Thursday, November 15, 2007


Proteins are multipurpose molecules. They are the most structurally and functionally diverse group of biomolecules. Proteins are also involved in almost everything. Proteins can act as enzymes such as pepsin and polymerase. Pepsin is the enzyme found in our stomachs which is used in digestion. Proteins such as keratin and collagen form structure, such as a bird's beak or hair. Proteins also take part in carrying and transporting information, and give defense with antibodies. Proteins are also used in contraction, signaling, and storage.


Proteins are made of twenty different amino acids. Amino acids are monomers. Polypeptides are polymers which are made from chain of amino acids bonded together. Proteins can be one or more polypeptide chains folded and bonded together.

Rubisco is a very important polypeptide because it allows plants to go through photosynthesis.

Amino acids have a central carbon with an amino group and a carboxyl group (acid) as well as a sidechain known as an group which confers unique chemical properties of the amino acid.

Nonpolar amino acids are hydrophobic. These are nonpolar and hydrophobic because they are made up of a lot of carbons which are nonpolar and hydrophobic, and so they want to push away from water. Polar amino acids are polar or charged and hydrophilic, meaning that they mix well with water.

The function of proteins depends on the structure. Proteins are twisted, folded, and coiled into a unique shape. Hemoglobin is a protein with both alpha and beta proteins which carry oxygen in the blood.

Primary Structure > Order of Amino Acids

Seconday Structure > "Local Folding"- folding long short sections of polypeptides

Has alpha helix and beta pleated sheet. There are hydrogen bonds against adjacent proteins.

Tertiary Structure > "Whole Molecule Folding" - determined by interactions between R groups. Tertiary structure has hydrophobic interactions and is anchored by disulfide bridges.

Quarternary Structure > more than one polypeptide chain joined together

Denaturing a Protein

This is unfolding a protein by disrupting tertiary structure. Disrupting the pH, salt, or temperature of a protein disruptsH bonds, ionic bonds and disulfide bridges, which destroys functionality. Some proteins can return to their functional shape after denaturation, but many can not.

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