Cellular Respiration Chemical Pathways Food chemical energy calorie

Cellular Respiration Chemical Pathways

Food = chemical energy • calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius • Calorie = kilocalorie = 1000 calories is what you see on food labels • Gradual process to release energy from food molecules begins with… • Glycolysis

Overview • Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen • Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid (a 3 -carbon compound)

Glycolysis, again • Glycolysis will not begin without the input of energy (ATP) • It can only be completed in the presence of the high energy electron carrier NAD+ • In the end it makes two more ATP than were “spent”

Fermentation • To get the most energy from food, cells use oxygen • IF no oxygen is present, cells continue generating energy through an anaerobic pathway (without O 2) known as fermentation • The two main types of fermentation are alcoholic fermentation and lactic acid fermentation

Fermentation (more) • Yeasts and some microorganisms produce carbon dioxide and ethanol as a waste product of fermentation • YOUR cells and the cells of animals produce lactic acid as a waste product of fermentation • Fermentation makes no ATP but regenerates NAD+ which can be used in glycolysis