Cellular Respiration Cellular Respiration Overview l l l

Cellular Respiration

Cellular Respiration Overview l l l Transformation of chemical energy in food into chemical energy cells can use: ATP These reactions proceed the same way in plants and animals. Process is called cellular respiration Overall Reaction: – C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O + ATP

Cellular Respiration Overview l l Breakdown of glucose begins in the cytoplasm, the liquid matrix inside the cell with a process called Glycolysis. At this point metabolism diverges into two pathways – – Anaerobic cellular respiration (aka fermentation) Aerobic cellular respiration

Anaerobic Respiration l l Glycolysis Fermentation – – Alcoholic (plants, yeast) Lactic Acid (muscle cells)

Aerobic Respiration l l Stage 1 - Glycolysis Stage 2 - Pyruvate Oxidation Stage 3 - Krebs Cycle (Citric Acid Cycle) Stage 4 - ETC (Oxidative phosphorylation) & Chemiosmosis

C. R. Reactions l Glycolysis – – Series of reactions which break the 6 -carbon glucose molecule down into two 3 -carbon molecules called pyruvate Process is an ancient one-all organisms from simple bacteria to humans perform it the same way Yields 2 ATP molecules for every one glucose molecule broken down Yields 2 NADH (electron carrier) per glucose molecule

Anaerobic Cellular Respiration l Some organisms thrive in environments with little or no oxygen – l l l Marshes, bogs, gut of animals, sewage treatment ponds No oxygen used= ‘an’aerobic Results in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis. End products such as ethanol and CO 2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Aerobic Cellular Respiration l l Oxygen required=aerobic 2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria – – 1. Kreb’s Cycle 2. Electron Transport Chain

Kreb’s Cycle l Completes the breakdown of glucose – – l Takes the pyruvate (3 -carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 and H 2 O Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH 2 Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3 rd stage

Electron Transport Chain l l l Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chainlike a series of steps (staircase). As electrons drop down stairs, energy released to form a total of 32 ATP Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

2 ‘s 32 ‘s

Energy Tally l l 36 ATP for aerobic vs. 2 ATP for anaerobic – Glycolysis 2 ATP – Kreb’s 2 ATP – Electron Transport 32 ATP 36 ATP Anaerobic organisms can’t be too energetic but are important for global recycling of carbon