Bioenergetics. Chapter 3. Objectives. Objectives. Introduction. Photosynthesis. Energy Forms

Transcription

1 Objectives Chapter 3 Bioenergetics Discuss the function of cell membrane, nucleus, & mitochondria Define: endergonic, exergonic, coupled reactions & bioenergetics Describe how enzymes work Discuss nutrients used for energy Identify high-energy phosphates Objectives Discuss anaerobic & aerobic production of ATP Describe how metabolic pathways are regulated Discuss the interaction of anaerobic & aerobic ATP production during exercise Identify the rate limiting enzymes Introduction Metabolism: total of all chemical reactions that occur in the body Anabolic reactions - Synthesis of molecules Catabolic reactions - Breakdown of molecules Bioenergetics Converting foodstuffs (fats, proteins, carbohydrates) into energy Substrate Substance used by body in metabolism Metabolite Byproduct of metabolism Energy Forms Energy originates in the sun Chemical Light Mechanical Electrical Heat Nuclear Photosynthesis Energy from the sun Solar energy from sun converted to chemical energy in plants Plants use energy + water and carbon dioxide Byproduct is oxygen Build food molecules 1

2 Thermodynamics 1 st Law Conservation of energy-energy cannot be created or destroyed. They can be interchanged Our bodies transform energy into a form that we can used. Biological Energy Cycle Food + O 2 CO 2 + H 2 O + energy Chemical Mechanical 60-70% of this energy is heat The rest is used for Muscle contraction Cellular operations (respiration) Digestion and absorption Synthesis of new compounds Glandular function Biological Energy Cycle Chemical energy transformation to mechanical energy Food (Chemical energy) is used for muscular contraction (Mechanical energy) Elements Basic chemical substances Oxygen Carbon Hydrogen Nitrogen Minor elements Sodium, Iron, Zinc, Potassium, Magnesium, Chloride, Calcium Organic substances contain carbon Inorganic substances - do not contain carbon Cell Structure Cell membrane Protective barrier between interior of cell and extracellular fluid Maintains ion concentrations (unequal) Nucleus Contains genes that regulate protein synthesis Cell Structure Cytoplasm Fluid portion of cell Contains organelles (mitochondria) Glycolysis enzymes Mitochondria 2

3 Structure of a Typical Cell Cellular Chemical Reactions Endergonic reactions Require energy to be added Photosynthesis solar energy to chemical energy Energy stored Exergonic reactions Release energy Breakdown of cellular bonds Fig 3.1 The Breakdown of Glucose: An Exergonic Reaction Coupled Reactions Fig 3.3 Fig 3.4 Cellular Chemical Reactions Coupled reactions Liberation of energy in an exergonic reaction drives an endergonic reaction Breakdown of glucose-exergonic Formation of ATP-endergonic Oxidation-Reduction Reactions Oxidation: removing an electron Removing a negative charge = + > (oxygen not required) Reduction: addition of an electron Adding a negative charge = - > Oxidation and reduction are always coupled reactions 3

4 Oxidation-Reduction Reactions Reducing agent: molecule that donates an electron Oxidizing agent: molecule that accepts an electron Oxidation-Reduction Reactions In cells often involve 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 Transfer of H + and e - Major transport molecules in bioenergetics Nicotinamide adenine dinucleotide Niacin (B 3 ) NAD oxidized form NADH reduced form Transfer of H + and e - Major transport molecules in bioenergetics Flavin adenine dinucleotide Riboflavin (B 2 ) FAD oxidized form FADH reduced form Enzymes Catalysts that regulate the speed of reactions Lower the energy of activation Energy required to initiate the reaction Speed up the rate of the reaction Increase the rate of product formation Enzymes Lower the Energy of Activation Fig 3.6 4

5 Enzymes Factors that influence enzyme activity Temperature Optimum temperature most active Slight increase increases activity of most enzymes Useful for muscular contraction ph Optimum ph Altered ph reduces enzyme activity High intensity exercise (LA) - ph Decreases ability to produce energy (ATP) Extreme acidity is a limiting factor in exercise. Enzymes Structural characteristics Large proteins with 3 D shape Characteristic grooves and ridges Active sites Interact with specific substrates Lock and key model Enzyme- Substrate Interaction Complex lowers energy of activation Reaction proceeds Fuels for Exercise Carbohydrates Glucose C 6 H 12 O 6 (4 kcal/gram) Monosaccharide Stored as glycogen (C 6 H 12 O 6 ) n Disaccharides Sucrose Polysaccharides Cellulose Starch Fig 3.7 Fuels for Exercise Fats Carbon, hydrogen, oxygen Groups Fatty acids energy source (9 kcal/gram) Stored as triglycerides-fat cells, skeletal muscle Lipolysis-fatty acids and glycerol Phospholipids not an energy source Structural component-cell membranes, myelin sheath Steroids not an energy source Structural component-cell membranes Synthesis of hormones Fuels for Exercise Proteins Not a primary energy source during exercise Amino acids Limited usage Extreme exercise conditions 5

6 Adenosine Triphosphate Structure of ATP We convert food: Fat, Carbohydrate (CHO), Protein (limited) Into energy: Adenosine TriPhosphate (ATP) Adenosine is a complex structure Phosphates (3 simpler structures) Adenosine (P) (P) (P) Fig 3.8 Model of ATP as the Universal Energy Donor Adenosine ATP (P) (P) (P) ATP + H 2 O ADP + Pi ATPase 7,000 to 12,000 calories or 7 to 12 kilocalories Breakdown requires regeneration Coupled reaction Fig 3.9 Coupled Reaction ATP + H 2 O ADP + Pi ATPase ADP + C~P ATP + C Creatine kinase Bioenergetics Cells need constant supply of ATP Minimal amounts stored for cellular processes Muscular contraction-exercise Constant, large supply Formation of ATP (3 metabolic pathways) 1. Phosphocreatine (PC) breakdown ATP-PC system (phosphagen system) 2. Degradation of glucose and glycogen Glycolysis (Glycolytic system) 3. Oxidative phosphorylation Tricarboxylic cycle, Krebs cycle 6

7 Bioenergetics Anaerobic pathways (do not involve O 2 ) 1. ATP-PC breakdown 2. Anaerobic glycolysis Aerobic pathway Requires O 2 3. Oxidative phosphorylation 1. ATP-PC (Phosphagens) Characteristics ATP and PC stored in the contracting mechanism of the muscle Simplest and fastest way to produce ATP ATP + H 2 O ADP + Pi ATPase Provides energy for short term, maximal exercise 5 sec High intensity activity 30 sec 1. ATP-PC (Phosphagens) Characteristics (cont) At onset of exercise-rapid breakdown followed by rapid resynthesis ADP + C~P ATP + C Creatine kinase ATP replenishment by PC maintains ATP levels for awhile. PC replenishment continues activity about 30 sec 1. ATP-PC (Phosphagens) Characteristics (cont) 3 times more CP than ATP stored in muscle Fastest rate of energy production, lowest stores (capacity) Used during Initial onset of exercise (oxygen deficit) Short term, high intensity exercise (< 5 sec) Resynthesis only during recovery Activities (examples) Sprints (< 30 sec) High jumping Weight lifting Energy Transfer Systems and Exercise 100% % Capacity of Energy System Anaerobic Glycolysis Aerobic Energy System ATP - CP 10 sec 30 sec 2 min 5 min + 7