Chapter 9 Cellular Respiration Production of ATP Pages: 162-182

Main Topics Anaerobic Respiration vs Aerobic Respiration Glycolysis & Fermentation (Anaerobic) Formation of Acetyl Coenzyme A Citric Acid Cycle (Kreb cycle) Electron Transport Chain & Chemiosmosis

Introductory Questions #8 How does aerobic and anaerobic respiration differ? What are the four main stages of aerobic Respiration? Write the chemical equation for cellular respiration. How can you tell which one is oxidized and what is reduced? Within a Eukaryotic cell, where does glycolysis take place? What about the citric acid cycle? List the ten enzymes needed for each conversion in the glycolytic process. (pg 166-167) What do Kinase enzymes do?

Introductory Questions #9 Name the two enzymes that are responsible for making ATP via substrate level phosphorylation during glycolysis. Which Enzyme splits the sugar molecule in the first part of glycolysis? What is so special about a Facultative Anaerobe? Give an example of one. Define what a strict and obligate anaerobe are? What is the main purpose of fermentation? Explain how alcoholic fermentation is different from lactic acid fermentation. What are two fates of Pyruvic acid?

Two Types of Respirations Anaerobic: -Most primative metabolic pathway -Produces two ATP’s per molecule of glucose -Main pathway in prokaryotic cell (bacteria) -Final electron acceptor is an inorganic molecule (nitrate or sulfate) Fermentation Aerobic: -Requires molecular oxygen (O2) = final electron acceptor -Produces up to 38 ATP’s per glucose molecule -Occurs in Eukaryotic cells within the mitochondria -Most common metabolic pathway

Pyruvate → Acetyl Coenzyme A Aerobic Respiration C6H12O6 + 6O2  6 H2O + 6 CO2 + Energy G = -686 kcal (2879.2 kJ) One ATP molecule has a G of -7.6 kcal/mol C6H12O6 – Oxidized O2 – Reduced Begins with: Pyruvate will be oxidized as it enters into the mitochondria to form Acetyl Coenzyme A. NADH is also produced. Pyruvate → Acetyl Coenzyme A

Efficiency of Cellular Respiration

Two methods of Producing ATP Substrate Level Phosphorylation (SLP) -Simplest way to make ATP -Requires no membrane -Uses a large enzyme: Kinase -Present in Anaerobic Respiration Chemiosmosis -Discovered by Peter Mitchell (1978) -Aerobic Respiration (mitochondria) -Requires a “Proton gradient” to be generated

Substrate Level Phosphorylation & Chemiosmosis Kinase

Redox Nature of Cellular Respiration Oxidizing agent Reducing Agent

Overview of Aerobic Respiration in Eukaryotic Cells

Four Stages of Respiration Glycolysis & Fermentation (SLP) Formation of Acetyl Coenzyme A Citric Acid Cycle (Kreb Cycle) Electron Transport Chain (Chemiosmosis)

Glycolysis Literally means “sugar-splitting” First metabolic pathway to evolve Does not require oxygen Can occur under anaerobic or aerobic respiration Observed in all cells Occurs in the cytosol (cytoplasm) of the cell Net profit of two ATP molecules via SLP

Key molecules of Glycolysis Start with: One molecule Glucose (six carbons) Two molecules of ATP Two molecules of NAD+ Two ADP and inorganic phosphates Enzymes for each step Dehydrogenase (for SLP) End with: Two Pyruvate molecules (three carbons each) Two ATP molecules (net) Two NADH molecules

Glycolysis: Overview

First Phase of Glycolysis-Use of 2 ATP’s Enzymes you need to know 1. hexokinase (1st ATP phosphorylates glucose) 2. Phosphoglucoisomerase (glucose into fructose) 3. phosphofructokinase (2nd ATP phosphorylates fructose) 4. aldolase (splits fructose into two 3 carbon sugars) DHAP 5. isomerase (converts Dihydroxyacetone (DHAP)into G3P)

Summary of First Phase of Glycolysis Glucose ↓ Fructose 1,6 Bisphosphate Glyceraldehyde-3-phosphate (x2) Enzymes involved: Phosphoglucoisomerase Hexokinase Phosphofructokinase Isomerase Aldolase **Put them in sequential order **What happens next?

NAD+ and NADH (pg. 163) Two e’s and one H+ are gained

Second Phase of Glycolysis-Energy Payoff Enzymes you need to know 6. Dehydrogenase Enzyme NAD+ (hydrogen acceptor from G3P) 7. Phosphoglycerokinase ADP to ATP via SLP 8. Phosphoglyceromutase (rearrangement) 9. (Enolase) 10. (Pyruvate Kinase) ADP to ATP via SLP

Summary of Chemical Changes-2nd Phase Glyceraldehyde-3-phosphate (x2) ↓ Enzyme #6 Phosphoglycerate (NAD+----NADH) ↓ 1,3-bisphosphoglycerate ↓ Enzyme #7 3-Phosphoglycerate ↓ Enzyme #8 2-phosphoglycerate ↓ Enzyme #9 Phosphoenolpyruvate (PEP) ↓ Enzyme #10 Pyruvate

Glycolysis end result End Result: 4 ATP’s made Two used initially (net = 2) 2 Pyruvate molecules (3 carbons) 2 NADH ‘s made 2 water molecules released

Overall Energetics of Glycolysis