Energy for life’s activities Cellular Respiration Energy for life’s activities

Overview of Cellular Respiration The life processes of all organisms require energy. The potential energy held in the bonds of food molecules CANNOT be used directly by the cell. Energy from food must be converted to the ONLY energy source that cells can use ATP!

Cellular Respiration Respiration is the process by which the energy in the bonds of nutrients are used to synthesize ATP. Respiration occurs continuously in all cells of all organisms.

Anaerobic Respiration Also called fermentation No oxygen is present 1 Glucose only partially broken down to form waste products and 2 ATP

Anaerobic Pathways Glucose  2 lactic acid + 2 ATP Happens in muscle cells when they run out of oxygen Happens in bacteria that make yogurt, cheese, dill pickles Glucose  2 ethanol + 2 CO2 + 2 ATP Happens in some bacteria Happens in YEAST

Aerobic Respiration Has to have oxygen VERY EFFICIENT Most organisms on earth are aerobic 1 glucose completely broken down to carbon dioxide and water. C6H12O6 + 6 O2  6 CO2 + 6 H2O + E

Aerobic Pathway Takes place mostly in mitochondria 3 primary steps: Glycolysis in cytoplasm: produces pyruvate and 2 net ATP (anaerobic) Kreb’s cycle in matrix of mitochondria: converts pyruvate to Acetyl-CoA (aerobic, makes carbon dioxide) Electron transport chain on membrane of mitochondria: moves electrons to produce 34 ATP (aerobic, makes water) http://www.teachersdomain.org/resource/tdc02.sci.life.cell.mitochondria/

Comparing Aerobic & Anaerobic Cellular Respiration Pathways Aerobic (needs oxygen) Anaerobic (no oxygen) Occurs in: Most organisms Mostly yeast and bacteria 1 glucose makes: 6 CO2 + 6 H2O Ethanol + CO2 or lactic acid Net ATP production: 36 2

Adaptations for Respiration Bacteria, protists & fungi Respiratory gases are exchanged by diffusion Plants Respiratory gases are exchanged through leaves, stems, and roots Moves in and out of cells by diffusion but leaves and stems also have openings to the environment (stomata and lenticels)

Adaptations for Respiration in Animals Techniques vary: Simple diffusion across cell membranes Diffusion across moist skin into a circulatory system Openings to the environment that can be flapped open and closed with a circulatory system to transport gases Specialized respiratory structures (e.g. lungs) to speed exchange of respiratory gases