Ch. 9 Cellular Respiration & Fermentation

9.1, Cellular Respiration Overview chemical energy & food food provides living things w/ chemical building blocks to grow & reproduce organisms get energy they need from food molecules have chemical energy that is released when chemical bonds are broken calorie: amount of energy needed to raise temperature of 1 gram of H2O by 1°C 1 Calorie on food labels(kilocalorie)= 1000 calories

9.1, Cellular Respiration cellular respiration: can occur two ways 1. Process that releases energy from food in presence of O2, called aerobic (with oxygen). 2. When no oxygen is present its called anaerobic (without oxygen).

Cellular Respiration: Harvesting energy stored in food Cellular respiration: the breaking down of food to produce ATP. Occurs in the MITOCHONDRIA Uses oxygen (O2) usually digesting glucose for the energy source. Movement of hydrogen atoms from glucose to water Cellular Respiration Equation glucose + oxygen  carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP  + + heat

9.1, Cellular Respiration Stages of Cellular Respiration Glycolysis: produces little energy; ~90% stays locked in pyruvic acid after glycolysis Krebs Cycle: little additional energy generated Electron Transport Chain: produces most energy in cellular respiration, using O2 as electron acceptor Fig. 9-2, pg. 252

9.1 Cellular Respiration Glycolysis: glucose, is broken down into two molecules called pyruvate. This change is accompanied by the production of 2 ATP molecules (ENERGY) and 2 NADH molecules (ENERGY TRANSPORTER). Those are the products.

9.1 Cellular Respiration Krebs Cycle: pyruvate is transported into the mitochondria and loses carbon dioxide to form acetyl-CoA. When acetyl-CoA is changed to carbon dioxide in the Krebs cycle, chemical energy is released and captured in the form of NADH, FADH2, and ATP (energy products).

9.1 Cellular Respiration Electron Transport Chain: The electron transport chain allows the release of the large amount of chemical energy stored in break down of NADH and FADH2 (gives up electron). The energy released is captured in the form ATP from ADP. 34 ATP made here. Respiration makes 36 ATP total.

9.1 Cellular Respiration Where does it happen? Glycolysis: outside the mitochondria Krebs Cycle: inside membrane of mitochondria Electron Transport Chain: inside membrane of mitochondria

Comparing Photosynthesis & Cellular Respiration 9.1, Cell Respiration Comparing Photosynthesis & Cellular Respiration photosynthesis removes CO2 from atmosphere, & cellular respiration puts it back. photosynthesis releases O2 into atmosphere, & cellular respiration uses O2 to release energy from food reactants of cellular respiration are products of photosynthesis & vice versa Fig. 9-3, pg. 253

9.2, process of cellular respiration glycolysis in glycolysis, 1 molecule of glucose (6-C compound) turns into 2 molecules of pyruvic acid (3-C compound) pyruvic acid is reactant in Krebs cycle ATP production 2 ATP needed to start 4 ATP made (gain = 2) Fig. 9-4, pg. 255

9.2, process, cont glycolysis, cont NADH production electron carrier NAD+ (nicotinamide adenine dinucleotide) accepts pair of high-energy electrons to become NADH NADH carries high-energy electrons to electron transport chain 2 NADH made for every molecule of glucose in glycolysis glycolysis works fast & w/o O2 for quick energy release

9.2, process, cont Krebs cycle in Krebs cycle, pyruvic acid broken down into CO2 by series of energy-extracting reactions a.k.a. citric acid cycle (citric acid is 1st compound formed in series) citric acid production pyruvic acid from glycolysis enters matrix (innermost part of mitochondrion)

9.2, process, cont Krebs, cont citric acid production, cont w/ pyruvic acid in matrix, NAD+ accepts 2 high-energy electrons to form NADH & 1 molecule of CO2 remaining 2 C atoms react to form acetyl-CoA acetyl-CoA combines w/ 4-C molecule to make citric acid

9.2, process, cont Krebs, cont energy extraction citric acid broken into 5-C compound, then 4-C compound; 2 CO2 released & 4-C compound can re-start cycle by combining w/ acetyl-CoA energy released by rearranging of C bonds captured as ATP, NADH, & FADH2 each turn of cycle converts 1 ADP into ATP

9.2, process, cont Krebs, cont energy extraction, cont electron carriers NAD+ & FAD accept pairs of high-energy electrons to form NADH and FADH2 for electron transport chain to generate ATP since glycolysis made 2 pyruvic acid, each glucose = 2 turns of cycle each glucose molecule makes 6 CO2, 2 ATP, 8 NADH, & 2 FADH2 in cycle

9.2, process, cont electron transport chain & ATP synthesis electron transport chain uses high-energy electrons from glycolysis & Krebs cycle to turn ADP into ATP NADH & FADH2 pass high-energy electrons to electron carrier proteins in electron transport chain energy from chain used to move H+ ions against concentration gradient across inner mitochondrial membrane into intermembrane space

9.2, process, cont chain & ATP, cont H+ ions go back across membrane through ATP synthase, so ATP synthase molecule spins w/ each rotation, ATP synthase attaches phosphate to ADP, making ATP Fig. 9-6, pg. 259

9.2, process, cont chain & ATP, cont @ end of chain, electrons combine w/ H+ ions & O2 to form H2O totals glycolysis, Krebs cycle, & electron transport chain release ~ 36 ATP per glucose molecule represents ~ 36 % of total energy of glucose; remaining 64 % released as heat

9.3, fermentation general fermentation w/o O2, fermentation releases energy from food molecules by producing ATP occurs in cytoplasm follows glycolysis; cells convert NADH from glycolysis back into NAD+, for glycolysis to continue producing ATP Fig. 9-8, pg. 263

9.3, fermentation, cont alcoholic fermentation in yeast & some other microorganisms, produces ethyl alcohol & CO2 used to make alcoholic beverages & raise bread dough word equation: pyruvic acid + NADH  alcohol + CO2 + NAD+ lactic acid fermentation in most organisms, converts pyruvic acid to lactic acid word equation: pyruvic acid + NADH  lactic acid + NAD+

9.3, fermentation, cont energy & exercise for short, quick bursts of energy, body uses ATP already in muscles & ATP made by lactic acid fermentation extra O2 needed afterward to get rid of lactic acid produced for exercise > 90 seconds, cellular respiration is only way to keep making ATP releases energy more slowly than fermentation cells in muscles have extra mitochondria for more cellular respiration

9.3, fermentation, cont energy & exercise, cont exercise > 90 seconds, cont body stores energy in form of glycogen glycogen stores are enough for 15 - 20 minutes of activity after that, body begins to break down other stored molecules (fats, etc.) for energy hibernating animals rely on stored fat for energy