level phosphorylation step, producing 2 ATPs/glucose, giving a net gain of zero ATP
26
What cofactors are required in pyruvate oxidation
Thiamine pyrophosphate (TPP, derived from vitamin B1), FAD (derived from vitamin B2), and fatty acid lipoate (lipoic acid)
27
What does pyruvate oxidation involve
The loss of a C from pyruvate as CO2 and the transfer of H to NAD+
28
What is the anaerobic fate of pyruvate
Reduction to lactate
29
Why does pyruvate reduction occur
To regenerate NAD+ so that some ATP can continue to be made in anaerobic conditions by glycolysis
30
What is a reducing equivalent
Hydrogen: 1 proton and 1 electron
31
What are the general features of coenzymes
Carrier molecules, exist in two forms, concentration in cells is low, usually derived from vitamins
32
What is NAD derived from (undergoes a 2 reducing equivalent reduction)
Niacin (vitamin B3)
33
What is FAD derived from (undergoes a 2 reducing equivalent reduction)
Riboflavin (vitamin B2) Remember B2 as it becomes FADH2
34
What is the name of a protein with FAD tightly bound
Flavoprotein
35
What does Coenzyme A carry
Acyl groups
36
What are the two forms of Coenzyme A
CoASH (free) and acetyl-CoA (acyl group attached)
37
What are major minerals
Large abundance in body, range of functions
38
What are minor minerals
Concentration low, difficult to identify/measure
39
What are water soluble vitamins
Not stored: B, C
40
What are fat soluble vitamins
Stored: E, D, A, K
41
What are the important characteristics of coenzymes
Low concentration in cells, act as carriers, have two forms
42
What are the two types of reactions in pathways for processing fuel molecules
Those involving ADP and ATP, and redox reactions (transfer of electrons)
43
How is energy released from fuel molecules in metabolic pathways (general understanding)
Series of oxidation reactions
44
What are enzymes that catalyse redox reactions commonly called
Dehydrogenases
45
What do lipids include
Phospholipids, sterols, triacylglycerols
46
What are the range of roles cholesterol has in the body
Membranes, signalling, bile salts
47
What are fatty acids
Carbon chain attached to carboxylic acid
48
What are lipases
Enzymes which hydrolyse TAGs to release FFA
49
How do lipases get access to non polar fatty acids
Bile salts solubilise
50
What is the exogenous pathway of fat digestion
TAGs broken into MAG and 2FFA, absorption from small micelles, TAGs packaged into chylomicrons in epithelial cells
51
Describe the structure of lipoproteins
Phospholipid membrane, unesterified cholesterol and Apo proteins in membrane, esterified cholesterol in lipoprotein, TAGs inside lipoprotein
52
What are the features of chylomicrons
Lots of TAG, low protein:lipid, function for TAG transport
53
What are the features of VLDL
Medium protein:lipid, function for TAG transport after liver
54
What is the function of LDL
Cholesterol transport
55
What is the function of HDL
Cholesterol regulation/mopping up
56
What is lipoprotein lipase
Enzyme found on endothelial surface of capillaries, hydrolyses TAGs in lipoproteins to MAG and FFAs, activated by Apo-CII. Chylomicron remnant remains in blood
57
What do defects in LPL or Apo-CII result in
Elevated levels of chylomicrons and plasma TAG
58
What is the difference between red and white muscle
Red: prefers fat (endurance) White: prefers glucose (sprinting)
59
Why are fats preferred over glucose as a storage molecule
More reduced, so more energy released when oxidised, take up less space (less water)
60
What lipoprotein does the liver make to release into blood
VLDL
61
What forms LDL for cholesterol transport
Hepatic lipase
62
What is the endogenous pathway of fat digestion
Remnants are recycled into VLDL (with TAGs), LPL releases fatty acids for uptake into tissues, cholesterol transport in LDL
63
What is coenzyme A derived from
Pantothenic acid (vitamin B5)
64
The presence of what shows that insulin was made endogenously
C peptide
65
What are the precursors of gluconeogenesis
Pyruvate (from alanine in muscle) and glycerol (from fat)

BIOC192 (5 decks)

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