Draw molecular diagrams to show the condensation reaction between two amino acids to form a dipeptide.

Outline the roles of the different binding sites for tRNA on ribosomes during translation.

Explain the production of antibodies.

a. each amino acid with a COO–/COOH group at one end AND a NH₂/NH₃⁺ at the other  
Both needed.
mp a requires the double bond to be shown between the C and O.

b. CH in middle with H or R group attached 

c. peptide bond correctly drawn between N and C=0 

d. COO–/COOH group at one end of dipeptide AND NH₂/NH₃⁺ at other end  
Both needed.

e. loss of water

a. A, P and E binding sites are on the large subunit of the ribosome 

b. initiation of translation starts with binding of met-tRNA to the start codon 

c. large sub-unit binds with «start» tRNA in the P site 

d. A binding site holds the tRNA with the next amino acid to be added 

e. peptide bond is formed between the amino acids of the A site and the polypeptide at the P site 

f. polypeptide is transferred to the tRNA in the A site 

g. the tRNA «with polypeptide» in A site then moves to P site
OR
P binding site holds the tRNA attached to the growing polypeptide 

h. E binding site «exit» is where the tRNA «from P site without amino acid» leaves the ribosome

Accept annotated diagrams of the sites.

a. each antibody corresponds to a specific antigen 

b. antibodies are necessary for immunity/resistance to «infectious» disease 

c. macrophage/phagocyte ingests/engulfs pathogen 

d. macrophage/phagocyte digests pathogen 

e. macrophage/phagocyte displays antigen from pathogen 

f. antigens of a pathogen correspond to a specific T lymphocytes/cells
OR
T lymphocytes/cells are activated by antigen binding 

g. T lymphocytes/cells activate B lymphocytes/cells 

h. «B cells» divide by mitosis to form many/clones of plasma cells 

i. plasma cells secrete specific antibody 

j. some «activated» B lymphocytes/cells act as memory cells

Accept annotated diagrams of the process