Lecture 25: Metabolic pathways and ATP synthesis

Question 1

What is conservation of energy?

Answer 1

Tells us that:

• energy cannot be created or destroyed
• energy can be converted between forms = chemical bonds, heat and mechanical

Question 2

What is Gibbs free energy?

• spontaneous
• non-spontanoues
• equilibrium

Answer 2

Indicates where a reaction will occur under standard conditions
if G is negative = spontaneous
If G is positive = non-spontaneous
If G is zero = equilibrium

Question 3

What is energy coupling ?

Answer 3

Enzymes often couple reaction to drive unfavourable reactions
- when you couple an unfavourable reaction to a favourable one
= enzymes are essential for

Question 4

How is energy coupling achieved ?

Answer 4

Unfavourable reactions can be coupled to ATP hydrolysis by the action of enzymes
= enzymes are essential for coupling reactions
= ATP hydrolysis releases G= -30.5kJmol-1

Question 5

What is the role reducing equivalents in redox reactions?

Answer 5

Reducing equivalents - transfers hydrogens(includes electrons)

• the co-enzymes NAD and FAD interact with various enzymes to accept and donate hydrogen/electrons
• the enzymes that catalyse these reactions are often called DEHYDROGENASES as they remove H+

Question 6

What is the role and actions of NAD?

- nicotinamide adenine dinucleotide

Answer 6

• Niacin vitamin B3

- Accepts hydrogens and electrons in metabolic pathways e.g glycolysis, fatty acid oxidation, CAC

Question 7

What is the role and actions of FAD?

- Flavin adenine dinucleotide

Answer 7

• Riboflavin vitamin B2
• accepts hydrogens in pathways e.g fatty acid oxidation , CAC
• Flavin coenzymes are tightly bound to the proteins with which they interact

Question 8

What is the role and action of coenzyme A?

Answer 8

• Carries fatty acid chains
• derived from pantothenic acid vitamin B5
• Carrier of acyl groups
  Two forms
  = free coenzyme A - CoASH
  = acyl group attached - AcCoA

Question 9

How can ATP be generated?

Answer 9

• substrate level phosphorylation = direct e.g glycolysis and CAC
• Oxidative phosphorylation = indirect e.g reduced co-enzymes

Phosphorylations reactions
ADP + Pi ——–> ATP

Question 10

What happens in redox reactions?

Answer 10

Redox: fuel molecules get oxidised, coenzymes get reduced