AP Biology 2006-2007

-Cellular Respiration-Breaking the bonds of sugar

to produce ATP

ATP

AP Biology

Cellular Respiration – makes ATP by breaking down sugars and other carbon-based molecules.

3 metabolic stages Anaerobic respiration

1. Glycolysis - “Glucose Breaking” Anaerobic respiration -respiration without O2

Located in the cytoplasm Produces a net of 2 ATP molecules/glucose

Aerobic respiration phase – respiration with O2

2. Krebs cycle Located in the mitochondria matrix Produces 2 ATP/glucose 3. Electron transport chain Located in the mitochondrial inner membrane Produces 32-34 ATP/glucose

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2 2 32-34

C6H12O6 6O2 36-38 ATP6H2O6CO2+ + +

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Mitochondria — Structure

intermembranespace inner

membrane

outermembrane

matrix

cristae

Double membraned energy harvesting organelle highly folded inner membrane increases surface area

Cristae Matrix

inner fluid-filled space enzymes

Found free in matrix & as well as membrane-bound

What cells would have a lot of mitochondria?

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Glycolysis –anaerobic respiration occurs in cytoplasm Sugar is broken into two pyruvic acid molecules and

releases 2 molecules of ATP/Glucose

Net gain of 2 ATP produced for every glucose

2x6C 3Cglucose pyruvate

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ATP2

ADP2

ATP4

ADP4

NAD+2

2Pi

2

-2 ATPs release energy-Phosphate is added to another compound.

-An electron moving down membranes, eventually bonding with NAD+.This gain of electrons attracts hydrogen ions, which bonds to NAD+, storing energy in the bonds of NADH

-ADP gains the third phosphate, forming ATP. Energy is stored in the phosphate bonds.

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Step 1. Two ATP molecules are used to energize a glucose molecule. The glucose molecule is split into two three-carbon molecules.

P PP

PP

2

2

PP

PP

C C C C C C

P PP

P P

C C C C C C PP

C C CP C C C P

C C C PC C CP

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Step 2. Energized electrons and hydrogen ions from the three-carbon molecules are transferred to molecules of NAD+, becoming NADH. A series of reactions converts the 3-carbon molecules to Acetyl Co-A which enters cellular respiration

P PP

P

PP

2

2

PP PP

P PP

PP2

2 P PP

PP2

2

NAD+2

2

NAD+2

2

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Glycolysis- The Song!

http://www.youtube.com/watch?v=jJvAL-iiLnQ

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If No Oxygen is present the pyruvate cannot enter the Kreb Cycle and goes into Fermentation instead.

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2 Types of Fermentation A. Alcoholic Fermentation – occurs in Plants & Bacteria Produces NAD+, 2 ATP, and ethanol. Used in the production of wines, cheeses, breads.

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B. Lactic Acid Fermentation – In Animals Produces NAD+ and Lactic acid

Causes pain in the joints.

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IV. STAGE 2: KREBS CYCLE – AEROBIC RESPIRATION

a. Occurs in the mitochondrial matrixb. A process that breaks pyruvate through a series of reactions

producing Electron Carrier compounds, ATP and carbon dioxide gas.

c. Produces large quantities of electron carriers like NADH, and FADH2 that go to the Electron Transport Chain.

Step 1. Pyruvate (from glycolysis) is broken down (loses a carbon).

Step 2 Coenzyme A (CoA) bonds to the two-carbon molecule. This intermediate molecule (Acetyl-CoA) enter the Krebs cycle.

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C C C

Wheredoes the

Carbon go?Exhale!+ Coenzyme A (CoA)

3C

Oxidation of Pyruvate

NAD+

e- & H+

Acetyl Group

C C

Acetyl-CoA C C

To the KrebsCycle!

Loss of CO2

C

Remember, this happens twice,once for each

Pyruvate!

2= 2 CO2

= 2 NADH = 2 Acetyl CoA

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Step 3 Citric Acid is formed by bonding acetyl-coA to a four carbon molecule.

Step 4: Citric acid is broken down by releasing a carbon, and a five-carbon molecule is made.

Step 5. The five-carbon molecule is broken down. A four-carbon molecule is made.

Step 6. The four-carbon molecule is rearranged. 2 ATPs are formed.

Products from breakdown of one molecule of pyruvate:•CO2 given off as a waste product each time a carbon is broken off.•2 ATP•4 NADH goes to ETC•1 FADH2 goes to ETC

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4C

6C

4C

4C

4C

2C

6C

5C

4C

CO2

CO2

citrate

acetyl CoA

Now for the Krebs Cycle-count the carbons!

3Cpyruvate

x2

oxidationof sugars

This happens twice. One for each pyruvate molecule.

CO 2

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4C

6C

4C

4C

4C

2C

6C

5C

4C

CO2

CO2

citrate

acetyl CoA

Now, count the electron carriers!

3Cpyruvate

Storing energyusing electron

carriers

This happens twice for each pyruvatemolecule x2

CO 2

NADH

NADH

NADH

NADH

ATP

FADH22

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So we fully oxidized glucose

C6H12O6

6CO2

& ended up with all of 4 ATP!2 from Glycolysis

2 from Krebs Cycle

Whassup with this?

What’s the point?

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What’s so important about

electron carriers?

H+

H+

H+

H+

H+H+

H+H+

H+

ATP

ADP+ Pi

Krebs cycle produces large quantities of

electron carriers 8 NADH 2 FADH2

go to Electron Transport Chain!

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STAGE 3: Electron Transport Chain

Takes place in the inner mitochondrial membrane A process that uses high electron carriers from the Krebs

cycle to generate ATP by oxidative phosphorylation. Produces 32-34 ATP molecules per molecule of glucose.

Step 1. H+ and e- are removed from NADH and FADH2.

Step 2. Hydrogen ions are transported across the membrane.

Step 3. ADP is changed into ATP when hydrogen ions flow through ATP Synthase.

Step 4. Water is formed when oxygen picks up electrons and hydrogen ions.

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AP Biology

Mitochondria

intermembranespace

innermembrane

outermembrane

matrixcristae

H+

H+H+

H+

H+ H+

H+H+

H+

NAD+

Q

C

NADH H2O

H+

e–

2H+ + O2

H+H+

e–FADH2

12

NADH dehydrogenase

cytochrome bc complex

cytochrome coxidase complex

FAD

e–

ADP+ Pi

TA-DA!!Moving electrons

do the work!

H+ H+ H+

P

H+

O-

O-O-

H+

ATP

H+

P PP PP P P H+

H+ O-H+H+H+

AP Biology H+

H+H+

H+

H+ H+

H+H+

H+

NAD+

Q

C

NADH H2O

H+

e–

2H+ + O2

H+H+

e–FADH2

12

NADH dehydrogenase

cytochrome bc complex

cytochrome coxidase complex

FAD

e–

ADP+ Pi

TA-DA!!Moving electrons

do the work!

H+ H+ H+

Chemiosmosis powers the proton pump!

P

H+

O-

O-O-

H+

ATP

H+

P PP PP P P H+

H+ O-H+H+H+

The diffusion of ions across a membrane build up of proton gradient just so H+ could flow

through ATP synthase enzyme to build ATP The final electron acceptor is oxygen, which forms

water.

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. SUMMARY - The products of cellular respiration – including glycolysis

are:

CO2 from the Kreb’s Cycle and from the breakdown of pyruvate before the Krebs cycleWater from the Electron Transport ChainA net gain of up to 36-38 ATP molecules for every glucose molecule – 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and up to 32-34 ATP from the electron transport chain.

C6H12O6 6O2 36-38 ATP6H2O6CO2+ + +

Kreb’s Cycle

Electron Transport Chain

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A single cell uses about 10 million ATP molecules per

second!

If you are chasing prey for food, or being chased by a predator,

it is probably higher…

http://www.hyperbaric-oxygen-info.com/aerobic-cellular-respiration.html

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ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H

ATP production ceases cells run out of energy and you die!

Taking it beyond… What is the final electron

acceptor in Electron Transport Chain?

O2

So what happens if O2 unavailable?

NAD+

Q

C

NADH H2O

H+

e–

2H+ + O2

H+H+

e–FADH2

12

NADH dehydrogenase

cytochrome bc complex

cytochrome coxidase complex

FAD

e–

AP Biology

http://www.youtube.com/watch?v=StXlo1W3Gvg&feature=related

What happens when you run out of Oxygen!

A single cell uses about 10 million ATP molecules per second –

http://www.hyperbaric-oxygen-info.com/aerobic-cellular-respiration.html