Biology
Rainier Jr/Sr High School
Mr. Taylor
• An atom is the smallest particle of an element.
• An element is made of only one kind of atom and cannot be
broken down further by ordinary chemical means.
• Each atom of an element contains the same number of protons in its
nucleus.
• Carbon, Hydrogen, Oxygen, and Nitrogen compose 95% of the
mass of humans ... and most other organisms are similar.
• A compound is two or more elements chemically combined.
• The chemical formula for a compound tells what kind and how
many atoms are present in the compound.
• An atom that has gained or lost electrons is an electrically
charged particle called an ion.
• Compounds that are formed between charged particles are called ionic
compounds.
• Ions are important in the body and are often called electrolytes.
• Some atoms share electrons to form covalent bonds.
• Covalent bonds tend to be stable.
• Most of the compounds in organisms are covalently bonded.
• All the processes of living organisms take place in water.
• Because of unequal sharing of electrons between hydrogen and
oxygen, water has a very slight electrical charge. This allows
water molecules to “stick” to each other and to other charged
(polar) substances.
• Hydrogen bonding creates certain properties of water:
• High specific heat: it takes a lot of energy to cause the molecules of
water to separate. That means it takes a lot of energy to increase the
temperature of water. (This stabilizes internal temperatures in cells.)
• Cohesion: the molecules of water stick to each other. This causes surface
tension of water drops.
• Adhesion: the molecules of water stick to other charged substances. This
helps plants transport water from roots to leaves.
• Water is often called the “universal solvent” because so many
things will dissolve in it.
• Water will dissolve other polar substances like salt and sugar.
• Water will NOT dissolve non-polar substances like oils and fats.
• Things that dissolve in water often change the pH (or acid-base
balance).
• pH measures Hydrogen ion concentrations
• Lots of hydrogen ions results in an acid (pH = 1-7)
• Few hydrogen ions present results in a base (or alkali) (pH = 7-14)
• Carbon atoms form the “backbone” of almost all molecules
made by organisms.
• These substances are called organic molecules.
• Carbon atoms have 4 electrons available for sharing.
• Carbon atoms often join in long chains that can be straight or
branched, or sometimes forms rings.
• Carbon compounds can also form sub-units that can unite to
form other substances
• The single sub-unit is called a monomer.
• The multiple-unit molecule is called a polymer.
• There are 4 main types of polymers in organisms:
1. Carbohydrates
•
•
•
•
•
Are made of Carbon, Hydrogen, and Oxygen
Simple carbohydrates are sugars; sugars are monosaccharides (a
monomer)
Complex carbohydrates are starches; starches are polysaccharides (a
polymer)
Carbohydrates are excellent sources of energy.
Cellulose (a starch) makes up the cell walls of most plants.
• There are 4 main types of polymers in organisms:
2. Lipids: non-polar molecules that make up fats, oils, and
cholesterol.
• The monomers of lipids are called fatty acids.
• Fats and oils are usually made of three long chains of fatty acids held
together by a molecule called glycerol.
• Cholesterol is needed as part of your cell membranes and forms the basic
structure of cortisones, estrogens, and testosterone.
• There are 4 main types of polymers in organisms:
3. Proteins: these molecules form most of the structures and
perform most of the work for organisms.
• The monomers for proteins are amino acids.
• Organisms use 20 different amino acids to make all proteins.
• The amino acids are held together by a covalent bond called a peptide
bond. Proteins are sometimes called polypeptides.
• Because the amino acids that make up proteins have specific shapes, the
resulting protein has a specific shape. It is the shapes that allow proteins
to do all that they do for organisms.
• There are 4 main types of polymers in organisms:
4. Nucleic acids: store the information to build proteins
• The monomers for nucleic acids are called nucleotides.
• There are two kinds of nucleic acids: DNA and RNA. These will be
covered in more detail later this semester.
• Enzymes are catalysts for reactions inside organisms.
• A catalyst increases the speed at which a reaction occurs.
• Enzymes basically work by holding two substances in the correct
position so they can be linked together or broken apart.
• Enzymes are usually proteins; it is their specific shapes that
allow them to hold the correct substances in the correct position.
• We’re finished!!