Chapter 8.1, 8.2, 8.4, 8.5

metabolism is the process of breaking down and creating molecules necessary for life◦ each step in this process is driven by an

enzyme which directs the speed of the reaction (enzymes are proteins!)

catabolic--breakdown molecules cellular respiration

anabolic--build molecules protein synthesis

energy is the capacity to cause change◦ kinetic (heat) vs. potential (chemical)

thermodynamics = energy transformations

◦ 1st law (matter cannot be created or destroyed, only change form)

◦ 2nd law (energy transfer increases the entropy of the universe) spontaneous reactions vs. reactions that need

energy

free energy--identifies if a reaction requires energy to proceed◦ higher free energy = unstable

does not require outside energy for the reaction to happen (spontaneous)

exergonic reaction (negative delta G) does not imply that it happens fast!

◦ lower free energy = stable requires outside energy for the reaction to

proceed (nonspontaneous) endergonic reaction (positive delta G)

Lower energy barriers for the reaction to happen at an increased rate (catalyst); not used up during the reaction◦ activation energy (energy required to get

reaction going) based on how difficult it is to break the chemical

bonds◦ speed up reactions that would occur anyway

substrate (reactant an enzyme acts on)◦enzyme binds to substrate, forming enzyme-

substrate complex◦each enzyme has a specific substrate (results

from unique sequence of amino acids)

active site (region of enzyme where substrate binds)◦when this occurs, the shape of the enzyme

changes which enhances the reaction

Rate in which enzyme converts substrate to product is determined by...◦ the initial concentration of the substrate (or

enzyme) more substrate molecules that are available

the more frequently they access active site. limited by the enzyme concentration

(saturated when rate of reaction is determined by how often substrate can move into active site)

◦ general environmental factors temperature, pH, and other chemicals each enzyme has optimal environment

depending on the organism and where it needs to work

competitive inhibition◦ reduce the productivity of

enzymes by blocking substrate from entering active site

◦ overcome by increasing concentration of substrate

noncompetitive inhibition◦ impede reactions by

binding to another part of the enzyme, thus changing the shape of the active site and making it less effective

◦ **often pesticides, antibiotics, and toxins are inhibitors

enzymes need to be told when and where to be active so only necessary reactions are occurring◦Allosteric regulation

protein function changed by binding of another molecule has active (activator binds) and

inactive (inhibitor binds) forms “Chemical on/off switch”

◦ feedback inhibition end product of reaction binds to

enzyme causing inhibition, thus slowing the reaction down