1.1 Cell structure and function 

Learning Objectives:

1. Examine under the microscope, animal cells and plant cells from any suitable locally available material, using an appropriate temporary staining technique, such as methylene blue or iodine solution

2. Draw diagrams to represent observations of the animal and plant cells examined above

3. Identify on diagrams, photomicrographs or electron micrographs, the ribosomes, mitochondria, nucleus, cytoplasm and cell membrane in an animal cell

4. Identify on diagrams, photomicrographs or electron micrographs, the ribosomes, mitochondria, chloroplasts, nucleus, sap vacuole, cytoplasm, cell membrane and cellulose cell wall in a plant cell

5. Describe the structure of a bacterial cell, limited to: ribosomes, circular deoxyribonucleic acid (DNA)and plasmids, cytoplasm, cell membrane and cell wall

Definitions:

6. Describe the functions of the above structures in animal, plant, and bacterial cells

Animal Cells:

Cytoplasm is a jelly-like, thick liquid with particles and organelles [mitochondria - nucleus]. Large numbers of chemical reactions take place in the cytoplasm, which keeps the cell alive. The liquid part of the cytoplasm contains 90% sugars and minerals dissolved in it. Suspended in this solution are larger molecules of lipids and proteins

Cell membrane: a partially permeable layer that forms a boundary around the cytoplasm. It prevents cell contents from escaping and controls what substances enter and leave the cell. Generally, food, oxygen and water are allowed in, and metabolic waste products are kept out

Nucleus: a circular or oval structure containing DNA in the form of chromosomes. A cell without a nucleus cannot reproduce. The nucleus controls cell division, cell development, and cell activities. It also controls the type and quantity of enzymes produced by the cytoplasm. In this way, it regulates the chemical changes in the cell

Mitochondria: circular or oval-shaped organelles inside the cytoplasm. It produces energy through the process of aerobic respiration. Most frequent in regions of rapid chemical activity.

Ribosomes: tiny structures that can be free within the cytoplasm or attached to a system of membranes within the cell known as the Endoplasmic Reticulum. Endoplasmic reticulum studded with ribosomes looks rough under the microscope; this gives rise to its name of Rough Endoplasmic Reticulum (often shortened to R.E.R. It is responsible for protein synthesis

Additional Plant Cell Structures:

Cell Wall: A tough, non-living layer made of cellulose surrounding the cell membrane. It is freely permeable. It prevents the plant cell from bursting due to turgor pressure.

Vacuole: a large, fluid-filled filled surrounded by a membranecontains cell sap, a watery solution of sugars, salts, and sometimes pigment. This vacuole pushes the cytoplasm outwards, creating a pressure on the cytoplasm and the cell wall that makes plant cells and their tissues firm

Chloroplast: an organelle that contains a green substance called chlorophyll. It traps light energy for photosynthesis

Credits: Notes compiled by Manahil Naeem