UNIT III CELLULAR ENERGY
Big Campbell ~ Ch 9, 10 1 I. THE CYCLE OF LIFE 2 II. ENERGY IN THE CELL Catabolic Pathway
Breakdown of molecules that releases stored energy; exergonic rxn _____________________ partial breakdown of sugars w/o O2 ___________________________ breakdown of sugars w/ O2 Similar to a car burning gasoline Although much energy is lost as heat, some can be used to generate ATP by phosphorylating ADP Oxidation-Reduction Reactions (Redox) Energy produced in catabolism comes from transfer of e- Movement of e- releases chemical energy of molecule Released energy is used to attach Pi to ADP to form ATP 1 molecule loses an e- and a 2nd molecule gains an e- 3 II. ENERGY IN THE CELL, cont
Oxidation-Reduction Reactions, cont _________________ Loss of e- _________________ Gain of e- _________________ agent- e- donor _________________ agent- e- acceptor Sometimes there is a complete transfer of e- and other times there is a change in the degree of e- sharing in covalent bonds Inorganic Example: Na + Cl Na+ + Cl- Organic Example: 4 II. ENERGY IN THE CELL, cont
Importance of Electron Carriers Energy contained in molecules (ex: glucose) must be released in a series of steps Electrons are released as hydrogen atoms with corresponding proton (hydrogen's are clipped off) Hydrogen atoms are passed to an _________________ Electron carriers are coenzymes Carry ______ electrons in the form of H-atoms Only 1 proton & 2 electrons are delivered One H+ is released into the surrounding solution Allow for max energy transfer, minimum energy loss 5 II. ENERGY IN THE CELL, cont
Electron Carriers (oxidative states) _________ e- acceptor in cellular respiration Becomes NADH when reduced Yields about ____ ATP __________ e- acceptor in Krebs Cycle / TCA Cycle / Citric Acid Cycle e- acceptor in light reaction of photosynthesis Not used in cellular respiration 6 II. ENERGY IN THE CELL, cont
A Closer Look at Electron Carrier Function in Cellular Respiration Reduction of NAD+ ___________________ oxidizes substrate by removing 2 H-atoms NAD+ is reduced, creating NADH + H+ NADH shuttles electrons to ___________________________________________________.Electrons fall down to _______________ in a series of steps, each releasing energy in small amounts. 7 III. CELLULAR RESPIRATION OVERVIEW
8 III. CELLULAR RESPIRATION OVERVIEW, contd
Cellular process to convert chemical energy in ___________ (and other molecules) into ________ Primarily takes place in ___________________ of eukaryotic cells Overall Reaction ____________________________________________________ Steps in Cellular Respiration Glycolysis occurs in cytosol Splitting of sugar Initial breakdown of glucose to pyruvate, some ATP Citric Acid Cycle occurs in mitochondria Completes oxidation of glucose to CO2 Produces ATP, but more importantly provides high-energy electrons for ETC Electron Transport Chain occurs in mitochondria Oxidative Phosphorylation Highest ATP yield; uses energy released from downhill flow of e- to generate ATP Citric Acid Cycle + Electron Transport Chain = Oxidative Respiration 9 IV. GLYCOLYSIS 10 steps Occurs in cytosol of cell
Does not require oxygen 1st part of pathway is energy investment phase (5 steps) 2nd part of pathway is energy pay-off phase (5 steps) Energy Investment Phase 10 IV.GLYCOLYSIS, cont Energy Pay-Off Phase 11 IV.GLYCOLYSIS, cont Summary of Glycolysis 12 V. OXIDATIVE RESPIRATION
2 pyruvates formed from glycolysis still contain a tremendous amount of chemical energy If oxygen is available, pyruvate enters mitochondrion for citric acid cycle and further oxidation Upon entering mitochondrion but prior to entering citric acid cycle Grooming Step Carboxyl group of pyruvate is removed, given off as CO2 Remaining 2-C molecule is oxidized to acetate NAD+ reduced to NADH + H+ Acetate binds to molecule known as Coenzyme A to form acetyl CoA 13 V. OXIDATIVE RESPIRATION, cont
Grooming Step 14 V. OXIDATIVE RESPIRATION, cont
In the citric acid cycle (AKAKrebs cycle or TCA Cycle), 2 3-carbon molecules go through a series of redox rxns. Occurs in mitochondrial matrix Produces NADH, FADH2, ATP, and CO2. CoA is not actually a part of the reaction it is recycled remember, it is an enzyme! 15 V. OXIDATIVE RESPIRATION, cont
16 V. OXIDATIVE RESPIRATION, cont
Electron Transport Oxidative Phosphorylation Traditionally called Electron Transport, now more commonly called ________ ________________________. Occurs in inner mitochondrial membrane Membrane organized into cristae to ________________ __________________________ Two components to Oxidative Phosphorylation _________________________ 17 V. OXIDATIVE RESPIRATION, cont
Electron Transport Chain Collection of molecules, each more electronegative than the one before it Molecules are reduced, then oxidized as electrons are passed down the chain __________ is ultimate electron acceptor Purpose is to establish H+ gradient on two sides of inner mitochondrial membrane Energy from falling electrons used to pump H+ from matrix into intermembrane space 18 V. OXIDATIVE RESPIRATION, cont
Chemiosmosis Enzyme complexes known as _________________ located in inner mitochondrial membrane H+ electrochemical gradientprovides energy Known as _________________ Movement of H+ions through membrane rotates enzyme complex Rotation exposes active sites in complex ATP is produced from ADP and Pi 19 V. OXIDATIVE RESPIRATION, cont
A summary of electron transport . . . 20 VI. CELLULAR RESPIRATION A SUMMARY
Total ATP Gain in Cellular Respiration = ___ (glycolysis) + ____ (citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP / glucose 21 VII. CELLULAR RESPIRATION & OTHER FOOD MOLECULES
22 VIII. METABOLIC POISONS
Blockage of Electron Transport Chain Inhibition of ATP Synthase Uncouplers Prevent creation of H+ ion gradients due to leakiness of mitochondrial membrane 23 VIII. METABOLIC POISONS, cont
24 IX. FERMENTATION Anaerobic pathway Occurs in cytosol Purpose
In glycolysis, glucose is oxidized to 2 pyruvate, 2 NAD+ are reduced to 2 NADH, and there is a net gain of 2 ATP In oxidative respiration, NADH is oxidized back to NAD+ in electron transport chain If oxygen is not present, another mechanism must be available to regenerate NAD+ or glycolysis cannot continue In fermentation, pyruvate is reduced thereby oxidizing NADH to NAD+ Allows glycolysis and net gain of 2 ATP per glucose to continue 25 IX.FERMENTATION, cont 26 IX.FERMENTATION, cont 27