Download Pyruvate to Acetyl Coenzyme A (Acetyl CoA)

Cellular Respiration:
Stage 2 – Citric Acid Cycle (Krebs Cycle)
Stage 3 – Oxidative Phosphorylation
(Electron Transport Chain and Chemiosmosis)
Pyruvate to Acetyl Coenzyme A (Acetyl CoA)
Pyruvate is first transported to the mitochondria.
Citric Acid Cycle
Pyruvate is modified before entering the Citric Acid Cycle
 One carbon atom is released as CO2.
 The remaining 2-carbon molecule is oxidized.
 NAD+ is reduced to NADH + H+.
 Coenzyme A is attached to the remaining 2-carbon
molecule to form Acetyl Coenzyme A.
How many molecules of Acetyl CoA are produced from
one molecule of glucose?
2
Stage 2: The Citric Acid Cycle (Krebs Cycle)
Takes place in the Matrix of the Mitochondria
For 1 Acetyl CoA molecule:
 The 2-carbon chain (not CoA) enters the CAC.
 The carbons are released as 2 CO2.
 Electrons (Hydrogen) are removed.
o 3 NAD+ are reduced to 3 NADH + 3H+
o FAD (another electron carrier) is reduced to
FADH2.
 1 ATP molecule is produced.
Since 2 molecules of Acetyl CoA enter the CAC, what are
the total products for one molecule of glucose?
 Carbons released: 4 CO2.
 Electrons (Hydrogen) carriers:
o 6 NADH + 6H+
o 2 FADH2.
 ATP produced: 2 ATP (Net Gain)
https://www.youtube.com/watch?v=hw5nWB0xN0Y
https://www.youtube.com/watch?v=ubzw64PQPqM
Stage 3: Oxidative Phosphorylation (ETC and
Chemiosmosis)
Location: Inner mitochondrial membrane of mitochondria
Mitochondria use the chemical energy released by redox
reactions to produce an H+ gradient and then use the energy
stored in that gradient to drive ATP synthesis.
https://www.youtube.com/watch?v=00jbG_cfGuQ
http://vcell.ndsu.edu/animations/atpgradient/movie-flash.htm
Song: http://www.youtube.com/watch?v=3aZrkdzrd04
Major Events:
 Electron/Hydrogen carriers (NADH and FADH2) drop
off their electrons and protons at the Electron
Transport Chain.
o Energy is released as electrons are passed from
protein molecule to protein molecule down to
Oxygen.
 The energy is used to pump H+ across the
innermembrane into the intermembrane
space.
 Concentration gradient is potential
energy.
o Protons (H+) flow through ATP Synthase from
the intermembrane space into the matrix.
 The flow of electrons releases enough
energy to attach phosphate groups to ADP to
generate ATP.
 Net Gain: 32 ATP
o 2 electrons and 2 protons (H+) attach to ½ O2 to
form water.
Poisons and Cellular Respiration
 Some block the ETC.
o Bond to carrier molecules; won’t accept electrons.
 Some block ATP Synthase
 Some prevent H+ gradients.
Organic Molecules as Fuel and Materials for
Biosynthesis
Glucose is not the only organic molecule used as fuel for
cellular respiration.
Polysaccharides, Proteins and Lipids are also used, but
must be broken into their monomer building blocks first.
Food is also used to build needed molecules for repair and
growth.
o Cells use ATP and Cellular Respiration intermediates
to build macromolecules.
Fermentation
Fermentation – Anaerobic Respiration – Energy production
in the absence of oxygen.
Tweak Glycolysis
Location: Cytoplasm
Net Gain: 2 ATP
Two Types of Fermentation:
1. Lactic Acid Fermentation – Animal muscle cells,
fungi, some bacteria and others
o NADH is oxidized, pyruvate is reduced to
lactate/lactic acid.
o Lactic acid is transported to the liver and
converted back to pyruvate.
2. Alcohol Fermentation – Plants and Some
Microorganisms (Ex. fungi – yeast, some bacteria)
o NADH is oxidized, ethyl alcohol and CO2 released.
o Used for baking and brewing.
https://www.youtube.com/watch?v=XREALVgxBEI
Review Stages of Cellular Respiration
http://www.sumanasinc.com/webcontent/animations/content/cellularrespiratio
n.html