where did ATP come from? find out

How Cells Make ATP
by PHOSPHORYLATION... adding a phosphate to ADP ADP + P ------> ATP

a) substrate level phosphorylation...
where a substrate molecule ( X-p ) donates its P to ADP making ATP b) chemiosmosis - [Oxidative Phosphorylation of Krebs cycle & ETC]... food substrates donate e- & protons to acceptor molecules [NADH], i.e., oxidation. NADH gives up electrons & protons are pumped out of mitochondria (or the chloroplasts in photosynthesis); protons diffuse back into mito thru an enzyme - ATPase, the ATPase enzyme makes ADP + P --> ATP figure * c) photophosphorylation.... e- of light energy, instead of food covalent bonds, are captured by chlorophylls to make a proton gradient across the chloroplast membranes... figure* protons move through a chloroplast ATPase enzyme to make ATP

http://student.ccbcmd.edu/biotutorials/energy/chemios.html

Oxidative Metabolism... (cell respiration) occurs in heterotrophic organisms that consume foods ... we say organisms oxidize (consume) foods (often glucose) to make energy because they remove & capture electrons... ... where is energy in foods? it's in the covalent bonds (e-)
Thus - METABOLISM is cells capturing e- via REDOX reactions REDOX REACTION... e- passed from one molecule to another [PGAL --> NAD+] in a chemical rx energy is transferred into the new molecule (a reeox couple) by holding e- OXIDATION = removal of electron &/or proton from food covalent bond REDUCTION = gaining electron &/or proton; adds an electron to an acceptor molecule

Cell RESPIRATION...


a more complete definition of cell respiration : - series of enzyme rx's (biochemical pathways) in the cytoplasm & mitochondria that, - remove e- (oxidation) from covalent bonds of substrates (as glucose), and - pass e- to acceptor molecules [coenzymes] such as NAD+ & FAD* which become reduced [ NADH & FADH2 ] - the reduced coenzymes [ NADH & FADH2 ] pass e- to other acceptors... a series of protein electron carriers called cytochromes, - the electron carriers [cytochromes] pass e- to O2 --reduction--> H2O - cytochromes also pump protons [H+] out of mitochondria into peri-mito space, - protons move back into mito thru a special enzyme (ATPase) & make ATP

KEY Reactions of KREBS CYCLE 1. NAD is reduced (NADH) and FAD is reduced (FADH2) 2. substrate level phosphorylation occurs (GTP <--> ATP) 3. decarboxylation [-COOH] 4.* an acylation reaction via coenzyme-A (forms Acetyl-coA) SUMMARY Reactions: [Krebs Cycle Quicktime Movie*] Summary figure full cycle*