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Chemical Reactions and Enzymes

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Chemical Reactions and Enzymes Energy and Matter Energy The ability to do work or cause change Occurs in various forms Can be converted to another form Forms ... – PowerPoint PPT presentation

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Title: 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
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