(a) What is a cell? (b) Describe the structure and state the function of each of the following: (i) Nucleus (ii) Mitochnodrion. (c)(i) Make a labelled diagr...

(a) A cell is the smallest structural and functional unit of life. It is the basic unit from which living organisms are built and is capable of carrying out life processes.

(b)(i) Nucleus

• Structure: The nucleus is usually spherical or oval and is surrounded by a double nuclear membrane containing pores. It contains nucleoplasm, chromatin materials (chromosomes/genes) and a nucleolus.
• Functions: It controls the activities of the cell, contains hereditary materials, and controls or initiates cell division.

(b)(ii) Mitochondrion

• Structure: A mitochondrion is an oval or rod-shaped organelle bounded by a double membrane. Its inner membrane is folded into cristae, enclosing a fluid-filled matrix containing enzymes and ribosomes.
• Function: It is the site of aerobic (tissue) respiration, where energy is released from food in the form of ATP.

(c)(i) Labelled diagram of Euglena, 9 cm long

(c)(ii) Animal-like features of Euglena

1. It possesses a flagellum for movement.
2. It has a contractile vacuole for osmoregulation.
3. It has a gullet/reservoir through which it can take in food; it can feed heterotrophically when light is absent.

Plant-like features of Euglena

1. It contains chloroplasts and manufactures food by photosynthesis.
2. It possesses pyrenoids/paramylum granules for food storage.