(i) Make a labelled drawing of a typical plant cell to show its essential features. (ii) Give the functions of two labelled organelles (b) Describe briefly ...

(a)(i) Labelled drawing of a typical plant cell

(a)(ii) Functions of two labelled organelles

1. Mitochondrion: it is the site of aerobic respiration, where energy is released from food and trapped in ATP for the activities of the cell.
2. Chloroplast: it contains chlorophyll, which absorbs light energy for the manufacture of food during photosynthesis.

(b) Two levels of cell organisation

1. Tissue level: a tissue is a group of similar cells working together to perform a particular function. For example, xylem tissue in a plant conducts water and mineral salts; muscle tissue in an animal brings about movement.
2. Organ level: an organ is made up of different tissues working together to carry out one or more functions. For example, a leaf is a plant organ for photosynthesis and gaseous exchange, while the heart is an animal organ that pumps blood.

(c) Roles of processes in a living cell

1. Osmosis: this is the movement of water molecules through a selectively permeable membrane from a region of higher water potential, or more dilute solution, to a region of lower water potential, or more concentrated solution. It enables root-hair cells to absorb water from the soil and keeps plant cells turgid for support. It also helps to maintain the water balance of cells.
2. Diffusion: this is the movement of particles from a region of higher concentration to a region of lower concentration. It enables cells to take in oxygen and soluble food substances and to remove wastes such as carbon dioxide. Thus, it is important in gaseous exchange and in movement of nutrients from tissue fluid into cells.