Protein Biochemistry Flashcards
what are proteins?
proteins are a chain of amino acids that have a variety of functions reflected by the wide structural properties of
name some functions of a protein
-Recognition of specific molecules including hormones, antibodies and DNA binding proteins
-Movement of other molecules like porins which sit on the outer membrane of bacteria that allows diffusion
-structural functions like the cytoskeleton which holds everything together in the cell
- Enzymes which speed up a rate of a chemical reaction
what are proteins joined into?
polypeptide chains
what are short chain proteins called?
peptides
(less than 50 amino acids)
what are native/ folded proteins
The final folded form which is a thermodynamically stable
Define a secondary protein structure
Regular repeating structures which are stabilised by hydrogen bonds
what is an alpha helix structure?
hydrogen bonds between amino (+) and carboxyl (-) groups of amino acids 4 residues apart
What is a beta sheet structure?
Hydrogen bonds between amino and carboxyl group of amino acids further away from each other in the primary sequence- on different strands
what is a quaternary protein structure?
when polypeptides come together to form a more complex structure with two or more subunits
what is phosphorylation
Reversible addition of phosphate (PO3) group by enzymes called kinases.
This is an important way of regulating enzyme function.
What are hormones?
Small proteins that travel around the bloodstream and bind to specific receptors elsewhere in the body
What are antibodies?
They are a type of protein that recognise foreign material allowing the immune system to respond
What are DNA binding proteins?
A type of protein that bind to specific DNA sequences and affects gene expression. This can be either Turing transcription ON or OFF
What varies within a protein? What is different about them?
The side chains vary in an amino acid and the shape, size, charge and polarity are different
What are the N and C terminus?
N- amino acid terminus
C- Carboxyl terminu
How do proteins fold into 3D structures?
The unfolded/ denatured amino acid chain is thermodynamically unstable.
Gradally bonds form between the amino acids
Forming a neatly folded native (thermodynamically stable)
What do some proteins need to help them fold into 3D structures?
Chaperones
What are tertiary proteins?
They are tightly packed proteins that are thermodynamically stable
Considering different amino acids interact differently with polar water molecules, how do hydrophobic and hydrophilic side chains interact?
Hydrophobic side chains- they have no Hydrogen bonds (want to stay away from water outside proteins)
Hydrophilic side chains- can form hydrogen bonds
Where do hydrophobic amino acids (with polarity or no charge) tend to be on tertiary structures of proteins?
Polar residues like water so they tend to stay in the outside of the protein, where they can interact with polar molecules
Non-polar residues tend to fold into the centre of the protein, away from the aqueous environment of the cell
What are “disulphide bridges” between cysteine residues?
Interactions between sulphur atms in cysteine amino acids
Oxidation happens so a bond form between 2 sulphur atoms (crosslink) between different parts of the protein
Which will strengthen the tertiary structure
What are domains found in tertiary structures?
Regions that fold tightly
Why is haemoglobin an example of quaternary structure?
Because it is made up of 2 alpha and 2 beta subunits. Quaternary proteins are made of 2 or more subunits
What is post-translation modification?
-Removal of specific parts of the sequence (e.g. of signal peptides)
-Addition of molecules , modulating protein function (e.g. methylation which is adding -CH3 groups)
What is the pathway that allows proteins to be targeted to the cell membrane?
The secretory pathway
