biochemistry of respiration
DESCRIPTION
Biochemistry of respiration. Raw materials…. Any organic molecule Carbohydrate Lipid Protein. They contain…. …too much chemical energy. So, respiration involves…. …breaking down large complex organic molecules to produce a molecule that contains a small amount of energy. ATP. - PowerPoint PPT PresentationTRANSCRIPT
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Biochemistry of respiration
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Raw materials…
Any organic molecule
Carbohydrate
Lipid
Protein
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They contain…
…too much chemical energy
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So, respiration involves…
…breaking down large complex organic molecules to produce a molecule that contains a small amount of energy
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ATP
ATP is an immediate source of energy because:-
Only one step is necessary to release the energy
The amount of energy released is small enough to be useful.
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Aim of respiration
Synthesis of ATP
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Carbohydrate is the major substrate for respiration
Soluble carbohydrates exist – so they can easily be transported
Insoluble carbohydrates exist – so they can be easily stored
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Overview
Four stages:-
1. Glycolysis2. Link reaction3. Krebs cycle4. Hydrogen / electron carrier system
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GLYCOLYSIS
Occurs in cytoplasm
Starts with Glucose
6 carbon compound
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GLYCOLYSIS
Ends with Pyruvate
3 carbon compound
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Glucose to TP
2 molecules of ATP are invested
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TP to Pyruvate
Triose phosphate is converted to pyruvate
(there are a number of intermediate stages)
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Energy is recovered…
ATP is made
Hydrogen is released and NAD is reduced
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Over all…
Net production of 2 ATP molecules from each molecule of glucose
and
2 reduced NAD molecules
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Pyruvate moves into the mitochondria
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Precisely…
Into the matrix
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LINK REACTION
Pyruvate is converted into
acetyl coenzyme A
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Pyruvate
3 carbon compound
Acetyl coenzyme A
2 carbon compound
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Oxidative … but no oxygen is involved
Hydrogen is removed Combines with NAD Producing reduced NAD
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KREBS CYCLE
Acetyl Co A (2 carbon compound) Combines with a 4 carbon compound Producing a 6 carbon compound
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In a number of steps…
6 carbon compound breaks down to form the same 4 carbon compound that combined with acetyl co A
Hence the Krebs CYCLE
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What is released?
Carbon – in the form of carbon dioxide
Hydrogen – combining with NAD and another coenzyme, FAD to form
reduced NAD and reduced FAD
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Anything else?
There is enough energy released in one of the steps to join ADP and Phosphate to make ATP
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ELECTRON / HYDROGEN CARRIER SYSTEM
Carriers are in the inner membrane
Cristae
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Hydrogen atoms
From hydrogen carriers –
reduced NAD and reduced FAD
Accepted by the carriers in the membrane
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Hydrogen atoms break down to electrons and hydrogen ions (protons)
Protons build up between the two membranes of the mitochondria
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Protons move back into the matrix
Through an enzyme – ATP synthetase
ADP and phosphate join forming ATP
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The protons rejoin with electrons and oxygen to form water
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Oxidative phosphorylation
Phosphate is added to ADP –
phosphorylation
The energy for the process is the result of the removal of hydrogen – oxidation
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Role of oxygen
Oxygen is the terminal electron acceptor in the electron carrier system
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‘Oxidation’
Oxidation occurs more than once in respiration
BUT In glycolysis the link reaction Krebs cycle
It is the removal of hydrogen
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‘Oxidation’
Only in the electron carrier system is oxygen needed
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Aerobic and anaerobic respiration
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Fermentation
Anaerobic respiration
Occurs when oxygen is limited
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NAD is oxidised
Hydrogen combines with pyruvate
Forming :-
lactate in animals
ethanol in plants / fungi
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Glycolysis can continue…
Producing some ATP
Forming 2 ATP per glucose molecule
Compared with 38 ATP per glucose molecule with aerobic respiration