1. Organisms obtain energy from food 2. Glucose is main source of food for cells 3. Cells break chemical bonds of glucose;

energy released

Slide # 2

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Cells Need Energy

Respiration

Cellular Respiration

If cellular respiration took place in just one step: All of the energy would be released at once Most would be lost in the form of light and heat.

Instead, a living cell has to release chemical energy in food molecules a little bit at a time. Must trap those little bits of energy by using

them to make ATP.

Cellular Respiration

Cellular Respiration - Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Cellular Respiration

Requires (Reactants):1. Glucose

2. Oxygen

Gives Off (Products):3. Water

4. Carbon Dioxide

5. Energy

3 Stages of Cellular Respiration

1. Glycolysis2. Krebs Cycle3. Electron Transport

Chain

Each stage captures some of the chemical energy available in food molecules and uses it to produce ATP.

First Stage: Glycolysis

Glycolysis –A molecule of glucose is broken into two molecules of pyruvic acid. Occurs in the cytoplasm Does not require oxygen (anaerobic)

1 Glucose 2 Pyruvic Acid

C-C-C-C-C-C C-C-C C-C-C

Glycolysis Glucose C-C-C-C-C-C

C-C-C C-C-C

2 Pyruvic Acid C-C-C C-C-C

2 ATP

2 ADP

4 ADP

4 ATP2 NADH

2 NAD+TO THE

ELECTRON TRANSPORT

CHAIN

Products of Glycolysis

1. NET Gain 2 ATP (Major Energy molecule)

2. 2 NADH (Minor Energy molecule)

3. 2 Pyruvic Acid Molecules

http://www.youtube.com/watch?v=C78BMJ7D68I (Glucose – Sugar Sugar Song)

Glycolysis

Fermentation Krebs Cycle

Anaerobic (no oxygen)

Aerobic (oxygen)

Second Stage: Fermentation or Krebs Cycle

Glycolysis can be followed by fermentation or the Krebs cycle depending if oxygen is present. Fermentation will occur if no oxygen is

present. Krebs Cycle will occur if oxygen is

present.

Second Stage: Fermentation

Fermentation - Releases energy from food molecules by producing ATP in the absence of oxygen. Anaerobic - Does not require oxygen Occurs in the cytoplasm (cytosol)

Fermentation

Two types of Fermentation:1. Alcoholic Fermentation

2. Lactic Acid Fermentation

Alcoholic Fermentation Produces:

1. Ethyl alcohol 2. Carbon dioxide

Examples: Used to produce beer and wine Causes bread dough to rise

Carried out by yeasts and a few other microorganisms

Lactic Acid Fermentation Produces:

1. Lactic Acid Examples:

Produced in your muscles during rapid exercise Buildup of lactic acid causes a painful, burning

sensation…why muscles feel sore Used in production of cheese, sour cream, yogurt,

and pickles. Carried out by animals and some unicellular

prokaryotes (bacteria).

At the End of Glycolysis

90% of the chemical energy that was available in glucose is still unused Locked in the high-energy electrons of pyruvic

acid Oxygen is required for the final steps of

cellular respiration. Oxygen is the world's most powerful electron

acceptor. Therefore, cellular respiration is aerobic

(requires oxygen).

Second Stage: Krebs Cycle

Krebs Cycle - Pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions.

Occurs in the mitochondrion.

Krebs Cycle

Starts: Pyruvic Acid Produces: Carbon Dioxide

Source of all the carbon dioxide in your breath. Energy Tally - Each Molecule of Pyruvic Acid

Produces: 1 ATP (and NADH/FADH2) All energy molecules!

Third Stage: Electron Transport Chain

The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP.

Oxygen serves as the final electron acceptor.

Occurs in the mitochondrion.

ATP Glycolysis: 2 ATP

molecules per glucose molecule Needs 2 ATP (Investment) Produces 4 ATP Net gain of 2 ATP

molecules. Krebs Cycle and Electron

Transport: 34 ATP molecules per glucose molecule

Total = 36 ATP

Black eyed peas review respiration song

http://www.youtube.com/watch?v=3aZrkdzrd04&feature=email

Exercise: Quick Energy

1. Muscles only contain enough ATP for a few seconds of intense activity

2. Then, muscle cells produce their ATP by lactic acid fermentation.

Lasts only about 90 seconds or about 200 - 300 meters.

Produces lactic acid, which requires oxygen debt (must repay after the race with plenty of heavy breathing).

Exercise: Long-Term Energy (Longer than 90 seconds)

Cellular Respiration is the only way to generate a continuing supply of ATP

Releases energy slowly (why athletes must pace themselves) Body stores energy in muscle and

other tissues in the form of the carbohydrate glycogen (usually enough to last for 15 - 20 min.)

After that, your body begins to break down other stored molecules, including fats, for energy

Photosynthesis vs. Respiration

Photosynthesis and cellular respiration take place in opposite directions!

Photosynthesis: Use light energy to build a sugar.

carbon dioxide + water + light energy → sugars + oxygen

Respiration: Break down sugar to release energy.

oxygen + sugars → carbon dioxide + water + energy

Respiration: Break Down Glucose Photosynthesis: Build Glucose

Photosynthesis vs. Respiration

Cellular Respiration Occurs In: All eukaryotes Some prokaryotes

Photosynthesis Occurs In: Plants Algae Some bacteria

F. Review

1. What is the source of carbon for cellular respiration?

Glucose (C6H

12O

6) is the carbon source.

F. Review

2. Where do Stages 2 and 3 of cellular respiration take place?

in mitochondria