Chemical Reactions and Enzymes

1
Chemical Reactions and Enzymes
2
Energy and Matter

• Energy
• The ability to do work or cause change
• Occurs in various forms
• Can be converted to another form
• Forms important to biological systems are
  chemical, thermal, electrical and mechanical
  energy
• Free energy is the energy in a system that is
  available for work

3
States of Matter

• Atoms are in constant motion
• The rate at which atoms or molecules in a
  substance move determines its state

4
States of Matter

• Solid
• Molecules are tightly linked.
• Little energy
• Liquid
• Molecules are not as tightly linked
• Medium amount of energy

5
States of Matter

• Gas
• Molecules have little or no attraction to each
  other
• Fill the volume of the occupied container
• Move most rapidly
• To cause a substance to change state, thermal
  energy (heat) must be added to or removed from a
  substance

6
Energy and Chemical Reactions

• Living things undergo thousands of chemical
  reactions as part of the life process

7
Energy and Chemical Reactions

• Many are very complex involving multistep
  sequences called biochemical pathways
• Chemical equations represent chemical reactions
• Reactants are shown on the left side of the
  equation
• Products are shown on the right side
• A B C D

8
Energy Transfer

• Much of the energy organisms need is provided by
  sugar (food)
• Undergoes a series of chemical reactions in which
  energy is released (cell respiration)
• The net release of free energy is called an
  exothermic reaction

9
Energy Transfer
Mix Barium hydroxide and aluminum salt, and the
products dissolve in water of hydration. This is
VERY COLD!

• Reactions that involve a net absorption of free
  energy are called endothermic reactions
• Photosynthesis is an example

10
Energy Transfer

• Most chemical reactions require energy to begin
• The amount of energy needed to start the reaction
  is called activation energy

11
Catalysts

• Certain chemical substances (catalysts) reduce
  the amount of activation energy required
• Biological catalysts are called enzymes

12
Catalysts

• Enzymes are an important class of catalysts in
  living organisms
• Mostly protein
• Thousands of different kinds
• Each specific for a different chemical reaction

13
Enzyme Structure

• Enzymes work on substances called substrates
• Substrates must fit into a place on an enzyme
  called the active site
• Enzymes are reusable!

14
Solutions
15
Solutions

• A solution is a mixture in which 2 or more
  substances are uniformly distributed in another
  substance

16
Solutions

• Solute is the substance dissolved in the solution
• Particles may be ions, atoms, or molecules
• Solvent is the substance in which the solute is
  dissolved
• Water is the universal solvent

17
Acids and Bases

• One of the most important aspects of a living
  system is the degree of acidity or alkalinity

18
pH Scale

• logarithmic scale for comparing the relative
  concentrations of hydronium ions and hydroxide
  ions in a solution
• ranges from 0 to 14

• Each pH is 10X stronger than next
• e.g. ph 1 is 10 times stronger than ph 2

19
Acids

• Compounds that donate a proton (H) when
  dissolved in a solution.
• the lower the pH the stronger the acid
• 0-6 on the pH scale
• HCl ? H Cl-

20
Bases

• Compounds that accepts a proton (H) when
  dissolved in a solution.
• the higher the pH the stronger the base
• 8-14 on the pH scale
• NaOH ? Na OH-

21
Acids and Bases

• pH 7.0 is neutral

22
Buffers

• Control of pH is very important
• Most enzymes function only within a very narrow
  pH
• Control is accomplished with buffers made by the
  body
• Buffers keep a neutral pH (pH 7)

23

• Buffers neutralize small amounts of either an
  acid or base added to a solution
• Complex buffering systems maintain the pH values
  of your bodys many fluids at normal and safe
  levels

24
(No Transcript)