Agenda

• Collect Homework #2• Go over Cellular Respiration Fill-in• Lecture:– Finish Cellular Respiration, etc– DNA Structure and Function

• Lab – Cellular Respiration• Lecture Quiz #4 this afternoon• Lecture – Protein Synthesis and Gene Expression

Cellular Respiration Review

• Occurs in all eukaryotes• Generates ATP• Involves oxidation – reduction reactions– Oxidation = loss of electron / H atom; gain of

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

charge

Glycolosis

• Takes place in cytoplasm• Starts with glucose• Uses 2 ATP to prepare

glucose• Generates 2 NADH– Is this oxidation or

reduction?• Generates 4 ATP• NET YIELD: 2 NADH (goes

to ETC) and 2 ATP

The Citric Acid (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

So far…

5

Oxidative Phosphorylation

• ETC: Takes place on inner mitochondrial membrane

• Electrons from NADH and FADH2 pass electrons down ETC

• O2 is the final oxygen acceptor

• Generates a H+ gradient

Oxidative Phosphorylation

• Chemiosmosis: H+ gradient powers ATP Synthase enzyme to phosphorylate ADP to make ATP ADP + P ATP

• Yield = 32-34 ATP molecules

So far…

8

What if there’s no Oxygen?

• O2 can’t act as final electron acceptor

• ETC can’t happen• Can still get 2 ATP from glycolysis (doesn’t

require O2)

What if there’s no Oxygen?

• Can generate 2 ATP• Makes 2 NADH

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

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

• Lactic Acid Fermentation• Ethanol Fermentation

Anaerobic RespirationLACTIC ACID FERMENTATION

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

(lactic acid)

Anaerobic RespirationAlCOHOL FERMENTATION

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

(ethyl alcohol)

Anaerobic Respiration

Lactic Acid Fermentation Alcohol Fermentation

Why we like fermentation

Often used by bacteria to make tasty foodies

• Used for thousands of years• 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: Hydrolyze fatty acids off of glycerolGlycerol glycolysisFatty Acids broken into 2-C pieces and sent to TCA

1 g fat yields 2x ATP as 1g starch

Other Organic Molecules as Fuel for Cellular Respiration

Proteins: Hydrolyze to amino acids, build more proteinsCan be used in glycolysis or TCA

Biosynthesis of Molecules

• ATP provides power for biosynthetic reactions

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