Chapter 9 CELLULAR RESPIRATION

Relationship of Processes Respiration: exergonic (releases E) C6H12O6 + 6O2  6H2O + 6CO2 + ATP (+ heat) Photosynthesis: endergonic (requires E) 6H2O + 6CO2 + Light  C6H12O6 + 6O2

location: mitochondrial cristae Cellular Respiration complex process whereby cells make ATP by breaking down organic compounds(glucose) many rxns in aerobic respiration are redox: (one reactant is oxidized while another is reduced) location: mitochondrial cristae

Oxidation and Reduction loses e- (donor) gains e- (acceptor) Not all electrons are transferred from one substance to another, some change the degree of e- sharing in covalent bonds.

Glucose Catabolism Catabolic Pathway Complex organic Simpler waste molecules products with less E Some E used to do work and dissipated as heat Oxygen is extremely electronegative Oxidation of glucose transfers e- to lower energy state- does main work of respiration releases energy to make ATP ** done in series of steps**

Moving Electrons Electron Carriers Electrons cannot move alone in cells Move as part of H atom Energy is released as electrons “fall” from organic molecule to O2. Electron Carriers Move electrons by shuttling H atoms around NAD+  NADH FAD+2  FADH2

NAD+ Coenzyme (nicotinamide adenine dinucleotide) Electron acceptor- carries electrons to ETC Acts as an oxidizing agent during respiration Dehydroginase(enzyme)- catalyzes NAD+  NADH NAD animation

Electron Transport Chain ETC breaks the fall of electrons of oxidation of glucose into series of smaller steps Released energy is used to make ATP Extra energy is released as heat.

Glycolysis (glucose/splitting) GLUCOSE(6C)is partially oxidized end products: 2 PYRUVATE(3C), 2 NADH, 2 ATP - occurs in cytosol - 1st step: always occurs before respiration or fermentation - occurs in the absence of oxygen - ancient pathway (early prokaryotes) - inefficient

Glycolysis Overview Stage 1: Energy Investment Cell uses ATP to phosphorylate glucose Endergonic Stage 2: Energy Payoff Two 3-C compounds oxidized Exergonic Yield 2 pyruvate 2 NADH 2 ATP- substrate-level phosphorylation - Phosphate comes from sugar substrate(PEP), not ETC

Steps of Glycolysis glycolysis animation

2 Possible Pathways for Pyruvate If O2 present If no O2 present respiration fermentation (aerobic) (anaerobic respiration) mitochondria cytosol

Stages of Cellular Respiration 1. Glycolysis 2. Citric Acid(Krebs)Cycle 3. Oxidative Phosphorylation

Cellular Respiration(aerobic) C6H12O6 + 6 O2  6 H2O + 6 CO2 + 32 ATP Process of breakdown of pyruvate in the presence of oxygen - prokaryotic cells: occurs in cytosol - eukaryotic cells: occurs in mitochondria - much more efficient than anaerobic respiration

2 Major Stages of Respiration 1. Citric Acid Cycle - oxidation of glucose is completed - NADH and FADH2 are produced 2. Electron transport chain - NADH is used to make ATP via oxidative phosphorolation - location where most ATP is made

Location of Processes Citric Acid Cycle (matrix) ETC (inner membrane of cristae)

Pyruvate oxidized to Acetyl CoA Occurs before the Citric Acid Cycle 3 step oxidation process NAD+ reduced to NADH (acetate formed) Coenzyme A attached to acetate to form Acetyl CoA CO2 by-product is released into atmosphere Pyruvate + CoA + NAD+  Acetyl CoA + CO2 + NADH

Citric Acid Cycle (Krebs Cycle) 2 pyruvate from glycolysis enter cycle Occurs in mitochondrial matrix Glucose is fully oxidized

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Oxidative Phosphorylation (production of ATP) Electron Transport Chain Occurs in inner membrane of mitochondria Produces ATP by oxidative phosphorylation via chemiosmosis Chemiosmosis H+ ions pumped across inner mitochondrial membrane H+ ions diffuse through ATP synthase to make ATP

Electron Transport Chain Collection of molecules embedded in inner membrane of mitochondria Tightly bound protein complexes FADH2 and NADH donate e- for electron transport (redox rxns) for ATP synthesis Does not make ATP directly, ATP made through chemiosmosis O2 is final e- acceptor from H+ to form H2O

Oxidative Phosphorylation

Energy Coupling of Chemiosmosis How ATP Synthase Works H+ ions enter stator (1/2 channel) in membrane H+ ions enter rotor- changes shape of subunits Rotor spins within membrane Each H+ ion makes one complete turn Passes into matrix Turning of rod produces ATP from ADP and Pi animation ETC

Fermentation = glycolysis + regeneration of NAD+ Lactate Fermentation (animals) - pyruvate converted to lactate A. NADH is oxidized and donates its H to pyruvate B. resultant NAD returns to glycolysis where it is reduced to NADH C no release of CO2 ** 2 ATP formed ** ** process is CYCLICAL** **lactate eventually diffuses into liver where it is converted back to pyruvate when O2 again present ** 2. Alcoholic Fermentation (yeasts, plant cells, microorganisms) - pyruvate converted to ethanol A. CO2 molecule is removed from pyruvate (3C) forming acetaldehyde (2 C) B. acetyldehyde is reduced to form ethanol 2 H (from NADH + H ion) are added to 2C compound to form ethanol C. NAD is formed (back to glycolysis) ** 2 ATP formed ** ** process is CYCLICAL** **causes alcohol in beer and wine, air bubbles in bread, beer, and wine**

NO ATP FORMED IN FERMENTATION PURPOSE OF FERMENTATION: TO REGENERATE NAD FOR GLYCOLYSIS 2 ATP produce enough energy for prokaryotes and small multi-cellular eukaryotes Useful for anaerobes and facultative anaerobes Very widespread metabolic pathway of Earth’s organisms

Alternative Energy Sources What if the body runs out of sugar for glycolysis? Can the body still make ATP? YES This is how the Atkins and South Beach diets work. They are low carb, high protein/fat diets.

Alternative Energy Sources Fats as fuel: Glycerol  PGAL  glycolysis FA tails  Acetyl CoA  Krebs Proteins as fuel: proteins  amino acids Amino acids  pyruvate or acetyl CoA  Krebs

review animation

Biofeedback Regulation of Cellular Respiration Importance of Phosphofructokinase: (regulates rate of respiration) Allosteric enzyme- receptors for specific inhibitors and activators controls rate of glycolysis and citric acid cycle Inhibited by ATP and citrate citrate citric acid cycle ATP glycolysis Stimulated by AMP AMP+ P + P ATP

Oxidative Phosphorylation Review of Respiration Glycolysis Citric Acid Cycle Oxidative Phosphorylation Electron Transport Chain Chemiosmosis