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Cellular Respiration

Biology 11A. Allen

http://fusionanomaly.net/mitochondria.htmlhttp://fusionanomaly.net/mitochondria.html

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Assessment Statements

CORE

3.7.1 Define cell respiration.

3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further

yield of ATP.

3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

AHL

8.1.1 State that oxidation involves the loss of electrons from an element, whereas reduction involves a gain of electrons; and that oxidation frequently involves

gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen.

8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs.

8.1.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen

8.1.5 Explain oxidative phosphorylation in terms of chemiosmosis.

8.1.6 Explain the relationship between the structure of the mitochondrion and its function.

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Cellular Respiration

• Cellular respiration is…

The process by which a cell breaks down sugar or

other organic compounds to release energy used for

cellular work; may be anaerobic or aerobic,

depending on the availability of oxygen. Aerobic

respiration can be summarized by the following

formula:

C6H12O6 + 6O2 � 6H20 + 6CO2 + energy (36 ATP)

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Activation Energy

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Glycolysis

• Glycolysis is the first stage of cellular respiration.

• Glycolysis has two parts; Glycolysis I & Glycolysis II. In order to ‘kick-start’ glycolysis I, activation energy is required (ATP). Sugar is split into two G3Ps. In glycolysis II, G3P is oxidized and ATP is produced. The overall pathway gets its name from this sugar splitting (glyco = sugar, lysis = split).

• Glycolysis occurs in the cytosol (The fluid portion of the cytoplasm, outside the organelles ).

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An overview of Aerobic Cellular Respiration

Can you find

Glycolysis?

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Coenzyme

• A substance that enhances or is

necessary for the action of enzymes. They are generally much smaller than enzymes

themselves. NAD (Nicotinamide adenine

dinucleotide) is a coenzyme that serves and an electron carrier.

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Glycolysis IGlucose6-C

Glucose ~P“glucose-6-phosphate”

6-C, 1 Phosphate

ATP

ADP

P~ Fructose ~P“Fructose 1,6-bisphosphate”

6-C, 2 Phosphates

ATP

ADP

X2X2X2X2G3P

AKA G3P(3-C, 1 phosphate)

• Glycolysis I is a series of endergonic

reactions

1. Glucose enters the cell by diffusion

2. ATP donates a phosphate to the substrate. (1 ATP used) Glucose-6-phosphate is produced.

3. Glucose-6-phosphate is rearranged to

fructose-6-phosphate (another 6-C sugar)

4. another ATP donates its phosphate (1 ATP used). Fructose 1,6-bisphosphate is produced.

5. The fructose 1,6 bisphosphate molecule is

split into 2 G3Ps (glyceraldehyde 3-phosphate), a 3-carbon compound. Note G3P is also known as glyceraldehyde 3-

phosphate (G3P)

**Glycolysis I …**•2 ATP (2 ATP’s are used.)

G3PAKA G3P

AnimationAnimation

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Fructose~P“fructose-6-phosphate”

6-C, 1 Phosphate

55DHAP

Glycolysis II

X2X2X2X2

G3P(3-C, 1 phosphate)

Pyruvate (Pyruvic Acid)(3-C, 0 phosphates)

PiNAD+

NADH

• In Glycolysis II, each G3P (2 from 1 molecule of glucose) is oxidized to release energy. This

process is exergonic.

1. G3P is oxidized. NAD takes electrons (NADH is formed). The oxidized G3P then accepts a

Pi from the cytosol. 1,3 bisphosphoglyerate

(BPG) is formed

2. ADP is phosphorylated to ATP (x2) as it removes the phosphate from the substrate.

3-phosphoglycerate is formed. (substrate level phosphorylation: when ADP removes Pi from the substrate to form ATP)

3. 3-phosphoglycerate is rearranged to 2-phosphoglycerate which is then rearranged to phosphoenolpyruvate (PEP). Water is given off in this process.

4. PEP gives a phosphate to ADP to make ATP.

Pyruvate (AKA Pyruvic acid) is formed.

ADP

ATP

**Glycolysis results in a net gain of …**•2 ATP (2 ATP’s are used and 4 are produced)

•2 NADH These hydrogens are transported

to the mitochondria for more ATP productionAnimationAnimation

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1,3 bisphosphoglycerate (BPG)(3-C, 2 phosphates)

22ATP

ADP

3-phosphoglycerate(3-C, 1 phosphate)

2-phosphoglycerate(3-C, 1 phosphate)

phosphoenolpyruvate (PEP)

H2O

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Substrate Level Phosphorylation

• The direct phosphate transfer of

phosphate from an organic molecule to ADP.

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Think Together!Partners `A` and `B` take turns answering the

questions below.

A. What is the basic difference between Glycolysis I and Glycolysis II?

B. What is the role of NAD?

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Vocabulary GAME!

• Glucose

• fructose

• G3P

• Pyruvate

• phosphate

• Glucose-6 phosphate

• NADH

• ADP

• endergonic

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Circle the end products of glycolysis. Where do they go next?13

• Decarboxylation-removal of a carboxyl

group

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Pyruvate Oxidation (IB calls this the ‘Link Reaction’)

Remember, in glycolysis, glucose was

oxidized to 2 pyruvate molecules.

Therefore, the above biochemical pathways

run twice for every molecule of glucose!

Pyruvate Oxidation ONLY HAPPENS IF O2

is present!

Pyruvate

(pyruvic acid)

(3-C)NAD+

NADH CO2

Acetate

(Acetic acid )

(2-C)

Coenzyme A

(or ‘CoA’)

acetyl coenzyme A

(or ‘acetyl coA’)X2

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2

2.2. Acetic acid combines with Acetic acid combines with coenzyme coenzyme

AA to form to form acetyl coenzyme Aacetyl coenzyme A..

1.1. The The twotwo pyruvate from glycolysis pyruvate from glycolysis

diffuse into the mitochondrion’s diffuse into the mitochondrion’s

matrix. Here, it is oxidized by matrix. Here, it is oxidized by NADNAD++

(which is reduced to(which is reduced to NADHNADH) to make ) to make

acetateacetate, a 2, a 2--carbon compound. (The carbon compound. (The

carbon is lost in the form of COcarbon is lost in the form of CO22))

AnimationAnimation**Pyruvate Oxidation results in a net gain of …**•2 NADH. These hydrogens are transported to the Electron Transport Chain for more ATP production

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Pyruvate Oxidation

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Can you find Pyruvate oxidation? Where does it occur?17

KrebsCycle

1. Acetyl coenzyme A enters the Krebs cycle and combines with Oxaloacetate (4-C), to make citrate (6-C). Coenzyme A is recycled for further use.

2. Citrate is rearranged to isocitrate(6-C)

3. NAD accepts hydrogens from isocitrate which is therefore oxidized. One molecule of CO2 is given off as isocitrate loses one carbon. α-ketoglutarate (5-C) is formed.

4. α -ketoglutarate (5-C) is oxidized to succinyl Co-A (4-C). A CO2 is removed, coenzyme A is added, and 2 hydrogen atoms reduced NAD to NADH. Succinyl C0-A is produced.

5. Succinyl Co-A (4-C) is converted to succinate (4-C). A Pi from the matrix displaces C0-A from succilyl Co-A. The phosphate is then tansfered to GDP (guanosine diphosphate) to make GTP. Then the Pi is transferred to ADP to make ATP!

CitrateCitrate (6-C)

α α --ketoglutarateketoglutarate (5-C)

SuccinateSuccinate

((4-C )

OxaloacetateOxaloacetate (4-C)

NAD

CO2

CO2

NAD

NADH

acetyl coenzyme A

(or ‘acetyl coA’)

11Coenzyme A

(or ‘CoA’)

NADH

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X2

AnimationAnimation

GTP GDP + Pi

ATP

ADP + Pi

IsocitrateIsocitrate (6-C)

SuccinylSuccinyl--CoACoA

((4-C )

CoCo--AA

CoCo--AA

2

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KrebsCycle

6. Succinate (4-C) is oxidized to fumarate (4-C). Not enough energy is released to reduce NAD, so FAD is instead reduced to FADH2.

7. Fumarate (4-C) is converted to malate (4-C).

8. Malate is oxidized to oxaloacetate (4-C). 2 hydrogens are reduced NADto NADH. Oxaloacetate has been restored, so the cycle can continue! Yahoo!

Only 2 ATP’s have been produced from Krebs cycle. ����

CitrateCitrate (6-C)

α α ketoglutarateketoglutarate (5-C)

OxaloacetateOxaloacetate (4-C)

NAD

CO2

FADFADH2

NAD

NADH

acetyl coenzyme A

(or ‘acetyl coA’)

11Coenzyme A

(or ‘CoA’)

NADH

3

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Final products of Krebs Cycle per molecule of glucose:Final products of Krebs Cycle per molecule of glucose:

3 x 2 = 3 x 2 = 6 NADH 6 NADH �� (to electron transport chain (to electron transport chain to make ATPto make ATP))

1 x 2 = 1 x 2 = 2 FADH2 FADH22 �� (to electron transport chain (to electron transport chain to make ATPto make ATP))

1 x 2 = 1 x 2 = 2 ATP2 ATP

X2

AnimationAnimation

NAD44

GTP GDP

ATP

ADP + Pi

SuccinateSuccinate

((4-C )NADH

CO2

IsocitrateIsocitrate (6-C)malatemalate (4-C)

fumaratefumarate (4-C)

HH2200

SuccinylSuccinyl--CoACoA

((4-C )

CoCo--AA

CoCo--AA

2

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Think Together!

• Why is there a “X2” on the diagram of the

Krebs Cycle?

• Krebs cycle only yields 2 ATP per

molecule of glucose, but it also results in 6 NADH and 2 FADH2 produced. What do

you think NADH and FADH2 is for?

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Oxidative Phosphorylation (Electron Transport Chain)

• The electron transport chain is located on the inner membrane of the mitochondrion.

It consists of several electron carriers which accept electrons from NADH and

FADH2 (from glycolysis and Krebs cycle). It requires O2!

Animation #1Animation #1

Animation #2Animation #2

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…Oxidative Phosphorylation (Electron Transport Chain)

[1] Energized electrons from Glycolysis and Krebs cycle are carried to the electron

transport chain via NADH...

[2] ...and FADH2

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Animation #1Animation #1

Animation #2Animation #2

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…Oxidative Phosphorylation (Electron Transport Chain)

[3] Electrons are passed through a series of electron carriers which become reduced/oxidized

as they pass off the electrons [complexes I -IV]. At different places along this chain, the

energy released from the electrons is used to ‘pump’ protons (H+) across the inner

membrane of the mitochondrion into the intermembrane space

[4] This creates a concentration gradient in the intermembrane space.

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NADH Dehydrogenase

(H+ pump)

Cytochrome bc1 complex (H+ pump)

Cytochrome c oxidase complex (H+ pump)

Animation #1Animation #1

Animation #2Animation #2

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…Oxidative Phosphorylation (Electron Transport Chain)

[5] The H+ ions are allowed to pass back into the matrix through ATP synthase.

[6] Using the energy from the flow of protons, ADP is united with Pi to form ATP.

Note that because NADH and FADH2 enter the electron transport chain at different locations,

they yield different amounts of ATP; NADH yields 3 ATP and FADH2 yields 2 ATP.

[7] The electrons unite with protons (H+) and oxygen at the end of the ETC to form water.

If insufficient O2 is available in the cell, the ETC will not work! What happens then?......

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NADH Dehydrogenase

(H+ pump)

Cytochrome bc1 complex (H+ pump)

Cytochrome c oxidase complex (H+ pump)

Animation #1Animation #1

Animation #2Animation #2

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Electron Transport and

Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

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Fig. 9.15

Electron Transport and

Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

Cyt C

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Fig. 9.15

Electron Transport and

Chemiosmosis

NADH

H+

NAD+

H+

H+

H+

CoQ

Cytochrome c

oxidase complex

Cyt C

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Fig. 9.15

Electron Transport and

Chemiosmosis

NADH

H+

NAD+

H+

H+H+

2 H+ + ½ O2 H20

Electron transport chain chemiosmosis

CoQ

Cyt C

Cytochrome c

oxidase complex

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Electron Transport and

Chemiosmosis

NADH

H+

NAD+

H+

H+H+

2 H+ + ½ O2 H20

H+

H+

H+H+

H+

H+H+

H+

H+

H+H+

H+

H+

H+ H+

H+ H+

ADP + P ATP

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Smokin’ Chemiosmosis & Electron Transport Animations

• http://vcell.ndsu.nodak.edu/animations/atp

gradient/movie.htm

• http://vcell.ndsu.nodak.edu/animations/etc/

movie.htm

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Can you see why FADH2 & NADH end in different ATP yields?

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Cyanide Blocks the Electron Transport Chain

• Cyanide is a poison that inhibits cytochrome oxidase activity. Why can cyanide cause death?

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Summary of Aerobic Cellular Respiration

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Structural Formula of ATP

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• Label the diagram

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Net Energy Yield of Aerobic Respiration

ATPs NADHs FADH2sATPs From

ETCTotal ATPs

Glycolysis 2 2 0 4 6

Pyruvic AcidOxidation

0 2 0 6 6

Krebs Cycle 2 6 2 22 24

Total 4 10 2 32 36

AA BB CC DD EE

FF GG HH II JJ

KK LL MM NN OO

PP QQ RR SS TT

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Anaerobic vs. Aerobic Respiration

• NOTE: What happens after glycolysis depends on whether or not oxygen is present…

If O2 is absent…. If O2 is present….

Pyruvate

(Pyruvic Acid)

(3-C)

NADH

NAD+ X2

Lactate

(Lactic acid)

(3-C)

Pyruvate Goes to the Kreb’s

cycle in the mitochondria

(aerobic

respiration) for complete

oxidation.

This process is called …

lactate (lactic acid)

fermentation

Lactic acid (animals) Once thought to make muscles fatigued after Strenuous exercise)

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Think Together!With your partner, discuss:

• Does lactic acid fermentation yield any energy?

• Assume the energy demands within a cell greatly exceeds the body’s ability to deliver oxygen. What is the point of pyruvic acid being converted to lactic acid? HINT: NAD is a limited commodity in the cell.

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Alcoholic Fermentation (in yeast)

• An anaerobic step that yeast use after glycolysis that breaks down pyruvate to

ethanol (aka ethyl alcohol) and carbon dioxide.

Pyruvate

(Pyruvic Acid)

(3-C)

NADH

NAD+ X2

Ethanol (the alcohol found in beer, wine, etc.)

(2-C)

Acetaldehyde (2-C)

C02

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Alternate Pathways• Carbohydrates are your body’s nutrient of choice.

• Proteins lipids and nucleic acids can also be used.

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Protein Catabolism

• Proteins are made of different

types of amino acids.

• The amino groups of amino acids are removed

(deamination).

• What remains of the amino

acids are then converted to various components of

glycolysis or Krebs i.e.

pyruvate, acetyl CoA, alpha ketoglutarate.

• You know the rest!

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Lipid Catabolism• Triglycerides are made of

glycerol and fatty acids. Your digestive system breaks triglycerides into these components.

• Glycerol may be converted into glucose via gluconeogenesis or to DHAP (what’s next…?)

• The fatty acids enter the matrix and undergo beta oxidation (acetyl groups are removed from the fatty acids and combine with CoA to form Acetyl CoA… 47