Chapter 9.3 Cellular Respiration Mrs. Geist Biology Swansboro High School Fall

Warm-Up 9/28/2010  Given the equation for cellular respiration, explain it using words and relate it to the equation for photosynthesis.  C 6 H 12 O O 2  6CO 2 + 6H 2 O

Essential Questions 9/28/2010  How do light reactions relate to the overall process of photosynthesis?  How does the Calvin cycle relate to the overall process of photosynthesis?  How does the glycolysis relate to the overall process of aerobic cellular respiration?

Photosynthesis vs. Cellular Respiration  The energy flows in photosynthesis and cellular respiration take place in opposite directions.  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 energy from food. Photosynthesis Cellular Respiration

9-3 Getting Energy to Make ATP  Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Plant Animal Cells Plant Cells Mitochondrion

Chemical Energy and Food  1g of glucose (C 6 H 12 O 6 ), when burned in the presence of oxygen, releases 3811 calories of heat energy.  A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.  Cells don't “burn” glucose. Instead, they gradually release the energy from glucose and other food compounds.  This process begins with a pathway called glycolysis.  Glycolysis releases a small amount of energy.  Takes place in the cytoplasm.

Overview of Cellular Respiration  Glycolysis does not require oxygen.  If oxygen is present, glycolysis is followed by the Krebs cycle and the electron transport chain.  3 Stages of Cellular Respiration:  Glycolysis  Occurs in the cytoplasm  the Krebs cycle  Occurs in the mitochondria  the electron transport chain  Occurs in the mitochondria  Each of the 3 stages of cellular respiration captures some of the chemical energy available in food molecules and uses it to produce ATP.

Copyright Pearson Prentice Hall  Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria. Animal Cells Plant Cells Mitochondrion Outer membrane Intermembrane space Inner membrane Matrix Mitochondria

Copyright Pearson Prentice Hall Overview of Cellular Respiration Cytoplasm Pyruvic acid Mitochondrion Electrons carried in NADH Electrons carried in NADH and FADH 2 Glucose Glycolysis

Cellular Respiration  Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.  The equation for cellular respiration is:  6O 2 + C 6 H 12 O 6 → 6CO 2 + 6H 2 O + Energy  oxygen + glucose → carbon dioxide + water + energy

Glycolysis  Glycolysis is the process in which one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid, a 3-carbon compound.  The cell uses up 2 molecules of ATP to start the reaction but produces 4 ATP molecules  2 net ATP. 2 ADP 4 ADP 4 ATP 2 Pyruvic acid 2 ATP

Glycolysis  One reaction of glycolysis removes 4 high-energy electrons, passing them to an electron carrier called NAD + and becomes an NADH molecule.  The NADH molecule holds the electrons until they can be transferred to other molecules in the Electron Transport Chain. 2 Pyruvic acid 4 ADP 4 ATP 2 ADP 2 ATP 2NAD + 2 To the electron transport chain

Fermentation  When oxygen is not present, glycolysis is followed by a different pathway.  The combined process of this pathway and glycolysis is called fermentation.  Fermentation releases energy from food molecules by producing ATP in the absence of oxygen.  Fermentation does not require oxygen—it is an anaerobic process.  During fermentation, cells convert NADH to NAD + by passing high-energy electrons back to pyruvic acid.  This action converts NADH back into NAD +  It allows glycolysis to continue producing a steady supply of ATP.

2 Types of Fermentation 1.Lactic Acid Fermentation  In many cells, pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid.  Ex: muscle cells  Build-up of pyruvic acid causes muscle soreness  Pyruvic acid + NADH → lactic acid + NAD + 2.Alcoholic Fermentation  Yeasts and a few other microorganisms  Ex: Bakers Yeast  Alcoholic fermentation gives off CO 2, which causes bread to rise  Ex: Milk is converted to yogurt by microorganisms in milk which undergo alcoholic fermentation producing acid  pyruvic acid + NADH → ethyl alcohol + CO 2 + NAD +

 The raw materials required for cellular respiration are  carbon dioxide and oxygen.  glucose and water.  glucose and oxygen.  carbon dioxide and water. 9-3 Question 1

Copyright Pearson Prentice Hall  Glycolysis occurs in the  mitochondria.  cytoplasm.  nucleus.  chloroplasts. 9-3 Question 2

Copyright Pearson Prentice Hall  The net gain of ATP molecules after glycolysis is  3 ATP molecules.  2 ATP molecules.  3 pyruvic acid molecules.  4 pyruvic acid molecules. 9-3 Question 3

Copyright Pearson Prentice Hall  Fermentation releases energy from food molecules in the absence of  oxygen.  glucose.  NADH.  alcohol. 9-3 Question 4

Copyright Pearson Prentice Hall  The first step in fermentation is always  lactic acid production.  the Krebs cycle.  glycolysis.  alcohol production. 9-3 Question 5

The Krebs Cycle & Electron Transport Chain  Oxygen is required for the final steps of cellular respiration.  Because the pathways of cellular respiration require oxygen, they are aerobic.  In the presence of oxygen, pyruvic acid produced in glycolysis passes to the second stage of cellular respiration, the Krebs cycle.  Occurs in the mitochondria  pyruvic acid is broken down into carbon dioxide.  The energy tally from 1 molecule of pyruvic acid is  3 NADH  1 FADH 2  1 ATP

Electron Transport Chain (ETC)  What does the cell do with all those high-energy electrons in carriers like NADH?  In the presence of oxygen, those high-energy electrons can be used to generate huge amounts of ATP.  The ETC uses the high-energy electrons from the Krebs cycle to convert ADP into ATP.  High-energy electrons from NADH and FADH 2 are passed along the electron transport chain from one carrier protein to the next.

Copyright Pearson Prentice Hall Electron Transport Chain  High-energy electrons from NADH and FADH 2 are passed along the electron transport chain from one carrier protein to the next.  As the final electron acceptor of the electron transport chain, oxygen gets rid of the low- energy electrons and hydrogen ions.  Net 32 ATP

Krebs Cycle & Electron Transport  On average, each pair of high-energy electrons that moves down the electron transport chain provides enough energy to produce three molecules of ATP from ADP.  Glycolysis produces just 2 ATP molecules per molecule of glucose.  Fermentation yields only 2 ATP.  The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

Copyright Pearson Prentice Hall  The Krebs cycle breaks pyruvic acid down into  oxygen.  NADH.  carbon dioxide.  alcohol. 9-2 Question 1

Copyright Pearson Prentice Hall  What role does the Krebs cycle play in the cell?  It breaks down glucose and releases its stored energy.  It releases energy from molecules formed during glycolysis.  It combines carbon dioxide and water into high-energy molecules.  It breaks down ATP and NADH, releasing stored energy. 9-2 Question 2

Copyright Pearson Prentice Hall  In eukaryotes, the electron transport chain is located in the  cell membrane.  inner mitochondrial membrane.  cytoplasm.  outer mitochondrial membrane. 9-2 Question 3

Copyright Pearson Prentice Hall  To generate energy over long periods, the body must use  stored ATP.  lactic acid fermentation.  cellular respiration.  glycolysis. 9-2 Question 4

Copyright Pearson Prentice Hall  Which statement correctly describes photosynthesis and cellular respiration?  Photosynthesis releases energy, while cellular respiration stores energy.  Photosynthesis and cellular respiration use the same raw materials.  Cellular respiration releases energy, while photosynthesis stores energy.  Cellular respiration and photosynthesis produce the same products. 9-2 Question 5