Protein Structure And Function Flashcards
What are the General function of proteins?
- carrier
- metabolic
- part of cellular machinery
- sensing molecules
Give the structure of an Amino acid in space
Tetrahedral arrangement of atoms with carbon at the centre.
R chain makes the specific physiochemical properties
Give the forms of Ionised amino acids
NH2-> NH3+
COOH->COO-
Can also be a zwitter ion (double ion) when both happen so its polar but also neutral as charges cancel out
How many isomers of each amino acid and which is the exception?
2 as you have both D (dextro) and L (Levo) isomers
Glycine as the R group is Hydrogen
How to remember difference between L and D amino acid structures
L - groups read CORN in the clockwise direction
D- groups read CORN in the anticlockwise direction
Which form of amino acid is found in living organisms and what does the other do?
L form is in living organisms
D form in bacterial cell walls and in some therapeutics
What is a peptide residue?
A repeated unit or polypeptide chain.
Consists of the α carbon, C=O and NH group
Almost always trans
Describe Secondary proteins
Hydrogen bonding between different parts of the same chain- causes either β sheets, α helixes or β turns
give the structure of β sheets
Can be either antiparallel or parallel
In parallel the loops (turns) linking the strands go over the rest of the chain and they don’t in antiparallel
what is an α helix structure?
Right handed helix, stabilised by hydrogen bonds
How many residues between each H bond in the α helix?
4 residues (on the 1st and 5th residue)
Why is the orientation of side chains in α helixes important?
It gives the proteins their properties as they protrude out from the structure
Give the structure of Tertiary and quaternary proteins
Generally globular
Depends on interaction between side chains
How are tertiary and quaternary protein structures held together?
Lots of weak chemical bonds but may also be stabilised by covalent bonds
How is the quaternary protein structure different to the tertiary protein structure
In quaternary the bonds are between different polypeptide chains, but in tertiary the bonds are between the same chain
