Fermentation

Chapter 9

What you need to know!

• The difference between fermentation and cellular respiration.

Anaerobic Cellular Respiration

• Production of ATP in the absence of oxygen

2 types of fermentation:

• Alcoholic fermentation

• Lactic acid fermentation

Organisms

• Facultative anaerobic organisms– Can do aerobic or anaerobic cellular respiration

(CR) depending on the situation– Ex: yeast

• Obligate Anaerobic Organisms– Require oxygen free environment (die in the

presence of O2)– Ex: certain soil and lake bacteria

• Obligate aerobic organisms– Require O2

– Ex: All vertebrates

Fermentation: 2 step process

1. Glycolysis• ATP generation• (NAD+) + (H+) + e- NADH

2. Fermentation (regeneration)• NAD+ regeneration• NADH (NAD+) + byproducts (specific to

fermentation type)

Alcoholic Fermentation

• Location: cytoplasm of yeast and other bacteria• Reason: NADH must be recycled back into NAD+

so glycolysis can continue

Rx: Pyruvic acid + NADH + H+ Ethanol + CO2 + NAD+

• CO2 creates carbonation in bear, fizz in champagne, and leavens dough

• Small quantities of alcohol are made whenever you eat by anaerobic organisms that live in your intestines

• The liver degrades alcohol using alcohol dehydrogenase

Lactic Acid Fermentation

• Location: cytoplasm of muscle cells

• Reason: O2 deficiencyRx: Pyruvic acid + NADH + H+ Lactic Acid + NAD+

• Lactic acid causes muscle soreness (burning)

• It takes days to break down lactic acid

Muscle Categories

• Fast Twitch

• Strength, large diameter, white color, produce lots of lactic acid

• Ex: biceps, chest muscles

• Slow Twitch

• Endurance, slim diameter, red color, have lots of mitochondria, intense vascularization

• Ex: posture muscles

ATP Yield

• Anaerobic yields 4 ATP during glycolysis– 2 ATP activation cost

• Net Gain 2 ATP

• Aerobic yields 38 ATP during all 3 steps– 2 ATP activation cost

• Net Gain 36 ATP

• Aerobic CR is 18 X’s more efficient per glucose molecule