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Chemical energy and foodWhere do organisms get energy?Organisms get the energy they need from

foodCells don’t just eat and burn the energy they

store some, get the protein they need, and capture the little bit of chemical energy.

Overview of cellular respirationWhat is cellular respiration?Cellular respiration is the process that

releases energy from food in the presence of oxygen.

602 + c6h1206 6co2 + 6h2o +energy

Stages of cellular respirationCellular respiration captures energy from

food in three main stages- glycolysis, the Krebs cycle, and the electron transport chain.

Oxygen and energyPathways of cellular respiration that require oxygen are

said to be aerobic (“in air”)Glycolysis is said to be anaerobic (“without air”).

Comparing photosynthesis to cellular respirationWhat is the relation ship between photosynthesis and

cellular respiration?Photosynthesis removes carbon dioxide from the

atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release food.

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Glycolysis What happens during the process of Glycolysis? During glycolysis, 1 molecule of glucose, a 6-carbon compound, is

transformed into 2 molecules of pyruvic acid, a 3-carbon compound.

The first set of reaction in cellular respiration I glycolysis

ATP productionEven though glycolysis is an energy-releasing

process, the cell needs to put in a little energy to get things energy.

NADH productionOne of the reactions of glycolysis removes 4

electrions, now in a high-energy state, and passes them tom an electron carrier called NAD+, or nicotinamide adenine dinucleotide.

The advantages of glycolysisThe speed of glycolysis can be a big

advantage when the energy demands of a cell suddenly increase.

Besides speed, another advantage of glycolysis is that the process itself does not require oxygen.

The Krebs cycleWhat happens during the Krebs cycle?During the Krebs cycle, pyruvic acid is

broken down into carbon dioxide in a series of energy-extracting reactions

The cycle is named after a British biochemist Hans Krebs

Citric acid productionThe matrix is the innermost compartment of

the mitochondrion and the site of the Krebs cycle reactions.

Energy extractionsEnergy is released by the breaking and

rearranging of carbon bonds, is captured in the forms of ATP.

The process of cellular respirationSC.912.L.18.8

Electron Transport and ATP Synthesis• How does the electron transport chain use high-energy

electrons from glycolysis and the Krebs cycle?• The electron transport chain uses the high-energy electrons

from glycolysis and the Krebs cycle to convert ADP into ATP• The electron transport chain is the last step of cellular

respiration

The process of cellular respirationSC.912.L.18.8

Electron Transport• NADH and FADH2 pass their high-energy

electrons to the electron transport chain• Oxygen is the final electron acceptor in the

electron transport chain• The end of a transport chain is an enzyme that

combines the electrons with hydrogen ions and oxygen to form water

The process of cellular respirationSC.912.L.18.8

ATP Production• The cell uses a process called chemiosmosis to

produce ATP.• In this ATP synthases grabs an ADP molecule and

attaches a phosphate group producing ATP• The full length of the electron transport chain

provides enough energy to produce 3 ATP molecules

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The Totals• How much ATP does cellular respiration

generate?• All together glycolysis, Krebs cycle, and the

electron transport chain releases about 36 molecules of ATP per glucose molecule

• The 36 ATP molecules generated represents about 36 percent of the total energy of glucose. The other 64 percent is released as heat.

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FermentationSC.912.L.18.10

Alcoholic Fermentation• An example of one type of fermentation is

alcoholic fermentation• This type of fermentation produces ethyl alcohol

and carbon dioxide.• Yeast and the production of alcoholic beverages

use this type of fermentation • Pyruvic acid + NADH = Alcohol + CO2 + NAD+

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Fermentation • Fermentation is the process by which cells

release energy in the absence of oxygen• How do organisms generate energy when oxygen

is not available?• In the absence of oxygen, fermentation releases

energy from food molecules by producing ATP.

FermentationSC.912.L.18.10

Lactic Acid fermentation• An other example of fermentation is lactic acid

fermentation • This is the most common fermentation carried

out by organisms • Lacctic acid fermentation unlike alcoholic

fermentation does not give off carbon dioxide • Pyruvic acid + NADH = lactic acid + NAD+

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Energy and exercise• How does the body produce ATP during different

stages of exercise?• The body produces ATP during different stages of

exercise through cellular respiration and lactic acid fermentation

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Quick Energy• When your body needs quick bursts of energy it

uses ATP produced by fermentation• The fermentation used to produce the ATP is

lactic acid fermentation• The ATP the body uses when in need of those

quick bursts of energy are already in your muscles

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Long-term Energy• Some times your body needs long bursts of

energy, and for that it uses cellular respiration. • Cellular respiration is the only way to continue

generating a supply of ATP when exercising for longer then 90 seconds

• Cellular respiration releases energy slower than fermentation does which is why everyone evidentially gets tired.