1. METABOLISM Chapter 8

2. Energy of Life  Metabolism is the combination of all the chemical reactions in an organism  Arises from interactions of molecules within an orderly cell  Facilitated by metabolic pathways which are altered series of steps that create new products  Often catalyzed by enzymes  Balances supply and demand of the cell (think traffic lights)

3. Types of Metabolic Pathways  Catabolic (C A + B)  Release energy by breaking down complex molecules into simpler ones; degradation  E.g cellular respiration: fuels and O 2 to energy, H 2 0, and CO 2  Anabolic (A + B C)  Use energy to make more complex molecules by consuming simpler ones; biosynthetic  E.g amino acids to form proteins  Energy from catabolic (downhill) reactions can be stored to drive anabolic (uphill) ones

4. A Review of Energy  The capacity to cause change or rearrange matter; to do work  KE is energy of movement or objects in motion Thermal energy (heat) is KE from random movement of atoms or molecules  PE is stored energy; energy due to structure or location Chemical energy is the PE available for release in a chemical reaction  Necessary for all metabolic processes  Organisms are energy transformers  Energy forms include: heat, light, and sound

5. Energy Moves Around  Energy enters the world (light E)  Sunlight is the ultimate source of all energy  Harnessed or captured by plants (converts to chemical E)  Photosynthesis produces sugars stored in plants  Energy transfer between organisms (converts to kinetic E)  Organisms that consume plants can use for metabolism Some lost as heat  Energy transfer again  Organisms that eat what ate plants

6. Thermodynamics  1st Law of Thermodynamics  Energy can not be created or destroyed, it is transferred or transformed  2 nd Law of Thermodynamics  During conversion of energy from one form to another, some is lost as heat Makes universe more disorderly An input of energy is needed to maintain order

7. Order vs. Disorder  Living systems create ordered structures from less ordered starting materials  Amino acids ordered into polypeptide chains  Living organisms are organized and complex  Take in ordered forms of matter and energy and replace them with less ordered forms  Consume food to catabolize into CO 2 and H 2 0  Organisms’ orderly state converted to disorder upon death

8. Classifying Reactions  Net release of energy  Magnitude is max work that can be done  Are spontaneous, no energy needed  Absorbs free energy  Magnitude is energy needed to drive reaction  Stores free energy, nonspontaneous Exergonic: ‘energy outward’Endergonic: ‘energy inward’

9. Metabolic Equilibrium  Matter that doesn’t interact with environment will reach equilibrium and stop reacting  Cell at metabolic equilibrium is dead (can’t work)  Cells maintain constant flow of materials in and out of cell  Keeps metabolic pathways from reaching equilibrium  Continues if product don’t accumulate C 6 H 12 O 6 and O 2 available and ways to excrete waste ≠ equilibrium

10. Energy Coupling  Use exergonic processes to drive endergonic  ATP mediates most processes  Immediate source of energy to power cellular work  3 main types of cellular work  Chemical: endergonic reactions, synthesizing polymers  Transport: pumping substances across membrane against [gradient]  Mechanical: beating of cilia or contraction of muscle cells

11. Adenosine Triphosphate (ATP)  Nucleotide consisting of sugar ribose, nitrogenous base adenine, and 3 phosphate groups  Bonds can be hydrolyzed  ATP ADP + P i + E Exergonic: -7.3 kcal/mol  Phosphate groups have (-) charge grouped together  Repulsion like a spring

12. Hydrolysis of ATP  Can heat cells when sole reaction  Shivering to generate heat from muscle contraction = inefficent  Proteins actually harness E to perform cellular work  Use exergonic to drive endergonic reactions  Involves transfer of P i from ATP to another molecule, called phosphorylation Molecule becomes more reactive  Can change protein shape and binding

13. Activation Energy (E A )  Amount of energy needed to ‘push’ reactants toward products  Barrier that determines the rate of a reaction  Enzymes, proteins that act as catalysts, act to lower E A so reactions occur faster Often end in ‘-ase’ Reaction specific  Reactants absorb E until unstable, allowing bonds to break

14. Enzyme Activity * Specific to a substrate, based on 3D shape

15. Enzyme Function Effects  Temperature: increase rate b/c molecules move faster  To a point, above will denature  pH: optimal 6-8, but exceptions exist (pepsin and trypsin)  Cofactors/coenzymes: inorganic or organic helpers  i.e. vitamins  Inhibitors: weak bonds = reversible, covalent bonds aren’t  Competitive inhibitors: prevents substrate from binding to active site b/c binds first or stronger (CO vs O 2 )  Counter by increasing substrate  Non-competitive inhibitors: binds to an alternate spot and changes active site so intended substrate can’t bind  i.e. sarin gas and DDT