Protein biochemistry Flashcards
Semester 1 year 1
What does the wide range of structural properties of proteins allow for?
A wide range of functions - versatile
What are hormones?
Small proteins that travel in blood + bind to specific receptors elsewhere in the body
What are antibodies?
Recognise foreign material, allowing the immune system to respond
What are DNA binding proteins?
Bind to specific DNA sequences + affect gene expression
What is porin?
-sits in outer membrane of bacteria
-allows diffusion of certain molecules into cell
What is ferritin?
Stores, transports + releases iron
What are enzymes?
-proteins that accelerate rate of chemical reactions
-don’t change final equilibrium
-reduce energy needed to carry out reaction
What are the 4 levels of protein structure?
-primary
-secondary
-tertiary
-quaternary
What is different in amino acid side chains?
-shape + size
-electric charge
-polarity
Describe the primary structure of a protein
-order of amino acids in the polypeptide
-protein sequence determined by gene sequence
What is a residue?
An amino acid in a polypeptide chain
How are amino acids joined in the primary structure?
-lose a water molecule to form peptide bond
-amino terminus + carboxyl terminus of 2 amino acids join
-no rotation around peptide bond
What are unfolded and folded polypeptide chains called?
-unfolded = denatured
-folded = native
Describe the stability of unfolded and folded chains
-unfolded = thermodynamically unstable
-folded = thermodynamically stable
How do chains go from unfolded to folded?
-some spontaneously, determined by primary sequence
-others require secondary protein - chaperone
Describe the secondary structure of an amino acid
-regular, repeating structures
-many weak hydrogen bonds between amino acids close together
-can fold into alpha helix or beta sheet
What stabilises the secondary structure of a protein?
Hydrogen bonds
Describe the alpha helix structure
-H bonds between amino + carboxyl terminals 4 residues apart
-side chains on outside of helix
Describe the beta sheet structure
H bonds between amino + carboxyl groups on different strands
What 2 forms can the beta sheet be in?
-parallel - adjacent strands run in same direction
-anti parallel - opposite directions
Describe the tertiary structure of a protein
-tightly packed, thermodynamically stable 3D structure
-determined by non-covalent interactions between side chains
How do amino acids with hydrophilic side chains interact with water?
Can form hydrogen bonds + ionic interactions
How do amino acids with hydrophobic side chains interact with water?
-non polar
-can’t form hydrogen bonds + ionic interactions
Which amino acids tend to be on the inside of the tertiary structure and why?
-hydrophobic amino acids
-polar residues on outside to interact with water
-non polar residues on inside, away from aqueous environment
