CHAPTER 3
BIOCHEMISTRY
CARBON COMPOUNDS
• Although water is the primary medium
for life on earth, most of the molecules from
which living organisms are made are based
on the element carbon.
• All compounds can be classified in two broad
categories: organic compounds and inorganic
compounds
• Organic compounds are made primarily of carbon
atoms.
• Inorganic compounds do not contains carbon atoms.
CARBON BONDING
• A carbon atom has 4 electrons in its
outermost energy level, therefore readily
forms four covalent bonds with the atoms of
other elements.
• Unlike other elements, however, carbon also
bonds with other carbon atoms forming
straight chains, branched chains, or rings.
FUNCTIONAL GROUPS
• In most organic compounds, clusters of atoms,
called functional groups, influence the
characteristics of the molecules they compose
and the chemical reactions the molecules
undergo.
• The common functional groups:
- Hydroxyl
- Carboxyl
- Amino
- phosphate
LARGE CARBON MOLECULES
• Many carbon compounds are built up from
smaller, simpler molecules called monomers.
• A polymer is a molecule that consists of
repeated, linked monomers.
• Large polymers are called macromolecules.
Condensation reaction
• Monomers link to form polymers through a chemical
reaction called a condensation reaction.
• Each time a monomer is added to a polymer, a water
molecule is released.
hydrolysis
• In addition to building polymers through
condensation reactions, living organisms also have to
break down polymers.
• The breakdown of polymers occurs through a
process called hydrolysis.
MOLECULES OF LIFE
• Four main classes of organic compounds are
essential to the life processes of all living
things: (macromolecules)
1.
2.
3.
4.
Carbohydrates
Proteins
lipids
Nucleic acids
CARBOHYDRATES
•
Carbohydrate is a fancy way of saying "sugar.“Scientists came up with the
name because the molecule has many carbon (C) atoms bonded to hydroxide
(OH-) groups.
• What's It Used For?
A carbohydrate is called an organic compound, because it is made up of a long
chain of carbon atoms. Sugars provide living things with energy and act as
substances used for structure.
• Saccharides
Scientists also use the word saccharide to describe sugars. If there is only one
sugar molecule, it is called a monosaccharide. If there are two, it is a disaccharide.
If there are three, it is a trisaccharide. You get the idea.
• Carbohydrates can exist as:
1. Monosaccharides – a monomer of a carbohydrate (simple
sugar)
- formula: (CH2O)n n= any whole number from 3 to 8.
* The most common monosaccharide are glucose ,fructose
and galactose
2. Disaccharide – two monosaccharides can
combine in a condensation reaction to form a
double sugar.
Ex: the monosaccharides fructose and glucose can
combine to form the dissaccharide sucrose.
3. Polysaccharide – a complex molecule composed
of three or more monosaccharides.
Ex: the polysaccharide glycogen, consists of
hundreds of glucose molecules.
PROTEINS
Proteins are made of amino acids. Even though a
protein can be very complex, it is basically a long
chain of amino acid subunits all twisted around like
a knot.
• Amino Acids – There are 20 different amino acids.
Amino acids are used in every cell of your body
and are used to build the proteins you need to
survive.
• The side groups (R-group) are what make each
amino acid different from the others.
Amino acid structure
• All amino acids share a basic structure. Each amino
acid contains a central carbon atom, covalently
bonded to 4 other atoms or functional groups. A
hydrogen atom (H), an amine group (NH2 ), a carboxyl
group (COOH) and a side chain/R –group.
Dipeptides & Polypeptides
• Dipeptide – In a condensation reaction, two
amino acids bond to form a dipeptide. The
two amino acids form a covalent bond called a
peptide bond.
• Polypeptide- very long chains of several
amino acids.
• Proteins are composed of one or more
polypeptides.
Enzymes
• Enzyme-RNA or protein molecules that act as
biological catalysts. (catalyst- reduce the
amount of activation energy that is needed for
a reaction to take place.)
• Enzyme reactions depend on the fit between
the substrate and the enzyme. The folds on
the enzymes are the active site where the
substrate binds.
Enzyme structure
LIPIDS
• When you think of fats, you should know that they are lipids.
Lipids are also used to make steroids and waxes. So, if you
pick out some earwax and smell it, that's a lipid, too!
• Lipids include: triglycerides, phospholipids, steroids and
waxes.
• Fatty acids
long carbon chains that make up most lipids.
The two ends of the fatty acid molecule have
different properties. The carboxyl end is
hydrophilic (attracted to water molecules).
The Carbon end is hydrophobic (water
fearing).
• Triglycerides- composed of three molecules of fatty
acid joined to one molecule of the alcohol glycerol.
• Ex: butter,
Fats in red
meat
• Phospholipids – composed
of two fatty acids attached
to a molecule of glycerol.
Ex: cell membrane
• Waxes- type of structural lipid consisting of a
long fatty-acid chain joined to a long alcohol
chain. Waxes are used to coat and protect things
in nature.
• Steroids- molecules composed of four fused
carbon rings with various functional groups
attached to them.
NUCLEIC ACIDS
• Nucleic acids are very large complex organic
molecules that store and transfer important
information in the cell.
• Two major types: -Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
DNA- contains information that determines the
characteristics of an organism and directs cell
activity.
RNA – stores and transfers information from DNA
that is essential for the manufacturing of proteins.
• Both DNA and RNA are composed of thousands
of linked monomers called nucleotides. Each
nucleotide is made of a phosphate group, a five
carbon sugar, and a ring-shaped nitrogenous
base.