Cellular Respiration

LEOxidized and GEReduced

H+ + e- -Therefore H atoms are removed electrons are also removed.

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energy

glucose

Reduction

Oxidation

6H2O6CO26O2C6H12O6 + ++

NAD+ and FAD

• Coenzyme of oxidation-reduction

• Electron Carriers

Cellular Respiration

• Glycolysis• Prep Phase (acetyl CoA)• Citric Acid Cycle (Kreb’s Cycle)• Electron Transport Chain (ETC)

An overview of cellular respiration (Layer 1)

Glycolysis

Glucose is broken down into two molecules of pyruvate

• Occurs in the cytoplasm• ATP is formed• Does not use oxygen

Glycolysis

Takes place in the cytoplasm

NAD+

What’s Happened so far?Glycolysis

O2

Used?

Glucose C now Product:

ATP

#

NADH

#

Glycolysis No 2 Pyruvates 2 2

pyruvate

pyruvate

glucose

Pyruvate as a key juncture in catabolism

If O2 is NOT available

• Fermentation, an anaerobic process, occurs in the cytoplasm. During fermentation, glucose is incompletely

metabolized to lactate, or to CO2 and alcohol (depending on the organism).

Fermentation Helps Produce Numerous Food Products

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Alcoholic Fermentation

Pyruvate + NADH

Ethanol + CO2 + NAD+

Vinegar

Lactic Acid Fermentation

Pyruvate + NADH

Lactic Acid + NAD+

If O2 is available

• Preparatory (prep) reaction, a aerobic process, occurs in the mitochondria.

• Occurs in mitochondria • Two carbons are released as CO2 (one from each

pyruvate)

14

What’s Happened so far?Krebs CycleOriginal C of glucose are

now

ATP NADH FADH2

Glycolysis 2 pyruvate 2 2

Acetyl CoA formation

2 CO2

& 2 acetyl CoA

2

Krebs Cycle

Total

glucose

An overview of cellular respiration (Layer 2)

Citric acid cycle

• Occurs in the matrix of the mitochondrion and produces NADH and FADH2

• Releases 4 carbons as CO2

• Produces 2 ATP molecules

17

What’s Happened so far?Krebs CycleOriginal C of glucose are

now

ATP NADH FADH2

Glycolysis 2 pyruvate 2 2

Acetyl CoA formation

2 CO2

& 2 acetyl CoA

2

Krebs Cycle 4 more CO2 2 6 2

Total 6 CO2 4 10 2

glucose

An overview of cellular respiration (Layer 3)

Mitochondrion Structure and Function

20© Dr. Donald Fawcett and Dr. Porter/Visuals Unlimited

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Cristae: locationof the electrontransportchain(ETC)

Matrix: locationof the prepreaction and thecitric acid cycleouter

membrane

innermembrane

intermembranespace

cristaematrix

45,0003X

Organization and Function of the Electron Transport Chain

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2

O212+

2

P

H+

e :

e :

Electron transport chain

high energyelectron

ATPchannelprotein

Intermembranespace

ATPsynthasecomplex

low energyelectron

cytochromeoxidase

cytochrome c

NADH-Qreductase

cytochromereductase

coenzyme Q

NADH

Matrix

FADH2 FAD+

NAD+

2

e-

2 ADP ATP32 ADPor 34

4 ADP

netATP

4 ATP total

2ADP

2ATP

Glycolysis

glucose pyruvatePreparatory reaction

Citric acidcycle

Electron transportchain and

chemiosmosis

NADH andFADH2

NADH

NADHe-

e-

e-e-

e-

e-

32 or34

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+H+

H+

H+

H+

ATP ADPH2O

H+

H+

H+

H+

H+

H+

H+

H+

H+H+H+

H+

H+

H+H+

H+

H+

ATPChemiosmosis

Electron Transport Chain (ETC)

• Extracts energy from NADH & FADH2

• Passes electrons from higher to lower energy states

• Produces 32 or 34 molecules of ATP

Max of 36 ATP per Glucose

Substrate-level ATP SynthesisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

P

P

P

enzyme

ADP

ATP

BPG

3PG

Inside the Mitochondria

• Electron Transport Chain (ETC)• Location:

Eukaryotes: cristae of the mitochondria Aerobic prokaryotes: plasma membrane

• The electron transport chain Receives electrons from NADH & FADH2

Produces ATP by oxidative phosphorylation

• Oxygen serves as the final electron acceptor Oxygen combines with hydrogen ions to form water

*H+ is pumped against its gradient into the mitochondrial matrix

*Energy for active transport comes from electrons

Inside the Mitochondria

• Energy yield from glucose metabolism: Net yield per glucose:

• From glycolysis – 2 ATP

• From citric acid cycle – 2 ATP

• From electron transport chain – 32 or 34 ATP

Energy content:• Reactant (glucose) 686 kcal

• Energy yield (36 ATP) 263 kcal

• Efficiency is 39%

• The rest of the energy from glucose is lost as heat

Energy rich molecules: carbohydrates, fats, and proteins

Catabolism: Break down molecules usually exergonic (release energy)

Anabolism build molecules: usually endergonic (consume energy)

29

ATP

ATP

Electrontransportchain

proteins carbohydrates fats

aminoacids

glucose fattyacids

glycerol

acetyl CoA

Glycolysis

pyruvate

ATPCitricacidcycle

Photosynthesis vs. Cellular Respiration

30

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O2

O2

enzymesgranaPhotosynthesis

NADP+

CH2O

NADPH

CO2

enzyme-catalyzedreactions

NADH

enzymes

H2O

membrane

ATP productionvia chemiosmosis

ADP ATP

H2O

membrane

Cellular RespirationNAD+

cristae

CH2O CO2