In $L-malic$ acid and $L-lysine$,what does the $L$ represent?

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.

What type of bond is the $-CO-NH-$ linkage?

Amino acids like methionine and cysteine contain

In the human body,the synthesis of non-essential amino acids occurs during:

Which bond connects Valine and Cysteine?