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F214 Communication, Homeostasis and Energy

Module 4 Respiration

4.4.1 Respiration

a. Outline why plants, animals and microorganisms need to respire, with
reference to active transport and metabolic reactions

All living organisms need energy so as to undergo their biological processes, of
which all of the reactions are known altogether as…

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A phosphate is released by hydrolysis of ATP.

d. Explain the importance of coenzymes in respiration, with reference to NAD
and coenzyme A

Coenzymes help to carry out the oxidation reactions of respiration as enzymes
are not very good at these.

o It is an organic non-protein molecule.

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o This activates the hexose sugar so it is now fructose 1,6-bisphosphate.
o It now becomes a phosphorylated sugar known as hexose
o Two molecules have been used for each molecule of glucose

Splitting of hexose bisphosphate
o Each molecule is split into two molecules of triose phosphate which…

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They can move about within in cells by the cytoskeleton.
o This is where the link reaction and the Krebs cycle take place.
o Here there are the enzymes needed for the reactions.
o There are molecules of NAD for the hydrogen molecules to attach to.
o There is…

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m. Outline the Krebs cycle with reference to the formation of citrate from
acetate and oxaloacetate and the reconversion of citrate to oxaloacetate and n.
Explain that during the Krebs cycle decarboxylation and dehydrogenation occur,
NAD and FAD are reduced and substrate phosphorylation takes place
Krebs cycle
o Acetate is…

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o The hydrogen atoms are split into protons and electrons.
o The first electron carrier accepts the electrons from reduced NAD. The
electron carrier is known as protein complex I and has an enzyme calle
NADH-coenzyme Q reductase otherwise known as NADH
o The electrons flow down the electron…

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s. Explain why the theoretical maximum yield of ATP per molecule of glucose is
rarely, if ever, achieved in aerobic respiration
The 10 molecules of reduced NAD theoretically could produce 26 molecules of
ATP. So for each molecule of reduced NAD up to 2.6 molecules of ATP should
be made.…

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for ATP and there is an oxygen pyruvate is decarbonised and
deficit. becomes ethanal.
Reduced NAD is reoxidised to The reaction is catalysed by the
NAD. enzyme Pyruvate decarboxylase.
Pyruvate accepts the hydrogen. Ethanal accepts hydrogen atoms
NAD is reoxidised so that it can from reduced NAD which becomes

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It has an efficiency transported into the Some can be
of about 32%. mitochondrial converted to
matrix where it is pyruvate, some to
Other broken down into acetate and some
monosaccharaides 2-carbon acetyl enter the Krebs
are changed to groups. cycle directly.
glucose for
respiration. Reduced NAD and The number…


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