Cell Respiration & Photosynthesis
BIO STUDY GUIDE (Ch. 9.1-9.5, 10.1-10.3)
I) CELLULAR RESPIRATION
A) Catabolic Pathways
A.1) Fermentation: partial degradation of sugar that occurs w/o oxygen A.2) Cellular Respiration: oxygen is used
A.3) Redox Reactions (Oxidation-Reduction that exchanges electrons) Oxidation: loss of electrons (energy must be added)
Reduction: addition of electrons. (-) charged electrons added to atom reduce amount of (+) charge of that atom A.4) Stepwise Energy Harvest via NAD+ & ETC (FOODNADHETCOXYGEN) Each electron travels with a proton, hydrogen atom
NAD+: functions as an oxidizing agent Hydrogen atom transferred here first most versatile electron acceptor Traps electrons from glucose by enzymes (dehydrogenases) to remove pair of hydrogen atoms(2 electrons & 2 protons) from substrate to oxidize it, then the enzyme delivers the 2 electrons & 1 proton (the other is released as hydrogen ion) to its coenzyme NAD+ The NAD+ has now neutralized its charge and is reduced to NADH Electron Transport Chain: Break the fall of electrons to oxygen in several steps Built in inner membrane of mitochondrion exergonic prevents from losing energy at once Electrons from food move by NADH to top of chain and at the bottom, oxygen capture these electrons along w/ hydrogen nuclei forming water electrons move down from one carrier mol. to the next losing little energy fall down a energy gradient to stable location where its more electroneg. A.5) Stages of Cellular Respiration (GLYCOSISCITRIC ACID CYCLEOXIDATIVE PHOSPHORYLATION) Glycosis: Occurs in Cytosol Begins degradation process by breaking down glucose into 2 compounds called pyruvate CAC (Krebs Cycle): Occurs in mitochondrial matrix completes breakdown by oxidizing a derivative of pyruvate to CO2 Oxidative Phosphorylation: ATP synthesis in which energy is released at each step of chain and stored in mitochondrion powered by redox reaction of ETC a lot of ATP takes place in inner membrane of mitochondrion and is made up of ETC and chemiosmosis Substrate-level Phosphorylation: small amount of ATP formed in few reaction of glycosis & CAC B) Glycosis harvest chemical energy by oxidizing glucose to pyruvate B.1) Energy investment phase
cell actually spends ATP but is repaid with dividends during energy payoff phase B.2) Energy Payoff Phase
ATP is produced by substrate-level phosphorylation & NAD+ is reduced to NADH by electrons released from oxidation of food(glucose) C) CAC completes energy-yielding oxidation of glucose
C.1) If molecular oxygen is present, pyruvate enters mitochondrion where enzymes of CAC complete oxidation of organic fuel C.2) Before CAC, pyruvate is converted into acetyl CoA through 3 reactions Pyruvate's carboxyl group is removed and given off as mol. of CO2 (CO2 that's released in respiration) remaining two-carbon fragment is oxidized forming acetate. enzyme transfers extracted electrons to NAD+ storing energy as NADH coenzyme A is attached to acetate by an unstable bond making it reactive The product is thus acetyl CoA is now ready to feed it acetyl group in the CAC cycle for further oxidization D) Oxidative Phosphorylation
D.1) Pathway of Electron Transport
Located in inner membrane of mitochondrion in cristae (folding=increase surface) electrons from NADH and FADH2 pass through the electron transport chain (ETC) to oxygen, which is reduced to water Electron carriers alternate betwn reduced and oxidized states as they accept & donate electrons. Each component of the chain becomes reduced when it accepts electrons from upper level, which has lower affinity for electrons. It then return to oxidized form as it passes electrons to downhill, a more electronegative level.
Inside inner membrane of mitochondrion are many copies of proteinATP Synthase ATP Synthase: enzyme that makes ATP from ADP & inorganic phosphate Uses energy of an existing ion gradient to power ATP synthesis Chemiosmosis:...
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