Which one of the following is most essential for the growth and formation of new cells?

Which conjugated protein is synthesized by copper?

Which element is common in both hemoglobin and myoglobin?

Haemoglobin is a

Given below are two statements:
Statement $I:$ Amino acids have a property of ionizable nature of $-NH_2$ and $-COOH$ groups,hence have different structures at different $pH$.
Statement $II:$ Amino acids can exist as Zwitterionic form at acidic and basic $pH$.
In the light of the above statements,choose the most appropriate answer from the options given below:

$A$ protein which exhibits $\beta$-pleated structure is