ENERGY

1. ENERGY

2. Energy • capacity to perform work • done when objects are moved against opposing forces & things move in directions in which they would not have moved if left alone • body needs energy • cells are biggest users of energy in the body • need energy to make complex molecules from monomer building blocks-anabolic reactions • need energy to break down macromolecules- catabolic reactions to obtain energy to do all of the activities they need to do everyday

3. First Law of Thermodynamics • energy cannot be destroyed nor created • energy can be converted from one form to another • plants convert energy in sunlight into chemical energy life forms use to perform activities of life • can’t use energy over & over • each time there is energy transfer some energy becomes unusable

4. Forms of Energy • Kinetic energy • energy of motion • Potential energy • stored energy • energy an object has as result of its locomotion or structure

5. Forms of Energy

6. Energy Flow • energy flows into our ecosystem as sunlight • kinetic energy (from sun) is transformed into chemical energy-potential energy of food & fuels by photosynthesis

7. Energy Flow • animals consume food products to provide ATP or energy for cells to perform work

8. Endergonic Reactions • yield potential energy • require input of energy • products acquire more energy than reactants • energy is stored in covalent bonds of products • photosynthesis is an endergonic reaction

9. Exergonic Reactions • release energy • reactions begin with reactants whose covalent bonds contain more energy than in products & release energy to the environment • occur in cells of body • cellular respiration • oxygen is used to convert chemical energy stored in fuel molecules (glucose) to chemical energy (ATP) cell uses to carry on its processes • Glucose + O2CO2 + H2O

10. ATP-Adenosine Triphosphate • provides energy for cellular work • consists of • adenine • nitrogenous base • ribose • five carbon sugar • called adenosine • 3 PO4 groups attached-triphosphate part • phosphate bonds are unstable • can be easily broken by hydrolysis in exergonic reactions • each PO4 group released from ATP yields 7Kcal of energy • one phosphate group removed • ATPADP + pi + 7Kcal of energy • adenosine diphosphate + inorganic phosphate + energy • another phosphate removed • AMP + pi + 7Kcal of energy • adenosine monophosphate

11. Cellular Metabolism • every working cell in body performs exergonic & endergonic reactions • sum-cellular metabolism • energy released from exergonic reactions is used to drive endergonic reactions • energy coupling • ATP functions in energy coupling

12. Energy Coupling

13. Factors in Chemical Reactions • many molecules in body store tremendous amount of potential energy • do not spontaneously break down into smaller components • to initiate reactions reactants need to overcome an energy barrier • amount of energy that compound must absorb before chemical reaction can begin-activationenergy • requires a catalyst • something to speed rate of reaction

14. Enzymes • speed rate of reactions • lower activation energy • globular proteins • names typically end in –ase • each has a unique 3-D shape • shape determines which reactions enzyme can catalyze

15. Enzymes • specific reactant for specific enzyme-substrate • fits into specific area-active site • once product forms • enzyme detaches from active site • free to start another reaction

16. Enzyme Action

17. Saturation Limit • reaction rate is proportional to concentration of substrate &concentration of enzyme • enzyme must meet with specific amount of substrate before catalysis can begin • higher substrate concentrations more frequently encountered by enzyme • when substrate concentrations are high enough so every enzyme molecule is cycling through its reaction sequence at top speed further increase in substrate concentration will not effect rate of reaction unless more enzyme is added • substrate concentration at which rate of a reaction is maximum is saturation limit

18. Regulation of Enzymatic Reactions • many variables turn enzymes on & off to control reaction rates • enzymes are proteins • protein shapes can be changed by the environment • Temperature • Salt concentration • pH

19. Regulators of Enzymatic Activity • Cofactors • ions or molecules that bind to enzyme before substrate can bind • allows enzymes to be active sometimes & inactive at other times • several important inorganic cofactors-zinc, iron & copper • organic cofactors are coenzymes • most made from vitamins or are vitamins

20. Inhibition of Enzymatic Activity • chemicals that interfere with enzyme function-inhibitors • competitive inhibitors • fit into active sites so real substrate cannot • noncompetitive inhibitors • bind at sites other than active site • changes enzyme’s shape • causes active site to no longer recognize substrate

22. Inhibition • Reversible inhibitors • can serve a regulatory function • turn enzyme on when needed • turn it off when not • Irreversible inhibitors • kill enzyme function • poisons • block metabolic processes that are essential to survival

23. Irreversible Inhibition • Penicillin • inhibits enzymes in bacteria needed to make cells walls • since humans do not have this enzyme penicillin can be used to kill the bug without effecting human cells