Download Ch. 2 The Chemistry of Life

Unit 1 The Nature of Life
Ch. 2 The Chemistry of Life
Atoms
Atom - the basic unit of matter
 The subatomic particles that make up
atoms are protons, neutrons, &
electrons

Atoms
Nucleus - the center of the atom
 Electron - a negatively charged particle

Elements & Isotopes
Element - a pure substance that
consists entirely of one type of atom
 Isotopes - atoms of the same element
that differ in number of neutrons


Because they have the same # of
electrons, all isotopes of an element have
the same chemical properties
Isotopes of Carbon
Chemical Compounds

Compound - a substance formed by the
chemical combination of 2 or more
elements

Ex.) NaCl
Chemical Bonds
The 2 main types of chemical bonds are
ionic bonds & covalent bonds
 Ionic bond - formed when 1 or more
electrons are transferred from 1 atom to
another
 Ions - positively & negatively charged
atoms

Sodium Chloride - An Ionic
Bond
Chemical Bonds
Covalent bond - forms when electrons
are shared between atoms
 Molecule - the smallest unit of most
compounds

Chemical Bonds

Van der Waals Forces - the slight
attraction between oppositely charged,
nearby molecules
The Water Molecule

A water molecule is polar because there
is an uneven distribution of electrons
between the oxygen & hydrogen atoms
The Water Molecule

Cohesion - an attraction between
molecules of the same substance

Ex.) Water
The Water Molecule

Adhesion - an attraction between
molecules of different substances

Ex.) Water molecules to glass
Solutions & Suspensions

Mixture - a material composed of 2 or
more elements or compounds that are
physically mixed together, but not
chemically combined
Solutions & Suspensions
Solution - all components evenly
distributed
 Solute - the substance that is dissolved
 Solvent - the substance in which the
solute dissolves


Ex.) In a saltwater solution, salt is the
solute & water is the solvent
Acids, Bases, and pH

pH scale - measurement system to
indicate the concentration of H+ ions in
solution, ranges from 0-14
Acids, Bases, and pH
Acid - any compound that forms H+ ions
in solution
 Acidic solutions have higher
concentration of H+ ions than pure
water & have pH values below 7
 The greater the concentration of H+
ions, the lower the pH number

Acids, Bases, and pH
Base - a compound that produces
hydroxide ions in solution
 Basic, or alkaline, solutions have lower
concentrations of H+ ions than pure
water & have pH values above 7
 The lower the concentration of H+ ions,
the higher the pH value (up to 14)

Acids, Bases, and pH

Buffers - weak acids
or bases that can
react with strong
acids or bases to
prevent sharp,
sudden changes in
pH
The Chemistry of Carbon
Organic compounds - compounds
created by organisms
 4 groups of organic compounds found in
living things are carbohydrates, lipids,
nucleic acids, & proteins

Carbohydrates
Carbohydrates - compounds made up
of carbon, hydrogen, & oxygen atoms
 Living things use carbohydrates as their
main source of energy


Ex.) Starches & sugars
Lipids
Lipids - made mostly from carbon &
hydrogen atoms
 They can be used to store energy


Ex.) fats, oils, waxes
Nucleic Acids
Nucleic acids - molecules that store &
transmit genetic information, made up of
nucleotides
 Nucleotide - has 3 parts: a 5-carbon
sugar, a phosphate group, & a
nitrogenous base

Nucleic Acids
There are 2 kinds of nucleic acids: RNA
(ribonucleic acid) & DNA
(deoxyribonucleic acid)
 RNA contains the sugar ribose, DNA
contains the sugar deoxyribose

Proteins
Proteins - molecules that contain
nitrogen, carbon, hydrogen, & oxygen
 Proteins are made up of chains of
amino acids

Proteins

Amino acids - compounds with an
amino group on one end & a carboxyl
group on the other end, there are more
than 20 in nature
Proteins
- Proteins help to carry out chemical
reactions, transport small molecules in
& out of cells, & fight diseases
Chemical Reactions

Chemical reaction - process that changes, or
transforms, 1 set of chemicals into another
 Reactants - the elements or compounds that
enter into a chemical reaction
 Products - elements or compounds produced
by a chemical reaction
 Chemical reactions always involve changes
in the chemical bonds that join atoms in
compounds
Energy in Reactions

Energy is released when chemical
bonds are broken, & absorbed when
chemical bonds are formed
Energy Changes
Chemical reactions that release energy
often occur spontaneously
 Reactions that absorb energy will not
occur without a source of energy

Energy Changes
Organisms need to carry out reactions
that require energy in order to stay alive
 Humans release the energy needed to
grow, breathe, think, & even dream
through chemical reactions
 Chemical reactions occur when humans
metabolize, or break down (digest) food

Activation Energy

Activation energy the energy needed
to get a reaction
started
Enzymes
Catalyst - a substance that speeds up
the rate of a chemical reaction
 Enzymes - proteins
that act as biological
catalysts


Enzymes speed up
chemical reactions
that take place in cells
Enzymes
Enzymes are specific, they catalyze
only 1 chemical reaction
 Enzymes provide a site where reactants
can be brought together to react
 Substrates - the reactants of enzymecatalyzed reactions

The Enzyme-Substrate
Complex

The enzyme-substrate
complex is a site
where reactants can
be brought together
to react
Regulation of Enzyme Activity
Enzymes may be affected by a change
in pH, temperature, or a change in
shape
 pH & temperature cause enzymes to
change their shape, preventing them
from fitting together in the enzymesubstrate complex
