F214 module 2 Respiration

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  • Created on: 14-02-14 12:03
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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 metabolism.
Metabolic reactions
o Those that build large molecules are anabolic.
o Those that break large molecules into smaller ones are catabolic.
o Active transport
It is when ions and molecules are moved across a membrane
against the concentration gradient. A lot of an organism's energy
is used for this.
o Secretion
When large molecules in some cells are removed via exocytosis.
o Endocytosis
The movement of large molecules into the cell.
o Synthesis of large molecules from smaller ones.
o Replication of DNA and synthesis of organelles.
o Movement e.g. cilia
o Activation of chemicals.
b. Describe the structure of ATP
c. State that ATP provides the immediate source for biological processes
ATP is a universal energy currency because it is in every living organism in
cells, and energy can be created by losing a phosphate group and can be added
to the molecule by adding a phosphate.
Each phosphate released releases 30.6Kj of energy.

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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.
o It helps dehydrogenase enzymes to carry out oxidation reactions.
o It is made up of two linked nucleotides, each having a ribose and an
adenine.…read more

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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 is a
three carbon sugar.
Oxidation of triose phosphate
o This is an aerobic anaerobic.
o From each triose phosphate two hydrogen atoms are removed, which also
involves dehydrogenase enzymes.…read more

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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 oxaloacetate which accepts acetate from the link reaction.
o There is mitochondrial DNA which codes for some of the proteins and
mitochondrial enzymes that may be needed.…read more

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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 removed from the coenzyme a and joins with oxyaloacetate to
form citrate.
o Citrate is decarboxylated (removing one carbon dioxide molecule) and
dehydrogenated (removing a pair of hydrogen atoms) to form a five
carbon compound.…read more

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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 transport chain releasing energy
which is used by the coenzymes associated with some of the electron
o The energy pumps the protons across the intermembrane space.…read more

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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.
The total yield of ATP including the ATP from glycolysis and Krebs cycle should
be about 30 per molecule of glucose.…read more

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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
accept more hydrogen atoms. reoxidised.
Glycolysis continues to produce Ethanal becomes ethanol and is
enough ATP needed. catalysed by ethanol
The enzyme lactate dehydrogenase dehydrogenase.…read more

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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 of
Reduced FAD is hydrogen atoms
formed.…read more


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