Proteins Flashcards
Describe the structure of an amino acid. (F)
- amine group (-NH2)
- carboxyl group (-COOH)
- alpha-carbon (C)
- R-group (variable)
State how many amino acids occur in life.
20
Explain how the variety of amino acids leads to a wide range of dipeptides and very quickly to an incredible variety of polypeptide chains.
- Dipeptide: 400 possible combinations (20^2)
- Tripeptide: 8000 possible combinations (20^3)
- etc.
Define the term “polypeptide chain”.
Chain of three or more amino acids
Describe how one end of a polypeptide chain differs from the other end.
One end is an amine group (-NH2) which has basic properties, and the other end is a carboxyl group (-COOH) and has acidic properties.
Define the term “primary structure” of a protein. (F)
The sequence of amino acids.
Define the term “secondary structure” of a protein and describe the two different types. (F)
The folding of the polypeptide chain into an alpha helix (coiled) or beta pleated sheet (flat).
Define the term “tertiary structure” of a protein. (F)
The 3D shape of a polypeptide chain.
Explain how the primary structure of a protein determines its tertiary structure.
The R-groups on the amino acids affect the bonding in the tertiary structure.
Define the term “quaternary structure” of a protein.
When two or more polypeptides associate.
Define the term “globular protein”. (F)
Spherical, water-soluble protein.
Define the term “prosthetic group”. (F)
Non-protein component of a conjugated protein
Give an example of a conjugated protein (the bloody one).
Haemoglobin
Give an example of an enzyme (the H2O2 one ;) ).
Catalase
Give an example of a peptide hormone (the sugary one).
Insulin
Give 3 examples of fibrous proteins.
- collagen
- elastin
- elastin
Describe the structure of collagen.
- 3 polypeptide chains
- triple helix
- every third amino acid is glycine
- hydrogen bonds
Describe the structure of keratin.
- lots of cysteine (with S)
- disulfide bridges (degree of disulfide bonds determines flexibility)