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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
Q

How does arsenic poison glycolysis

A

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

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26
Q

What cofactors are required in pyruvate oxidation

A

Thiamine pyrophosphate (TPP, derived from vitamin B1), FAD (derived from vitamin B2), and fatty acid lipoate (lipoic acid)

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27
Q

What does pyruvate oxidation involve

A

The loss of a C from pyruvate as CO2 and the transfer of H to NAD+

28
Q

What is the anaerobic fate of pyruvate

A

Reduction to lactate

29
Q

Why does pyruvate reduction occur

A

To regenerate NAD+ so that some ATP can continue to be made in anaerobic conditions by glycolysis

30
Q

What is a reducing equivalent

A

Hydrogen: 1 proton and 1 electron

31
Q

What are the general features of coenzymes

A

Carrier molecules, exist in two forms, concentration in cells is low, usually derived from vitamins

32
Q

What is NAD derived from (undergoes a 2 reducing equivalent reduction)

A

Niacin (vitamin B3)

33
Q

What is FAD derived from (undergoes a 2 reducing equivalent reduction)

A

Riboflavin (vitamin B2)
Remember B2 as it becomes FADH2

34
Q

What is the name of a protein with FAD tightly bound

A

Flavoprotein

35
Q

What does Coenzyme A carry

A

Acyl groups

36
Q

What are the two forms of Coenzyme A

A

CoASH (free) and acetyl-CoA (acyl group attached)

37
Q

What are major minerals

A

Large abundance in body, range of functions

38
Q

What are minor minerals

A

Concentration low, difficult to identify/measure

39
Q

What are water soluble vitamins

A

Not stored: B, C

40
Q

What are fat soluble vitamins

A

Stored: E, D, A, K

41
Q

What are the important characteristics of coenzymes

A

Low concentration in cells, act as carriers, have two forms

42
Q

What are the two types of reactions in pathways for processing fuel molecules

A

Those involving ADP and ATP, and redox reactions (transfer of electrons)

43
Q

How is energy released from fuel molecules in metabolic pathways (general understanding)

A

Series of oxidation reactions

44
Q

What are enzymes that catalyse redox reactions commonly called

A

Dehydrogenases

45
Q

What do lipids include

A

Phospholipids, sterols, triacylglycerols

46
Q

What are the range of roles cholesterol has in the body

A

Membranes, signalling, bile salts

47
Q

What are fatty acids

A

Carbon chain attached to carboxylic acid

48
Q

What are lipases

A

Enzymes which hydrolyse TAGs to release FFA

49
Q

How do lipases get access to non polar fatty acids

A

Bile salts solubilise

50
Q

What is the exogenous pathway of fat digestion

A

TAGs broken into MAG and 2FFA, absorption from small micelles, TAGs packaged into chylomicrons in epithelial cells

51
Q

Describe the structure of lipoproteins

A

Phospholipid membrane, unesterified cholesterol and Apo proteins in membrane, esterified cholesterol in lipoprotein, TAGs inside lipoprotein

52
Q

What are the features of chylomicrons

A

Lots of TAG, low protein:lipid, function for TAG transport

53
Q

What are the features of VLDL

A

Medium protein:lipid, function for TAG transport after liver

54
Q

What is the function of LDL

A

Cholesterol transport

55
Q

What is the function of HDL

A

Cholesterol regulation/mopping up

56
Q

What is lipoprotein lipase

A

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
Q

What do defects in LPL or Apo-CII result in

A

Elevated levels of chylomicrons and plasma TAG

58
Q

What is the difference between red and white muscle

A

Red: prefers fat (endurance)
White: prefers glucose (sprinting)

59
Q

Why are fats preferred over glucose as a storage molecule

A

More reduced, so more energy released when oxidised, take up less space (less water)

60
Q

What lipoprotein does the liver make to release into blood

A

VLDL

61
Q

What forms LDL for cholesterol transport

A

Hepatic lipase

62
Q

What is the endogenous pathway of fat digestion

A

Remnants are recycled into VLDL (with TAGs), LPL releases fatty acids for uptake into tissues, cholesterol transport in LDL

63
Q

What is coenzyme A derived from

A

Pantothenic acid (vitamin B5)

64
Q

The presence of what shows that insulin was made endogenously

A

C peptide

65
Q

What are the precursors of gluconeogenesis

A

Pyruvate (from alanine in muscle) and glycerol (from fat)

BIOC192 (5 decks)

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