AP Test Cellular Respiration and Photosynthesis

Cellular Respiration How our body turns food and oxygen into ENERGY called ATP 3 Steps: Glycolysis Kreb’s Cycle ETC (Electron Transport Chain)

Redox Reactions Chemistry review: Oxidation = losing an electron Reduction = gaining an electron A redox reaction is a chemical reaction in which one molecule gains electrons and one loses them Example of cellular respiration: glucose is oxidized into carbon dioxide, oxygen is reduced to water

Glycolysis Glycolysis is the first step of cellular respiration It means “splitting sugar” One molecule of glucose is split in half into 2 molecules of pyruvic acid (pyruvate) C 6 H 12 O 6  2 C 3 H 6 O 3

Glycolysis Input: glucose Output: 2 molecules of pyruvate, 2 ATP, and 2 NADH NADH is a molecule that carries electrons from glycolysis and the Kreb’s Cycle to the ETS (it gains electrons = reduced) Once there, it releases the electrons to make ATP (it is oxidized to NAD+)

Kreb’s Cycle Step 2 of Cellular Respiration is called the Kreb’s Cycle, and is also known as the Citric Acid Cycle It ONLY occurs in the presence of oxygen It takes place in the mitochondrial matrix, the space between the inner folded membranes of the mitochondria

Kreb’s Cycle Acetyl coA undergoes a series of redox reactions in the Kreb’s cycle, rearranging its formula and transferring electrons The net output for 2 TURNS of Kreb’s is: 6 NADH, 2 FADH 2 (another electron carrier), and 2 ATP A byproduct, carbon dioxide, is released

Electron Transport Chain The last step is called the electron transport chain (ETC) or system (ETS), or oxidative phosphorylation (means losing electrons and adding a phosphate group to ADP to make ATP) It occurs in the cristae of the mitochondria, on the membranes on the inside

ETC As ADP is getting phosphorylized (called chemiosmosis), the electrons have reached the bottom of the waterfall The electrons are attracted to a super electronegative atom, oxygen Oxygen is the final electron acceptor. It gains electrons (is reduced) and joins with the H+ ions coming through ATP synthase to make water We breathe out the water (along with the CO 2 from Kreb’s)

ETC At the end of the ETC, approximately 34 ATP are generated through the processes of Oxidative Phosphorylation (the electrons moving down the waterfall) and chemiosmosis (the diffusion of H+ ions through ATP synthase)

Summary Oxygen we breathe in becomes water Glucose we eat is used to make ATP and CO 2 (waste) A total of approximately 38 ATP are made per glucose molecule

stroma thylakoid ATP

I’m green with envy! It’s not easy being green!

NADPADP

CO 2 H2OH2OC 6 H 12 O 6 O2O2 light energy  +++ Sugar Building Reactions Energy Building Reactions Plants make both:  energy  ATP & NADPH  sugars sunlight O2O2 H2OH2O sugars CO 2 ADP ATP NADPH NADP

photosynthesis photorespiration