Overview of Cellular Respiration

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ATP Supplies Energy for Cellular Function

• What activities require ATP?

• Where does this energy come from?– Food and O2 are needed to make ATP.

• How does it work?

Figure 9.1

The big picture

• Photosynthesis light

6 CO2 + 12 H20 -------> C6H12O6 + 6 H20+6O2

• Cellular Respiration C6H12O6 + 6 H20+6O2 -----> 6 CO2 + 12 H20 +energy

The big picture

• Photosynthesis

6 CO2 + 12 H20 ---> C6H12O6 + 6 H20+6O2

• Cellular Respiration

C6H12O6 + 6 H20+6O2 -----> 6 CO2 + 12 H20

Figure 9.2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

CO2 H2O O2

Organicmolecules

ATP powersmost cellular workATP

Heatenergy

Catabolic Pathways and Production of ATP

• The breakdown of organic molecules is exergonic

• Fermentation is a partial degradation of sugars that occurs without O2

• Aerobic respiration consumes organic molecules and O2 and yields ATP

• Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

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Energy Procurement

• Chemical bonds are broken in small steps that maximize the energy that is made available to the cell from food.

• Energetic Electrons are not haphazardly thrown throughout the cell...

NADH and FADH2 ARE ELECTRON SHUTTLES

• NAD is reduced to NADH, FAD is reduced to FADH2

• These high energy e-s are carried to inner mitochondrial membrane to make ATP.

• Electron cascade-- e-s then pass down a complex of carriers on a membrane, releasing packets of energy in small increments.

• We talked about enzyme complexes (ch 8), this uses several. (see page 175, electron transport chain, ETC)

Figure 9.5

(a) Uncontrolled reaction (b) Cellular respiration

Explosiverelease of

heat and lightenergy

Controlledrelease ofenergy for

synthesis ofATP

Fre

e en

erg

y, G

Fre

e en

erg

y, G

H2 1/2 O22 H 1/2 O2

1/2 O2

H2O H2O

2 H+ 2 e

2 e

2 H+

ATP

ATP

ATP

Electro

n tran

spo

rt

chain

(from food via NADH)

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain• In cellular respiration, glucose and other organic

molecules are broken down in a series of steps

• Electrons from organic compounds are usually first transferred to NAD+, a coenzyme

• As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration

• Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP

© 2011 Pearson Education, Inc.

Figure 9.4

Nicotinamide(oxidized form)

NAD

(from food)

Dehydrogenase

Reduction of NAD

Oxidation of NADH

Nicotinamide(reduced form)

NADH

This is NAD+

Does this remindyou of anything?

Oxidation of Organic Fuel Molecules During Cellular Respiration

• During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced

© 2011 Pearson Education, Inc.

The Principle of Redox• Chemical reactions that transfer electrons

between reactants are called oxidation-reduction reactions, or redox reactions

• In oxidation, a substance loses electrons, or is oxidized

• In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced)

© 2011 Pearson Education, Inc.

2 ways to make ATP• Oxidative Phosphorylation-Proton gradient across

membrane stores potential energy. – This occurs alongside ETC– - Chemiosmosis-Protons pass thru ATP synthase to make

ATP

• Substrate level phosphorylation– Simpler, not membrane bound– Phosphate transferred from a substrate to ADP, forms ATP– GYCOLYSIS AND KREB’S

Aerobic Respiration occurs in four stages1) Glycolysis-

1) Glucose to pyruvate, in cytoplasm

2) Pyruvate Oxidation1) Pyruvate ---> Acetyl CoA, in Mitochondrial

Intermembrane Space

3) Citric Acid Cycle (same as Kreb’s Cycle)1) Acetyl CoA---> CO2, ATP, NADH, FADH2 in

Mitochondrial Matrix

4) Electron Transport Chain1) NADH, FADH2 ----> High Levels of ATP and water

Inner mitochondrial membrane

Figure 9.6-3

Electronscarried

via NADH

Electrons carriedvia NADH and

FADH2

Citricacidcycle

Pyruvateoxidation

Acetyl CoA

Glycolysis

Glucose Pyruvate

Oxidativephosphorylation:

electron transportand

chemiosmosis

CYTOSOL MITOCHONDRION

ATP ATP ATP

Substrate-levelphosphorylation

Substrate-levelphosphorylation

Oxidative phosphorylation

Where processes take place:

Figure 9.9-4

Glycolysis: Energy Investment Phase

ATP ATPGlucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate

Dihydroxyacetonephosphate

Glyceraldehyde3-phosphate

Tostep 6

ADP ADP

Hexokinase Phosphogluco-isomerase

Phospho-fructokinase

Aldolase

Isomerase

12 3 4

5

Figure 9.9-9

Glycolysis: Energy Payoff Phase

2 ATP 2 ATP2 NADH

2 NAD + 2 H

2 P i

2 ADP

1,3-Bisphospho-glycerate

3-Phospho-glycerate

2-Phospho-glycerate

Phosphoenol-pyruvate (PEP)

Pyruvate

2 ADP2 2 2

2 H2O

Phospho-glycerokinase

Phospho-glyceromutase

Enolase Pyruvatekinase

67 8

910

Triosephosphate

dehydrogenase

Figure 9.12-8

NADH1

Acetyl CoA

CitrateIsocitrate

-Ketoglutarate

SuccinylCoA

Succinate

Fumarate

Malate

Citricacidcycle

NAD

NADH

NADH

FADH2

ATP

+ H

+ H

+ H

NAD

NAD

H2O

H2O

ADP

GTP GDP

P i

FAD

3

2

4

5

6

7

8

CoA-SH

CO2

CoA-SH

CoA-SH

CO2

Oxaloacetate

Citric Acid Cycle(Kreb’s Cycle)

Figure 9.14

INTERMEMBRANE SPACE

Rotor

StatorH

Internalrod

Catalyticknob

ADP+P i ATP

MITOCHONDRIAL MATRIX

What are we looking at? _____________

Figure 9.15

Proteincomplexof electroncarriers

(carrying electronsfrom food)

Electron transport chain

Oxidative phosphorylation

Chemiosmosis

ATPsynth-ase

I

II

III

IVQ

Cyt c

FADFADH2

NADH ADP P i

NAD

H

2 H + 1/2O2

H

HH

21

H

H2O

ATP

Figure 9.19

CarbohydratesProteins

Fattyacids

Aminoacids

Sugars

Fats

Glycerol

Glycolysis

Glucose

Glyceraldehyde 3- P

NH3 Pyruvate

Acetyl CoA

Citricacidcycle

Oxidativephosphorylation

Figure 9.20

Phosphofructokinase

Glucose

GlycolysisAMP

Stimulates

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Pyruvate

Inhibits Inhibits

ATP Citrate

Citricacidcycle

Oxidativephosphorylation

Acetyl CoA

NEGATIVE FEEDBACKEXAMPLE

Anaerobic Respiration

• ATP is made in glycolysis only

• NADH needs to be recycled

• Ethanol (Alcohol) fermentation– Acetaldehyde intermediate

– CO2, ATP and ethanol are products. How do products benefit humans?

• Lactic Acid fermentation– Only lactate and ATP produced. What is the benefit to

humans?

Anaerobic Respiration

• See animation

Remember: Protein Kinase

• A protein kinase or kinase is an enzyme that adds a phosphate group from ATP to a target protein.

• HARVARD MITOCHONDRIA ANIMATION

Effect of poisons and toxins

• Cyanide- competive inhibitor of cytochrome C oxidase. Blocks ATP production.

• Rotenone (rat poison and insecticide)- competive inhibitor of NADH producing enzyme, which inhibits ATP production

• Carbon monoxide (CO) – binds with Hb 300 X more efficiently than O2. No oxygen, no final electron acceptor

What you will be tested onin Respiration

• These notes

• Major Products and Reactants of each stage

• Meaning what goes in, and what comes out. You need to know number of ATP derived from each stage.

• Fill in the blank items on handouts.