Download Proteins and DNA

Proteins and DNA
Proteins- are one of the most diverse and complex organic molecules. Proteins control the
chemistry of the cell. Genes produce proteins. There are literally thousands of different kinds of
proteins. Proteins are made from building blocks called amino acids. There are 20 different
types of amino acids. Proteins vary in length from 40 to 500 amino
acids long.An amino acid is composed of a central carbon. Attached
the central carbon are four groups. One of the four components
attached to the carbon is hydrogen. The second group attached to the
carbon is a carboxyl group. It is the carboxyl group that makes the
amino acid an acid.
A third group that is attached to the central carbon is an amine group. This group can ionize and
is a base. The fourth group that is attached to the central carbon is a variable group (R). There
are twenty amino acids and each one has a different variable
group.
Amino acids are put together forming a
polypeptide chain. Peptide bonds hold the amino
acids together..These bonds are called peptide
bonds. When a peptide bond is formed, a molecule
of water is removed (dehydration synthesis). The
sequencing of amino acids is known as its primary
structure. The substituting of one amino acid for
another can have serious consequences. For
example sickle cell anemia results when one amino
acid is substituted with another one. Very seldom
does a polypeptide chain stay as a straight
molecule. Usually it folds on itself forming a three
dimensional structure. The proteins' structure is
usually a key to its function. Hydrogen bonding
between the hydrogen on the amine group and
oxygen on the carboxyl group allows for secondary structure to exist. There are two main types
of secondary structure, beta pleated sheets and alpha helices.Seldom will polypeptide chains
remain folded just once. Instead, the protein folds on itself again, forming the tertiary structure
of the protein. This is myoglobin, demonstrating tertiary structure. Tertiary structure is held
together by R group interactions-ionic
bonding, covalent bonding, bonding,
hydrogen bonding and hydrophoic
interactions.
Proteins can have more than one
polypeptide chain in their structure.
When they do, the protein demonstrates
quaternary structure. Below is
hemoglobin, which is composed of four
polypeptide chains. Each chain has an
iron atom on it.Functions for Proteins
Proteins are the "workers" in the cell.
-Structural Proteins (hair, horns, etc.)
-Storage Proteins (albumin, casein)
-Sensory Proteins (rhodopsin)
-Hormonal Proteins (insulin)
-Contractile Proteins (muscles)
-Antibodies
-Enzymes
-Receptor Proteins
Note- Unlike carbohydrates and lipids, the "blue prints" for proteins are coded for by genes or
DNA. Proteins are actually made on the ribosome during a process called protein synthesis.
(How original). Lipids and carbohydrate synthesis are controlled by enzymes which are
proteins.In 1869, Johann Friedrich Miescher discovered DNA.
Nucleic Acids are some of the largest molecules in the cell. There are two type of nucleic acids,
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are involved in
carrying genetic information from one
cell to the next. Nucleic acids direct the
production of proteins in a cell. Nucleic
acids are made of monomers called
nucleotides.
A nucleotide consists of a pentose
sugar, a nitrogenous base and a
phosphate group. The pentose sugar
used in RNA is ribose, but the sugar
used in DNA is deoxyribose which is
missing an atom of oxygen
The phosphate group is responsible
for make DNA and RNA an acid. The
phosphate group is connected to
carbon #5.
There are five different nitrogenous bases. Adenine, guanine, and cytosine are
used by both DNA and RNA. Thymine is used by only DNA and RNA uses
uracil in place of thymine. The single ring nitrogenous base is a pyrimdine and
the double ring nitrogenous base is a purine. Nucleic acids are made by bonding
the phosphate of one nucleotide to the sugar of the next nucleotide. Each added
nucleotide bonds with carbon #3 of the last nucleotide on the chain. This results
in a backbone with a repeating pattern of sugar-phosphate-sugar- phosphate.
Along this backbone are the nitrogenous base extending outward. RNA is usually
single stranded but DNA is double stranded and is analogous to a ladder. The
sides of the ladder are alternation sugars and phosphate groups running
antiparallel. The rungs of ladder are nitrogenous bases. Adenine base pairs with
thymine and cytosine base pairs with guanine.