Cellular respiration
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Cellular Respiration. Chemical Energy and Food. A Calorie (with a capital C) is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. Note: The calorie you see on a cereal box is actually a kilocalorie or 1,000 Calories. 1 Calorie = 4,184 joules.

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Cellular Respiration

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Cellular respiration

Cellular Respiration

Chemical energy and food

Chemical Energy and Food

  • A Calorie (with a capital C) is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.

    • Note: The calorie you see on a cereal box is actually a kilocalorie or 1,000 Calories.

  • 1 Calorie = 4,184 joules

Cellular respiration1

Cellular Respiration

  • Cellular Respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

  • Cellular Respiration Equation:

  • 6O2 + C6H12O6 6CO2 + 6H2O + Energy



  • First part of cellular respiration: Glycolysis.

  • Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid (a 3-carbon compound)

  • 2 ATP molecules are needed go into glycolysis

  • The cell uses those two ATP and makes 4 ATP molecules and 2 NADH molecules

  • Therefore, a net gain of 2 ATP and 2 NADH

No oxygen no problem sort of

No oxygen? No problem… sort of

  • When oxygen is not present, glycolysis is followed by fermentation.

  • Fermentation releases energy from food molecules by producing ATP in the absence of oxygen

  • Fermentation is anaerobic – does not require oxygen.

  • Two main types:

    • Lactic acid fermentation

    • Alcoholic fermentation

Alcoholic fermentation

Alcoholic Fermentation

  • Yeast uses alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes

  • Pyruvic acid + NADH  alcohol + CO2 + NAD+

  • This process makes bread rise and of course alcohol

Lactic acid fermentation

Lactic Acid Fermentation

  • Lactic acid can be made from pyruvic acid in the absence of oxygen

  • This occurs in your muscles during rapid exercise when you’re not getting enough oxygen to your cells

  • Pyruvic acid + NADH  Lactic acid + NAD+

  • Lactic acid build up is painful = pain in muscles while working out

Lactic acid fermentation1

Lactic Acid Fermentation

  • Unicellular organisms going through lactic acid fermentation are used to make cheese, yogurt, buttermilk, and sour cream.

The krebs cycle

The Krebs Cycle

  • In the presence of oxygen (aerobic), after glycolysis, pyruvic acid goes to the Krebs Cycle (also called the Citric Acid Cycle).

  • During the Krebs Cycle, pyruvic acid is broken down into carbon dioxide and energy is extracted

  • Step 1: Pyruvic acid enters mitochondria. One carbon is wasted as carbon dioxide. Two carbons become acetyl-CoA and forms citric acid.

The krebs cycle1

The Krebs Cycle

  • Step 2: The citric acid is broken down, more carbon dioxide is released, and electrons are transferred to electron carriers.

    • This carbon dioxide that is released is what you breathe out.

    • NAD+ and FAD (flavine adenine dinucleotide) are the electron carriers. They are converted into NADH and FADH2.

Electron transport

Electron Transport

  • Electrons from the Krebs Cycle are passed from NADH and FADH2 to the electron transport chain (ETC).

  • The ETC uses these electrons from the Krebs cycle to convert ADP into ATP.

  • Step 1: Electrons passed through carrier proteins located on membrane of mitochondria (eukaryotes) or cell membrane (prokaryotes).

    • Oxygen is the final electron acceptor and combines with H+ to form water.

Electron transport1

Electron Transport

  • Step 2: Every time 2 electrons move down the chain, H + is moved across the membrane.

    • These H + ions make the membrane positive

  • Step 3: As the H + ions move across the membrane, ATP synthase attaches a phosphate group to ADP making ATP.

Electron transport chain

Electron Transport Chain

Totals of cellular respiration

Totals of Cellular Respiration

  • 36 total ATP produced in presence of oxygen

Energy and exercise

Energy and Exercise

  • Exercise that is intense and ends quickly will utilize fermentation.

    • Example: 200 m dash

    • Body only has enough ATP for a few minutes of intense activity

  • Exercise that is long-lasted and steady will use cellular respiration.

    • Example: aerobic exercises like swimming, running, dancing.

    • Cell respiration generates a continuous, steady supply

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