ENERGY AND CELLULAR RESPIRATION

Energy n Chemical energy – found in the bonds of food n Activation energy – energy needed to get a reaction started n Endothermic reaction – uses more energy than it gives off; will be cold n Exothermic reaction – gives off more energy than it uses; will be warm

Energy for the Cell – ATP n All cells have ATP, but some transform light into ATP and others get ATP from food –Autotrophs – plants; photosynthesize to get ATP & then glucose made is broken down to make more ATP –Heterotrophs – animals; get food and break it down to get energy (ATP)

ATP n ATP is like a “storage bank” n ATP ADP + P n Energy is released when a phosphate bond is broken n Energy is stored when a phosphate bond is made

Structure of ATP AdenineRibose3 Phosphates High energy bond

CELLULAR RESPIRATION n It is the process by which the chemical bonds of organic molecules are broken, energy is released and stored as ATP n Occurs in both plant & animal cells n Occurs on the surface of and inside the mitochondria (that’s why mitochondria are nicknamed the “powerhouse”)

Structure of Mitochondrion Cristae – folds of the mitochondrion

Chemical Equation enzyme C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O + ATP glucose oxygen carbon water energy dioxide

CELLULAR RESPIRATION n 2 Types: n 1. Aerobic (Cellular Respiration) - requires oxygen – produces 36 ATPs from 1 glucose molecule n 2. Anaerobic (Fermentation) - without oxygen – produces 2 ATPs from 1 glucose molecule

Aerobic Respiration n Occurs with the presence of oxygen n Occurs in the folds of the mitochondria (cristae) n Cristae contain the enzymes needed for aerobic respiration to take place n Happens in 3 stages: Glycolysis (2 ATPs), Krebs cycle (2 ATPs) & Electron Transport chain(32 ATPs) = 36 Total ATPs n Yields more energy (ATP) than anaerobic respiration (34 more ATPs)

Anaerobic Respiration n Occurs in the absence of oxygen n Occurs in the cytoplasm n First step is called Glycolysis (glucose is broken down into 2 pyruvic acids – gain 2 ATPs) n Next step, fermentation occurs if the process continues without oxygen (no ATPs) n Glycolysis + Fermentation = Anaerobic Respiration (2 ATPs TOTAL)

2 Fermentation (Anaerobic) Pathways: n 1. Alcoholic Fermentation –Occurs in yeast –Produces carbon dioxide and alcohol –Used to make bread and alcoholic beverages

2 Fermentation (Anaerobic) Pathways: n 2. Lactic Acid Fermentation n Occurs in muscle cells during rapid exercise n Produces lactic acid n A buildup of lactic acid causes a burning, painful sensation and the muscles may become sore