intro to protein structure Flashcards
what are proteins made of
amino acids
what are conformational changes
structural arrangement changes associated with function
what are enzymes
proteins that are highly efficient and specific catalysts, substrate binds to its active site
general structure of amino acids
primary amino group (NH2)
carboxyl group
hydrogen atom
variable R group
-all are enantiomers except glycine
how are enantiomers of amino acids distinguished
optical rotations of plane polarised light
right-D
left-L
L mostly found in proteins, D mostly found in bacteria cell wall
how are amino acids distinguished
by their R chain
2 main classes of amino
hydrophobic and hydrophillic
describe a zwitterion, cation and anion
zwitterion=normal amino acid form, NH3+ and COO-
cation= at low pH, NH3+ and COOH
anion= high pH, NH2 and COO-
as pH decreases, a H+ will be added to carboxylate, as pH increases, H+ is removed to the NH3+
what joins amino acids together
peptide bonds
-amino group and carboxyl group joins, covalent, partial double bond character, planar, restricts movement of the backbone
why are rotations about the peptide bond restricted
due to the resonance of the double covalent bond that helps define how proteins are folded
describe the different structures of proteins
primary- linear structure of amino acids (polypeptide)
secondary- localised organisation of parts of the polypeptide chain, alpha helix and beta sheets, folding due to H bonds
tertiary- 3D arrangement of polypeptide chain maintained by VDW, H bonds, disulphide bonds
quaternary- two or more polypeptide chains into a multi subunit complex
describe the primary structure of proteins
linear structure of amino acids (polypeptide)
describe the secondary structure of proteins
localised organisation of parts of the polypeptide chain, alpha helix and beta sheets, folding due to H bonds
describe the tertiary structure of proteins
3D arrangement of polypeptide chain maintained by VDW, H bonds, disulphide bonds
describe the quaternary structure of proteins
two or more polypeptide chains into a multi subunit complex, can also contain prosthetic groups
describe alpha helix structure
-repetitive local hydrogen bonding between carboxyl and amino group
-cylindrical rod shape with R groups outside of helix
describe beta pleated sheet structure
-repetitive hydrogen bonding between adjacent sections of the polypeptide
-parallel sheets=sections running in same direction
-antiparallel sheets= sections running in opposite directions
-R groups appear above and below plane of sheet
describe the structure of connecting loops/coils
-not repetitive hydrogen bonding
-less hydrogen bonds
-connects alpha helices and beta sheet
what is a domain
distinct region with specific structure performing specific functions
what does homomeric and heteromeric mean when describing quaternary structure
homomeric- identical chains
heteromeric- different chains
how can protein contribute to diseases
errors in protein folding can contribute to diseases like alzheimers
location of hydrophobic and charged residues on proteins
-hydrophobic residues are usually buried in the core of the protein
-charged residue on the water exposed surface
what are the two main classes of domains
functional- mediate a particular activity of the protein
structural- region of 40+ amino acids that form a stable secondary and tertiary structure
describe globular proteins
high water solubility, compactly folded, includes most enzymes/transporters like haemoglobin and regulators
