Download Cellular Respiration

Cellular Respiration
Ch. 9
Energy for Life - ATP
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All cells require energy (ATP) to carry out life
functions they do so through Cellular Respiration.
To make the maximum amount of energy (ATP)
oxygen is needed (aerobic conditions).
In the absence of oxygen (anaerobic conditions)
organisms can still make energy (ATP) but they make
very low amounts.
This energy for life comes from the breakdown of
glucose.
Part 1 - Glycolysis
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1st part of the process of cellular respiration is
anaerobic - does not require oxygen!
One molecule of glucose is broken in half,
producing two molecules of pyruvic acid (3carbon compound)
Takes place in cytoplasm (cytosol)
2 molecules of ATP are used up
4 molecules of ATP are produced = a net gain
of 2 ATP molecules
Part 2 - Aerobic Cellular
Respiration
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Only happens if oxygen is present!
Process that releases energy by
breaking down glucose and other food
molecules in the presence of oxygen.
6O2 + C6H12O6  6CO2 + H2O +ENERGY
 Requires: oxygen and glucose
 Gives off: carbon dioxide, water, and
energy
Glycolysis Steps – Part 1
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Two molecules of ATP provide energy to
split glucose
Glucose splits, releasing enough energy
to form 4 ATP
Hydrogen is released and picked up by
an NAD+ NADH
Glycolysis Electron Carrier NAD+
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Like NADP+ in photosynthesis, each
NAD+ accepts a pair of high energy
electrons
NADH holds the electrons until they can
be transferred to other molecules.
Fermentation
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When oxygen is not present
Releases energy from food molecules
by producing ATP in the absence of
oxygen (anaerobic)
Cells convert NADH to NAD+ by passing
electrons back to pyruvic acid
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Alcoholic Fermentation:
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Used by yeast and a few other
microorganisms
Pyruvic acid + NADH  alcohol + CO2 + NAD+
Waste: ethyl alcohol and carbon dioxide
Causes: bread to rise
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When yeast runs out of oxygen, it begins to
give off bubbles of carbon dioxide that form the
air spaces you see in a slice of bread.
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Lactic Acid Fermentation:
Pyruvic acid that accumulates as a result of
Glycolysis can be converted to lactic acid
Pyruvic acid + NADH  lactic acid + NAD+
Lactic acid is produced in your muscles during
rapid exercise when the body cannot supply
enough oxygen to the tissues
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Your cells rapidly begin to produce ATP
by lactic acid fermentation
The buildup of lactic acid causes a
painful, burning sensation.
This is why muscles may feel sore after
only a few seconds of intense activity
Aerobic Stage – Part 2
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Occurs after Glycolysis if oxygen is
present.
The chemical bonds of pyruvic acid are
broken down in a series of reactions
Occurs in the mitochondria
Requires oxygen (aerobic)
Divided into The Krebs Cycle and The
Electron Transport Chain.
Krebs Cycle
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The first part of the
Krebs Cycle is called the
Citric Acid Cycle.
Pyruvate is converted to
Acetyl CoA which is
converted to Citric Acid.
Citric Acid is broken
down (two carbons are
removed) releasing CO2,
NAD+ and FAD which
pick up electrons and
become NADH and
FADH2.
Krebs Cycle (cont.)
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Each turn of the cycle yields 4
molecules of NADH, two molecules of
ATP, and one molecule FADH2.
The NADH formed during the citric-acid
cycle feeds the next step - the electron
transport system.
Electron Transport Chain
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NADH releases electrons and hydrogen
atoms NAD+
The electrons contained in the
hydrogen atoms pass through a series
of steps
Each time an electron moves from one
acceptor to another, energy is released.
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At the end of the chain, the electron
still exists, but it has less energy than at
the beginning of the electron transport
chain
This energy is used to form ATP from
ADP + P
Energy Total:
Source
Number ATP Produced
Glycolysis
2 ATP
Transport of NADH into
Matrix.
-2 ATP
Krebs Cycle
2 ATP
Electron Transport
34 ATP
NET TOTAL
36 ATP