Catabolic Pathways and Glycolysis The ability to do that work depends on catabolic process that harvest the potential energy found in organic molecules. The 2 catabolic processes that occur in organisms are fermentation (breakdown without O 2 )and cellular respiration (breakdown with O 2 ).

Chemical Energy and Food Chemical energy can be found contained within the foods that we eat. Calories are the basic measurement of the energy contained in foods. – 1cal = 4.184J – 1000cal = 1kcal = 1Cal (standard for our food labeling) – The average diet is built around 2000Cal Not all Calories are created equally – 1g carbohydrate = 4Cal – 1g protein = 4Cal – 1g fat = 9Cal RDA recommendations – carbohydrate = 55% – protein = 15% – fat = 30%

Cellular Respiration primary catabolic pathway used in organisms to produce energy (ATP) – although fats & proteins can be broken down, glucose is the primary fuel used – C 6 H 12 O 6 + 6O 2  6CO 2 + H 2 O + Energy (ATP & Heat) Stages of Cellular Respiration Glycolysis Citric Acid Cycle Oxidative Phosphorylation

Glycolysis Catabolic process that degrades glucose into 2 Pyruvate molecules + 2 H 2 O molecules – occurs in the cytosol – requires the input of 2 ATP molecules and produces 4 ATPs (net of 2) – 2 NAD + are reduced to 2 NADH + 2 H + (net gain of 4e - ) Pyruvate is then transported into the mitochondria to begin the Citric Acid Cycle Reaction does not require oxygen (anaerobic process) – No CO2 is produced! – All C atoms are present in the final products of the reactions Simplified equation – Glucose + 2ATP + 2NAD +  2Pyruvate + 4ATP + 2NADH + 2H + – The left side is called the Energy Investment phase – The right side is called the Energy Payoff phase