Chapter 9Cellular 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 #81. How does aerobic and anaerobic respiration differ?2. What are the four main stages of aerobic

Respiration?3. Write the chemical equation for cellular respiration.

How can you tell which one is oxidized and what is reduced?

4. Within a Eukaryotic cell, where does glycolysis take place? What about the citric acid cycle?

5. List the ten enzymes needed for each conversion in the glycolytic process. (pg 166-167)

6. What do Kinase enzymes do?

Introductory Questions #91) 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?

2) What is so special about a Facultative Anaerobe? Give an example of one. Define what a strict and obligate anaerobe are?

3) What is the main purpose of fermentation?4) Explain how alcoholic fermentation is different

from lactic acid fermentation.5) 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

Aerobic RespirationC6H12O6 + 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 mitochondriato form Acetyl Coenzyme A. NADH is also produced.

Pyruvate → Acetyl Coenzyme A

Efficiency of Cellular Respiration

Two methods of Producing ATP 1) Substrate Level Phosphorylation (SLP)

-Simplest way to make ATP-Requires no membrane-Uses a large enzyme: Kinase-Present in Anaerobic Respiration

2) 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

Reducing Agent

Oxidizing 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

1. hexokinase

3. phosphofructokinase

4. aldolase

5. isomerase

Enzymes you need to know

(1st ATP phosphorylates glucose)

2. Phosphoglucoisomerase (glucose into fructose)

(2nd ATP phosphorylates fructose)

(splits fructose into two 3 carbon sugars)

(converts Dihydroxyacetone (DHAP)into G3P)

DHAP

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

6. Dehydrogenase Enzyme

Enzymes you need to know

NAD+ (hydrogen acceptor from G3P)

7. PhosphoglycerokinaseADP 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