Describe the processes of ethanolic and lactic acid fermentation. Do Now 12/18 (HW check 6.7-6.9) OBJECTIVES: Define oxidation, reduction, and redox; explain how these reactions occur in metabolism. Describe the processes of ethanolic and lactic acid fermentation. TASK: 1. There is a total of about 3,000 kJ of energy stored in the bonds of one glucose molecule. When a cell hydrolyzes ATP to ADP, about 50 kJ of energy is released. What is the approximate energy efficiency (%) of glycolysis?

Redox Reactions

Redox: LEO the Lion Says GER. The Loss of Electrons is Oxidation; the Gain of Electrons is Reduction. Whenever something is oxidized, something else must be reduced (i.e. the electrons have to go somewhere!) In fermentation, NADH is oxidized, and pyruvate is reduced.

Adding Oxygen to Carbon Releases Energy Respiration oxidizes carbon; the more the carbon gets oxidized, the more energy is released. Compound Carbon is H:O Ratio Amount of energy stored in molecule CH4 Fully Reduced 4:0 High C6H12O6 (Glucose) C3H4O3 (Pyruvate), C2H4O (Ethanol), C3H6O3 (Lactic Acid) Partially oxidized 4:1 – 4:3 Moderate CO2 Fully Oxidized 0:4 Low

Lactic Acid Fermentation – you do this! Notice: No CO2 produced. NADH is oxidized to NAD+ Pyruvate is reduced to lactic acid.

Fermentation: To recycle NAD+ The top section is glycolysis. The bottom is ethanolic fermentation. Ethanol and CO2 are the waste products Alcoholic Fermentation

Fermentation is Wasteful The products of fermentation (ethanol or lactic acid) contain MORE energy than pyruvate! The NADH used loses valuable energy – in anaerobic conditions anyway.

So Why Do They Do it? The electrons ripped from food have to go somewhere! In aerobic respiration they eventually end up in water after being attached to oxygen. When there’s no oxygen around, the cell deposits the electrons on what’s available: the leftovers from glycolysis. This is ONE of the ways in which aerobic respiration is more efficient than anaerobic.

Yummy Yummy Fermentation In addition to making lots of yummy food products from soy sauce to kimchi, fermentations done by engineered microbes can produce useful enzymes or drugs!

Other Notable Types of Fermentation

Recap Fermentation is the second step in anaerobic respiration; its function is to recycle the NAD+ needed for glycolysis to continue. Alcoholic fermentation (like done by yeast) produces CO2 and ethanol. Lactic acid fermentation (like done by human muscle cells) produces lactic acid. There are many other types as well. Fermentation is inefficient: the waste products of glycolysis are REDUCED by NADH, which adds chemical energy to them.