Respiration

Question 1

link reaction

Answer 1

pyruvate is oxidised as it loses hydrogen atoms to NAD. this will be used to form ATP.
decarboxylation removal of hydrogen and carbons
the remaining axetyl group are combined with coenzyme A to form acetyl coA.

Question 2

Glycolysis

Answer 2

Glucose is broken down into two pyruvate molecules.
ATP transports phosphate to glucose making it unstable

(6C) is broken in half to GP X2

` These two split glucose molecules get oxidised (electrons and hydrogen) are taken away by NADH.

Phosphates get transferred from our sugars to ADP making ATP which makes 2x molecules of pyruvate and 4 molecules of ATP

Net gain of atp is 2.

Question 3

krebs cycle

Answer 3

Acetyl coenzyme A acts as a carrier for the two-carbon acetyl group. It reacts with oxaloacetate (a four-carbon molecule) to produce citrate (a six-carbon molecule).
CoA is now available to be recycled and reused in the link reaction.
The production of citrate allows the Krebs cycle to begin.

6C → 5C

Citrate is converted to a five-carbon molecule (5C) by decarboxylation and dehydrogenation.
CO2 is produced as a by-product.
NAD is reduced to NADH.

5C → 4C

The five-carbon molecule is decarboxylated and dehydrogenated again to a four-carbon compound.
CO2 is produced.
NAD is reduced to NADH.
ATP is also produced by substrate-level phosphorylation.

Regeneration of oxaloacetate

This 4C molecule is then dehydrogenated again to produce another molecule of NADH. FAD is also reduced to FADH2.
No decarboxylation takes place at this stage.
These intermediate reactions regenerate oxaloacetate. This allows the cycle to continue again.

The net gain of the Krebs cycle is:
2 CO2 molecules.
3 NADH molecules.
1 ATP molecule.
1 FADH2 molecules.
For each molecule of glucose, there are two cycles (this is because two molecules of pyruvate are produced in glycolysis).

Question 4

Oxidative phosphorylation

Answer 4

Oxidative phosphorylation takes place at the inner mitochondrial membrane.
There are several features of the membrane that allows production of ATP on a large scale:
Three electron carrier proteins (electron transport chain, ETC).
ATP synthase enzyme.
The space between the inner and outer mitochondrial membranes is called the intermembrane space.

Electron transport chain

NADH and FADH2 (from the Krebs cycle) are oxidised by the first electron carrier protein in the inner mitochondrial membrane.
This initiates oxidative phosphorylation because NADH and FADH2 release two protons and two electrons each.
The electrons are then transferred along the ETC.

As the electrons move down the ETC, they lose energy.
This energy pumps the protons from NADH and FADH2 into the intermembrane space.
This creates a proton gradient (also known as an electrochemical gradient).

Chemiosmosis

The protons diffuse down the concentration gradient through the ATP synthase enzyme.
As protons flow through the ATP synthase, energy is released.
This energy converts ADP and inorganic phosphate to ATP.
This process is called chemiosmosis.

The final electron acceptor

After the electrons have reached the end of the ETC and protons have flowed through the ATP synthase enzyme, they combine with O2 to form water (H2O).
Oxygen is called the final electron acceptor for this reason.