CELLULAR RESPIRATION

  Where do we get our E from?  Food!  Food gives us:  Ability to grow/reproduce  Raw materials  E needed to “use” these materials 9-1 Chemical Pathways

  Calorie: amount of E needed to raise 1g of water 1°C  “calorie” on food labels = kilocalorie  1 kilocalorie = 1000 calories  Cells release E stored in food  Starts with process called “glycolysis”  “glyco” = sugar  “lysis” = split Chemical E and Food

  Releases E by breaking down glucose and other food molecules in the presence of O 2  6O 2 + C 6 H 12 O 6 = 6CO 2 + 6H 2 O + E  Look familiar?  Happens in gradual steps  Traps E in ATP Cellular Respiration

  1 st step of cellular respiration  Happens in cytoplasm  GOAL: 1 glucose converted to 2 pyruvic acid  ATP production  NADH production- accepts electrons/E  Starts as NAD+  Just like NADPH in photosynthesis! Glycolysis

  E yield is small but occurs fast so LOTS of ATP can be made  No need for O 2  When all NAD+ filled with electrons (making NADH), ATP production pauses  When do you think it will start again?  When more NAD+ is available! Glycolysis

  If O 2 is present, move on with cell respiration  If no O 2 present...FERMENTATION!  Fermentation: releases E in food by producing ATP without O 2 Now what?

  NADH is converted back to NAD+  If more NAD+, ATP production can continue  “anaerobic” process- no O 2 needed Fermentation Fermentation!

  1. Alcoholic fermentation  Pyruvic acid + NADH = alcohol + CO 2 + NAD+  ex: yeasts, bread dough  2. Lactic acid fermentation  Pyruvic acid + NADH = lactic acid + NAD+  ex: muscle cells, food/beverages Fermentation (creating more NAD+)

  At end of glycolysis, 90% of E is still unused  Stored in pyruvic acid  MUST have O 2 (aerobic!)  O 2 = electron acceptor  When O 2 present, pyruvic acid moves to Krebs Cycle 9-2 Krebs Cycle and Electron Transport Chain

  GOAL: Pyruvic acid  CO 2 + E  Aka: citric acid cycle (1 st compound formed)  Happens in the mitochondria  Occurs in 2 steps Krebs Cycle

  Citric acid production  Pyruvic acid  acetyl CoA +CO 2 +NADH  CO 2 = waste product  NADH = electron/E acceptor  Then Acetyl CoA  citric acid Krebs Cycle Step 1

  Energy extraction  Citric acid  CO 2 +NADH + FADH 2 + ATP  + a series of C compounds  E totals: 4 NADH, 1 FADH 2, 1 ATP Krebs Cycle Step 2

  1. CO 2 - released as waste  2. ATP- E used for cell activities  3. NADH + FADH 2 - E carriers  move onto electron transport chain… Products of Krebs Cycle ATP NADH FADH 2

  Uses electrons carried from glycolysis and Krebs cycle  NADH and FADH 2  Travel down ETC- lose E  E picked up and used to bring H+ into intermembrane space of mitochondria- buildup Electron Transport Chain (ETC)

  O 2 is final electron acceptor in chain  O 2 + H + + electrons = water!  H+ buildup in intermembrane space  Move thru ATP synthase protein  ADP + P  ATP  LOTS of ATP! Electron Transport Chain (ETC)

  36 ATP produced by 1 glucose  Any E not used is released as heat  Why you feel warm after exercise  Waste products = CO 2 and water Totals: 6O 2 + C 6 H 12 O 6 = 6CO 2 + 6H 2 O + E ATP oxygen glucose carbon dioxide water

  3 places to get ATP  1. Stored ATP  2. New ATP from lactic acid fermentation  3. New ATP from cell resp.  At first, you can use all three  Over time, stored ATP and lactic acid ferm. run out  Then must rely on cell resp. alone Energy and Exercise

  Used stored ATP (only lasts a few sec)  Then lactic acid ferm. (lasts ~90 sec)  Then you go into O 2 debt  Must be “repaid” by heavy breathing Quick Energy

  Must rely on cell resp.  Slower at supplying ATP but lasts longer (15-20 min)  E stored in muscles as glycogen  After 20 min. the body will breakdown other compounds for E (fats, proteins, etc) Long-term Energy

  Opposite E flows  Photosynthesis provides the food (for plants)  Cell Respiration turns it into E for release Comparing and Contrasting Photosynthesis and Cell Respiration PhotosynthesisCell Respiration FunctionMake food (E source) Energy release from food Locationchloroplastsmitochondria ReactantsCO 2, H 2 O, light EC 6 H 12 O 6 and O 2 ProductsC 6 H 12 O 6 and O 2 CO 2, H 2 O and E (ATP) Equation6CO 2 + 6H 2 O + light E  C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + E