Energy Production From Carbohydrates Flashcards

1
Q

What are the major functions of the pentose phosphate pathway?

A

Produce NADPH in cytoplasm, reducing power for anabolic processes, maintains free -SH in RBC on cysteine, produce C5 ribose

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2
Q

Write a reaction for phase I of pentose phosphate pathway

A

G6P + 2NADP —> C5 sugar phosphate + 2NADPH + 2H+ + 2CO2

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3
Q

Write a reaction for phase II of pentose phosphate pathway

A

3C5 sugar phosphate —> 2 fructose-6-phosphate + glyceraldehyde-3-phosphate

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4
Q

What happens in G6PDH deficiency?

A

Disulphide bridge formation in RBC due to low levels of NADPH. Insoluble aggregates called heinz bodies form - premature destruction of RBC

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5
Q

Draw out the glycolysis pathway

A
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6
Q

Give the equations for the 3 committing steps in glycolysis

A

Glucose —> G6P

F6P —> F-1,6-P

PEP —> pyruvate

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7
Q

What does pyruvate dehydrogenase catalyse?

A

This reaction is irrversible

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8
Q

What control mechanisms is PDH subject?

A

Acetyl CoA allosterically inhibits PDH, ADP promotes, ATP/NADH inhibit, activated when there is a lot of glucose

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9
Q

What are the functions of glycolysis?

A

Oxidises glucose, 2 NADH produced, net synthesis of 2 ATP, produces C6 and C3 intermediates (glycerol phosphate, 2,3-BPG)

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10
Q

What ismoers are carbohydrates usually found in the body?

A

D isomers

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11
Q

List the main features of glycolysis

A

Oxidative, exergonic, C6–>2 C3, no loss of CO2, ATP generated, useful intermediates, substrate level phosphorylation

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12
Q

Write an equation for dihydroxyacetone phosphate going to glycerol phosphate

A
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13
Q

What stimulates pyruvate kinase?

A

High insulin:glucagon ratio

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14
Q

What inhibits phosphofructokinase?

A

High levels of ATP cause allosteric inhibition

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15
Q

Where would you find glucokinase and hexokinase?

A

Hexokinase - liver and muscle

Glucokinase - liver only

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16
Q

What stimulates hexokinase and glucokinase?

A

An increase in glucose (or a decrease in G6P)

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17
Q

Why is lactate dehydrogenase needed?

A

RBC cannot regenerate NAD+ any other way

18
Q

Write the reaction that occurs in RBC to produce pyruvate

19
Q

Write the overall equation for glycolysis

A

Glucose + 2Pi + 2ADP + 2NAD+ —> 2 pyruvate + 2H2O + 2H+ + 2NADH + 2ATP

20
Q

Draw out the TCA cycle

21
Q

Where does the TCA cycle occur?

A

Mitochondiral matrix

22
Q

What does the TCA pathway require?

A

NAD+, FAD and oxaloacetate

23
Q

What is the main function of the TCA cycle?

A

Break the C-C bond in acetate and oxidise the atoms to CO2. Doesn’t function anaerobically

24
Q

Approximately how many molecules of ATP are produced per molecule of glucose in the TCA cycle?

A

36 molecules of ATP per molecule of glucose

25
What are the catabolic functions of the TCA cycle?
Produces intermediates and interconvertible acids
26
What are the anabolic functions of the TCA cycle?
Synthesis of non-essential amino acids, synthesis of haem and glucose, synthesis of fatty acids
27
What are the two major signals for the TCA cycle?
ATP/ADP ratio and NADH/NAD+ ratio
28
What is removed from acetate and which molecules accept them?
H+ and e- are removed by NAD+ and FAD
29
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane
30
Briefly describe oxidative phosphorylation
e-'s from NADH and FADH2 are transferred to O2, releasing energy. This can be used to drive ATP synthesis
31
What is the role of proton translocating complexes?
Move protons from inside the inner mitochondrial matrix to outside the inner mitochondrial matrix, causing an increase in H+ and therefore creating proton motive force. 3 out of 4 complexes are PTC
32
Describe the effect of the proton motive force
As the inner mitochondrial membrane is impermeable to protons there is a build up of H+. Protons can only re-enter the mitochondrial matrix via ATPsynthase complexes.
33
How many moles of ATP can 2 moles of NADH produce?
5 moles of ATP
34
How many moles of ATP can 2 moles of FADH2 produce?
3 moles of ATP
35
Describe what happens in the mitochondria when ATP is high
ATPsynthase stops (lack of substrate), prevents H+ moving back into the mitochondria, H+ conc out increases such that protons cannot be pumped out, electron transport stops
36
What is the function of uncoupling proteins?
Uncouple electron transport from ATP production to produce heat (leaky membranes)
37
What does UCP1 do?
Expressed in brown adipose and is involved in non-shivering thermogenesis
38
What does UCP2 do?
Linked to obesity, metabolic syndrome and heart faiulre
39
What does UCP3 do?
Found in skeletal muscle, brown adipose and heart. Involved in modifying fatty acid metabolism and in protecting against ROS damage
40
What does noradrenaline stimulate?
Lipolysis - fatty acids - NADH/FAD2H - increase in pmf Also activates UCP1
41
Describe the differences between substrate level phosphorylation and oxidative phosphorylation
42