4 Coupled Reactions and Metabolic Pathways

Question 1

what is oxidation

Answer 1

• loss of electrons or gain of a hydrogen

Question 2

what is reduction

Answer 2

• gaining of an electron or loss of a hydrogen

Question 3

what is the first law of thermodynamics

Answer 3

energy cannot be created of destroyed, only converted from one form to another

Question 4

what is the second law of thermodynamics

Answer 4

• Entropy increases over time

Question 5

Gibbs free energy expresses the change in entropy, what type of reaction occurs if delta G is negative

Answer 5

• an exergonic reaction, which shows an overally loss of Gibbs free energy and so the reaction is energetically favourable

Question 6

is and endergonic reaction spontaneous and why

Answer 6

• no
• in exergonic reactions delta G > 0, products have more free energy than the reactants so this reaction is not favourable

Question 7

Describe how activated carrier molecules work

Answer 7

• Carrier molecules get activated as the collect the Gibbs free energy released from catabolic favourable reactions
• These now activated carrier molecules use this energy to push forward a non-favourable reaction like anabolism until they have no more energy and are recycled

Question 8

Give 2 examples of activated carrier molecules and how they work

Answer 8

• ATP
• it carries its energy in covalent bonds and readily releases it via hydrolysis
• NADH
• It is activated carrying energy in the form of 2 electrons and a proton, it this is readily released by oxidation to NAD+

Question 9

Summarise what is produced via glycolysis

Answer 9

• 2 ATP and glucose invested

- 4 ATP and 2NADH are produced

Question 10

What is Beta-oxidation

Answer 10

• This it the cycle where fatty acids are broken down by 2 carbons per cycle
• This cycle has 4 enzyme reactions
• This cycle continues until the tail of the fatty acid is fully degraded

Question 11

what is produced per cycle of beta oxidation

Answer 11

• 1 NADH
• 1 FADH2
• 1 acetyl CoA

Question 12

What is the Krebs or TCA cycle

Answer 12

• Acetyl CoA (2C) enters and binds with oxaloacetate (4C) forming citric acid (6C)
• a series of 8 reactions regenerate the 4 Carbon oxaloacetate, releasing energy in the form of 3NADH, GTP and FADH2

Question 13

What is produced from the Krebs cycle

Answer 13

• 3NADH
• 1GTP
• 1 FADH2
• 2 CO2