Download ppt - Fig. 9.1 Respiration. Cellular Energy Harvest: an Overview Stages of Aerobic Cellular Respiration –Glycolysis –Oxidation of Pyruvate –Krebs Cycle –Electron

Fig. 9.1

Respiration

• Cellular Energy Harvest: an Overview

• Stages of Aerobic Cellular Respiration– Glycolysis– Oxidation of Pyruvate– Krebs Cycle– Electron Transport Chain

• Anaerobic Respiration and Fermentation

• Catabolism of Protein and Fat

Outline – Cellular Respiration

• Autotrophs – use inorganic sources of energy

• Photoautotrophs– harvest sunlight – convert radiant energy into chemical energy.

• Heterotrophs – use organic sources of energy– live off the energy produced by autotrophs.– extract energy from food catabolism

Energy to Drive Metabolism

Cellular Respiration

• How do cells harvest energy – cells break chemical bonds– shift electrons from molecule to molecule

• Where do the electrons go?– Aerobic respiration

• final electron acceptor is oxygen

– Anaerobic respiration • final electron acceptor is not oxygen• Fermentation - final electron acceptor is an

organic molecule

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

Glucose molecules broken down to CO2

Glucose loses electrons (as hydrogen atoms) to oxygen

Cells tap energy from electrons

Cells bank energy in ATP

C6H12O6 6 O2 6 CO2 6 H2O

Loss of hydrogen atoms (oxidation)

Gain of hydrogen atoms (reduction)

Energy

(ATP)

Glucose

+ + +

Cellular Aerobic Respiration


Oxidation - Dehydrogenase removes electrons from substrate

Reduction - Electrons in Hydrogen Transferred to NAD+

OH H O 2H

Reduction

Dehydrogenase (Enzyme)

(carries2 electrons)

NAD 2H

2H 2e

NADH H

Oxidation

+

+

+

+

Transferring Energy


H2O

NAD

NADH

ATP

H

H

Controlled release of energy for ATP

synthesis

Electron Transport

Chain

O2

2e

2e

1. NADH passes electrons to an electron transport chain

2. Energy is released as electrons “fall” and lose energy

Transferring Energy – Electron Transport Chain

Fig. 9.5 (TEArt)

Mitochondrion

Krebscycle

Glucose

Glycolysis

Pyruvate

Acetyl-CoA

ATP

ATP

ATP

NADH

NADH

NADH

FADH2

Electrontransport chain

H2O

CO2

NAD+ and FAD

Mitochondrial matrix

Inner mitochondrial membrane

Cytoplasm

Intermembranespace

e-

Pyruvateoxidation

CO2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Aerobic Cellular Respiration – Overview

1. Glycolysis

2. Pyruvate oxidation

3. Krebs (Citric Acid) Cycle

4. Electron Transport Chain

Fig. 9.6 (TEArt)

Aerobic Respiration Stage 1: Glycolysis1 2 3

(Starting material)

6-carbon sugar diphosphate

6-carbon glucose

2

P P

6-carbon sugar diphosphate

P P

3-carbon sugarphosphate

P P P P

Priming reactions.

3-carbonpyruvate

2

NADH

ATP

ATP 2

NADH

ATP

Cleavage reactions. Energy-harvesting reactions.




3-carbonpyruvate


Fig. 9.7a (TEArt)

Pi

3

6

4,5

ADP

NAD+

Glucose

Glycolysis

Pyruvateoxidation

Krebscycle

Electron transportchain

Glucose

Hexokinase

Phosphoglucoseisomerase

Phosphofructokinase

Glyceraldehyde 3-phosphate (G3P)

Dihydroxyacetonephosphate

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Isomerase

Glyceraldehyde3-phosphate

dehydrogenase

Aldolase

1,3-Bisphosphoglycerate(BPG)


1. Priming

4–5. Six-carbon molecule split into 2 three-carbon moleculesone G3P & dhap which is converted to G3P

1

2

ATP

ADP

ATP

NADH

NAD+

NADH6. Oxidation followed byphosphorylation produces two NADH molecules andtwo molecules of BPG, each with one high-energyphosphate bond.

Pi

P O CH2

C O

CH2OH

P O

CH2 O P

O

CHOH

C

CH2 O P

O

CHOH

CH2 O PO

CH2OP

O

PO

CH2

H

CH2OHO

CH2 POO

CH2OH


Glycolysis - Steps

2. Cleavage

1. Priming

3. Energy HarvestC

Fig. 9.7b (TEArt)

7

8

H2O9

10

ADP

ATP3-Phosphoglycerate

(3PG)3-Phosphoglycerate

(3PG)

2-Phosphoglycerate(2PG)

2-Phosphoglycerate(2PG)

Phosphoenolpyruvate(PEP)

Phosphoenolpyruvate(PEP)

Pyruvate

7. Removal of high-energy phosphate by two ADP molecules produces twoATP molecules and leaves two 3PG molecules.

Phosphoglyceratekinase

Phosphogly-ceromutase

Enolase

Pyruvate kinase

ADP

ATP

ADP

ATP

ADP

ATP

8–9. Removal of water yields two PEP molecules, each with a high-energy phosphate bond.

10. Removal of high-energyphosphate by two ADPmolecules produces twoATP molecules and twopyruvate molecules.

H2O

CH2OH

CH3

CH2

O-

O

C

PH

CHOH

O-

O-

O-

C

C

C

C

C

C

P

P

O

O

O

O

O

O

CH2


Glycolysis - Steps3. Energy Harvest

3. Energy Harvest

Pyruvate


Catabolic pathway with 3 major events 1. Priming2. Cleavage3. Energy Harvesting

Substrate-level phosphorylation

Nets two ATP molecules

Universal: All living organisms

Glycolysis - Summary

Aerobic Respiration Stage 2Oxidation of Pyruvate

1. Releases CO2 2. Produces NADH and acetyl Coenzyme A3. Acetyl CoA is transferred to the mitochondrion

Aerobic Respiration Stage 3: KREBS CYCLE

Mito

chon

drio

n

Krebs Cycle Summary

1. Location: Mitochondrial matrix

2. Loss of 2 CO2 = completion of pyruvate oxidation

3. ATP synthesis

4. Reduction of Coenzymes…for each turn of cycle: 3 NAD+ 3 NADH… or 6 for each glucose 1 FAD 1 FADH2 …or 2 for each glucose


Mitochondrion Structure

OuterMembrane

InnerMembrane

Cristae

Matrix

Intermembrane Space


1.Electron Flow occurs in mitochondrial membrane

2.Protons are transported across the inner mitochondrial membrane

3.ATP is synthesized by Chemiosmosis

Intermembrane space

Inner mitochondrial membrane

Mitochondrial matrix

Protein complex Electron

carrier

NAD+

FAD

H2O ATPADP

ATP synthase

H+ H+ H+

H+

H+ H+

H+H+

H+

H+

H+

H+

H+

H+

P

O2

Electron Transport Chain Chemiosmosis

.

OXIDATIVE PHOSPHORYLATION

+ NADH

FADH2

H+ H+

Stage 4: Oxidative Phosphorylation


1. Occurs in the mitochondria

2. Uses the energy released by electrons to pump H+ across a membrane

3. Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP

Stage 4: Oxidative Phosphorylation

Oxidation-Reduction and Aerobic Respiration

– With continuous Glycolysis • NADH Increases• NAD+ Decreases

– NADH must be recycled into NAD+

Recycling NADH

Fermentation: Recycling NADH

22

Summary: Respiration without oxygenSummary: Respiration without oxygen

1. Glycolysis produces a net of 2ATP 1. Glycolysis produces a net of 2ATP 2. Fermentation - 2. Fermentation - recycles NADH to NADrecycles NADH to NAD++

Lactic acid fermentationLactic acid fermentation

COCO22 and Ethanol fermentation and Ethanol fermentation

3. Anaerobic Respiration3. Anaerobic RespirationMethanogensMethanogens

COCO22 CH CH44

Sulfate-reducing BacteriaSulfate-reducing Bacteria

SOSO44 H H22SS

2

2 6 ATP

Pyruvate

Glucose

Acetyl-CoANADH

2 4 ATPNADH

2 ATP

2 ATP

6 18 ATPNADH

2 4 ATP

Total net ATP yield = 36 ATP

FADH2

Krebscycle

ATP Glycolysis


Respiration Efficiency

Fig. 9.20 (TEArt)

Macromolecules

Cellbuilding blocks

Nucleicacids Proteins FatsPolysaccharides

Nucleotides Aminoacids

FattyacidsSugars

NH3 H2O CO2

Oxidativerespiration

Metabolic Waste

products

Pyruvate

Acetyl-CoA

Krebscycle


Energy Sources for Cellular Respiration

END

Respiration