CHAPTER 9 - CELLULAR RESPIRATION

CELLULAR RESPIRATION Process that releases energy by breaking down food molecules in the presence of oxygen 6 O 2 + C 6 H 12 O 6 --> 6 CO H 2 0+ATP oxygen + glucose --> carbon dioxide + water + energy

3 Stages of Cellular Respiration 1.Glycolysis 2.Krebs Cycle 3.Electron Transport Chain Each stage captures some of the chemical energy available in food molecules and uses it to produce ATP

Energy Molecules of Cellular Respiration In cellular respiration, several molecules are used as energy carriers. These molecules carry energy from one step of cellular ADP + P = ATP NAD + H = NADH FAD + + H 2 = FADH 2

GLYCOLYSIS Glycolysis – First step in releasing the energy of glucose. A molecule of glucose is broken into two molecules of pyruvic acid (a 3-carbon compound). –takes place in the cytoplasm –does not require oxygen - anaerobic

GLYCOLYSIS Requires: 1 Glucose molecule (C 6 H 12 O 6 ), 2 ATP Produces: 2 ATP, 2 NADH and 2 pyruvic acid

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.

Glycolysis Glycolysis Fermentation Krebs Cycle Fermentation Krebs Cycle Anaerobic (no oxygen) Aerobic (oxygen)

Without Oxygen - Fermentation Anaerobic - without the presence of oxygen Fermentation - releases energy from food molecules in the absence of oxygen two types: Alcoholic and Lactic Acid Fermentation Occurs in the cytoplasm

Types of Fermentation Alcoholic - causes bread to rise, used to make beer and wine Lactic Acid - produced in muscles during rapid exercise when body can’t supply enough O 2 –causes painful, burning sensation and muscle soreness

With Oxygen - Kreb’s Cycle Aerobic - in the presence of oxygen Kreb’s Cycle also called Citric Acid Cycle Kreb’s Cycle - 2nd stage of cellular respiration, in which pyruvic acid is broken down into CO 2 in a series of energy-extracting reactions, creating energy molecules. –Occurs in the mitochondria

Kreb’s Cycle Requires: 1 Pyruvic Acid Produces: CO 2, NADH, FADH 2, ATP

Kreb’s Cycle As a pyruvic acid molecule enters the mitochondria, a carbon is removed, forming CO 2. Carbons continue to be rearranged, releasing more CO 2, while allowing the energy carriers to be charged. This cycle will happen twice for every molecule of glucose broken down in glycolysis.

Third Stage: Electron Transport Chain The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP. –Occurs in the mitochondrial matrix.

Electron Transport Chain (ETC) Requires: NADH, FADH 2, ADP Produces: H 2 O, NAD, FAD, ATP

Electron Transport Chain 1.The Krebs Cycle generates high- energy electrons that are passed to NADH and FADH 2. 2.The high-energy electrons (H+) from NADH and FADH 2 are used up and passed along the proteins in the ETC.

Electron Transport Chain 3.Oxygen serves as the final electron acceptor forming a water molecule. 4.As H+ ions move through the ETC, ATP synthase spins adding ADP to P forming ATP.

Cellular Respiration Totals 1 molecule of glucose produces: –2 ATP in glycolysis –34 ATP in Kreb’s Cycle and Electron Transport Chain –water –CO 2

Types of Energy Quick Energy - Muscles only contain enough ATP for a few seconds of intense activity. Then, muscle cells produce their ATP by lactic acid fermentation. Long Term Energy - Cellular Respiration is the only way to generate a continuing supply of ATP –energy is released more slowly than fermentation, which is why athletes have to pace themselves –15 to 20 min. of activity from carbohydrate stored in the body –after 20 min., energy comes from break down of fats

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

Photosynthesis vs. Respiration Photosynthesis: –Use light energy to build a sugar. –Process that “deposits” or captures energy. –Removes carbon dioxide from the atmosphere. –Releases oxygen into the atmosphere.

Photosynthesis vs. Respiration Respiration: –Break down sugar to release energy. –Process that “withdraws” or releases energy. –Removes oxygen from the atmosphere. –Releases carbon dioxide into the atmosphere.