Ch 6

Cellular Respiration

Energy for lifeECOSYSTEM

Photosynthesisin chloroplasts

Glucose

Cellular respirationin mitochondria

H2O

CO2

O2

(for cellular work)

ATP

Heat energy

Breathing vs Cellular Respiration

• Breathing- gas exchange• Cellular respiration- aerobic harvesting of

energy from food molecules by cells

Cellular Respiration• Energy stored in ATP

C6H12O6 + 6 O2

Glucose Oxygen

6 CO2

Carbondioxide

+ 6 H2O

Water

+ ATPs

Energy

Cell Respiration

Redox

• Oxidation- loss of e-• Reduction- addition of e-

Loss of hydrogen atoms(oxidation)

6 CO2 + 6 H2O + Energy

Gain of hydrogen atoms(reduction)

(ATP)C6H12O6 + 6 O2

Glucose Oxidation• Significant in oxidation f Glucose

– Dehydrogenase– NAD+--coenzyme, electron carrier molecule

• Becomes NADH• ***FADH

2 H+ + 2 e–

Oxidation

Dehydrogenase

ReductionNAD+ + 2 H NADH+ H+

(carries2 electrons)

Electron Transport Chain• NADH transfer e-

to ETC• Redox reactions as

e- travel through chain

• O2 final e- acceptor

• Energy released at each step

ATPNAD+

NADH

H+

H+2e–

2e–

Electron transport

chain

Controlledrelease ofenergy forsynthesis

of ATP

+

O2

H2O

12

Cell Respiration

Glycolysis

• Splits sugar• Breaks Glucose from 6- C

sugar into two 3- C sugars• Yields 2 pyruvate

molecules – Net gain of 2 ATP, 2

NADH, 2 H2O

Glucose

NAD++ 2

2 ADP

NADH2

P2

2

ATP2+

H+

2 Pyruvate

Glycolysis• Substrate-level phosphorylation

– Transfer of P from substrate to ADP to become ATP

• Energy banked in ATP and NADH

ADP

ATP

Enzyme

Product

Enzyme

P

P

PSubstrate

Glycolysis

• 3 “phases”– Energy consuming– Glucose split– Energy producing

• G3P is significant intermediate– Glyceraldehyde-3-phosphate

Steps – ATP and pyruvateare produced.

Step A redox reactiongenerates NADH.

Step A six-carbon intermediate splitsInto two three-carbon intermediates.

Steps – A fuel molecule is energized,using ATP.

Fig. 6-7cENERGY INVESTMENT

PHASEGlucose

Glucose-6-phosphate

1

Fructose-6-phosphate

Step

ADP

ATP

P

3

ADP

ATP

P

2

P

4

P Fructose-1,6-bisphosphate

5 5

PP

P

P

P

P

NAD+

PP

ENERGY PAYOFF PHASE

Glyceraldehyde-3-phosphateGlyceraldehyde-3-phosphate(G3P)(G3P)

1,3-Bisphosphoglycerate

NADH

NAD+

NADH

+ H+ + H+

ADP ADP

ATP ATP6 6

3-Phosphoglycerate

2-Phosphoglycerate

7 7

8 8

P P

P P

P P

H2O H2O

ADP ADP

ATP ATP

9 9

Phosphoenolpyruvate(PEP)

Pyruvate

1 3

4

5

6 9

Pyruvate

• Cannot enter Citric Acid Cycle directly• 3 reactions take place

1. Carboxyl group removed, given off as CO22. Remaining 2-C compound oxidized, NAD+

reduced (2 NADH formed)3. Coenzyme A combines with 2-C compound to

form Acetyl Coenzyme A

Formation of Acetyl CoA

Coenzyme A

CoA

NAD+ NADH H+

CO2

13

2

Acetyl coenzyme APyruvate

Cell Respiration

Krebs Cycle

• AKA the Citric Acid Cycle– Mitochondrial matrix

• Starts with Acetyl Coenzyme A– Only Acetyl part joins cycle (2-C)– Coenzyme A is recycled

• Nets 2 CO2, 3 NADH, 1 FADH2 and 1 ATP per turn– 1 glucose=2 pyruvate=2 Acelty CoA=2 turns Kreb

Cycle

Krebs Cycle

Cell Respiration

Oxidative Phosphorylation

• Stage where most ATP is produced– Membrane of mitochondria

• 2 parts– ETC– Chemiosmosis

• ETC creates gradient• Chemiosmosis uses gradient to generate ATP

ATP

H+

Intermembranespace

O2

H2O

12

Innermitochondrialmembrane

H+NAD+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

Mitochondrialmatrix

Electronflow

Electroncarrier

Proteincomplexof electroncarriers

NADH

FADH2FAD

ATPsynthase

PADP +

Chemiosmosis

+ 2

OXIDATIVE PHOSPHORYLATION

Electron Transport Chain

Oxidative Phosphorylation

Overall

• Start with 1 glucose molecule– Split into 2 pyruvate in Glycolysis– Yields 2 ATP, 2 NADH, 2 H20

• 2 Pyruvate converted to 2 Acetyl CoA– Yields 2 NADH

• Acetyl CoA enters Kreb Cycle– Yields 2 ATP, 6 NADH, 2 FADH (per glucose)

• Oxidative Phosphorylation– Yields 34 ATP

ATP yieldCytoplasm

Glucose

FADH2

Mitochondrion

Maximum per glucose:

OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)

CITRIC ACIDCYCLE

Electron shuttleacross membrane

2NADH

2 NADH

2NADH

6 NADH 2

(or 2 FADH2)

2 AcetylCoA

GLYCOLYSIS2

Pyruvate

About38 ATP

about 34 ATP

by substrate-levelphosphorylation

by oxidative phosphorylation

2 ATP

by substrate-levelphosphorylation

2 ATP

Stopping the chain• Poisons can act during Oxidative

Phosphorylation– Rotenone

• Blocks ETC by binding to e- carrier molecules– Cyanide, CO

• Blocks ETC by binding to e- carrier molecules• O2 cannot accept e-

– Oligomycin• Blocks ATP synthase

– Uncouplers (DNP)• Creates leaky membrane

Fig. 6-11

ATP

H+

O2

H2O

12 H+

NAD+NADH

FADH2FAD

PADP +

Chemiosmosis

+ 2

Electron Transport Chain

H+

H+H+

H+

Rotenone Cyanide,carbon monoxide

H+ H+

Oligomycin

ATPsynthase

DNP

H+

H+

H+

Alternate Pathways

• Aerobic v Anaerobic• Obligate anaerobes• Facultative anaerobes

Fermentation

• Anaerobic– Allows cells to generate ATP in absence of O2

• Regenerates NAD+ to break down glucose• Only yields 2 ATP• Lactic Acid in animal muscles• Ethanol in bacteria and yeast

FermentationGlucose

NADH

NAD+

2

2 2 ADP

P

ATP2

NADH

2

NAD+

2

2 ADP

P

ATP2

2 Pyruvate

2 Lactate

GL

YC

OL

YS

IS

GL

YC

OL

YS

IS

NADH

NAD+

2

2

NADH2

NAD+2

2 Pyruvate

2 Ethanol

Glucose

CO22

released

2 2

We eat more than just glucose

• Different foods enter the process at different stages

• Typically broken down before entering cycles

Fig. 6-15

Food, such aspeanuts

ProteinsFatsCarbohydrates

Glucose

OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)

CITRICACID

CYCLE

AcetylCoA

GLYCOLYSIS

Pyruvate

Amino acidsGlycerolSugars Fatty acids

Amino groups

G3P

ATP

• ETC• http://www.youtube.com/watch?v=Idy2XAlZIVA&fea

ture=related• http://www.youtube.com/watch?v=xbJ0nbzt5Kw• Glycolysis• http://www.youtube.com/watch?v=x-stLxqPt6E• Kreb• http://www.youtube.com/watch?v=aCypoN3X7KQ&f

eature=related• Overview• http://www.youtube.com/watch?v=iXmw3fR8fh0• Fermentation• http://www.youtube.com/watch?v=y_k8xLrBUfg