Proteins Flashcards
Functions of proteins.
- enzymes
- integral membrane proteins
- antibodies
- structural proteins like myosin and actin
- signalling compounds like hormones and cytokines
Types of variation in protein.
- alternative slicing
- post-translation modification
- number of amino acids
- sequence of amino acids
Types of alternative splicing.
- constititive
- exon
- intron
- mutation
- alternative 5
- alternative 3
Name the 4 steps in protein structure.
Primary, secondary, tertiary, and quaternary
What is protein mass measured in?
Daltons. Eg, molecular mass of 64 000 g/mol is equivalent to 64 000 daltons/65kDa
Bigger polypeptide, bigger mass
Describe primary structure.
Amino acids covalently bond together to form polypeptide chain. Peptide bond. Components of amino acid is called residue/moiety. Start is amino terminal and end is carboxyl terminal.
Describe secondary structure.
H-bonding between amino and carboxyl groups.
Two types of secondary structure.
Alpha helix and beta sheets.
Explain alpha helix.
Polypeptide chins curl up clockwise. Common.
Describe keratin.
- 2 helices wound up together to form coiled structure. Have van der waal and ionic bonding in between.
- Strong covalently disulfide bridges between cystine residue side chains.
- found in nair, skin and nails.
- helices provide strength and rigidity. More bonds, more strong
Give two examples of alpha helices.
Keratin and collagen
Describe collagen.
- fibrous protein meaning it’s made up of secondary structure (alpha helices)
- found in skin, tendon, cartilage, and teeth (connective tissues)
- formed of 3 helices held together by H-bonds from hydroxyproline residue
Describe beta pleated sheets.
- Beta strands held together by H-bonds.
- strands run adjacent to each other.alternate from above to below.
Two types of beta sheets.
Parallel and anti-parallel
Explain parallel beta sheets.
H-bonds formed with groups sitting on 2 separate amino acid from another opposite beta strand. Less stable.
Explain anti-parallel beta sheets.
Groups on one amino acid form H-bonds with groups on one amino acid sitting on opposite beta strand. H-bonds more closely together. Stronger.
Example of where beta sheets may be found.
In the trans-membrane in form of porins. Usually embedded in cell membrane.
Explain tertiary structure.
Backbone interactions and side chain interactions, define overall 3D structure of polypeptide chain. Held together by different forces like disulphide, H, electro interactions, hydrophobic and hydrophilic interactions.
Explain quaternary structure.
If molecular mass is over 100kDa there is more than one polypeptide chain. Consist of same bonds in secondary structure (H, disulphide, and ionic).
