Transcript Cell Respiration

Cell Respiration
Mrs: Jackie
Respiration defined
Respiration- series of chemical
reactions that occur inside a living
cell.
 Involves breakdown of large
substances into smaller substances
 Substance most commonly used is
glucose
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Stages of respiration
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1. Glycolysis
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Occurs in the cytosol (semifluid
part of the cytoplasm)
Involves the phosphorylation of
glucose into glucose-6-phosphate
Follow by many reactions resulting
in the splitting of glucose in half to
form 2 pyruvic acid molecules (
each with 3 Carbons)
Other important products 2NADH +
H+ and 2 ATP
Glycolisis continues
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1. Glucose 6-phosphate is formed when
the 6th carbon on the glucose molecule is
phosphorylated by an ATP molecule.
2. Glucose 6-phosphate is converted into a
5-carbon ring isomer, fructose 6phosphate.
3. Fructose 6-phosphate is phosphorylated
by another ATP to form fructose 1, 6diphosphate.
4. Fructose 1, 6-diphosphate is processed
by an enzyme into two glyceraldehyde 3phosphate molecules.
5. Two molecules of glyceraldehyde 3phosphate are oxidized, losing hydrogen
atoms and gaining phosphate groups to
form 1, 3-diphosphoglycerate. Two
molecules of NAD+ are converted into
NADH2+ in the process.
Glycolysis continues
6. Two 1,3-diphosphoglycerate
molecules phosphorylate ADP (adenine
diphosphate) to yield two molecules of
3-phosphoglycerate and two ATPs
are produced.
7. The phosphate groups on 3phosphoglycerate move to the 2nd
carbon, forming 2-phosphoglycerate.
8. The two 2-phosphoglycerate
molecules are dehydrated and forms
two high-energy
phosphoenolpyruvate molecules.
9. The two phospoenolpyruvate
phosphorylates two ADPs and
produces two more ATPs and two
molecules of pyruvate.
Glycolysis summary
In the next sequence of
reactions 4 molecules of ATP
are produced and the total
energy harvest of ATP can be
calculated as shown on the
table
Number of ATP
molecules used
2
Number of ATP
molecules
produced
4
Net number of ATP 2
molecules gained
in glycolysis
Glycolysis
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NAD+ is a coenzyme
Hydrogen carrier
 NADH + H formed by removing hydrogen
from glucose (oxidation of glucose), and
giving this H to NAD+ (reduction)
 NAD+ +2H
NADH+ H+
 Glucose is reduced (removal of H) and
NADH is oxidized
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Glycolysis
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NAD+  NADH + H+
Glucose
Pyruvic
oxidation
pyruvate
acid made in glycolysis can now enter
into aerobic or anaerobic pathways of respiration
Anaerobic respiration
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If respiration is anaerobic
 Pyruvate is reduced into either lactic
acid releasing NAD+ or
 Alcohol is produced with the release of
NAD+ and carbon dioxide
 The reduction of pyruvate into lactic
acid or ethanol does not release
energy.
 Only serves in the release of NAD+
Anaerobic respiration
These NADs can be used again in
glycolysis
 This step produced ethanol or lactic acid
which is less toxic as a waste product in the
surroundings of these organisms
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Anaerobic respiration
Occurs in mostly small animals which
do not need much energy for the way
of life
 The two ATP formed are enough for
providing energy to these simple
organisms such as bacteria and yeast
 Also occurs during strenuous exercise
in mammals
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Anaerobic respiration
Glycolysis
Phosphorilation
Oxidation
Lysis
2 pyruvate + 2 ATP +2NADH + H+
Fermentation
Fermentation
2 pyruvate either
2NADH + H
2NADH + H
2NAD
2NAD +
CO2
LACTIC ACID
Ethanol
Oxidation and reduction
Oxidation involves the loss of electrons from
an element
 Reduction involves a gain of electron
 Phosphorylation is a process in which ATP
is made.
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Industrial uses of anaerobic
respiration
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Alcoholic fermentation
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Manufacture of alcoholic drinks
• Wine – make by incubating crushed
grapes in a sealed container at a
temperature of 40 degrees celsius.
• Need the correct bacterias and yeast that
carry out anaerobic respiration and
breakdown of sugar in grapes into ethanol
and CO2
Industrial uses of anaerobic
respiration
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Manufacture of Yogurt
Milk is incubated over night with
bacteria at around 40 degrees
 Lactic acid makes the milk to clot into
yogurt
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Aerobic respiration
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After glycolysis the pyruvic
acid enters into the
mitochondria
In the matrix of the
mitochondria, pyruvate is
decarboxylated (CO2 mol is
removed)
Decarboxylase remove CO2
Dehydrogenase oxidised
(hydrogen removed)
Aerobic respiration
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Resulting molecule is called acetyl
group (2 carbons)
 Results from the removal of
Carbon dioxide and combination
with coenzyme A= Acetyl Co A
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This reactions are called link
reactions since they link pyruvate
with the Krebs cycle
This compound Acetyl Co A then
enters into the matrix of the
mitochondria.
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The Krebs Cycle
Starting molecule is 2
carbon compound called
oxaloacetic acid
 It reacts with acetyl CoA
and forms a 6 carbon
compound called Citric
acid
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The Krebs Cycle
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Coenzyme A comes out
unaffected
Citric acid loses CO2 and
becomes a 5 carbon
compound
A different stages in the
cycle compounds loses
Hydrogen which comes out
in the form of NADH+H and
FADH2
The Krebs Cycle
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Final output
2ATP,
 4CO2,
 6NADH +H
 and 2FADH2
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Chemiosmotic oxidative
phosphorylation and the electron
transport chain
Chemiosmotic oxidative phosphorylation and the
electron transport chain
NADH + H and FADH2
coming out of all the
reaction of respiration
are processed in the
mitochondria to produce
ATP
 This is carry out by
electron carriers that are
situated in the inner
membrane of the
mitochondria and cristae
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Electron transport chain
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NADH +H gives its electron to the
first electron carrier in the ETC, thus
NADH +H becomes NAD+, in other
terms NADH+H is oxidized and the
first carrier in the chain is reduce
The first carrier passes the electron
to the next carrier and so on
electrons are passed from one
carrier to the next in the electron
transport chain
As the electrons are passed from
one carrier to the next they go down
to a lower and lower energy level.
Electron transport chain
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These electrons are finally
taken by oxygen to form water.
Oxygen is the final recipient of
the electrons passing down the
electron transport chain. In this
process oxygen becomes
reduced into water.
Going down the energy
gradient, the electrons released
energy
Electron transport chain
The energy released
from the electrons is
used to pump protons
(H+) from the matrix to
the intermembranal
space.
 Due to the small volume
of this space, it become
highly concentrated with
protons very quickly
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Electron transport chain
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This created two compartments
in the mitochondria with
different proton concentrations.
The matrix with a low
concentration and the
intermembranal space with a
high concentration.
This results in the protons
moving down their
concentration gradient from the
intermembranal space to the
matrix.
However the only path they can
pass is through channels
provided by the enzyme ATP
synthetase.
Electron transport chain
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Protons diffuse quickly
through the ATPase
channels, thus activating
this enzyme.
When ATPase becomes
active, it catalyses the
phosphorilation of ADP
into ATP, and so ATP is
formed in this way from
NADH+H
All the above steps are
called oxidative
phosphorilation.
Products
NAD+ and FAD take hydrogen
stripped off the glucose molecule into
the ETC where they are processed
into ATP.
 Carbons of the glucose are released
in the form of CO2.
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