Cellular Respiration Harvesting Chemical Energy ATP AP Biology

Cellular Respiration Harvesting Chemical Energy ATP AP Biology 2006 -2007

What’s the point? The point is to make ATP! ATP AP Biology

Harvesting stored energy § Energy is stored in organic molecules carbohydrates, fats, proteins Heterotrophs eat these organic molecules food u digest organic molecules to get… u § § raw materials for synthesis § fuels for energy w controlled release of energy w “burning” fuels in a series of step-by-step enzyme-controlled reactions AP Biology

Harvesting stored energy § Glucose is the model respiration u catabolism of glucose to produce ATP glucose + oxygen energy + water + carbon dioxide C 6 H 12 O 6 + 6 O 2 ATP + 6 H 2 O + 6 CO 2 + heat COMBUSTION = making a lot of heat energy by burning fuels in one step fuel AP Biology carbohydrates) RESPIRATION = making ATP (& some heat) by burning fuels in many small steps ATP enzymes O 2 CO 2 + H 2 O + heat ATP O 2 CO 2 + H 2 O + ATP (+ heat) glucose

How do we harvest energy from fuels? § Digest large molecules into smaller ones u break bonds & move electrons from one molecule to another § as electrons move they “carry energy” with them § that energy is stored in another bond, released as heat or harvested to make ATP loses e- gains e- + AP Biology e- oxidized reduced + – + eoxidation ereduction redox

How do we move electrons in biology? § Moving electrons in living systems u electrons cannot move alone in cells § electrons move as part of H atom § move H = move electrons loses e- gains e- oxidized + + oxidation H e p reduced + – H reduction oxidation C 6 H 12 O 6 + AP Biology H e- 6 O 2 6 CO 2 + 6 H 2 O + ATP reduction

Coupling oxidation & reduction § REDOX reactions in respiration u release energy as breakdown organic molecules § break C-C bonds § strip off electrons from C-H bonds by removing H atoms w C 6 H 12 O 6 CO 2 = the fuel has been oxidized § electrons attracted to more electronegative atoms w in biology, the most electronegative atom? w O 2 H 2 O = oxygen has been reduced u O 2 couple REDOX reactions & use the released energy to synthesize ATP oxidation C 6 H 12 O 6 + AP Biology 6 O 2 6 CO 2 + 6 H 2 O + ATP reduction

Oxidation & reduction § Oxidation § Reduction adding O u removing H u loss of electrons u releases energy u exergonic u removing O u adding H u gain of electrons u stores energy u endergonic u oxidation C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + ATP reduction AP Biology

like $$ in the bank Moving electrons in respiration § Electron carriers move electrons by shuttling H atoms around u NAD+ NADH (reduced) u FAD+2 FADH 2 (reduced) NAD+ nicotinamide Vitamin B 3 niacin O– O – P –O O phosphates O– O – P –O O AP Biology H reducing power! NADH O H H O C NH 2 N+ + adenine ribose sugar H C NH 2 reduction O– O – P –O oxidation O O– O – P –O O carries electrons as a reduced molecule N+ How efficient! Build once, use many ways

Overview of cellular respiration § 4 metabolic stages u Anaerobic respiration 1. Glycolysis w respiration without O 2 w in cytosol u Aerobic respiration w respiration using O 2 w in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C H O 6 + AP Biology 6 12 6 O 2 ATP + 6 H 2 O + 6 CO 2 (+ heat)

What’s the point? The point is to make ATP! ATP AP Biology 2006 -2007

H+ And how do we do that? H+ H+ § ATP synthase enzyme u H+ flows through it § conformational changes § bond Pi to ADP to make ATP u set up a H+ gradient ADP + P § allow the H+ to flow down concentration gradient through ATP synthase § ADP + Pi ATP APBut… Biology How is the proton (H+) gradient formed? H+