Protein structures
- Created by: Jasmin
- Created on: 13-01-14 20:18
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- Protein Structures
- PRIMARY STRUCTURE
- Polypeptide - chain of 100s of AAs
- Sequence of AA in the polypeptide chain
- Is this structure that determines its ultimate shape and function
- Change in shape of AA can lead to change in shape of protein and may stop it carrying out its function
- A protein shape is very specific to its function
- SECONDARY STRUCTURE
- C=O group and NH group on either side of peptide bond form H bonds
- H of the NH has a + charge and the O from C=O has a - charge
- These then form weak bonds called H bonds
- This causes the long polypeptide chain to be twisted into a 3D shape - a coil, alpha helix or beta pleated sheet
- The coiling or folding parts of a protein molecule due to the formation of H bonds formed as protein is synthesised
- TERTIARY STRUCTURE
- Overall 3D shape. Result of interaction between parts of protein molecule such as H, disulphide, ionic bonding, interactions.
- Hydrophobic: inside, do not like water. Hydrophilic: outside, attracted to water
- Twisted or folded even more
- Disulphide bonds
- Fairly strong and therefore not easily broken down
- Less frequent than H bonds form due to interactions between R groups of polypeptide chains
- Form between R groups containing sulphur bonds
- Ionic bonds
- Formed between any carboxyl and amino group that are not involved in forming peptide bonds
- Weaker than disulphide bonds
- Easily broken down by changes in pH
- Form between R groups with charges +ve and -ve
- Hydrogen bonds
- Numerous but easily broken - weak
- Lots of them together make a molecule hold its shape
- But individually easily broken down
- For proteins made from a single polypeptide chain the tertiary structure forms their final 3D structure
- Overall 3D shape. Result of interaction between parts of protein molecule such as H, disulphide, ionic bonding, interactions.
- QUATERNARY STRUCTURE
- Protein consists of more than 1 polypeptide chain. Haemoglobin/insulin/collagen
- Way these polypeptide chains are assembled together
- May also be non-protein (prosthetic) groups associated with the molecules
- E.g. iron containing haem group in haemoglobin
- For proteins made with more than 1 polypeptide chain the quaternary structure is the proteins final 3D structure
- Protein consists of more than 1 polypeptide chain. Haemoglobin/insulin/collagen
- PRIMARY STRUCTURE
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