Fermentation

ATP - Adenosine TriPhosphate

ATP is “spring-loaded”

• The phosphates have a negative charge –repel each other• This means

potential energy is stored in the bonds

Aerobic Respiration

• The oxygen is electronegative and pulls the electrons down the ETC• Without it, no oxidative

phosphorylation happens

NAD+ regeneration

• To keep cycling glycolysis, we need NAD+ to be in sufficient supply• This is done by

transferring the electrons from NADH back to pyruvate

Fermentation

• Glycolysis still happens – NAD+ oxidizes glucose to 2 pyruvate• No ETC, so no 32 ATPs• Fermentation cycles

glycolysis again and again

Two types

Alcohol Fermentation• Pyruvate is converted to

ethyl alcohol (ethanol)• Yeast – used for bread,

wine, beer

Lactic Acid Fermentation• Pyruvate is converted to

lactate (ionized form of lactic acid)• Fungi and bacteria –

used for cheese and yogurt• Humans – in our muscle

cells

Which is better?

Aerobic Respiration

• 19 times as much ATP • 38 ATP per glucose

38 x 7.3 kcal/mol = 277.4 kcal

Fermentation

• 2 ATP per glucose

2 x 7.3 kcal/mol = 14.6 kcal

Two types of anaerobes

Obligate anaerobes• Can only do

fermentation or anaerobic respiration

• Can’t survive in the presence of oxygen

Facultative anaerobes• Can do both

• Our muscle cells behave this way

Feedback Regulation of Respiration