Cellular Respiration AP Biology

Photosynthesis….then Photosynthesis captures the sun’s energy and converts it to glucose Cellular respiration is the breakdown of glucose to produce ATP ATP is useable energy This process is carried out by plants and every other organism in the various trophic levels

Cellular Respiration C 6 H 12 O 6 + 6O 2 6CO 2 +6 H 2 O This is the summary: showing beginning and end There are three stages in between

Cellular Respiration Occurs in three stages: Glycolysis Kreb’s Cycle Electron Transfer Phosphorylation Net ATP yield depends on whether oxygen is present

ATP Yield Anaerobic respiration yields two ATP Aerobic respiration yields 36 ATP Bacteria do not need much ATP You depend on the aerobic pathway

Glycolysis This is the first stage for both aerobic and anaerobic respiration The first energy releasing pathways to evolve were anaerobic Glucose is converted to pyruvate

Glycolysis Many steps: to convert glucose into pyruvate 2 ATP invested; 4 produced

Glycolysis Occurs in the cytoplasm First step requires 2 ATP The next steps form 4 ATP by substrate level phosphorylation This is the direct transfer of a phosphate group from a substrate to some other molecule (in this case ADP) Meanwhile, NAD picks up electrons and H liberated from the PGAL

Glycolysis Pyruvate and NADH are used in the next stage of aerobic respiration If no oxygen is present, the pyruvate goes into a fermentation pathway Produces either lactic acid or alcohol (ethanol)

2 nd stage ( Krebs Cycle) Pyruvate molecules enter the inner compartment of the mitochondria Electrons and hydrogen carried by NADH are transferred to many coenzymes A carbon is removed from each pyruvate and joins Coenzyme A, becoming Acetyl-CoA. This molecule enters the Krebs cycle

Krebs Cycle Three functions: Loads electrons and hydrogen onto NAD+ and FAD, making 6NADH 2 and 2FADH 2 (This is important for ATP production in the 3 rd stage) Forms 2 ATP Cycles back to oxaloacetate, which is the molecule that acetyl CoA reacts with to start the Krebs cycle

Phosphorylation Substrate level: production of ATP by transferring a phosphate group from an intermediate directly to an ADP Oxidative: production of ATP from the reactions of an electron transport chain Includes chemiosmosis H+ conc gradient

Substrate level phosphorylation An enzyme catalyses the joining of P to ADP Happens during glycolysis and Krebs cycle

Oxidative phosphorylation (Each NADH molecule represents stored energy that can “fall” down the energy gradient with oxygen as the final acceptor) Controlled release of energy The ETC creates the H+ gradient

3 rd stage ATP formation kicks into high gear Uses electron transfer chains and the enzyme ATP synthase NADH 2 and FADH 2 give up electrons and hydrogen into the chains H+ is pumped out to create a concentration gradient. When the H+ is released, ATP is formed

Glycolysis In the Glycolysis stage 4 ATP molecules are produced,but 2 ATP's are used in the process so the net yield is 2 ATP's. In this stage 2 NAD's become NADH's. Krebs Cycle BEFORE the cycle 2 NADH's are created in the creation of Acetyl Coenzyme A. IN the cycle 2 GTP's are created. 6 NADH's are created, & 2 FADH2's too. Electron Chain Every NADH produces 3 ATP's. We have 10 NADH's, therefore 30 ATP's are created. Every FADH2 produces 2 ATP's. We have 2 FADH2's, therefore 4 ATP's are created. Total Balance 2 ATP + 2GTP +34 ATP :38 ATP Glycolysis Krebs Cycle Electron Chain Total

Alternative Energy Sources Proteins, broken down into amino acids, can also be broken down into pyruvate and therefore enter the Krebs cycle Fats, broken down into fatty acids and glycerol, can also enter the cycle at two different points, resulting in the same end result