Structure of proteins Flashcards
What is the role of proteins?
- provide structure
- transport molecules
- defence
- biological catalysts
- regulation of genes
What is a peptide bond?
a covalent bond formed when the carbon from the carboxylate group shares electrons with the nitrogen from the amino group of a second amino acid
What is secondary structure?
the initial folding pattern of the linear polypeptide stabilised by H bonds
What type of reaction is the formation of a peptide bond?
condensation reaction
What are the 3 main types of secondary structure?
alpha-helix
beta-sheets
bend/loop
What is tertiary structure?
the 3D folding of secondary structure - hydrophobic residues are buried and hydrophilic residues are exposed outwards
What are the 5 kinds of bonds that stabilise tertiary structure?
H bonds van der Waals interactions hydrophobic interactions ionic interactions disulphide bridges
What is quaternary structure?
the association of more than one polypeptide
What is the structure of haemoglobin?
a symmetrical assembly of two different subunits - 2 alpha globin and 2 beta globin chains
Describe oxygen binding to haemoglobin
it is known as cooperative oxygen binding and it creates a sigmoid binding curve
How is sickle cell anaemia caused?
by a single amino acid change at position 6 in the beta chain of haemoglobin
What is collagen?
the main protein that helps bind cells together to form tissues
What is tropocollagen and what is it’s structure?
a building block of the collagen fibre
- consists of 3 polypeptide chains with a left handed twist would together in a right handed supercoil
What model can be used to describe the formation of the collagen fibre?
‘Quarter-stagger’ model - molecules are stitched together by covalent crosslinks
How do collagen fibres have strength built in all levels?
- close packing of subunits
- opposing twists of subunits and superhelix
- hydrogen bonding
- cross-linking
