Transcript Slide 1

Cellular Respiration – Chapter 9
• Cellular Respiration Equation:
C6H12O6 + 6O2  6CO2 +6H2O + energy
Cellular Respiration – Chapter 9
• Cell Respiration – is a complex process
in which cells make ATP by breaking down
organic compounds
• The break down of organic compounds
releases energy; some is used to make
ATP.
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Glycolysis and Fermentation:
Cell respiration begins with a biochemical
pathway called glycolysis. Glycolysis
makes little ATP. The products of
glycolysis can then follow one of two
pathways. Each pathways depends on
whether there is oxygen or not.
Cellular Respiration – Chapter 9
Organic Compounds
Glycolysis
Fermentation
(Anaerobic)
Oxygen Absent
Aerobic
Respiratio
n
Oxygen Present
ATP
Cellular Respiration – Chapter 9
Glycolysis
• A pathway in which glucose a 6-carbon
compound is oxidized to produce two 3Carbon molecules of pyruvic acid. (All
reactions of glycolysis occur in the cytosol
of the cell.)
Cellular Respiration – Chapter 9
• Oxidized – a reaction where a reactant
loses one or more electrons, and becomes
more positive
Cellular Respiration – Chapter 9
There are 4 steps to Glycolysis:
1. Two phosphates are added to glucose and it
becomes a new 6-carbon compound
2. The 6-carbon compound splits into two 3-carbon
PGAL’s
3. The two PGAL’s are oxidized and each gains a
phosphate. At the same time 2 NAD molecules
each gain a Hydrogen molecule.
4. The phosphates from step 1 and 3 are removed
and the compound pyruvic acid is made. The 4
phosphates attach to ADP molecules and 4
molecules of ATP are made.
Cellular Respiration – Chapter 9
• Two ATP molecules are used in gylcolysis
and 4 molecules of ATP are made
therefore there is a net yield of 2 ATP
molecules for every molecule of glucose
that is converted to pyruvic acid.
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Fermentation:
• Conversion in absence of oxygen of
pyruvic acid into other compounds
• Happens in the cell’s cytosol
Cellular Respiration – Chapter 9
Lactic Acid Fermentation
• Enzyme converts pyruvic acid into
another 3-carbon compound, called lactic
acid
• 2 hydrogen (H) atoms from NADH and H
add to pyruvic acid to make the final
product of lactic acid
Cellular Respiration – Chapter 9
Examples of Lactic Acid:
Plays a role in food production
» Yogurt and cheese made because of
the fermentation of
microorganismsOccurs in muscle cells
» Strenuous exercise – muscles use the
oxygen faster than it’s delivered.
Muscles turn to lactic acid fermentation,
cells build up with the acid
» Results in muscle fatigue, pain, and
cramps
Cellular Respiration – Chapter 9
Alcoholic Fermentation
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Converts pyruvic acid into ethyl alcohol
Carbon dioxide is removed from pyruvic
acid leaving a 2-carbon compound.
Hydrogen atoms are added to the 2carbon compound resulting in ethyl
alcohol.
Cellular Respiration – Chapter 9
Examples of Alcoholic Fermentation:
• Wine and beer
– Yeast cells are added to the fermentation
mixture to produce the enzymes needed for
alcoholic fermentation
– Ethyl alcohol increases to the point where
fermentation stops
– Carbon dioxide accumulates, creates
“carbonate” of the beverage
• Bread
– Ethyl alcohol evaporates in baking but carbon
dioxide created the bubbles in the dough
Cellular Respiration – Chapter 9
Energy Yield of Glycolysis:
• Efficiency of glycolysis = Energy required to make ATP /
Energy released by oxidation of glucose
• Glycolysis is only 3.5% efficient.
• Most of the energy that was contained in
the glucose is still contained the pyruvic
acid.
Cellular Respiration – Chapter 9
HISTORY
• Anaerobic organisms evolved very early in
the history of life on earth.
• Oxygen was not produced until
photosynthetic organisms came along
about a billion years later
• Most anaerobic organisms are unicellular,
any anaerobic multicellular organisms are
very small
Cellular Respiration – Chapter 9
Aerobic Respiration:
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•
In most cells the pyruvic acid made in
glycolysis does not go into fermentation
but instead if oxygen is available the
pyruvic acid enters cellular respiration.
There are 2 major steps to Aerobic or
Cellular Respiration:
1. Krebs Cycle
2. Electron Transport Chain
Cellular Respiration – Chapter 9
Where the reactions for Kreb’s cycle
and Electron Transport take place:
– Prokaryotes – in the cytosol of the cell
– Eukaryotes – inside the mitochondria
• When the pyruvic acid enters the
mitochondria it combines with a molecule
called coenzyme A to form acetyl
coenzyme A. (Abbreviated acetyl coA)
Cellular Respiration – Chapter 9
The Kreb’s Cycle:
• Is a biochemical pathway that breaks
down acetyl CoA, producing CO2,
hydrogen atoms, and ATP.
• The person who identified the reactions
that make up the cycle was Hans Krebs a
German-British biochemist.
Cellular Respiration – Chapter 9
The Krebs Cycle has 5 main steps:
• Acetyl CoA combines with oxaloacetic acid to produce
citric acid
• Citric acid releases a Carbon dioxide molecule to form a
five-carbon compound
• The five-carbon compound releases a carbon dioxide
molecule to form a four-carbon compound
• The four-carbon compound is converted into a new fourcarbon compound
• The new four-carbon compound is converted back into
oxaloacetic acid
Cellular Respiration – Chapter 9
Krebs Cycle Continued
• In addition to the carbon dioxide produced,
each turn of the Kreb’s cycle produces
ATP, NADH, and FADH2
• Each glucose molecule makes 2 pyruvic
acid molecules in glycolysis. The 2
pyruvic acid molecules then make 2 acetyl
CoA molecules (Each will go through the
Kreb’s Cycle.)
Cellular Respiration – Chapter 9
From the two acetyl CoA molecules in the
Kreb’s Cycle these are produced (2 turns
of the Kreb’s Cycle):
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6 NADH
2 FADH2
4 CO2
2 ATP
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Electron Transport Chain:
• The second stage of aerobic or cellular
respiration
• Electron transport chain lines the inner
membrane of the mitochondria
Cellular Respiration – Chapter 9
What happens in the Electron
Transport Chain:
• NADH and FADH2 supply electrons and
protons to the electron transport chain
• The electrons move down the chain from
molecules to molecule in a series of
reactions
• The protons are pumped outside the
mitochondria
Cellular Respiration – Chapter 9
Electron Transport Chain Cont.
• As the protons return to the mitochondria
matrix through ATP synthase, they
release energy, that energy is used to
make ATP
• The electrons and protons are joined with
oxygen this reaction makes ATP
Cellular Respiration – Chapter 9
Energy Yield for Aerobic
Respiration:
• Efficiency of Aerobic Respiration = Energy
used to make ATP
Energy released by oxidation of glucose
• Aerobic Respiration is 66% efficient (20 x
more than glycolysis)
• 1 molecule of glucose can produce up to
38 ATP in cellular respiration (see
diagram) usually 36 ATP net yeild
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9
Cellular Respiration – Chapter 9