KINE 2P90 Bioenergetics 1

• One form of energy -> transducer -> another form of energy
• Conversion is occurring all the time

  • low demands when sedentary
  • high demands in sport
• Process of converting nutrients (fuels) into energy

  • fuels include
  • fats, proteins, carbohydrates
  • only a small amount of proteins because they are the building blocks of the body
  • fuels converted to a common high-energy compound
  • adenosine triphosphate (ATP)
  • all external and internal work powered by ATP
• Internal work includes

  • ion trafficking across membrane
  • regulating calcium levels
  • actin-myosin interactions
  • protein synthesis
• Energy defined as ability to do work
• Cellular Chemical Reactions

  • Free Energy in Food --no direct link --> ATP transfers the free energy needed to do biological work
  • in between:
  • metabolic pathways
  • extract energy contained in food
  • step by step modification
  • energy used to make ATP
• Cellular Chemical Reactions

  • not 100% of what is consumed is converted to ATP
  • usually about 60% and the rest is used along the way
• Exergonic - energy yielding

  Endergonic - energy requiring
• Exergonic reactions power endergonic reactions
• Oxidation - removal of an electron (H)
• Reduction - addition of an electron (H)
• Oxidation-Reduction Reactions

  • how energy is transferred within the cell (from molecule to molecule)
  • oxidation and reduction are always coupled reactions
  • one cannot occur without the other
• Reducing agent - the molecule that donates H+
• Redox Reactions

  • One compound is reduced
  • the other is oxidized
• Endergonic (or endothermic) reactions

  • energy requiring reactions
  • e.g., storing glycogen, protein
  • Anabolic
• Exergonic (or exothermic) reactions

  • reactions that release energy
  • e.g., cellular respiration
  • catabolic
• Enzymes are proteins that catalyze metabolic reactions

  • lower the "activation energy" required for a reaction to proceed
  • speed up reactions by x1000 fold
  • reactions are already thermodynamically favourable
• Specific enzymes for specific pathways

  • enzyme activity controls bioenergetics
  • these are rate-limiting enzymes
  • control flux through pathways
• Rate-limiting enzymes

  • used to measure activity
  • the most important enzyme in a series of reactions
  • there will only be one rate-limiting enzyme in each series of reactions
• Catalytic activity of rate limiting enzymes highly regulated

  • by various factors via allosterism (+ or -)
• Allosterism

  • the process by which the interaction of a protein at one location on a protein or macromolecular complex (the allosteric site) influences the binding or function of the same or another protein at a distinct site
  • the prefix "allo" has a Greek origin meaning "other"
  • the concept was developed initially in the frame of a common oligomeric structure of regulatory enzymes
• Enzymes lower the energy of activation

  • increase catalytic rate - decrease activation energy
  • increase rate of disappearance of substrate
  • increase rate of appearance of products

  
  

  • enzymes do not alter energy release
  • enzymes are not consumed in the reaction
• Factors that alter enzyme activity

  • temperature
  • pH
  • exercise
• Temperature

  • a small rise in body temperature increases enzyme activity
  • we release heat and are influenced by external temperature
  • very small range, therefore small changes affect enzyme activity
• pH

  • cellular pH is 7.2; blood pH is 7.4
  • changes in pH from this range reduce enzyme activity
• The critical role of ATP

  • the energy currency of the cell - "universal energy donor"
  • cellular work is accomplished by proteins - example of endergonic-extegonic coupling
  • proteins/enzymes that couple ATP to work are called ATPases - harness energy released by hydrolysis of ATP
  • the main ATPases in musce: myosin (40-50%), Sarco/Endoplasmic Reticulum Calcium or SERCA (40-50%), Na/K (10%)
• Adenosine Triphosphate

  • 3 phosphates connected to adenosine backbone
  • terminal phosphate connected by a high energy bond - "hydrolyzing' this bond releases energy (formed using food energy)
• Adenosine triphosphate (ATP)

  • adenine, ribose, and three linked phosphates
• Adenosine diphosphate (ADP)

  • adenine, ribose, and two linked phosphates
• ATP hydrolysis by ATPases:

  • ATP -> ADP + Pi + energy (out)(exergonic)
  • myosin ATPase
• ATP synthesis by metabolic pathways

  • ADP + Pi + energy (in) --> ATP (endergonic)
  • glycolysis
• Bioenergetics

  • process of converting food energy to a more usable form
  • carbohydrates, fats, and proteins to ATP
• Metabolism is an endless series of coupled reactions

  • endergonic: energy using
  • exergonic: energy releasing
• Oxidation-reduction reactions are KEY to metabolism

  • NADH/FADH are vital reducing equivalents
  • H+ carriers (electrons)
• Enzymes facilitate reactions to make metabolism possible

  • require homeostatic range for optimal performance
• ATP is the "universal energy donor"

  • food energy stored in high energy bonds
  • metabolism is phosphate driven
  • endless cascade of making and breaking phosphate bonds
• ATP --(ATPase)--> ADP + Pi + Energy
• Anaerobic - no oxygen, quick
• Aerobic - uses oxygen, long term
• ATP is remade by anaerobic and aerobic metabolic pathways