Cellular Respiration Review

• Occurs in all eukaryotes• Generates ATP• Involves oxidation – reduction reactions

– Oxidation = loss of electron / H atom; Reduction = gain of electron / H atom;

Glycolosis

• Takes place in cytoplasm• Starts with glucose• NET YIELD: 2 NADH (goes

to ETC) and 2 ATP

The Prepatory Step & the Krebs Cycle

• Takes place in mitochondrial matrix

• Uses Coenzyme A to prepare pyruvate

• Completes breakdown of glucose to CO2

• Each molecule of pyruvate processed generates– 4 NADH– 1 FADH2

– 1 ATP

Electron Transfer Chain

• ETC: Occurs across inner mitochondrial membrane

• Electrons from NADH and FADH2 move down ETC

• O2 is the final oxygen acceptor

• Generates a H+ gradient

• H+ gradient powers ATP Synthase enzyme to phosphorylate ADP to ATP (Chemiosmosis)ADP + P ATP

• ETC Yield = 32-34 ATP molecules

Electron Transfer Chain

So far…

6

What if there’s no Oxygen?

• O2 can’t act as final electron acceptor

• ETC can’t happen• Can still get 2 ATP from and 2 NADH glycolysis

(doesn’t require O2)

What if there’s no Oxygen?

PRESENCE OF O2

• NADH goes to ETC

ABSENCE OF O2

•ETC can’t function•NADH must be oxidized back to NAD+

Anaerobic Respiration

• Respiration in the absence of oxygen• Oxidizes NADH to replenish NAD+

• Lactic Acid Fermentation• Alcohol Fermentation

Anaerobic Respiration

LACTIC ACID FERMENTATION

• Occurs in muscle cells• Oxidizes NADH to NAD+ by reducing pyruvate to lactate

(lactic acid)

Anaerobic Respiration

Lactic Acid Fermentation Alcohol Fermentation

Anaerobic Respiration

AlCOHOLIC FERMENTATION• Occurs in yeast• Oxidizes NADH to NAD+ by reducing pyruvate to ethanol

(ethyl alcohol)

Why we like fermentation

Often used by bacteria to make tasty foods

• Used for thousands of years• A method of preserving

food

Other Organic Molecules as Fuel for Cellular Respiration

Carbohydrates: Enter at beginning of glycolysis•Examples: Starch, Glycogen

Other Organic Molecules as Fuel for Cellular Respiration

Fats: Glycerol enters glycolysisFatty Acids broken into 2-C pieces and sent to Citric Acid Cycle

1 g fat yields 2x ATP as 1g starch

Other Organic Molecules as Fuel for Cellular Respiration

Proteins: broken into amino acids Can enter respiration at many points

Biosynthesis of Molecules

• We need to build up molecules as well as break them down

• ATP provides the energy f/ biosynthetic reactions

• Some are reverse of break-down pathways, some are not