Oxidative phosphorylation

Question 1

From the reactions of glycolysis, pyruvate dehydrogenase complex, and the TCA cycle, how many NADH and FADH2 are formed

Answer 1

• 10 NADH + H+
• 2FADH₂

Question 2

How many electrones do each molecule of NADH and FADH2 carries

Answer 2

2 high energy electrones

Question 3

Describe the basis of oxidative phosphorylation

Answer 3

• Electrones from the oxdication of NADH and FADH2 are used to Reduce O₂ into H₂O
• The energy from the electrones are used to pump H+ into the mitrochondiral space - which increases its PH
• PH in the inner membrane space decreases - More H+
• PH in the matrix increases - Less H+
• Protons flow back into the maxtric following their electrochemical gradient
• This energy is used to phosphorylate ADP into ATP

Question 4

NADH from the TCA cycle is already in the matrix, how does NADH from glycolysis enter the matrix?

Answer 4

• glycerol-3-phosphate
• malate-aspartate shuttles

​NADH cannot cross the inner-membrane of the mitochondria it cannot be directly oxidised into NAD+ using the electron transport chain

Question 5

Describes how the NADH enters using the malate-aspartate shuttles

Answer 5

• NADH from glycolysis with combine with oxaloacetate to generate Malate and NAD+
• Malate is then transported into the matrix via the malate transporter
• Once in the Matrix the malate will join with NAD+ to form oxaloacetate + malate in TCA cycle in addition that arises from Fumerate
• Increases yeild of NADH
• The oxaloacetate will then turn into Aspartate which will cross the mitochonrial membrane into the cystol to form oxaloacetate and the cycle goes on

Question 6

What are the two ways malate is produced

Answer 6

• Malate arising form fumerate in the TCA cycle
• Cyctol-derived Malate from the malate-aspartate shuttle

Question 7

What are the two types of potentials

Answer 7

In oxidative phosphorylation, the Electrone transfer potential of NADH is converted to the Phospohryl tranfer potential of ATP

• Phosphoryl Transfer potential - can be measured by the free energy change Detla G, for the hydrolysis of ATP
• Electron transfer potential - can be measured in redox potential E’o

Question 8

What is the Standard redox potential

Answer 8

A measure of how readily a reduced substance donates an electrone in comparison to H₂

Question 9

What does a Negative and postive E’_o mean

Answer 9

• Negative E’_o = Reduced form has a lower affenity for electrones compared to H2 so donates electrones easily - Strong reduces
• Postive E’_o = Reduced form has a higher affinity for electrones compared to H2 so doesnt donate electrones readily - strone oxidisers

Question 10

What is the relationship between standard free energy change and redox potentials

Answer 10

The standard free energy change is proportional to the change in standard redox potential and the number of electrons transferred

Question 11

What is the driving force of oxidative phosphorylation

Answer 11

The energy relased by the reduction of O2 by NADH