Which of the following ions are toxic to enzymatic activity?

Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure. Many of these functional groups are ionisable. As they are weak acids and bases in chemical nature,this ionisation is influenced by the $pH$ of the solution. For many enzymes,activity is influenced by the surrounding $pH$. This is depicted in the curve below. Explain briefly.

Non-competitive inhibitors alter:

Enzymes are active at ...... temperature.

What is the effect of substrate concentration on the rate of reaction?

In most plant cells,most enzymes have their optimum activity at: (in $^\circ C$)