Cellular Respiration

Cellular Respiration Overview 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: C6H12O6 + 6O2 → 6CO2 + 6H2O

Obtaining Energy Photoautotrophs – change light energy into chemical energy stored in bonds of glucose and polysaccharides (green plants, cyanobacteria) Heterotrophs – feed on other organisms for chemical energy Chemoautotrophs – microorganisms that can obtain energy from inorganic sources (Fe or S compounds in volcanoes, deep sea vents…)

Glucose – primary source of energy for most organisms Cellular respiration – process by which glucose is broken down and energy stored in bonds is released, can be aerobic or anaerobic Aerobic – oxygen used as an oxidizing agent (electron acceptor) Anaerobic – uses a molecule other than oxygen as an oxidizing agent

Cellular Respiration Overview Purpose of Cellular Respiration: Trap free energy into forming ATP Move H atoms (electrons) from glucose to oxygen creating 6 H2O Break bonds between 6C atoms in glucose creating 6 CO2

2 Ways ATP is formed during Cellular respiration: Formation of ATP 2 Ways ATP is formed during Cellular respiration: Substrate-level Phosphorylation ATP formed directly in enzyme catalyzed reaction P containing compound transfers P to ADP making ATP 4 ATP created this way from 1 molecule glucose

Oxidative Phosphorylation ATP formed indirectly in more complex process co-enzyme NAD+ (nicotinamide adenine dinucleotide) removes 2 H atoms and is reduced to NADH + H+ another co-enzyme, FAD (flavin adenine dinucleotide) also reduced by 2 H to become FADH2 these co-enzymes act as mobile energy carriers in cell, moving energy from one stage of cellular respiration to another where its used to create ATP

4 Stages of Cellular Respiration Name Details Stage 1 Glycolysis 10 step process in cytoplasm Stage 2 Pyruvate Oxidation 1 step process in mitochondria Stage 3 Kreb’s Cycle 8 step cycle in mitochondria Stage 4 Electron Transport Chain multi-step process in mitochondrial membrane

Glycolysis A series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate. Occurs in the cytoplasm of the cell and is anaerobic. 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 (creates 4 ATP but uses 2) Yields 2 NADH per glucose molecule (used later to create more ATP) cellResp_main