Answer and Explanation:
a. form the antigen-binding site ⇒ both chains
The antigen-binding site is formed by one hypervariable region of the light chain (VL) and one hypervariable region of the heavy chain (VH). So, both type of chains contributes to antigen recognition.
b. contain multiple variable domains ⇒ none
Both chains - light and heavy - contain <u>only one</u> variable domain (VL and VH).
c. are found in the Fab fragment ⇒ both chains
The Fab fragment is composed of portions of both light and heavy chains: each portion contains one variable domain and one constant domain. The Fab fragment binds specifically the antigen.
d. are found in the FC fragment ⇒ heavy chains
The Fc region is composed of portions of heavy chains (CH² and CH³), so it contains constant domains.
e. contain only one constant domain ⇒ light chains
Each light chain contains one variable domain (VL) and one constant domain (CL).
f. contain multiple constant domains ⇒ heavy chains
Each heavy chain contains three constant domains: CH¹, CH² and CH³.
g. contain only one variable domain ⇒ both chains
Both light and heavy chains contain one variable domain. The difference is given by the number of constant domains: light chains have 1 constant domain while heavy chains have 3 constant domains.
