Cellular Respiration Chapter 9

Overview of CR Reverse process of photosynthesis Photosynthesis: energy → food Respiration: food → energy

Overview of CR Occurs in all organisms –In eukaryotes – mitochondria –In prokaryotes – cytoplasm Two types: –Aerobic – needs O 2 –Anaeobic – does not need O 2

What do cells need E for? Movement Cellular transport Growth Muscle contraction

Aerobic Resp. Reaction Sugar and oxygen are converted into water, carbon dioxide and 36 ATP molecules ATP = useable energy

Steps of Aerobic Resp. 1.Glycolysis – in cytoplasm 2.Kreb’s Cycle – in mitochondria 3.Electron Transport Chain – in mitochondria

Glycolysis Glyco-: sugar -lysis: break Makes 4 ATP, uses 2 ATP = 2 ATP Produces 2 NADH (electron carrier)

Kreb’s Cycle Pyruvic acid broken down into CO 2 molecules –Produces 2 ATP, several NADH and FADH 2 molecules (more school buses for e - and H + )

Kreb’s Cycle

Electron Transport Chain Same concept as in photosynthesis Electrons from NADH and FADH 2 pass down a chain of molecules –Energy released used to pump H + into intermembrane space –H + diffuse back into matrix through ATP synthase Yields 34 ATP/glucose

Why do we need O 2 ? At end of ETC, e - “caught” by O 2 –combines with H +, makes H 2 O No O 2 means e - has no where to go ETC backs up with electrons Respiration stops = death

ETC

What happens when no O 2 is available?? Fermentation or Anaerobic Resp. Occurs after glycolysis Regenerates empty NAD + so that glycolysis can continue Two types: –Alcohol ferm. In plants, fungi –Lactic acid ferm. In animals

Alcohol Fermentation Pyruvic acid + NADH → Ethanol + CO 2 + NAD + Produces alcohol for beverages CO 2 produced by yeast makes bread rise

Lactic Acid Fermentation Pyruvic acid + NADH→ lactic acid + NAD + Creates burning sensation in muscles during intense exercise

Photosynthesis vs. Cellular Respiration