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Chapter 5 Section 3
Cellular Respiration
Cellular Respiration
• The conversion of organic matter
into energy within the cell
• Stored potential energy used to convert
ADP into ATP
• Happens in both environments
• Anaerobic= No Oxygen
• Aerobic= In the presence of
Oxygen
− More efficient!!!!!!!
Stages of Cellular Respiration
1.
Glucose is split into two
molecules of pyruvate
•
Glycolysis
2a. Aerobic Respiration
•
In the presence of oxygen
•
anaerobic conditions
2b. Fermentation
Equation
C6H12O6
+
6O2 ------> 6CO2 +6H2O
Glucose
-------------
Glycolysis
2 pyruvates
2B. Fermentation
2A. Krebs Cycle
Electron Transport
Glycolysis
• Glucose (6 Carbons) split into 2 molecules of
pyruvate (3 Carbons)
• Small enough to cross the mitochondrial membrane
• Takes place in the cytoplasm of the cell
• All cells have cytoplasm
• 2 ATP in 4 ATP out = net +2 ATP
• 2 NAD+ converted to 2 NADH by stripping
high energy e- from pyruvate
• NADH must donate the H to other compounds to
recycle NAD+
• NO O2 required!!!! (anaerobic)
Glycolysis Diagram
Aerobic Respiration
• In the presence of oxygen pyruvate
enters the mitochondria and is
converted into a 2 carbon molecule.
• This releases 1 CO2 and converts a NAD+ into
a NADH
• The 2 carbon molecule joins a
coenzyme A to form acetyl CoA
• The acetyl CoA enters the Krebs
Cycle or citric acid cycle
Krebs Cycle
• First described by Sir Hans
Krebs in 1937
• It is a series of chemical
reactions in which high energy
electrons are stripped from
organic molecules and used to
create NADH and FADH2
– Small amounts of ATP and CO2 are also
generated
Acetyl CoA Formation
Krebs Cycle
Electron Transport Chain
• So far we have generated just
ATP
4
• 2 from glycolysis and two from the Krebs
Cycle
• You use 1,000,000 ATP/cell/second which is
equal to 100,000,000,000,000,000,000/ sec
• But we have created many
molecules that contain high energy
electrons
• NADH (10) and FADH2 (2)
Mitochondria Review
•It has an outer
membrane and an
inner membrane
•The inner
membrane is folded
up forming cristae
•Surface area
•The very inside is
called the matrix and
the rest is
intermembrane
space
ETC Continued
• NADH and FADH2 enter into the ETC
• ETC located in the inner mitochondrial
membrane
• High energy electrons enter and move
down the chain NAD+ and FAD+ are recycled
• H+ pumped out of the matrix to form a
gradient
• Protons (H+) are allowed back into the
matrix, but through an enzyme that
converts ADP -- into ATP
• The final electron acceptor is O2 which
pairs with H+ to form water
• C6H12O6
+
6O2 ------> 6CO2 +6H2O
34
Aerobic Net Gain
• 2 ATP from Glycolysis
• 2 ATP from Krebs cycle
• Approx 34 ATP from ETC
_____________________________________
38 ATP/Molecule of Glucose in
the presence of Oxygen
Fermentation
• Takes place in anaerobic conditions
• NADH produced in glycolysis must
release its high energy electron, but
there is no O2 to be the final electron
acceptor
• NADH donates the high energy
electron back to pyruvate to form
either lactic acid or ethanol and CO2
• Then NAD+ is recycled and glycolysis can
proceed
Fermentation Cont.
• No ATP produced after glycolysis so
net gain of 2 ATP/molecule of
glucose
• As compared to 38 in aerobic conditions
• Lactic acid can cause muscle
fatigue, but it is better that the
alternative = no ATP
• Fermentation used in the production
of some foods and beverages
• Beer and wine
• bread