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Aerobic Metabolism. The 3 stage cycle. Aim & Objectives. Aim To develop and understanding of the aerobic metabolism and how each system interrelates. Objectives Understand the whole process of aerobic metabolism. Aerobic Metabolism – 3 stage cycle.
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Aerobic Metabolism The 3 stage cycle
Aim & Objectives • Aim • To develop and understanding of the aerobic metabolism and how each system interrelates. • Objectives • Understand the whole process of aerobic metabolism.
Aerobic Metabolism – 3 stage cycle “The release of energy through the breakdown of food fuels in the presence of O2” STAGE ONE – GLYCOLYSIS • Breaks down glucose to pyruvic acid. • By enzyme phosphofructokinase (PFK) • Takes place in muscle cell SARCOPLASM • Pyruvate converted into lactate (lactic acid) by enzyme Lactate Dehydrogenase • ATP regenerated = 2 ATP yield per molecule of glucose
Aerobic Metabolism STAGE TWO - KREB’S CYCLE (CITRIC ACID CYCLE) “A series of chemical reactions which occur in the matrix of the mitochondria”. • Occurs in the presence of O2 • Yields sufficient energy to resynthesise 2 ATP. • Oxidation of acetyl-coenzyme-A; The removal of hydrogen atoms from the compound is then used in the ‘electron transport system’. • Production of CO2; Carbon & hydrogen combine to form carbon dioxide, this is transported to the lungs and breathed out.
Aerobic Metabolism STAGE THREE - ELECTRON TRANSPORT SYSTEM The final stage of glycogen & fat breakdown • occurs in the presence of O2 • Within the cristae of the muscle cell MITOCHONDRIA. • Hydrogen given off @ the ‘Krebs cycle’ is carried here. • Water (H2O) is formed when the hydrogen ions (H+) & electrons (e-) combine with O2 through enzyme reactions. • A yield of 34ATP can be used for resynthesis.
Carbohydrate Blood glucose Muscle glycogen Fat Plasma FFA (from adipose tissue lipolysis) Intramuscular triglycerides Blood lactate Gluconeogenesis via the Cori cycle Summary Sources of Fuel During Aerobic Exercise
Carbohydrate is stored as GLYCOGEN in the muscles and liver. • the breakdown of glycogen provides the energy to rebuild ATP from ADP • The breakdown of glycogen in this way is facilitated by the enzymesglycogen phosphorylase (GPP), phosphofructokinase (PFK) • This process is ANAEROBIC and takes place in the SARCOPLASM of the muscle cell - no oxygen is needed • The by product of this reaction (in the absence of oxygen) is lactic acid • The enzyme facilitating the conversion from pyruvic acid to lactic acid is lactate dehydrogenase (LDH)
STAGE ONE - GLYCOLYSIS • STAGE TWO - KREB’S (CITRIC ACID) CYCLE • 2 molecules of pyruvic acid combine with oxaloacetic acid (4 carbons) and acetyl coA (2 carbons) • to form citric acid (6 carbons) • the cycle produces H+ and electron pairs, and CO2, and 2 ATP • Fats & protein enter the cycle • STAGE THREE - THE ELCTRON TRANSPORT CHAIN • the H+ and electron pairs have potential energy • which is released in a controlled step by step manner • oxygen combines with final H+ ions to produce water and 32 ATP
THE AEROBIC SYSTEM • requires CHO (sugar molecule) in the form of glucose. • which is derived from glycogen stored in muscle cells (mostly ST slow twitch fibres) or in the liver. The graph shows how the rate of usage of muscle glycogen is high during the first 30 minutes of steady exercise. The amount of glycogen remaining depends on • The intensity and duration of the exercise. • The CHO content of diet prior to exercise. • Once the glycogen is used it may take days to fully replenish. • Again depending on diet.
Breakdown of a fat molecule The energy yield from 1 g of glycogen and 1 g fat Food fuels supplied against time
