AP Biology notes

• living organisms require a constant input of energy 
• the first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another 
• also known as the law of conservation of energy 
• the second law of thermodynamics states that during energy conversions, the universe becomes more disordered 
• free energy is represented by the letter G 
• if energy is released the reaction is exergonic 
•  if in a chemical reaction energy is absorbed the reaction is endergonic 
• exergonice reactions power endergonic reactions 
• metabolism is the sum of all the chemical reactions that take place in cells 
• catabolism- the break down of molecules 
• anabolism the building up of molecules 
• metabollic reactions take place in a series called pathways 
• these pathways are controlled by enzymes 
• catalytic proteins speed up reaction by lowering the activation energy 
• the transition state is the reactive (unstable) condition of the substrate after sufficient energy has been absorbed to initiate the reaction 
• enzymes a globular structures that exhibit tertiary structure 
• as the substrate eneters the active site, it includes the enzyme to alter its shape slightly so the substrate fits better
• the enzyme binds to its substrate, forming an enzyme substrate complex 
• enzymes are reused in a reaction 
• enzymes often require assistance from cofactors or coenzymes 
• the efficiency of an enzyme is affected by temperature and pH 
• In competitive inhibition some compounds resemble the substrate molecules and compete for the same active site enzyme
• these competitive inhibitors reduce the productivity of enzymes by preventing or limiting the substrate from binding to the enzyme 
• allosteric- a change in shape alters efficiency 
• noncompetative inhibitors bind to a site distinct from the active site of the enzyme 
• in feedback inhibitors the end product of the pathway is the allosteric inhibitor for an enzyme that catalyzes an early step in the pathway 
• coopertivity is the binding of one substrate molecule to one active site of one subunit of the enzyme causes a change in the entire molecue and locks all subunits in an active position 
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