Which cell organelle controls most of the activities of the cell?

State the reason for the following:
$(i)$ Mitochondria are known as the powerhouse of the cell.
$(ii)$ Plastids are able to make their own protein.
$(iii)$ Plant cells shrink when kept in a hypertonic solution.

Which of the following cell organelles is covered by a single membrane?

Why are lysosomes known as 'suicide-bags' of a cell?

State whether the following statement is true or false:
Leucoplasts are the coloured plastids.

Which kind of plastid is more common in:
$(a)$ Roots of the plant
$(b)$ Leaves of the plant
$(c)$ Flowers and fruits