ai What is a cell? ii name three scientists that are associated with the discovery of the cell. b. make a diagram, 6cm to 8cm long of a plant cell and label...

(a)(i) A cell is the basic structural and functional unit of life; it is the smallest unit capable of carrying out all the activities necessary for the survival of a living organism.

(a)(ii) Three scientists associated with the discovery of the cell are:

• Robert Hooke
• Anton van Leeuwenhoek
• Matthias Schleiden

(b)(i) A labelled diagram of a plant cell (drawn 6 cm to 8 cm long), with the nucleus - the organelle responsible for cell reproduction (cell division) - clearly labelled, is shown below.

The blood cell in humans that does not possess the nucleus is the red blood cell (erythrocyte). The mature mammalian red blood cell has no nucleus.

(b)(iii) Because the red blood cell has no nucleus, it lacks the DNA that controls cell division. The biological implications are:

• It cannot divide, reproduce or replace itself, so it has a short, limited lifespan (about 120 days) and must be continually replaced by new cells made in the red bone marrow.
• It cannot repair itself or synthesise new proteins and enzymes once damaged.
• The absence of the nucleus creates more internal space for haemoglobin, increasing the cell's oxygen-carrying capacity.

(c) Six organelles found in a plant cell:

1. Nucleus
2. Chloroplast
3. Mitochondrion
4. Endoplasmic reticulum
5. Golgi apparatus
6. Ribosome