alisonstrueth
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I have a bio test on respiration can someone please explain all the topics in here ASAP pls
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Reanna.xxx
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Is it gcse biology and if so, which topics specifically would you like me to explain?
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Hellllpppp
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I’m going to assume this is A-level biology- if not I’m sorry - ignore it will confuse u if ur doing GCSE

Here are my notes

Glycolysis is the first stage of both aerobic and anaerobic
-It does not require oxygen
-It occurs in the cytoplasm

Glycolysis involves two stages:
-Phosphorylation - The glucose has two phosphate groups added to it from two ATP molecules. Phosphorylation makes the glucose-2-phosphate unstable and it splits into two triose phosphate (TP) (3-carbon).
-Oxidation - The two TP molecules are both oxidised to form two pyruvate molecules by removing a hydrogen from each. The hydrogen is picked up by two NAD molecules to become NADH. This process also releases 4 ATP.

The NADH and pyruvate are both needed for next stages in aerobic respiration so they are actively transported into the mitrochondrial matrix.

The overall products from glycolysis per glucose molecule are:
2 NADH
2 pyruvate
2 ATP

Link Reaction
-It occurs in the mitochondrial matrix

-A carbon is removed and forms carbon dioxide. This is known as decarboxylation.
-2 hydrogen atoms are also removed from pyruvate (oxidation) to create acetate and reduce NAD. This is known as dehydrogenation. The NAD picks up the hydrogen to become NADH.
-The coenzyme CoA combines with the acetate that is formed to create acetyl CoA, this is to assist in acetyl reacting in the Krebs cycle.

The reaction occurs twice per glucose molecule as there are two pyruvate molecules.

The overall products from the link reaction per glucose molecule are:
2 x Acetyl CoA
2 CO2
2 reduced NAD


Krebs Cycle
-occurs in mitochondrial matrix

The acetyl CoA reacts with a four-carbon molecule, releasing coenzyme A and producing a six-carbon molecule that enters the Krebs cycle.
The krebs cycle is a series of oxidation-reduction reactions. The Krebs cycle is also known as the citric acid cycle.

The overall products from the link reaction per glucose molecule are:

4 CO2
6 reduced NAD
2 reduced FAD
2 ATP

Oxidation Phosphorylation
This is the final stage of aerobic respiration where most ATP is synthesised.

-In this stage all of the reduced NAD and FAD release hydrogens and these split into protons (H+) and electrons (e-). The e- are passed down a series of electron carrier proteins embedded in the inner mitochondrial membrane, losing energy as the move (electron transport chain).
-The small amount of energy the electrons release pumps protons from the mitochondrial matrix into the intermembrane space.
This creates an electrochemical gradient across the membrane.
-Therefore the protons move down the electrochemical gradient back into the matrix via ATP synthase making ATP.
-This movement of H+ is known as Chemiosmosis.
-Oxygen is the final electron acceptor in the electron transport chain.
-The oxygen combines with the electrons and the protons to form water.

Anaerobic Respiration
In the absence of oxygen respiration occurs anaerobically. The pyruvate produced in glycolysis is reduced to form ethanol (in plants and microbes) or lactate (in animals) by gaining the hydrogen from reduced NAD. This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

Ethanol fermentation - pyruvate to ethanal to ethanol
pyruvate to ethanal involves decarboxylation
Ethanal to ethanol involves reduction with NADH

1 reduced NAD can result in a yield of 3 ATP molecules, whereas 1 reduced FAD can result in a yield of 2 ATP molecules. Therefore, the total yield of ATP from one glucose in aerobic respiration molecule should be 32 molecules of ATP.

Anaerobic respiration is even less efficient, because only 2 ATP molecules and produced from one glucose molecule.
Last edited by Hellllpppp; 7 months ago
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