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Guiding Questions...
- What is the relationship between amino acid sequence and the diversity in form and function of proteins?
- How are protein molecules affected by their chemical and physical environments?
B1.2.1 Generalized Structure of an Amino Acid...
Students should be able to draw a diagram of a generalized amino acid showing the alpha carbon atom (Carbon in the center of the diagram) with amine group, carboxyl group, R-group and hydrogen attached.
B1.2.2 Condensation reactions form dipeptides and longer chains of amino acids...
Polypeptides...
Polymers built of amino acid monomers during a condensation reaction. The amino group, (NH2) of one amino acid and the carboxyl group (COOH) of another form a peptide bond, forming a dipeptide. This can continue to from a string of amino acids, called a polypeptide.
A polypeptide is the primary structure of a protein. The sequence of the amino acids within a polypeptide is determined by genetic code.
Building a protein...
When a polypeptide either folds and connects to itself, or to other polypeptides it becomes a protein.
Primary structure...
Amino acids form a sequence, known as a polypeptide.
Secondary structure...
The polypeptide beings to coil up and bond with itself through hydrogen bonds.
Tertiary (3rd Level) Structure...
Secondary structures fold over once more and Ionic bonds and disulfide bridges form.
Quaternary (4th Level) Structure...
Quaternary structures are composed of two or more linked polypeptides.
Functions of proteins...
The function of a protein is determined by the shape of its molecule. Proteins are divided into two main types: globular and fibrous proteins.
| Protein | Function |
|---|---|
| Rubisco | An enzyme involved in carbon fixation in photosynthesis. |
| Insulin | A hormone produced by the pancreas which stimulates the liver to take up glucose from the blood and store it as glycogen. |
| Immunoglobulin | A large protein (antibody) produced by the immune system to fight infection. |
| Rhodopsin | A protein linked to a pigment found in the photoreceptor cells in the retina of the eye. |
| Collagen | A structural protein which builds muscle, tendons, ligaments and the skin of vertebrates. |
| Spider silk | A strong and elastic fibrous protein created by spiders to form their webs. |
Denaturation...
Denaturation is an irreversible process when a protein loses it's form due to a PH or Temperature outside it's operating range. The primary structure of the protein will usually remain but secondary, tertiary and quaternary structures are usually lost.
For example enzymes, which are tertiary proteins, are easily denatured by extremes of pH or temperature and lose the ability to function as catalysts.
A fresh egg with clear albumin protein and a cooked egg where the albumin has been denatured.
