The Chemistry
of Life
Atoms and Their Interactions
Atoms and Their Interactions
Objectives Relate the structure of an atom to the
identity of elements Relate the formation of covalent and ionic
chemical bonds to the stability of atoms Reexamine mixtures and solutions Define acids and bases and relate their
importance to biological systems
Elements Everything is made of elements
An element cannot be broken down into a simpler chemical substance
Only 25 are essential to living organisms Carbon, hydrogen, oxygen and nitrogen make
up more than 96% of the mass of the human body
Each element is identified by a one or two letter abbreviation called a symbol
Atoms: The Building Blocks of
Elements Atoms are the smallest part of an element
that has the characteristics of that element
Atoms are the basic building blocks of all matter
The way atoms are put together affects the properties of the chemical they make up
Sugar vs. Coal and Water
Glucose
Carbon, Hydrogen and
Oxygen
C6H12O6
Coal and Water
Carbon, Hydrogen and Oxygen
H2O (water)
Carbon and Hydrogen (coal)
Sugar vs. Coal and Water
Glucose Coal and Water
The Structure of an Atom
Isotopes of an Element
Atoms of the same element always have the same number of protons
Atoms of the same element with different numbers of neutrons are called isotopes
Compounds and Bonding
A substance composed of 2 or more different elements that are chemically combined is a compound
Atoms combine with other atoms when the resulting compound is more stable (this happens most of the time)
Stability = full energy level
How do atoms fill their energy levels? Share Give / take
Covalent Bond
Covalent Bond When two atoms share electrons, the force
that holds them together is called a covalent bond
A group of atoms held together by covalent bonds is called a molecule
H2O 2 Hydrogen atoms 1 Oxygen Atom
Ionic Bond
Ionic Bond An atom (or group of atoms) that gains or
loses electrons is electrically charged
An atom (or group of atoms) that is charged is called an ion
The attractive force between two ions of opposite charge is called an ionic bond
Chemical Reactions
Occur when bonds are formed or broken, causing substances to recombine into different substances
All chemical reactions that occur within an organism are referred to as that organisms metabolism
These reactions breakdown and build molecules important for the functioning of organisms
Cl2 + NaBr NaCl + Br2
How do we balance this equation?
Mixtures and Solutions
A mixture is a combination of substances in which the individual components retain their own properties
A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent)
Solutions are important in living things
In organisms, many vital substances (such as sugar and mineral ions) are dissolved in water
The more solute dissolved in a given amount of solvent, the greater the concentration
Organisms must keep concentrations of dissolved substances within a specific, narrow range
Acids and Bases Organisms must also keep the amount of
bases and acids within a narrow range
We measure this with the pH scale
Acids An acid is any substance that forms (H+)
ions in water
Bases A base is any substance that forms (OH-)
ions in water
Top Related