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PROTEINS,
The Stuff of
Life
PROTEINS
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.
Structure of the Amino Acid
An amino acid is composed of a central
carbon. Attached the central carbon are four
groups.
4 Functional groups of Amino
Acids:
An amino acid is composed of a central carbon.
Attached the central carbon are 4 groups.
1. Attached to the carbon is hydrogen.
Structure of Amino Acid cont’d
2. The second group attached to the carbon is a
carboxyl group. It is the carboxyl group that
makes the amino acid an acid.
Structure of Amino Acid cont’d
3. A third group that is attached to the
central carbon is an amine group. This
group can ionize and is a base.
Structure of Amino Acid cont’d
4. 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.
What groups do these amino acids
have in common? What groups are
different?
Above are two different amino acids. They
differ in their R groups. Glycine has a H
whereas alanine has a methyl group CH.
Why is it called a variable
group in an amino acid?
Amino acids are made of 4 groups attached to a central carbon-20
different amino acids.
1.
Hydrogen
2.
Amine group (base) NH3
3.
Carboxyl group (acid)
4.
Variable-
20 amino acids. What group is
different?
How many water molecules must
be removed in order to form this
polypeptide?
Amino acids are put together forming a polypeptide
chain. Bonds hold the amino acids together.These
bonds are called peptide bonds. When a peptide
bond is formed, a molecule of water is removed.
Amino acids are bonded (peptide bond) together to
form polypeptide chain, removing a molecule of
water between two amino acids. A peptide bond is
made between the carbon and nitrogen.
Primary Structure of a protein:
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.
This is the primary
structure of bovine insulin.
Secondary Structure of a
protein:
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 exists.
There are two main types of secondary structure, beta
pleated sheets and alpha helices.
Secondary protein structurecollagen
This is the protein
collagen. Collagen is
found in ligaments,
tendons and a part of
cartilage. It is
demonstrating the
alpha helix structure.
-Secondary structure- Hydrogen bonding between the amine
groups and carboxyl group.
2 Types-Alpha helix-collagen in tendons and legaments
-Beta pleated sheet-nails
This is the protein
collagen. Collagen is
found in ligaments,
tendons and a part of
cartilage. It is
demonstrating the alpha
helix structure.
Tertiary Structure of a protein:
Seldom will polypeptide chains remain folded
just once.
Instead, the protein folds on itself again,
forming the tertiary structure of the protein.
The next slide is myoglobin, demonstrating
tertiary structure.
Tertiary structure is held together by R group
interactions-ionic bonding, covalent bonding,
bonding, hydrogen bonding and hydrophobic
interactions.
-Tertiary structure- the folding of a polypeptide
chain. Held together by hydrogen bonding and
interaction of the R groups. Ex. myoglobin
Quaternary Structure of a
protein:
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.
Quaternary structure can be held together
by hydrogen bonding, hydrophobic
interactions, and ionic bonding of the the R
groups.
-Quaternary structure-Occurs when there is
more than 1 polypeptide chain. Ex.
Hemoglobin Caused by the interaction of the
R groups. Hydrogen and ionic bonding and
nonpolar interactions.
Hemoglobin is composed of 4 polypeptide
chains. Each chain has a group with iron on it.
Functions of proteins:
Proteins are the "workers" in the cell.
-Structural Proteins (hair, horns, etc.)
-Storage Proteins (albumin, casein)
-Transport Proteins (across membranes)
-Hormonal Proteins (insulin)
-Contractile Proteins (muscles)
-Antibodies
-Enzymes
DNAGENES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.
DNAGENESPROTEINS