IntroducMon to bioenergemcs

Transcription

1 BIOQUÍMICA E BIOLOGIA CELULAR António Ascensão, José Magalhães IntroducMon to bioenergemcs Faculdade de Desporto, Universidade do Porto, 1º Ciclo, 1º Ano 2012_2013

2 Aims 1. Define the following terms: (1) endergonic reac+ons, (2) exergonic reac+ons, (3) coupled reac+ons, and (4) bioenerge+cs. 2. Describe the role of enzymes as catalysts in cellular chemical reacmons. 3. List and discuss the nutrients that are used as fuels. 4. IdenMfy the high- energy phosphates.

3 Aims 6. Discuss the biochemical pathways involved in anaerobic ATP producmon. 7. Discuss the aerobic producmon of ATP. 8. Describe the general scheme used to regulate metabolic pathways involved in bioenergemcs. 9. Discuss the interacmon between aerobic and anaerobic ATP producmon. 10. IdenMfy the enzymes that are considered rate limimng in glycolysis and the Krebs cycle.

4 Outline Biological Energy Transforma2on Cellular Chemical Reac+ons Oxida+on- Reduc+on Reac+ons Enzymes Fuels for Exercise Carbohydrates Fats Proteins High-Energy Phosphates Bioenergetics Anaerobic ATP Production Aerobic ATP production Aerobic ATP Efficiency of Oxidative Phosphorylation Control of Bioenergetics Control of ATP-PC System Control of Glycolysis Control of Krebs Cycle and Electron Transport Chain Interaction Between Aerobic/Anaerobic ATP Production

5 General concepts and nomons Metabolism Sum of all chemical reacmons that occur in the body Anabolic reacmons Synthesis of molecules Catabolic reacmons Breakdown of molecules BioenergeMcs ConverMng foodstuffs (fats, proteins, carbohydrates) into energy

6 General concepts and nomons Study of molecular structures and events underlying biological processes RelaMonship between genes and cellular characterismcs they control Genes code for specific cellular proteins Process of protein synthesis Exercise training results in modificamons in protein synthesis Strength training results in increased synthesis of muscle contracmle protein Molecular biology provides tools for understanding the cellular response to exercise

7 Steps leading to protein synthesis 1. DNA contains information to produce proteins. 2. Transcription produces mrna. 3. mrna leaves nucleus and binds to ribosome. 4. Amino acids are carried to the ribosome by trna. 5. In translation, mrna is used to determine the arrangement of amino acids in the polypeptide chain.

8 Cellular chemical reacmons Endergonic reacmons Require energy to be added Endothermic Exergonic reacmons Release energy Exothermic Coupled reacmons LiberaMon of energy in an exergonic reacmon drives an endergonic reacmon

9 Glucose breakdown as an exergonic reacmon

10 Coupled reacmons The energy given off by the exergonic reaction powers the endergonic reaction

11 OxidaMon- reducmon reacmons OxidaMon Removing an electron ReducMon AddiMon of an electron OxidaMon and reducmon are always coupled reacmons Ofen involves the transfer of hydrogen atoms rather than free electrons Hydrogen atom contains one electron A molecule that loses a hydrogen also loses an electron and therefore is oxidized Importance of NAD and FAD

12 OxidaMon- reducmon reacmons involving NAD and NADH

13 Enzymes Catalysts that regulate the speed of reacmons Lower the energy of acmvamon Factors that regulate enzyme acmvity Temperature ph Interact with specific substrates Lock and key model

14 Enzymes Enzymes lower the energy of activation

15 The Lock- and- Key Model of Enzyme AcMon a) Substrate (sucrose) approaches the active site on the enzyme. b) Substrate fits into the active site, forming enzyme-substrate complex. c) The enzyme releases the products (glucose and fructose).

16 DiagnosMc Value of Measuring Enzyme AcMvity in the Blood Damaged cells release enzymes into the blood Enzyme levels in blood indicate disease or Mssue damage DiagnosMc applicamon Elevated lactate dehydogenase or creamne kinase in the blood may indicate a myocardial infarcmon

17 ClassificaMon of Enzymes Oxidoreductases Catalyze oxidamon- reducmon reacmons Transferases Transfer elements of one molecule to another Hydrolases Cleave bonds by adding water Lyases Groups of elements are removed to form a double bond or added to a double bond Isomerases Rearrangement of the structure of molecules Ligases Catalyze bond formamon between substrate molecules

18 ClassificaMon of Enzymes

19 Factors That Alter Enzyme AcMvity Temperature ph Small rise in body temperature increases enzyme acmvity Exercise results in increased body temperature Changes in ph reduces enzyme acmvity LacMc acid produced during exercise

20 The Effect of Body Temperature on Enzyme AcMvity

21 The Effect of ph on Enzyme AcMvity

22 Macromolecules - Carbohydrates Glucose Blood sugar Glycogen Storage form of glucose in liver and muscle Synthesized by enzyme glycogen synthase Glycogenolysis Breakdown of glycogen to glucose

23 Macromolecules - Fats Fajy acids Primary type of fat used by the muscle Triglycerides Storage form of fat in muscle and adipose Mssue Breaks down into glycerol and fajy acids Phospholipids Not used as an energy source Steroids Derived from cholesterol Needed to synthesize sex hormones

24 Macromolecules - Proteins Composed of amino acids Some can be converted to glucose in the liver Gluconeogenesis Others can be converted to metabolic intermediates Contribute as a fuel in muscle Overall, protein is not a primary energy source during exercise

25 BioenergeMcs FormaMon of ATP PhosphocreaMne (PC) breakdown DegradaMon of glucose and glycogen Glycolysis OxidaMve formamon of ATP Anaerobic pathways Do not involve O 2 PC breakdown and glycolysis Aerobic pathways Require O 2 OxidaMve phosphorylamon

26 Overview of carbohydrate and amino acid metabolism

27 Anaerobic ATP ProducMon ATP- PC system Immediate source of ATP Glycolysis Glucose 2 pyruvic acid or 2 lacmc acid Energy investment phase Requires 2 ATP Energy generamon phase Produces 4 ATP, 2 NADH, and 2 pyruvate or 2 lactate