Chapter 2

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Transcript Chapter 2

Chapter 2
The Chemistry of Life
Section 1 – The Nature of Matter
• Atoms are the basic unit of matter.
• Subatomic particles that make up atoms are
protons, neutrons, and electrons.
• Protons – positively charged particles
• Neutrons – carry no charge, neutral
• Protons and neutrons are found in the nucleus
of the atom
• Electron – negatively charged particle
• In constant motion in the space surrounding
the nucleus.
• Element – pure substance that consists
entirely of one type of atom.
– Represented by a one- or two- letter symbol.
– Elements are arranged into the periodic table.
Chemical Compounds
• A chemical compound is a substance formed
by the chemical combination of two or more
elements in definite proportions.
Chemical Bonds
• Ionic bonds – formed when one or more
electrons are transferred from one atom to
• Covalent bonds – formed when electrons are
shared between atoms.
• Van der Waals forces – when molecules are
close together, a slight attraction can develop
between oppositely charged regions of nearby
molecules. These attractions are not as strong
as ionic or covalent bonds.
Section 2 - Properties of Water
• Polarity – a molecule in which the charges are
unevenly distributed is a polar molecule.
– A water molecule is polar because there is an
uneven distribution of electrons between the
oxygen and hydrogen atoms.
Hydrogen Bonds
• A single water molecule may be involved in as
many as four hydrogen bonds at the same
– Cohesion: an attraction between molecules of the
same substance.
– Adhesion: an attraction between molecules of
different substances.
• Mixture – a material composed of two or
more elements or compounds that are
physically mixed together but not chemically
• Solution – all components are evenly
distributed throughout.
– Solute – the substance that is dissolved
– Solvent – the substance in which the solute
• Suspension – mixture of water and nondissolved materials.
– Materials will separate into pieces but do not
settle out
Acids, Bases and pH
• The pH scale – a measurement system that
indicates the concentration of H+ ions in a
– Ranges from 1 – 14
– 7 is neutral
– Under 7 is acidic
– Above 7 is basic
• Any compound that forms H+ ions in
– pH value below 7
• Any compound that produces hydroxide (OH-)
– pH value above 7
• Weak acids or bases that can react with strong
acids or bases to prevent sharp, sudden
changes in pH.
– Help control pH and retain homeostasis in the
Section 3 – Carbon Compounds
• Macromolecule: LARGE carbon molecule
• Polymer: Large molecule formed when many
smaller molecules bond together
• 2 H atoms for every O & C
– 1. Simplest carbs: Called Monosaccharides
(one sugar)
-Ex: glucose; fructose
- 2. Disaccharides – two sugars
-Sucrose (glucose + fructose)
- 3. Polysaccharides – many sugars
-Starch, glycogen, and cellulose
• Lipids: Fats; Organic compounds that have a
large proportion of C-H bonds and less O than
• Insoluble in water because lipids are nonpolar
• Saturated Fat: Animal fats
• Unsaturated Fat: Oils
• A large, complex polymer composed of
carbon, hydrogen, oxygen, nitrogen, and
usually sulfur; have an “R” group that makes
each different
• Made from amino acids
• 20 common amino acids
• Proteins are the building blocks of many
structural components
• Amino Acids are linked together when an Hgroup and –OH group are removed to form
• The covalent bond formed between A.A. is a
Nucleic Acids
• A complex macromolecule that stores cellular
info. in the form of a code
• Nucleic acids are made up of smaller subunits
called Nucleotides
• Nucleotides consist of three basic parts:
– 1. Nitrogen-containing base
– 2. Pentose sugar
– 3. Phosphate group
Types of Nucleic Acids
• 1. DNA: Deoxyribonucleic acid
– Master copy of organism’s genetic info.
– Contains instructions used to form organism’s
enzymes and proteins
2. RNA: Ribonucleic acid
– Forms a copy of DNA for use in making copies and
Section 4 - Chemical Reactions
• Chemical formulas describe the substances in
the reaction and arrows indicate the process
of change
• Reactants – starting substances on the left
side of the arrow
• Products – substances formed during the
reaction on the right side of arrow
• Arrow can be read as “yields” or “react to
Energy in Reactions
• Key to starting a chemical reaction is energy
• Energy in the form of heat is need
• Most compounds in living things cannot
undergo chemical reactions without energy
Activation Energy
• Minimum amount of energy needed for
reactants to form products in a chemical
Energy Change in Chemical
• In every chemical reaction, there is a change in
energy due to the making and breaking of chemical
• Exothermic reactions – energy of the product is
lower than the energy of the reactants
– Energy is released in the form of heat
• Endothermic reactions – energy of the products is
higher than the energy of the reactant
– Heat energy is absorbed
Endothermic Reaction
Exothermic Reaction
• Catalyst – substance that lowers the activation
energy needed to start a chemical reaction
• Enzymes – special proteins that are the biological
catalysts that speed up the rate of chemical reactions
in biological processes
Essential to life
Not used up by the chemical reaction
Can be used again
Most enzymes are specific to one reaction
• Substrates – reactants that bind to the
• Active Site – specific location where a
substrate binds on an enzyme
– The active site and substrates have
complementary shapes
– Only the substrate with the same shape as the
active site will bind to the enzyme
– Example : Lock & Key
• Once the substrates bind to the active site, the
site changes shape and forms the enzymesubstrate complex
• The new complex helps chemical bonds in the
reactants to be broken and new bonds are
• The substrates react to form products
• The enzyme then releases the products
• Factors such as pH, temperature, and other
substances affect enzyme activity
• Enzymes affect many biological processes
– Examples:
Snake bite
Fruit ripening