Fermentation H. Biology Ms. Kim

Fermentation Fermentation enables some cells to produce ATP without the use of oxygen (O2) Cellular respiration – Relies on oxygen to produce ATP In the absence of oxygen – Cells can still produce ATP through fermentation

Cellular respiration vs. fermentation Oxygen Present → Aerobic Respiration (efficient!) Oxygen NOT Present → Fermentation (not efficient) Respiration = 66% efficient Fermentation = 3.5% efficient

Fermentation If there is no oxygen present (anaerobic) the pyruvate (from glycolysis) goes to fermentation The main goal of fermentation is: NAD+ – To make NAD+ to put back into glycolysis NO ATP – This makes NO ATP on its own (it just keeps glycolysis going so that it can make 2 ATP at a time) Occurs in the cytosol 2 types of fermentation – 1) Alcohol – 2) Lactic acid

Glycolysis – Can produce ATP with or without oxygen, in aerobic or anaerobic conditions – Couples with fermentation to produce ATP

Types of Fermentation Fermentation consists of – Glycolysis plus reactions that regenerate NAD +, which can be reused by glyocolysis

Alcohol Fermentation Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO 2 Ex: bacteria and yeast

In alcohol fermentation – Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO 2 GLUCOSE  Pyruvate  Ethanol and CO 2 Ex: bacteria and yeast do this

- Pyruvate is turned into ethanol - CO 2 is released (bubbles!) - Done by yeast for brewing 3C Pyruvate → 2C Ethanol Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP Alcoholic Fermentation

Lactic Acid Fermentation During lactic acid fermentation – Pyruvate is reduced directly to NADH to form lactate as a waste product – NO CO 2 is released Ex #1: fungus and bacteria in dairy industry to make cheese/ yogurt Ex #2: Human muscle cells

Lactic acid fermentation - Pyruvate is turned into Lactate (or lactic acid) -Lactate is eventually carried away by the blood to the liver where it gets converted back into pyruvate -Example: Muscle Cells - The lactic acid is what makes your muscles sore after lifting or intensive exercise - No CO 2 is released 3C Pyruvate → 3C Lactate Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP

Lactic acid vs. alcohol fermentation Similarities: 1. Both start with pyruvate from glycolysis 2. Both create NAD+ to be sent back to glycolysis 3. Neither make any ATP on their own Differences: 1. Lactic acid is made and does NOT give off CO 2 2. Alcohol makes ethanol and gives off CO 2

Fermentation - Overview Obligate Aerobes → needs oxygen; can do respiration only Obligate Anaerobes → can’t have oxygen; fermentation only Facultative Anaerobes → can live with or without oxygen; prefer oxygen b/c more efficient Respiration is 19 times more efficient than fermentation (38 ATP vs. 2 ATP)

2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde (gets reduced by NADH. It is the oxidizing agent.) 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Lactate (b) Lactic acid fermentation H H OH CH 3 C O – O C CO CH 3 H CO O–O– CO CO O CO C OHH CH 3 CO 2 2 NO CO2 made 2 Pyruvate (gets reduced by NADH. It is the oxidizing agent.)

Fermentation and Cellular Respiration Compared Both fermentation and cellular respiration – Use glycolysis to oxidize glucose and other organic fuels to pyruvate Fermentation and cellular respiration – Differ in their final electron acceptor Cell respriraition uses O 2 Fermentation uses NAD+ Cellular respiration – Produces more ATP (~36-38 ATP) Fermentation – Produces 2 ATP per cycle

Exit Slip 1)Alcoholic fermentation converts glucose to 2)Alcoholic fermentation is utilized by what organisms? 3) Lactic acid fermentation converts glucose to 4) Lactic acid fermentation is utilized by what organisms? 5) What is the final acceptor for alcoholic fermentation? 6) What is the final acceptor for lactic acid fermentation? 7) What is the final acceptor for cellular respiration? 8) Draw and label the diagram