2A: Protein Structure and Function Flashcards
What are proteins/polypeptides?
Polymers of amino acids
What is the ‘proteome’ of a cell?
All the proteins expressed by the cell at any given time
Functions of proteins
- Transport (Channel/carrier proteins)
- Antibodies
- Hormones (insulin)
- Enzymes (Cas9)
Parts of amino acids
- Side chain (R group)
- amine group
- caboxyl group
- alpha carbon
How do amino acids join together?
One amino acid breaks off a Hydrogen from their Amine group and a neighbouring Carboxyl group breaks off a Hydroxyl. Amino acid residues form a peptide bond between their Amine group and Carboxyl group to make a ‘dipeptide’
How can a peptide chain become amino acids again?
A dipeptide splits and a nearby water molecule provides a Hydrogen and a Hydroxyl to complete the Amine group and Carboxyl group of the amino acids
Primary structure
‘Linear arrangement of amino acids’
Secondary structure
‘Shape of local segments in the polypeptide, formed by side chain interactions’
adjacent side chains will bend towards/away from eachother depending on polarity or charge
*Includes ‘alpha helices’, ‘beta pleated sheets’ and ‘random coiling shapes’
Tertiary structure
‘Overall 3D structure of the polypeptide’
Lowest level of structure required for a protein to have functionality
How is tertiary structure maintained?
- Disulfide bonds between cysteine amino acids
- Hydrogen bonds
Do hydrophilic chains point outwards/inwards in the cytosol? Why?
The protein’s hydrophilic side chains point out into the cytosol to enable the protein to stay suspended in the cytosol instead of sinking
Why do proteins need tertiary structure at a minimum to fulfill its function?
Because tertiary strucutre determines the overall 3D shape of a protein, and a protein’s shape determines its function in an organism.
Quaternary structure
‘When a protein is made of multiple BONDED polypeptide chains’
Can also include ‘prosthetic groups’ (e.g. carbohydrates, lipids)
