Section 8.3Cellular Respiration

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Concept MapCellular Respiration

3 Stages

Glycolysis

Anaerobic

Pyruvic Acid

Fermentation

Lactic Acid Fermentation

Alcoholic Fermentatio

n

Citric Acid Cycle(Krebs Cycle)

Electron Transport Chain

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Getting Energy to Make ATP

C6H12O6 + 6 O2 6CO2 + 6 H2O + ATP

The mitochondria in cells breaks down glucose and produces energy-in this case ATP.

EXERGONIC: Releases energyCATABOLIC: Breaking down

molecules

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Cellular Respiration

Three stages of cellular respiration1. Glycolysis - anaerobic2. The Citric Acid Cycle (Kreb’s Cycle) -

aerobic3. The electron transport chain – aerobic

The aerobic phase produces the most ATP

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Overview of Cellular Respiration

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Glycolysis

Takes place in the cytoplasm of the cell It requires no oxygen (anaerobic). Glucose (a 6 carbon molecule) is broken

down into 2 molecules of pyruvate (a 3 carbon compound).

It requires 2 ATP It produces 4 ATP A net gain of 2 ATP

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Glycolysis

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The Krebs Cycle

Takes place in the mitochondria of the cell (in the matrix).

The pyruvate from glycolysis is slightly modified before the citric acid cycle begins.

These new molecules are broken down to form ATP and CO2.

One ATP per cycle is produced, two cycles occur per glucose molecule – therefore 2 ATP’s are produced by Krebs Cycle.

*Also generates high energy electrons carried by NADH and FADH2.

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Kreb’s Cycle/Citric Acid Cycle

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The Electron Transport Chain (makes up to 34 ATP)

The final stage of respiration Takes place on inner mitochrondrial membrane

(cristae) Similar to the events in the light-dependent

reactions of photosynthesis. Electrons are passed from protein to protein, and

the energy they give off is used to produce more ATP’s.

The final electron acceptor is an oxygen atom. This is why we cannot live without oxygen!

Collects H+ ions and low energy electrons! (waste) CREATES H2O (water)

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Electron Transport Chain

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Where do the electrons come from?

Electrons for the ETC come from electron carriers: FADH2 and NADH Work like NADPH (from photosynthesis)

Formation of FADH2 and NADH occurs during glycolysis and citric acid cycle Glycolysis

NAD+ and H+ combine with e- to make NADH

Citric Acid Cycle More NADH forms FAD+ and H+ combine with e- to make FADH2

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Respiration

One glucose molecule is capable of producing a net amount of 36-38 ATP during the entire process of cellular respiration. 2 in glycolysis 2 from the Krebs Cycle 32 to 34 from the electron transport chain

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Fermentation

When oxygen isn’t available, the aerobic stages of respiration obviously can’t begin.

In this situation, fermentation begins after glycolysis as an alternate form of respiration. Why can glycolysis still go on?

Fermentation provides small amounts of ATP until the cell can once again obtain enough oxygen to begin the aerobic stages of respiration. **does not last long**

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Fermentation

Two main types – Alcoholic Fermentation

Common in yeast cells. CO2 and alcohol is produced.

Example: bread

Lactic Acid Fermentation Occurs in animal muscle cells. Lactic

acid is produced. Example: pain in muscles from exercise

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Yeast in Bread

Yeast is a fungus It consumes theSugar in the dough-Dough is left to “rise”-Yeast produces

alcohol and CO2 during fermentation

-Alcohol evaporates as bread cooks

-CO2 makes bubbles – holes in bread

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ATP and Exercise Running Sprinting uses energy:

Stored in muscles: runs out quickly; within seconds Made by lactic acid fermentation: (oxygen depleted)

made quickly, runs out quickly (about 90 seconds); lactic acid produced = burning sensation in legs

Explains why a sprinter breathes very heavily at the end of a race

Long Term Energy Made by cellular respiration: needs oxygen which is

why runners breathe heavily Makes energy slower than fermentation; runners pace

themselves Glycogen stores last for about 15-20 minutes of activity After that, body breaks down fats and other stored

molecules for energy Aerobic Exercises = help with weight control