Respiration: Link Reaction And Krebs Cycle

Question 1

Where does link reaction happen

Answer 1

Mitochondrial matrix

Question 2

Steps of link reaction

Answer 2

-pyruvate enters mitochondrial matrix
-carbon dioxide removed via decarboxylation
-NAD removes hydrogen from pyruvate and becomes reduced NAD
-oxidation and decarboxylation of pyruvate is known as oxidative decarboxylation
-produces 2C acetyl group
-acetyl group binds to coenzyme A to form acetylcoenzyme A to be used in Krebs cycle

Question 3

What is produced in link reaction from 1 pyruvate molecule

Answer 3

1 CO2
1 reduced NAD
1 acetyl coenzyme A

Question 4

What is link reaction also called

Answer 4

Oxidative decarboxylation

Question 5

How many times does link reaction occur for every glucose molecule

Answer 5

2

Question 6

Where does Krebs cycle occur

Answer 6

Mitochondrial matrix

Question 7

Process of Krebs cycle

Answer 7

-acetylcoenzyme A breaks down (from link reaction) and released acetyl group (2C)
-coenzyme A recycled and used again in link reaction
-acetyl group joins with oxaloacetate (4C) to form citrate (6C)
-oxidative decarboxylation: 2 CO2, 3 NAD reduced to form reduced NAD (removed three hydrogens) and 1 FAD reduced to reduced FAD (removed two hydrogens)
-ADP then phosphorylase’s and 1 ATP made (substrate level phosphorylation)
-created oxaloacetate (4C) and cycle continues

Question 8

Differences between NAD and FAD

Answer 8

-NAD used in all stages of cellular respiration, FAD only in Krebs cycle
-NAD accepts one hydrogen, FAD 2 hydrogen
-reduced NAD oxidised at start of ETC, reduces FAD oxidised further along chain
-reduced NAD synthesised 3 ATP, reduced FAD 2ATP (as accepts two hydrogen)

Question 9

Is Krebs cycle aerobic or anaerobic

Answer 9

Aerobic

Question 10

Process of oxidative phosphorylation

Answer 10

-reduced NAD and FAD give up their hydrogens which breakdown into H+ and e-
-electrons excited by energy released from breakdown of glucose (glycolysis) and pass down electron transport chain and release energy by series of redox reactions with proteins in ETC
-this energy used to move proton via active transport by carrier proteins from matrix into intermembrane space of cristae
-this creates proton gradient and they move out of intermembrane space back into matrix via chemiosmosis via facilitated diffusion by ATP synthase used to combine ADP and Pi to make ATP
-electrons passed down ETC combine with oxygen and hydrogen from reduced NAD/FAD to produce water which maintains concen gradient for H+

Question 11

Why does respiration stop if no oxygen

Answer 11

Then no concen gradient for H+ so coenzymes no longer give up H+ and e- so Link and Krebs reaction stop as NAD and FAD not restored

Question 12

Why can glycolysis happen with no oxygen

Answer 12

As NAD and FAD not involved which are not restored if no oxygen