Transcript Ch. 6 Cellular Respiration

Cellular Respiration:
Harvesting Chemical Energy
Ms. Haut
Energy Flow and Chemical Cycling
in the Biosphere
– Fuel molecules in food represent solar
energy.
Energy stored in food can be traced back to
the sun.
– Animals depend on plants to convert solar
energy to chemical energy.
This chemical energy is in the form of sugars
and other organic molecules.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Chemical Cycling between
Photosynthesis and Cellular Respiration
– The ingredients for photosynthesis are
carbon dioxide and water.
CO2 is obtained from the air by a plant’s
leaves.
H2O is obtained from the damp soil by a
plant’s roots.
– Chloroplasts rearrange the atoms of these
ingredients to produce sugars (glucose)
and other organic molecules.
Oxygen gas is a by-product of photosynthesis.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Chemical Cycling between Photosynthesis
and Cellular Respiration
Both plants and
animals perform
cellular respiration.
– Cellular respiration
harvests energy from
organic molecules.
Occurs in mitochondria.
– The waste products of
cellular respiration, CO2
and H2O, are used in
photosynthesis.
Cellular Respiration
ATP-producing process in which the
ultimate electron acceptor is Oxygen
Is an exergonic process (releases
energy)
The Relationship between Cellular
Respiration and Breathing
Cellular respiration
requires a cell to
exchange gases
with its
surroundings.
Breathing
exchanges these
gases between the
blood and outside
air.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Cellular Respiration
Carbohydrates, Proteins, and fats can
all be broken as fuel, but cellular
respiration most often described as:
C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP + Heat)
Process transfers energy stored in
food molecules to ATP
Electrons “fall” from Organic Molecules to
Oxygen during Cellular Respiration
Oxidation
C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP + Heat)
Reduction
The Process of Cellular Respiration
Cummulative function of three
main metabolic stages:
1.Glycolysis
2.Krebs Cycle
3.Electron
Transport Chain
and Oxidative
Phosphorylation
Glycolysis
Catabolic pathway
Occurs in the cytoplasm
Partially oxidizes glucose (6C) into
two pyruvic acid (pyruvate) (3C)
molecules
Glycolysis
Glycolysis
Glycolysis
Glycolysis
Glycolysis
Small amount of
ATP is produced
directly by the
enzymatic transfer
of phosphate from
an intermediate
substrate in
catabolism to ADP
http://faculty.ircc.edu/faculty/tfischer/micro/substrate%20level%20phosphorylation.jpg
Substrate-Level Phosphorylation
Krebs Cycle
Catabolic pathway
Occurs in mitochondrial matrix
Completes glucose oxidation by
breaking down a acetyl-CoA into CO2
Pyruvate Oxidation:
Conversion of Pyruvate to Acetyl CoA
Electron Transport Chain
Located near inner membrane of
mitochondrion
Accepts energized electrons from
reduced coenzymes (NADH and
FADH2) that are harvested during
glycolysis and Krebs Cycle
– Oxygen pulls electrons down ETC to a
lower energy state
Electron
Transport System
NADH and FADH2
are electron shuttles
Oxygen is the final
electron acceptor
Chemiosmosis:
AKA Oxidative
Phosphorylation
Enzyme is
ATP synthase
Intermembrane space
Mitochondrial
matrix
1 NADH = 3 ATP
1 FADH2 = 2 ATP
10 NADH = 30 ATP
2 FADH2 = 4 ATP
34 ATP
The Versatility of Cellular
Respiration
Cellular respiration can
“burn” other kinds of
molecules besides glucose:
– Starchglucose in
digestive tract
– Liver converts
glycogenglucose
– Excess amino
acidspyruvate, acetyl
CoA, and αketoglutarate
– Fatsglycerol + fatty
acids
– Glycerolglyceraldehyd
e phosphate
– Fatty acidsacetyl CoA
(beta oxidation)
Fe
rm
en
t
at
io
n
Aerobic: existing in
the presence of
oxygen
Anaerobic: existing
in the absence of
oxygen
Fermentation
Anaerobic catabolism of organic
nutrients
After pyruvate is produced in
glycolysis, it is reduced, and NAD+ is
regenerated
– Prevents cell from depleting the pool of
NAD+, needed in glycolysis
– No additional ATP is produced
Alcoholic Fermentation
• Many bacteria and
yeast carry out alcohol
fermentation under
anaerobic conditions
Lactic Acid Fermentation
Commercially important products: cheese &
yogurt
Human muscle cells switch to lactic acid
fermentation when O2 is scarce. Lactate
accumulates, slowly carried to liver and
converted back to pyruvate when O2 is available