Transcript Metabolism
Metabolism The sum of all chemical reactions within the living cells • Anabolism • Catabolism • Building new structures • Requires energy • Smaller molecules larger molecules • Breakdown of substances • release of energy • Larger molecule smaller molecules Nutrient Pool • Source of substrates : amino acids, lipids, sugars, vitamins, minerals Stored in the liver, and delivered to all tissues/cells via blood Cells produce energy in the mitochondria Adenosine Triphosphate [ATP] Carbohydrate Metabolism • Glycolysis breaking sugar into pyruvic acid occurs in cytoplasm of cell. O2 nondependent • TCA or Krebs Cycle O2 dependant. Occurs in mitochondria • Electron transport system [respiratory chain] occurs in mitochondria • Anaerobic metabolism lactate production Activation Energy • Need to ‘spend’ energy to make energy • To begin the process of Glycolysis – the cell uses 2 ATP. The process of glycolysis yields 4 ATP – net gain 2 ATP +4 -2 +2 ATP ATP ATP from phosphorylation activation energy net gain to cell Glycolysis: the Lysis or breaking apart of glucose occurs in the cytoplasm of all cells. This process does not require oxygen. It is therefore referred to as an anaerobic process. The net yield of energy in glycolysis is 2 ATPs & 2 NADH NADH = Nicotinamide adenine dinucleotide The production of lactate is a common fate of pyruvate in skeletal muscles, which have been working very hard and have used up all their oxygen but are still producing pyruvate. As the lactate (lactic acid) builds up in the muscles they will feel sore Intermediate Step • The First Step in the Krebs Cycle is to convert pyruvate into a two-carbon fragment, then attach it to another coenzyme known as coenzyme A or COA. The enzyme that accomplishes thus is a large enzyme known as the pryruvate dehydrogeneses complex • Gives off 1 NADH for each acetyl CoA produced [ 2 NADH total/glucose] Krebs Cycle • Cycle goes thru a revolution for each Acetyl CoA that enters [ 2 Acetyl CoA are formed from each glucose molecule] • Will give off ATP, NADH & FADH as well as CO2 Energy Yield of TCA Cycle 1 ATP produced by each turn of cycle Each turn of cycle also produces 3 NADH & 1 FADH2 FADH2 = flavin adenine dinucleotide NADH and FADH2 will then go into the electron transport system to yield ATP 2 turns of cycle are completed for each glucose molecule 2 ATP + 6 NADH +2 FADH2 Electron Transport System • Imbedded in the inner mitochondria membrane are a series of electron carriers. These electron carriers pass electrons from NADH and FADH to one another down a red-ox stairway. The net result of this series of step-wise electron exchanges is to pump H+ (protons) out of the matrix into the outer compartment between the outer and inner membrane of the mitochondria. Energy Generated in ETS NADH –2 from intermediate step + 6 from TCA cycle = 8 NADH [ each NADH will yield 3 ATP] The 2 NADH from glycolysis is said to only yield 4 ATP in the ETS FADH2 – 2 from TCA cycle [ each FADH2 will yield 2 ATP] Total ATP generated in ETS = 24 + 4 = 28 + 4 ATP = 32 ATP [+ 4 ATP = 36 total ATP] Metabolic Rate • Total amount of energy produced and used by the body per unit of time • Daily input of energy should be equivalent to the metabolic expenditure • If too low will cause weight loss [ negative energy balance] • If too high will cause weight gain [positive energy balance] Metabolic Energy Use • Basal Metabolic Energy [BMR] – energy needed to maintain resting body functions • Thermic Effect of Food [TEF]– energy needed to digest and ingest nutrients – accounts for ~10% of daily energy needs • Muscular Activity – energy needed to perform all functions above BMR – accounts for ~30% of daily energy needs Basal Metabolic Rate • Roughly 1 kcal/kgBW/hr for men and 0.9 kcal/kgBW/hr for women • Example: 130 lb woman 1. Convert lb to kg 130 / 2.2 = 59 kg 2. Multiply 59 kg x 0.9 kcal/hr x 24 hrs = 1274 kcals/day Example: 170 lb man – 170/2.2 =77.2 kg 77.2 kg x 1.0 kcal/hr x 24 hrs = 1852.8 kcals/day Basal Metabolic Rate of selected Organs • When at rest, the percent of total body energy that is used by various organs: LIVER = 27% BRAIN = 19% SKELETAL MUSCLE = 18% KIDNEYS = 10% HEART = 7%