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Summary A* A Level Biology respiration notes
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RespirationThe structure of a mitochondria
Why do mitochondria contain DNA?
To contain the information needed for mitochondria to replicate
Where are enzyme molecules found?
Bound to the inner membrane
What are the enzyme molecules needed for?
To carry out electron transport
What does the matrix contain?
The enzymes involved in the link reaction and Krebs cycle
What does the outer membrane do?
Controls the passage into and out of the mitochondrion
What else do mitochondria contain?
The intermembrane space and inner membrane
What are the roles of the outer and inner membrane?
Maintain a proton gradient and have different (channel and carrier) proteins for e.g., ATP synthase
(inner) and pyruvate channels (outer)
What is the role of the cristae?
They are extensions of the inner membrane providing a larger surface area for a faster rate of
respiratory enzyme action
What is the role of the matrix?
Contains circular DNA, ribosomes and proteins to allow for a faster rate of protein synthesis (to
produce respiratory enzymes) for a faster rate of ATP production
Glycolysis:
Where does glycolysis occur?
In the cytoplasm
Does it require energy/ O2?
No
What is stage one?
The phosphorylation of glucose, to glucose phosphate using 2 x ATP which are hydrolysed to provide
energy to activate glucose and lower activation energy for enzyme-controlled reactions that follow
, What is stage two?
The production of 2 triose phosphate molecules
What is stage three?
The oxidation of TP to produce pyruvate with a net gain of ATP and reduced NAD (as ATP is formed
and the hydrogens lost by TP are gained by the coenzyme NAD)
So overall what is produced?
2xATP (2 used at the start), and 2 x NADH
How does it show indirect evidence of evolution?
Because it is a universal feature of every living organism
The link reaction:
Stage one:
Pyruvate and NADH molecules are actively transported from the cytoplasm to the mitochondrial
matrix
Stage two:
Pyruvate is oxidised to acetate (2C compound)
Stage three:
NAD picks up a hydrogen atom and becomes NADH/ reduced NAD
What else does this produce?
CO2 and acetylcoenzyme A as acetate combines with coenzyme A
Occurs…
2x for every glucose molecule (as 2x pyruvate released)
The Krebs cycle:
Stage one:
Acetylcoenzyme A reacts with a 4C molecule, releasing coenzyme A and producing a 6C molecule
that enters the Krebs cycle
Stage two:
In a series of redox reactions, the krebs cycle generates reduced coenzymes and ATP by substrate
level phosphorylation and CO2 is lost
So, the products produced per cycle are…
3 x red NAD, 1 x red FAD, 1 x ATP and 1 x CO2
And the products produced per glucose molecule are…
6 x red NAD, 2 x red FAD, 2 x ATP and 2 x CO2
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