What is Cellular Respiration? “The process that releases energy from food in the presence of oxygen”… this is how organisms get the energy they need from food 6O ₂ + C ₆ H ₁₂ O ₆  6CO ₂ + 6H ₂ O + 36 ATP (energy) 6 oxygen + glucose  6 carbon dioxide + water + energy What equation does this look similar to?

Two Types of Cellular Respiration Aerobic respiration- involves the use of oxygen Anaerobic respiration- does not involve the use of oxygen

3 Stages of Cellular Respiration Glycolysis Krebs Cycle Electron Transport Chain

1 st Stage:Glycolysis- “sugar-breaking” Starting ReactantEnd Product 1 molecule of glucose2 molecules of pyruvic acid & 2 NADH Takes place in the cytoplasm Is very quick Does not require oxygen Synthesizes the following: Net gain of 2 ATP NADH and pyruvic acid  used in other processes of cellular respiration in the presence of oxygen

Investment! Net Gain! Each PGAL gives up 2 e- forming NADH… sent to e- transport chain P P P P +P P P P P

2 nd Stage: Krebs Cycle AKA Citric Acid Cycle Occurs in the presence of O ₂ Takes place in the mitochondria when pyruvic acid passes through its two membranes into the matrix Starting ReactantEnd Products Pyruvic Acid CO ₂, ATP, NADH,& FADH 2

Energy Extraction Every molecule of glucose  2 molecules of pyruvic acid Every pyruvic acid turns the Krebs Cycle once On every turn, 4 molecules of NADH &1 molecule of FADH ₂ are produced 1 molecule of ATP is produced to power cell activity

2 Acetyl-CoA 2 Pyruvic Acid 2CO ₂ Combines w/ 4 C cmpd. Forms Citric Acid 2 To e- transport chain This diagram represents two turns of the cycle! 2

Electron Transport Chain Occurs in the presence of O ₂ Occurs in the mitochondria e- transport chain: series of e- carriers in the inner membrane of the mitochondria Uses high energy electrons from glycolysis and Krebs cycle to convert ADP to ATP High energy e- are found in NADH and FADH 2

Electron Transport When 2 e- are passed down e- transport chain, energy transports H ions across membrane (to intermembrane) H ions build in the intermembrane compartment (space between the inner & outer membrane)

ATP Production Inner mitochondrial membrane has ATP synthases Concentration difference across the membrane forces H ions through channels  causes ATP synthetases to spin Each spin causes synthetase to grab ADP, attach a phosphate group  ATP Every pair of high energy e- produces ATP NADH- 3 ATP FADH2- 2ATP

Which occurs most often? Photosynthesis or Cellular Respiration? Photosynthesis... 21% oxygen in the atmosphere &.035% CO ₂ in the atmosphere Surplus of carbs… source for all food chains Plants need O ₂ to do aerobic respiration Cellular respiration needs the sugars made by photosynthesis

Glycolysis Glucose 2 Pyruvate 6 H ₂ O 6 O ₂ 2 CO ₂ 4 CO ₂ 2 ATP 34 ATP 4 ATP Coenzymes E- and H In the cytoplasm In the mitochondria 6O ₂ + C ₆ H ₁₂ O ₆  6CO ₂ + 6H ₂ O + up to 36 ATP

Glycolysis & Beyond If oxygen is present at the end of glycolysis, products move to Krebs Cycle. If oxygen is not present, the products of glycolysis move on to fermentation (stays in cytoplasm). Fermentation: the process by which cells release energy w/o the presence of oxygen

When O ₂ is not available… Cells generate ATP quickly from glycolysis, in a few seconds all the cell’s NAD+ are filled with e-  NADH W/o oxygen, the e- transport system does not run and NADH can not deposit its e-… this is where fermentation comes in

Glycolysis to Fermentation During fermentation, NADH is converted to NAD+ by passing high energy electrons back to pyruvic acid… thus glycolysis can continue producing ATP P P P P +P P P P P

Two Types of Fermentation Alcoholic fermentation: produces ethyl alcohol & CO ₂ Alcohol used for yeast to make bread & alcoholic beverages Lactic Acid fermentation: converts pyruvic acid to lactic acid Used to make a wide variety of dairy products Is the cause of muscle cramping… charley horse!

Quick vs. Long-Term Energy QuickLong-Term The body uses ATP already in muscles as well as ATP made by lactic acid fermentation Lactic Acid supplies enough ATP for 90 sec. Heavy breathing eventually restores the oxygen debt & return to cellular respiration Cellular respiration releases energy slower than fermentation Cellular respiration supplies energy for anything longer than 90sec. The body uses glycogen then other macromolecules for energy