Practise IB Biology HL B1.2.4 by relating amino-acid number and order to polypeptide diversity, and tracing how a gene encodes a protein sequence.
Proteins are an extraordinarily diverse group of carbon compounds that have a wide range of roles in cells.
Describe the structure of proteins, including features that are common to all proteins and features that vary.
a. composed of one or more polypeptides / some are single polypeptides others made of 2 or more polypeptide chains / all proteins consist of, at least, one polypeptide chain;
b. a polypeptide/protein is a chain of amino acids;
c. (chains of) amino acids linked by peptide bonds;
d. twenty different amino acids/ amino acids have different R groups/ R groups can be hydrophilic/polar or hydrophobic/non-polar;
e. primary structure is the sequence/order (and number) of amino acids in the polypeptide;
f. any sequence/order of amino acids could be linked together hence many possible polypeptides/proteins;
g. secondary structure is the formation of alpha/ α helices and beta/ β pleated sheets;
h. secondary structure stabilized by hydrogen bonding;
i. tertiary structure is the further folding of the polypeptide / tertiary structure is the threedimensional (3-D) conformation/structure/shape of a protein;
j. tertiary structure stabilized by interactions / ionic bonds/hydrogen bonds/disulfide bridges between R groups;
k. fibrous or globular are the two main classes of conformation/three-dimensional/ 3-D structure/shape;
l. conformation/three-dimensional (3-D) structure determined by amino acid sequence;
m. quaternary structure if two or more polypeptides are linked to form a (single) protein OR quaternary structure if a prosthetic group is linked (to form a conjugated protein);
Marking guidance:
Accept clearly annotated diagrams.
Mpc: accept a clearly annotated diagram of the bond between 2 drawn amino acids.