CHAPTER 9 - AP BIOLOGY

Anabolic

• Small molecules are ASSEMBLED INTO LARGE ONES.

• Energy is required

Catabolic

• Larger molecules are BROKEN DOWN INTO SMALL ONES

• Energy is released

Fermentation (Catabolic Reaction)

The partial degradation of sugars that occurs without the use of oxygen.

Aerobic Respiration (Catabolic Reaction)

The most prevalent and effcient catabolic pathway in which oxygen is consumed along with the organic fuel

What is the Organic Fuel?

• Carbohydrates, fats, and proteins can all be used to release energy

• Glucose is the primary source of energy

Oxidation

Lose e = Lost of energy

Reduction

Gain e = Gain of energy

Electron Carriers

• Carry energy to one location to another

• NAD+

• FAD

NAD+ (Electron Carrier)

• Coenzyme derived form the vitamin niacin

  • NAD+ (doesn't have the energy with it) ----> NADH (has energy with it)

FAD (Electron Carrier)

• Coenzyme derived from riboflavin ( a B vitamin)

  • FAD (doesn't have electrons) ----> FADH2

Three Stages of Cellular Respiration

• Glycolysis

• Pyruvate oxidation and Citric Acid Cycle

• Oxidative Phosphorylation (electron transport and chemiosmosis)

Phosphorylation

• Substrate-Level Phosphorylation

• Oxidative Phosphorylation

Substrate-Level Phosphorylation

• Make ATP when a phosphate group from a substrate is transferred to ADP

Oxidative Phosphorylation

Make ATP by using energy from redox reactions (90% of ATP) - EX. Electron Transport Chain

Glycolysis (Cellular Respiration - Stage 1)

• "sugar splitting"

• Glucose (6 C sugar) is broken down into 2 molecules of pyruvate (3 C)

• Occurs in the cytosol

• No O2 required

• Energy Investment - 2 ATP - Glucose

• Energy Payoff - 2 pyruvate molecules (3 C) - 4 ATP via substrate - 2 NADH and 2 H+ ions - 2 molecules of water

Pyruvate Oxidation (Cellular Respiration - Stage 2)

• CO2 is produced (1)

• NADH and H+ is produced (1)

• Pyruvate ----> Acetyl CoA (1) NOTE* 2 pyruvate = the above x2

Citric Acid Cycle (Krebs)

• Occurs in mitochondria matrix

• Net gain per pyruvate molecule

  • 1 ATP (produced through substrate level phosphorylation)

  • 3 NADH + 3H+ (electron carrier)

  • 1 FADH2 (electron carrier)

  • 2CO2

Oxidative Phosphorylation (Cellular Respiration - Stage 3)

• Electron Transport Chain

• Chemiosmosis

Electron Transport Chain (ETC)

• Collection of molecules (mostly proteins) embedded in the inner membrane of the mitochondria

  • In prokaryotic cells, molecules are in the cell membrane

• The electrons from NADH & FADH2 are passed from one electron carrier to the next.

• Electron carriers alternate between reduced/oxidized states as accept / donate e - Each component becomes reduced when it accepts electrons from its "uphill" neighbor (gains energy) - Returns to it oxidized form when passes electrons to its "downhill" neighbor (loses energy)

• Does NOT make ATP directly

• The loss of energy by e is used to power proton pumps

• At the end of the e - chain, O2 acts as the final acceptor

Chemiosmosis

• Mechanism that uses energy stored in the form of a H+ gradient to perform work

Proton-Motive Force

• A force that uses the proton (H+) gradient to perform work

ATP Synthase

• Transmembrane channel protein

• Makes ATP by harnessing proton - motive force

• Use energy from proton H+ gradient (the flow of H+ back across the membrane) to power ATP synthesis

Anaerobic Respiration

• Certain prokaryotes

• Generate ATP without oxygen - Use other electron acceptors - Sulfate (SO4), nitrate, sulfur

• Still use and electron transport chain EX. Sulfate reducing bacteria

Fermentation

• Keeps glycolysis going by regenerating NAD+

  • ATP is made during glycolysis by substrate-level phosphorylation

• Does NOT use and electron transport chain EX. Facultative anaerobes

• Occurs in the cytosol

• Creates ethanol and (CO2) or lactate

• 2 ATP (glycolysis)

• Without Oxygen

Alcohol Fermentation

• Pyruvate ----> Ethanol (ethyl alcohol + CO2)

• Intermediate is reduced by NADH EX. Some bacteria and yeast

• Used in brewing, wine making, and baking

Lactic Acid Fermentation-

• Pyruvate ----> Lactate

• Pyruvate is reduced by NADH EX. Some fungi, bacteria, human muscle cells

• Used to make cheese, yogurt, and acetone

Respiration (Glycolysis)

• With Oxygen

• Release energy from breakdown of food

• Occurs in mitochondria

• Produces CO2, H2O

• And up to 30 ATP

Organisms - Facultative Anaerobes

• Make ATP by aerobic respiration if oxygen is present

• Can switch to fermentation under anaerobic conditions (at cellular level) EX. Yeasts and many bacteria, human muscle cells

Organism - Obligate Anaerobes

• Only carry out fermentation or anaerobic respiration

• Cannot survive in the presence of oxygen EX. Some bacterial species

Various Sources of Fuel

• Carbs, fats, and proteins call ALL be used as fuel for respiration

• Monomer enter glycolysis or citric acid cycle at different points

Phosphofructokinase

• Allosteric enzyme that controls rate of glycolysis and citric acid

• Receptors for inhibitors and activators

• Inhibited by high levels of ATP & Citrate

• Stimulated by AMP

• "Pacemaker" of respiration