1. KEY CONCEPT Fermentation pathways break down carbohydrates without using oxygen

2. What is Fermentation?
Fermentation is an anaerobic process that allows glycolysis to continue
Fermentation is completed in the cytoplasm and yields 2 ATP per glucose molecule

3. Metabolic pathways after glycolysis
Glycolysis can be followed by two different pathways
With oxygen – cellular respiration
Without oxygen – fermentation

4. NADH production in glycolysis
One reaction of glycolysis removes high-energy electrons and H+ and passes them to NAD+
NAD+ accepts the electrons and a H+ ion and travels to the electron transport chain as NADH if oxygen is available
At the end of the ETC, oxygen combines with the H+ and electrons to form water and regenerates NAD+

5. What if there is no oxygen?
No electron and H+ acceptor
No NAD+ regeneration for glycolysis

6. What if there is no oxygen?
So…If oxygen is not available, something else has to accept the electrons and H+ from the NADH from glycolysis and regenerate NAD+

7. Electron acceptors other than oxygen result in two kinds of fermentation
Alcoholic fermentation
Pyruvate is split into acetaldehyde and CO2
Acetaldehyde receives electrons and hydrogen from NADH, forming NAD+ and ethanol
Pyruvic acid + NADH → alcohol + CO2 + NAD+
Lactic Acid fermentation (lactate fermentation)
Pyruvate receives electrons and hydrogen from NADH, forming NAD+ and lactic acid (lactate)
Pyruvic acid + NADH → lactic acid + NAD+

8. Two kinds of fermentation

9. Fermentation is used in food production.
Yogurt - Soy Sauce
Cheese - Vinegar
Bread - Olives/Pickles
Beer/ Meade - Wine/ Ale
Sauerkraut - Malt

11. Alcoholic fermentation
Occurs in yeasts and some bacteria

12. Alcoholic Fermentation

13. Alcoholic Fermentation
Fermentation gives “rise” to doughs by CO2 release

14. Alcoholic fermentation
Yeast powers the fermentation of alcohol making and baking

15. Lactic acid fermentation
Slow-twitch muscle fibers (“red” muscles) make ATP by aerobic respiration
Have many mitochondria
Dominate in prolonged activity
Fast-twitch muscle fibers (“white” muscles) make ATP by lactic acid fermentation
Have few mitochondria
Sustain short bursts of activity

16. Lactic acid fermentation
Sprinters use lactic acid fermentation

17. Lactic acid that builds up in the tissue causes a burning, painful sensation.