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