proteins Flashcards
(8 cards)
What are amino acids?
Monomers which make up polypeptide polymers that form proteins. 20 out of 100 amino acids occur naturally in proteins and in all living organisms (evidence for evolution). Amino acids contain: -NH2 (amino group), -COOH (carboxyl), -R (side group; every amino acid contains a different R group).
How are peptide bonds formed?
Peptide bonds are formed between the hydroxyl group of an amino acid’s -COOH and the -H from the -NH2 of another amino acid in a condensation reaction, resulting in a bond between the carbon atom and the other amino acid’s nitrogen atom.
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain, determined by DNA. The primary structure determines its ultimate shape and therefore function.
What is the secondary structure of proteins?
The linked amino acids in a polypeptide chain contain -NH (with an overall positive charge) and -C=O (with the O having an overall negative charge) on either side of every peptide bond, forming hydrogen bonds that cause the polypeptide to twist into a 3D shape.
What is the tertiary structure of a protein?
A complex 3D structure determined by the chemical interactions between units of amino acids and their R-groups. It allows each protein to be distinctive and to recognize and be recognized by other molecules. Tertiary structure is important to how the protein functions. Three types of bonding include: - disulfide bridges (S-S bonds, strong), - ionic bonds (attractions between positively and negatively charged R-groups, weaker than disulfide bridges and easily broken by changes in pH), - hydrogen bonds (easily broken).
What is the quaternary structure of a protein?
Structure formed by interactions between polypeptides. It may also include prosthetic (non-protein) groups associated with the molecules, e.g., hemoglobin containing a haem group (which has iron in it).
What is the test for proteins?
Biuret test: Add biuret reagent. A purple color indicates the presence of peptide bonds (hence protein). If no proteins are present, the solution remains blue.
