Which of the following are the most diverse molecules in the cell?

The simplest amino acid is .....

Which one of the following amino acids is an essential part of the human diet?

Which amino acids have polar and positively charged $R$ groups?

Which of the following statement$(s)$ is/are true?
$(i)$ All amino acids contain one chiral centre.
$(ii)$ Some amino acids contain one, while some contain more chiral centres or even no chiral centre.
$(iii)$ All amino acids in proteins have $L$-configuration.
$(iv)$ All amino acids found in proteins have $1^{\circ}$ amino group.

Which of the following is a sulfur-containing amino acid?