Energy Releasing PathwaysC6H12O6 + 6O2 6CO2 + 6H2O + ATP

(Harvesting Chemical Energy)

• Glycolysis• Fermentation

• Aerobic respiration

Begins with the biochemical pathway glycolysis.

Glycolysis animation http

://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html

Redox Reaction Oxidation: loss of e- (glucose) Reduced: Gain of e- (Co2)

Glycolysis

Takes place in the cytosol 1, 6 carbon molecule of glucose goes

through a series of chemical reactions catalyzed by specific enzymes to produce 2, 3 carbon molecules of pyruvic acid.

NAD+ similar to NADP+

NAD+ carry electrons and Hydrogen ions (NADH)

Glycolysis

Glycolysis

1 Glucose 2 Pyruvic acid 2 ATP 4 ATP 2 NAD+ 2 NADH 4 ADP + 2Phospates

Net 2 ATP

What Next?

Organic Compound

Glycolysis ATP

no oxygen oxygen

Fermentation Aerobic Respiration

FermentationAnaerobic Respiration

Prokaryotes and protists in anaerobic habitats (mainly unicellular organisms)

Does not produce ATP Many Fermentation pathways differ in

the types of enzymes and final products produced

Two most common produced are lactic acid and ethyl alcohol

Lactic Acid Fermentation Occurs in muscle cell when strenuous

exercise causes muscle cells to use up all the oxygen available to them. They switch to anaerobic respiration and lactic acid builds up in the cells, changing the acidity of the cytoplasm.

Increased acidity decreases the cells ability to contract causing cramps and fatigue.

Eventually it diffuses out of cell into blood stream and is transported to liver where it is converted back into pyruvic acid.

Used to make cheese and yogurt

Lactic Acid Fermentation

Alcoholic Fermentation

Used by some plants and unicellular organisms such a yeast

Bread making

Fermentation Animation

http://www.cst.cmich.edu/users/schul1te/animations/fermentation.swf

Aerobic Respiration

Requires O2

Approximately 20 times as much ATP produced then glycolysis

Two major stages: Krebs cycle and the electron transport chain

In eukaryotic cell takes place in the mitochondria.

Krebs cycle occurs in the mitochondrial matrix Electron transport chain occurs in the inner

membrane

Mitochondrion

Transition Reaction

Pyruvic acid enters the mitochondrial matrix

It reacts with a molecule called coenzyme A (CoA) to form acetyl CoA

CO2 and NADH and H+ are produced

The Krebs CycleAnimation

http://www.1lecture.com/Biochemistry/How%20the%20Krebs%20Cycle%20Works/index.html

The Krebs CycleFive Main Steps

Step 1: Acetyl CoA combines with Oxaloacetic acid to form citric acid (regenerates CoA)Step 2: Citric acid releases CO2 and a H atom that combines with NAD+ to form NADH + H+ to form 5 carbon compound. Step 3: 5 carbon compound releases CO2

and a Hydrogen atom (combines with NAD+ to form NADH + H+) to form a 4 carbon compound. A molecule of ATP is formed.

Krebs Cycle

Step 4: 4 Carbon compound releases a hydrogen atom ( combines with FAD to Form FADH2) and is converted to another 4 carbon compound.

Step 5: The 4 carbon compound releases a hydrogen atom and is (combines with NAD+ to form NADH + H+)converted back into Oxaloacetic acid.

What is Produced?

1 glucose molecule = 2 turns of the Krebs cycle

6 NADH 2 FADH2

2 ATP 4 CO2

The Krebs Cycle

Most of the energy from glucose still have not been transferred to ATP

10 NADH and the 2 FADH2 produced so far to drive the electron transport chain

Electron transport ChainAnimation

http://www.science.smith.edu/departments/Biology/Bio231/etc.html

Energy Yield