Aerobic Respiration + The 1980s? Check it out! Check it out!

7-2: Aerobic Respiration  In most cells, glycolysis does not result in fermentation.  Instead, if O 2 is available, pyruvic acid undergoes aerobic respiration, or cellular respiration that requires O 2 Also known as oxidative respiration Also known as oxidative respiration

Overview of Aerobic Respiration  Aerobic Respiration has 2 major stages: 1. Krebs Cycle – oxidation of glucose is completed; makes molecules of NADH; produces a small amount of ATP 2. Electron Transport Chain + Chemiosmosis – uses NADH to make ATP; produces most of the ATP

Prokaryotes vs. Eukaryotes  In Prokaryotes, the reactions of the Krebs Cycle and ETC takes place in the cytosol of the cell  In Eukaryotes, the reactions of the Krebs Cycle and ETC takes place in the mitochondria Pyruvic acid diffuses across the membrane of mitochondria into the mitochondrial matrix Pyruvic acid diffuses across the membrane of mitochondria into the mitochondrial matrix The matrix contains enzymes needed to catalyze the rxns of the Krebs cycle The matrix contains enzymes needed to catalyze the rxns of the Krebs cycle

Overview (cont.)  Pyruvic acid reacts with a molecule called Coenzyme A to form acetyl CoA CO 2 is given off and NAD + is reduced to NADH CO 2 is given off and NAD + is reduced to NADH

Stage I - Krebs Cycle  Biochemical pathway that breaks down acetyl CoA producing CO 2, H atoms, + ATP AKA – TCA Cycle or Citric Acid Cycle AKA – TCA Cycle or Citric Acid Cycle  Identified + named after German scientist Hans Kreb  Reactions take place in the mitochondrial matrix

Krebs Cycle (5 Steps) 1. Acetyl CoA combines w/ a 4-C compound, oxaloacetic acid to produce a 6-C compound, citric acid. Reaction regenerates coenzyme A Reaction regenerates coenzyme A

Krebs Cycle 2. Citric acid releases a CO 2 and H to form a 5-C compound Citric acid gets oxidized Citric acid gets oxidized H atom transfers to NAD NAD + reduced to NADH H atom transfers to NAD NAD + reduced to NADH

Krebs Cycle 3. The 5-C compound releases a CO 2 molecule and H to form a 4-C compound NAD + is reduced to NADH NAD + is reduced to NADH ATP created from ADP ATP created from ADP

Krebs Cycle 4. The 4-C compound releases a H atom to form another 4-C compound H transferred to FAD (accepts e - during redox) H transferred to FAD (accepts e - during redox) FAD gets reduced to FADH 2FAD gets reduced to FADH 2

Krebs Cycle 5. The 4-C compound releases a H atom to regenerate oxaloacetic acid, which keeps the Krebs cycle going NAD + reduced to NADH NAD + reduced to NADH

Krebs Cycle  Video clip Video clip Video clip

What’s been accomplished thus far…  One glucose molecule = 2 pyruvic acid molecules = 2 acetyl CoA molecules = 2 turns of Krebs Cycle  These turns produce: 6 NADH 6 NADH 2 FADH 2 2 FADH 2 2 ATP 2 ATP 4 CO 2 4 CO 2  NOT ENOUGH ENERGY TO LIVE OFF OF…

So what now?  Use our energy-carrying molecules NADH + FADH 2NADH + FADH 2 Total # of Molecules:Total # of Molecules: 10 NADH (2 – Gly; 2 – PA to Acetyl CoA; 6 – Krebs) 10 NADH (2 – Gly; 2 – PA to Acetyl CoA; 6 – Krebs) 2 FADH 2 (2 – Krebs) 2 FADH 2 (2 – Krebs)  Take them and go to next stage of AR…… THE ELECTRON TRANSPORT CHAINTHE ELECTRON TRANSPORT CHAIN

Stage II – ETC + Chemiosmosis  Series of molecules that transfer electrons from one molecule to another  In Eukaryotes, the ETC takes place in the inner membrane of mitochondria  In Prokaryotes, the ETC takes place in the cell membrane ATP is produced by ETC when NADH + FADH 2 release H atoms ATP is produced by ETC when NADH + FADH 2 release H atoms

THE ELECTRON TRANSPORT CHAIN (5 Steps) 1. NADH + FADH 2 donate electrons to the ETC. They also donate protons (H + ) NADH – 3 e - NADH – 3 e - FADH 2 – 2 e - FADH 2 – 2 e - NADH = 10 * 3 = 30 total e - FADH 2 = 2 * 2 = 4 total e -

ETC (cont.) 2. The e - are passed along a chain from molecule to molecule in a series of redox reactions. As they are passed, they lose energy.

ETC (cont.) 3. The energy lost by electrons are used to pump protons from the matrix outside the inner mitochondrial membrane (cristae). A concentration gradient and electrical gradient are created.

ETC (cont.) 4. The concentration + electrical gradients drive the synthesis of ATP by Chemiosmosis. As protons move through molecules of ATP synthase, ATP is made from ADP + phosphate

ETC (cont.) 5. The final acceptor of electrons is oxygen. It also accepts protons and combines to make molecules of water

ETC (cont.)  Note: If electrons weren’t able to be picked up by oxygen at the end of the ETC chain, the entire process of chemiosmosis would stop! NO ATP MADE FOR CELLS TO DO WORK NO ATP MADE FOR CELLS TO DO WORK

Efficiency of Cellular Respiration  ATPs produced ~38 Actually get only 36 ATPs due to active transport of NADH molecules across cristae of mitochondria Actually get only 36 ATPs due to active transport of NADH molecules across cristae of mitochondria  Cellular Respiration Efficiency ~ 39% 20x more efficient that glycolysis alone 20x more efficient that glycolysis alone More efficient than most machines (25%) More efficient than most machines (25%) Some energy lost as heat Some energy lost as heat

Energy Yield of Cellular Respiration

What is the equation for the complete oxidation of glucose?  C 6 H 12 O 6 + 6O > 6CO 2 + 6H energy (heat and ATP)

 In addition to glucose, other compounds can be broken down by cells as a source of fuel. They can also enter Glycolysis and/or the Krebs Cycle at any time to yield more energy to an organism.  What are these other compounds? FATS FATS PROTEINS PROTEINS CARBOHYDRATES CARBOHYDRATES

Why isn’t CR the reverse of Photosynthesis?  Involve different biochemical reactions P – Light Rxns (ETC/Chemiosmosis) + Calvin Cycle P – Light Rxns (ETC/Chemiosmosis) + Calvin Cycle CR – Glycolysis, Krebs Cycle,+ ETC/Chemiosmosis CR – Glycolysis, Krebs Cycle,+ ETC/Chemiosmosis  Occur at different sites in cells P – Chloroplasts P – Chloroplasts CR - Mitochondria CR - Mitochondria

Functions of CR  Major: CR provides the ATP that all cells need to support the activities of life CR provides the ATP that all cells need to support the activities of life Body uses 100,000,000,000,000,000,000 (1x10 20 ) ATP each secondBody uses 100,000,000,000,000,000,000 (1x10 20 ) ATP each second  Minor: Building of macromolecules Building of macromolecules Can’t get them from food – so must be made from compounds in Glycolysis + Krebs CycleCan’t get them from food – so must be made from compounds in Glycolysis + Krebs Cycle

C.R. video Video Recap Video Recap