Ch. 9 notes

Ch. 9 notes - 15:57 Catabolic pathway stored energy is...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
15:57 Catabolic pathway stored energy is released by breaking down complex molecules Some catabolic processes Fermentation – partial degradation of sugars or other organic fuel that occurs without the use of oxygen Aerobic respiration – oxygen is consumed as a reactant slong with the organic fuel Organic compounds + O 2 H 2 O + energy v. anaerobic respiration – use substances other than oxygen Cellular respiration: both aerobic and anaerobic, but used to refer to aerobic processes Breakdown of glucose ΔG = -686 kcal/mol Redox reactions – the relocation of electrons releases energy stored in organic molecules, which is used to synthesize ATP Oxidation – loss og electrons from one substance Reduction – addition of electrons to another substance Reducing agent – electron donor Oxidizing agent – electron acceptor An electron loses potential energy when it shifts from a less electronegative atom toward a more electronegative one In general .organic molecules that have an abundance of hydrogen are excellent fuels because their bonds are a source of energy with lots of potential energy, When they “fall” down and energy gradient (transferred to oxygen), they release energy In respiration, oxidation of glucose transfers electrons to a lower energy state, liberating energy that becomes available for ATP synthesis Stepwise energy harvest via NAD + Each electron travels with proton = H atom (not passed directly to oxygen, but first to an electron carrier NAD + - a coenzyme, nicotinamide adenide dinucleotide, can cycle easily between oxidized (NAD + ) and reduced (NADH) states = oxidizing agent during respiration
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Enzymes (dehydrogenases) remove a pair of H atoms from substrate and oxidize it, enzyme delivers the 2 electrons along with 1 proton to its coenzyme, NAD + . The other proton is released as an H + ion into surrounding solution NAD + is reduced to NADH (since it received 2 electrons and 1 proton) NADH = stored energy that can be tapped to make ATP when the electrons complete their “fall” down their energy gradient from NADH to oxygen Electron transport chain – breaks the fall of electrons to oxygen into several energy-releasing steps, molecules built into mitochondria’s inner membrane, oxygen captures electrons + H + H 2 O Electron transfer from NADH to O 2 = exergonic ΔG = -53 kcal.mol (-222 kJ/mol) O 2 = terminal electron acceptor Energy released at each step Each “downhill” carrier is more electronegative than, and thus capable of oxidizing, its “uphill” neighbor Glucose NADH electron transport chain oxygen Stages of cellular respiration Preview Glycolysis Pyruvate oxidation + citric acid cycle Oxidative phosphorylation: electron transport + chemiosmosis Glycolysis – break glucose into 2 molecules of pyruvate, which enter mitochondrion in eukaryotes while staying in the cytosol for prokaryotes Pyruvate: enters mitochondria oxidized to acetyl coA enters citric acid cycle
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/14/2012 for the course BISC 220 taught by Professor Mcclure during the Spring '09 term at USC.

Page1 / 10

Ch. 9 notes - 15:57 Catabolic pathway stored energy is...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online