Ch. 9 pwpt

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Ch. 9: Cellular Respiration

The process by which cells break down

glucose (C6H12O6), or a nutrient that has

been converted to glucose or one of its

simpler products, into carbon dioxide

(CO2) and water (H2O).

Potential energy stored in covalent bonds

is released (heat and ATP). ATP allowscells to do work.

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TERMS TO KNOW

Activation energy: energy required to

destabilize chemical bonds to initiate a

chemical reaction

Oxidation: loss of an electron by an atom

or molecule

Reduction: gain of an electron by an atom

or molecule. Oxidation-reduction

reactions transfer energy in living systems.

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Fig. 9.3

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Fig. 9.4

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Making ATP from Glucose

Catabolism

Substrate level phosphorylation: a

phosphate is transferred directly to ADP

Aerobic Respiration: Electrons (H+) are

harvested, transferred along the Electron

Transport Chain making ATP, and finally

donated to O2, releasing H2O

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Cellular Respiration

- Process that releases energy by breaking down

glucose and other food molecules in the presence of

oxygen.

6O2 + C6H12O6 -> 6CO2 +6H2O + ATP+heat(reactants) (products)

- Three Stages of Cellular Respiration:

1. glycolysis2. Krebs Cycle (citric acid cycle)

3. Electron Transport

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Fig. 9.6

Fi 9 7

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Fig. 9.7

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Glycolysis:

1. requires no oxygen (anaerobic)

2. occurs in the cytosol catalyzed byenzymes

3. 2 molecules of ATP are used to breakone molecule of glucose in 1/2, producing

two molecules of pyruvic acid, NADH(containing high energy electrons), and 4molecules of ATP

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Glycolysis cont.

A small portion of the energy in the glucose isreleased and some makes 4 molecules ofATP (substrate-level phosphorylation)

Remainder of small portion of energyreleased (H+) are transferred to an energytrransferring molecule(NAD+) which then

become NADH.

Fi 9 9

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Fig. 9.9

Fig 9 12

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Fig. 9.12

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- Krebs Cycle (citric acid cycle)

1. requires oxygen (aerobic)

2. occurs in the inner membrane of mitochondria (where necessaryenzymes are located)

3. pyruvic acid is oxidized into carbon dioxide (released) and

acetyl-CoA. (co-enzyme)4. Acetyl-CoA joins with a 4-carbon molecule and becomes citric acid

5. Citric acid is oxidized,more carbon dioxide is released, and 10molecules of NADH and 2 FADH2 (high energy electronmolecules) are produced

6. These high energy molecules and their accompanying protons

move on to the ETC

**If no oxygen is present, fermentation will occur instead of theKrebs Cycle.

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Cellular Respiration- Electron Transport:

1. The high energy electrons of NADH and FADH2 are transferred tospecial energy accepting molecules (Electron Transport System)within the cristae of the inner mitochondria

2. As energized electrons leap from one of these molecules to thenext, their energy is used to pump their accompanying protons

from the inner chamber of the mitochondria to the outer chamber.A concentration gradient builds, and special carrier proteins bring(pump) protons back in. The energy released from this pumping isused to convert ADP and a phosphate into 34 more ATPfromeach molecule of glucose (chemiosmosis)

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ETC cont.

3. De-energized electrons are then accepted by oxygenmolecule and act as final electron acceptors

4. The electrons are reunited with their accompanying

protons (H+) and water is formed and released If thisfinal acceptor (O2) is not available, the electrons andH+ ions will not move down the ETC and no additionalATP will form in this step.

**36 molecules of ATP represents 38% of total energyfrom glucose. Remaining 62% is given off as heat.

Fig 9 16

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Fig. 9.16

Fig 9 17

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Fig. 9.17

Fig 9 18

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Fig. 9.18

Fig 9 19

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Fig. 9.19

Fig. 9.10

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Fig. 9.10

Fig. 9.24a

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Fig. 9.24a

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Anaerobic Respiration

Alcohol Fermentation

Ex. Yeast activity in bread dough

1. Yeast break the sugar in the bread dough into

pyruvate and NADH. The pyruvate is then brokendown into acetaldehyde and CO2 gas (bread

rises)

2. The acetaldehyde becomes the electron acceptor

for NADH, and ethyl alcohol is produced (up to12%).

Fig. 9.24b

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g

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Anaerobic Respiration

Lactic Acid Fermentation

1. Muscle cells use NADH to convertpyruvate into lactate (ionized form of

lactic acid)2. Circulating blood removes excess

lactate, but if production exceeds

removal capability, lactic acid will build inmuscles and interfere with function (andcause cramps)

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Ch. 9 pwpt