Enzymes & E a 3.3

Activation Energy (E a )

What if… …organisms used heat for E a ? not a practical source because… can disrupt or denature proteins is non-specific (would speed up all reactions)

Enzymes and E a

How is E a reduced? Enzymes… provide proper orientation of substrate(s) provide specific environments that promote catalysis put strain on substrate bonds, making them easier to break

Animation Activation Energy & Enzymes: /animations/content/enzymes/enzymes. htmlhttp:// /animations/content/enzymes/enzymes. html

Food As Fuel 3.4

Redox Reactions electrons are lost from one atom and gained by another atom [see also 1.1, page 17] oxidation reduction

Redox Reactions oxidizing agent reducing agent sometimes entire atoms (with their electrons) are transferred during redox reactions

Redox… redox can occur because of relative loss or gain of electrons due to electronegativity differences… CH 4 + 2O 2 --> CO 2 + 2H 2 O C is effectively oxidized, O is reduced

Cellular Respiration glucose is oxidized combustion (oxidation) of glucose releases a large amount of thermal E in cells, oxidation of glucose occurs in a series of steps (controlled oxidation) to minimize E loss

Energy Carrier: NAD + NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in all living cells vitamin B 3 (niacin) derivative

Reduction of NAD+

Energy Carrier: FAD FAD (flavin adenine dinucleotide) is a coenzyme involved in respiration vitamin B 2 (riboflavin) derivative

Reduction of FAD