enzymes
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ENZYMES
College Prep BiologyMr. Martino
Energy and Organization of Life
Energy: the capacity to perform work Energy makes
change possible All organisms
require it 2 forms: 1. Kinetic
energy: energy of
motion Moving mass of
matter performs work by transferring its motion to other matter
Ex. Heat and light
2. Potential Energy:
stored energy – capacity to do work Result of
location or arrangement of matter
Chemical Energy: potential energy of molecules - the most important type of energy for life
ATP
1st Law of Thermodynamics: (Law of E conservation) total amount of E in universe is constant. E cannot be created or destroyed E can be transferred or
transformed 2nd Law of Thermodynamics: E
conversions reduce the order of the universe Increases the amount of disorder
in a system (entropy) Energy input is necessary to
maintain organization
Doing Cellular Work
Two main types of chemical reactions: 1. Endergonic:
requires a net input of E
Energy is absorbed from surroundings as rxn occurs
Products are rich in potential energy
Ex. photosynthesis
2. Exergonic: releases energy
Bonds of reactants contain more E than bonds in products
Remainder of the E is released to surroundings during reaction
Ex. Wood is burning or cellular respiration: breakdown of glucose and the storage of a usable form of E
ATP : (Adenosine triphosphate) cell’s energy molecule powers nearly all
forms of cellular work
3 parts connected by covalent bonds:
adenine, ribose, and a chain of 3 phosphate groups
nucleotide
Bond between 2nd & 3rd P-group is unstable Easily broken by hydrolysis Break bond & 3 things occur:
P is removed ATP becomes ADP
(adenosine diphosphate) E is released
An exergonic rxn which can be coupled with an endergonic rxn
Phosphorylation: the transfer of a P-group to a molecule
Most cellular work depends on ATP energizing other molecules by phosphorylation
Enzyme Structure and Function
ATP’s E is immediately available when needed Energy of Activation
(Ea): amount of E reactants must absorb to start a chemical rxn
In ATP – Ea is the amount of E needed to break the bond between the 2nd and 3rd P group
Enzymes: protein molecules that serve as biological catalysts
Enzymes have a unique 3-D shape
Each enzyme recognizes only specific substrates Substrate: the substance
an enzyme works on Active site: small part of
enzyme that binds to substrate
Enzymes are specific because its active site fits only 1 kind of substrate
Important characteristics of enzymes: Cannot make anything
happen that could not happen on own
Increase rate of reaction hundreds to millions of times
Are not changed during reaction
Lowers the barrier Ea
Reusable Work in forward and reverse Very specific for substrate Essential to life
5.4 Factors Influencing Enzyme Activity
Temperature - a measure of molecular motion Temp. increases the
rate of substrates colliding with active sites
If too low, substrates and active sites won’t connect
If too high, the increase molecular motion will break bonds holding enzyme into 3-D shape
People die if temperature reaches 112 F
pH: measure of the concentration of H+
Most all enzymes need a pH of 6-8
pH changes denature enzymes
Ion concentration Ions can disrupt
the enzyme maintaining its shape
Ex. salt
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