Cellular Energetics Review Chapters 9 & 10

Cellular respiration Catabolic, energy-yielding pathway Glucose + oxygen → carbon dioxide + water Energy released is ATP and heat Glycolysis Kreb’s/Citric Acid Cycle Electron Transport Chain and oxidative phosphorylation

Glycolysis “splitting of sugar” glucose into 2 pyruvate Occurs in cytoplasm Net result: use 2 ATP, make 4 ATP, 2 pyruvates, and 2 NADH NAD+ gets reduced (electrons added) to make NADH Carries electrons to transport chain

Middle Step Pyruvate enters mitochondria Enzyme chops off a carbon dioxide, transfers an electron to make NADH, and creates acetyl CoA 2 pyruvates makes 2 of each of the above

Kreb’s Cycle Acetyl CoA enters cycle For every one, you get 3 NADH, 1 FADH2, 2 carbon dioxides, 1 ATP 2 acetyl CoA makes double of above

Electron Transport Chain The 10 NADH and 2 FADH2 carry electrons to a chain of membrane bound enzymes The electrons move down the chain A gradient of hydrogen ions begins to build Oxygen is the final electron acceptor… water is made

Oxidative Phosphorylation Build up of H+ goes through ATP synthase ATP synthase spins… uses kinetic energy to assemble ATP from ADP and P Typically each NADH will make 3 ATP and each FADH2 will make 2 ATP for a maximum of 34 ATP

Fermentation Cellular respiration requires oxygen Fermentation does not In absence of oxygen, glycolysis occurs You get 2ATP, 2 pyruvate and 2 NADH Fermentation takes the pyruvate and NADH and converts them to waste and NAD+ This allows for more glycolysis Wastes: alcohol (plants) lactic acid (animals)

Food and Energy Proteins, carbohydrates, and fats can all be converted to molecules that can enter the cellular respiration pathway They can all be broken down and used to make ATP!

Photosynthesis Carbon dioxide + water → glucose + oxygen Light dependent reactions Light independent reactions Chloroplasts and chlorophyll

Photolysis/Light Reactions The energy of light splits water into oxygen and electrons NADP+ becomes reduced to NADPH Chemiosmosis uses H+ gradient to make ATP Cyclic electron flow: generates extra ATP for Calvin cycle Noncyclic electron flow: only makes NADPH

Dark Reactions/Calvin Cycle Uses ATP and NADPH created in light reactions to perform carbon fixation (turning carbon dioxide into sugars) Rubisco is main enzyme; it joins carbon dioxide to RuBP (5 carbon sugar) Every turn of Calvin cycle uses 3 carbon dioxides and nets one 3 carbon sugar and regenerates RuBP for the next turn

C4/CAM Photosynthesis C4: when stomata are closed, oxygen can build up and compete with carbon dioxide for Rubisco (photorespiration) C4: PEP carboxylase has higher affinity for carbon dioxide (mesophyll cell collects carbon dioxide and funnels into bundle sheath cell for Calvin cycle CAM: open stomata only at night, carbon fixation occurs at night, and calvin cycle in day