Lecture 27: EXTRACTING ENERGY FROM FUEL MOLECULES Flashcards

1
Q

What is the major energy intermediate of the cell?

A

ATP

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2
Q

What are phosphate bonds?

A

High energy (storing lots of energy)

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3
Q

What does the delta G of a reaction tell us about?

A

The relative abundance of the substrates and products, also the energy stored in the chemical bonds of the products and substrates

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4
Q

What does it mean when delta G is less than 0?

A

The reaction is spontaneous, energy is released, it is energetically favourable (A has more energy than B)

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5
Q

What does it mean when delta G is 0?

A

The reaction is at equilibrium, no change in the energy

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6
Q

What does it mean when delta G is more than 0?

A

The reaction is not spontaneous, energy is required, energetically unfavourable

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7
Q

What is the delta G for ATP hydrolysis?

A

-30 kJ/mol (energetically favourable)

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8
Q

What is the delta G for ATP synthesis?

A

30 kJ/mol (energetically unfavourable)

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9
Q

What does delta G o’ mean?

A

Gibbs free energy under standard conditions at pH of 7

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10
Q

How can a reaction with a positive delta G be made to occur?

A

By coupling it with a reaction that has a negative delta g so that the overall delta g is negative and the reaction is spontaneous

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11
Q

What may unfavourable reactions be coupled to?

A

ATP hydrolysis

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12
Q

What is an example of a reaction coupled to ATP hydrolysis?

A

The hexokinase reaction (glucose + phosphate&raquo_space;> glucose-6-phosphate + water) has delta G of 14 kJ/mol and is coupled to ATP hydrolysis to become spontaneous

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13
Q

What are the key reactions?

A

Those involving ADP and ATP, redox reactions

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14
Q

What is involved in redox reactions?

A

Fuel molecules get oxidised so something must be reduced and provide the oxidising power (NAD and FAD coenzymes)

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15
Q

What is the oxidised molecule in a redox reaction?

A

The reducing agent (provides reducing power)

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16
Q

What is the reduced molecule in a redox reaction?

A

The oxidising agent (provides the oxidising power)

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17
Q

How are the reactions which oxidise fuel molecules described?

A

As energetically favourable (release energy)

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18
Q

How does oxidation of fuel molecules occur?

A

‘stepwise’ so that all of the energy can be captured for ATP production and not just released as heat

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19
Q

What do biological redox reactions often involve?

A

The transfer of hydrogen atoms (includes an electron)

20
Q

What is hydrogen referred to as?

A

The reducing equivalent

21
Q

What are the enzymes which catalyse redox reactions often called?

A

Dehydrogenases

22
Q

What are coenzymes a subclass of?

A

Cofactors

23
Q

What are coenzymes?

A

Small organic molecules often derived from vitamins

24
Q

What is the concentration of coenzymes in a cell?

A

Low

25
Q

What also couples to ATP?

A

Glucokinase reaction

26
Q

What do coenzymes act as?

A

Carriers

27
Q

How do coenzymes exist?

A

In two forms

28
Q

What is NAD?

A

Nicotinamide adenine dinucleotide

29
Q

What is NAD derived from?

A

Niacin (vitamin B3)

30
Q

What does NAD do?

A

Accepts hydrogen and electrons in metabolic pathways (glycolysis, fatty acid oxidation, citric acid cycle)

31
Q

What does NAD undergo?

A

2 electron reduction

32
Q

What does NAD carry?

A

2 electrons and 1 H+

33
Q

What is the oxidised form of NAD?

A

NAD+

34
Q

What is the reduced form of NAD?

A

NADH

35
Q

What is FAD?

A

Flavin adenine dinucleotide

36
Q

What is FAD derived from?

A

Riboflavin (Vitamin B2)

37
Q

What does FAD do?

A

Accepts hydrogen in pathways (fatty acid oxidation, citric acid cycle)

38
Q

How are flavin coenzymes found?

A

Tightly bound to the proteins with which they interact (flavoproteins)

39
Q

How is NAD found?

A

Soluble

40
Q

What does FAD undergo?

A

2 electron reduction

41
Q

What does FAD carry?

A

2 electrons and 2 H+

42
Q

What is the oxidised form of FAD?

A

FAD

43
Q

What is the reduced form of FAD?

A

FADH2

44
Q

What is coenzyme A derived from?

A

Pantothenic acid (vitamin B5)

45
Q

What is CoA a carrier of?

A

Not electrons so isn’t reduced or oxidised. It carries an acyl group

46
Q

What are the two forms of CoA?

A

Free CoA: CoASH

Acyl group attached: Acyl-CoA(AcCoA)