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Cellular Respiration

Filename: Respire.ppt

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Lecture Outline

• Using Chemical energy to drive metabolism• Production of ATP• Cellular respiration

– Clycolysis– Krebs cycle– Electron transport – Chemiosmosis

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Lecture Overview

• All organisms drive their metabolism with ATP generated from

• Rearrangement of chemical bonds • Energetic electrons from proton pumps• Electrons from photosynthesis • Electrons from oxidation of sugars and fats

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Background Terms & Concepts

• Glucose• Chemiosmosis• Oxidation- reduction• ATP• Exergonic vs endergonic reactions

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Concepts from OAC

• Synthesis of ATP• Glycolysis: Krebs cycle• anaerobic vs aerobic glucose catabolism• Energy from fats & proteins

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Energy Flow & Recyling

Energy Poor

Energy Rich

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Cellular Respiration

• Release of energy stored in organic compounds

– Carbohydrate– Fats– Proteins (net energy loss)

• Oxygen is consumed as a reactant• Carbon dioxide and water are byproducts• Energy is used indirectly

– trapped as ATP

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Pathways in Cellular Respiration

• Glycolysis• Krebs cycle• Electron transport chain

Cellular RespirationCumulative function of three

metabolic pathways and chemiosmosis

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Catabolism of various foods

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Overview of Cellular RespirationA room of your own...

ATP ATPATP

Glycolysis occurs whether or not oxygen is

present

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Glycolysis

• OCCURS in the CYTOPLASM• Glucose (6 carbon sugar) >>>

2 pyruvate (3 carbon sugar)• Energy investment phase• Energy yielding phase• Net yield of energy

No Carbon dioxide is released No Carbon dioxide is released during glycolysisduring glycolysis

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Electron Transport

System

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Glycolysis

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Glycolysis: Energy Investment

• Glucose + ATP-> glucose-6-P + ADP– hexokinase

• Glucose-6-P -> Fructose-6-P– phosphoglucoisomerase

• Fructose-6-P + ATP -> Fructose 1,6, diphosphate + ADP– phosophofructokinase

• Fructose 1,6,diphosphate -> glyceraldehyde phosphate + dihydroxyacetone phosphate– aldolase

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Energy Investment Phase

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More ATP investment

ATP Investment

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Isomerization

• glyceraldehyde phosphate & dihydroxyacetone phosphate are isomers– Isomerase interconverts– glyceraldehyde phosphate removed next as

next step

• THUS Equilibrium between the two sugars is in direction of glyceraldehyde phosphate

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Glycolysis: Energy Yield Phase

• Glyceraldehyde-P + 2NAD+ +2Pi ->

1,3 glycerophosphate + 2 NADH + 2 H+• !,3 glycerophosphate + 2ADP -> 3 phosphoglycerate + 2 ATP• Relocate phosphate group• Remove water to create phosphoenolpyruvate• Remove phosphate from PEP• PEP + 2ADP -> pyruvate + 2ATP

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The first payoff (substrate-level phosphorylation)

Substrate level Phosphorylation

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More dividends (substrate-level phosphorylation)

More Energy Payoff

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Glycolysis: Net Energy Yield

• Glucose >>> 2 pyruvate• 2 ADP >>> 2 ATP• 2 NAD+ >>> 2NADH

NADH>>> electron transport chain NADH>>> electron transport chain if oxygen is presentif oxygen is present

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Alternate Glycolytic Pathway• Glycolysis• Embden-Meyerhof• Glucose>> glucose-6

phosphate• Fructose-6 phosphate• Fructose 1,6 diphosphate• ISOMERS

– dihydroxyacetone phosphate

– Glyceraldehyde 3 P

• Alternate• Enter-Doudoroff• Glucose>> glucose-6

phosphate• 6 phosphogluconic acid• Keto deoxy 6 phoshogluconic

acid• pyruvic acid + Glyceraldehyde

3 P

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Pyruvate

Fermentation

Oxidativephosphorylation

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Role of Pyruvate

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Formation of Acetyl CoA

• Pyruvate translocated from cytoplasm to mitochrondial matrix

• Pyruvate + NAD+ -> Acetate + NADH + CO2

• Acetyl group attached to Coenzyme A

Acetyl CoA links glycolysis to the Krebs cycle

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Formation of Acetyl CoA

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Krebs cycle• oxidation of pyruvate generated by glycolysis

– glucose->2 pyruvate• Generates 1 molecule of ATP/ pyruvate

– substrate level phosphorylation• Generates 4 molecules of NADH / pyruvate• Generates 1 molecule of FADH2/ pyruvate • Generate 3 molecules of carbon dioxide

• OCCURS in MITOCHONDRIAL MATRIX• occurs in prokaryotic cytoplasm

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Krebs cycle

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Summary of Krebs Cycle

IN

IN

IN

IN

Out

Out

Out

Out

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Krebs Cycle Balance Sheet

• Input• Water• ADP• NAD+• FAD+• Acetyl CoA

• Output• Carbon Dioxide• ATP• NADH• FADH