…transferring a phosphate group to another molecule = phosphorylation -- use a little ATP to net a larger amount of kinetic E (work)

…have to make $ to spend $

How do cells do work? ATP is involved What organelles are responsible for energy conversion? Converting E from sugar in the presence of O 2 = cellular respiration …the cell captures E released as ATP

Respiration vs. Breathing Exchange of gases… O 2 in & CO 2 out Aerobic energy harvesting = cellular respiration …more work requires more O 2

Energy extraction by cells… Glucose = = C 6 H 12 O 6 = potential E electrons (energy) transfer as carbon - hydrogen bonds break …hydrogen-oxygen bonds form as water Transfer of electrons from reactants to products side of reaction = oxidation-reduction reaction (redox reaction)

3 main stages of cellular respiration Glycolysis –Breaking glucose into –a 3-carbon, pyruvate Citric acid cycle –Modifies pyruvate Oxidative phosphorylation –Uses the E from electron transport chain to phosphorylate ADP

Electrons are shuttled by NAD + –an enzyme, nicotinamide adenine dinucleotide, that gets reduced (gain of H) to NADH

6.8 Pyruvate is chemically groomed for the citric acid cycle The pyruvate formed in glycolysis is transported to the mitochondria, where it is prepared for entry into the citric acid cycle –The first step is removal of a carboxyl group that forms CO 2 –The second is oxidization of the two-carbon compound remaining –Finally, coenzyme A binds to the two-carbon fragment forming acetyl coenzyme A Copyright © 2009 Pearson Education, Inc.

Coenzyme A Pyruvate Acetyl coenzyme A CoA NAD + NADH  H + CO

6.10 Most ATP production occurs by oxidative phosphorylation Oxidative phosphorylation involves electron transport and chemiosmosis and requires an adequate supply of oxygen –NADH and FADH 2 and the inner membrane of the mitochondria are also involved –A H + ion gradient formed from all of the redox reactions of glycolysis and the citric acid cycle provide energy for the synthesis of ATP Copyright © 2009 Pearson Education, Inc.

ATP H+H+ Intermembrane space O2O2 H2OH2O 1212 Inner mitochondrial membrane H+H+ NAD + H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Mitochondrial matrix Electron flow Electron carrier Protein complex of electron carriers NADH FADH 2 FAD ATP synthase P ADP + Chemiosmosis + 2 O XIDATIVE P HOSPHORYLATION Electron Transport Chain

Electron transport chain NADH delivers electrons (e - ) to a cascade of reactions …like a slinky moving down a staircase…keeps momentum resulting in a net release of greater E

6.9 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH 2 molecules With the help of CoA, the acetyl (two- carbon) compound enters the citric acid cycle –At this point, the acetyl group associates with a four-carbon molecule forming a six-carbon molecule –The six-carbon molecule then passes through a series of redox reactions that regenerate the four-carbon molecule (thus the “cycle” designation) Copyright © 2009 Pearson Education, Inc.

C ITRIC A CID C YCLE NAD + NADH 3 H + CO 2  CoA Acetyl CoA P ADP + ATP FADH 2 FAD

C ITRIC A CID C YCLE CoA 2 carbons enter cycle Acetyl CoA CoA 1 Oxaloacetate 1 Step Acetyl CoA stokes the furnace.

C ITRIC A CID C YCLE CoA 2 carbons enter cycle Acetyl CoA CoA 1 Oxaloacetate 1 Step Acetyl CoA stokes the furnace. 2 3 NAD + NADH CO 2 Citrate ADP + + H + P Alpha-ketoglutarate leaves cycle ATP NAD + NADH CO 2 + H + leaves cycle Steps – NADH, ATP, and CO 2 are generated during redox reactions. 23

C ITRIC A CID C YCLE CoA 2 carbons enter cycle Acetyl CoA CoA 1 Oxaloacetate 1 Step Acetyl CoA stokes the furnace. 2 3 NADH CO 2 Citrate ADP  P Alpha-ketoglutarate leaves cycle ATP NADH CO 2 leaves cycle Steps – NADH, ATP, and CO 2 are generated during redox reactions NAD + NADH Malate + H + 4 FADH 2 FAD Succinate Steps – Redox reactions generate FADH 2 and NADH. 45 NAD + + H + NAD + + H +

How much energy or ATP is produced for each glucose molecule?

Is this system efficient? 38 ATPs = 40% of the potential E in glucose 60% escapes as heat Auto engine converts 25% E from fuel Muscle use 10,000,000 ATP per second

Fermentation (animal cells) Oxidize organic fuel & produce ATP without oxygen –Anaerobic alternative –Relies on glycolysis (1 st step of respiration) Only 2 ATPs –Then…converts pyruvate to lactate –muscle burn –Lactate is recycled by liver

Fermentation (yeast) Oxidize organic fuel & produce ATP without oxygen –Anaerobic alternative –Relies on glycolysis (1 st step of respiration) Only 2 ATPs –Then…converts pyruvate to ethanol and CO 2 –Gas bubbles in beer & champhagne, dough to rise –Alcohol is produced as yeast waste…eventually killing ‘em