Basic Proteins Wk1 Flashcards
1
Q
What is the primary structure of proteins? (3)
A
- Individual sequence of amino acids held together by peptide bonds that determines the property of proteins
- R group will determine the polarity/water solubility of the molecules e.g. hydrophobic R group = tryptophan
- The charge of the R group contributes to the properties of the protein e.g. aromatic structure and aliphatic side groups
2
Q
What is the secondary structure of a protein? (2)
A
- Folding of the primary structure into chain coils of alpha helix or folds of a beta pleated sheet.
- Weak bonds between amino acids, but hydrogen bonds stabilise the structure.
3
Q
What is the tertiary structure of a protein? (2)
A
- Further folding of the polypeptide chain to give a more complex 3D structure closely related to the function of a particular protein.
- Proteins fold into a tertiary structure requiring the least amount of energy.
4
Q
What bonds hold the tertiary structure together? (4)
A
- Hydrogen bonds - weak bonds between R groups (easily broken)
- Ionic bonds between positively and negatively charged R groups of amino acids
- Disulphide bonds - strong covalent bonds formed between sulphurs in the R group of the amino acid C(ysteine)
- Hydrophobic interactions between non-polar R groups which tend to cluster together towards centre of molecule.
5
Q
What is a quaternary protein structure? (1)
A
A complex of more than one polypeptide chain (e.g. haemoglobin contains 4 polypeptide chains, 2 alpha and 2 beta)..
6
Q
What are globular proteins? (4)
A
- Tertiary structure
- For secretion from the cell - more water soluble than fibrous
- Small, condense, early transported, fold up into a compact ball like shape (hydrophobic R groups facing inwards and vice versa)
- E.g. enzymes (metabolic role)
7
Q
What are fibrous proteins? (3)
A
- Tertiary structure
- Long fibres formed of regular, repetitive sequences and usually insoluble in water
- Elongated for strength
8
Q
How is structure determined? (2)
A
- X-ray crystallography
- NMR
