Introduction to cells
Definitions and Basics
- Cell is the basic structural and functional unit of life.
- All organisms are made up of one or more cells. The unicellular organisms, such as bacteria and yeast, are made up of a single cell, while multicellular organisms, such as human and plants, are composed of many cells.
- All cells originate from pre-existing cells through the process of cell division.
Cellular Structures
- The cell membrane also referred to as the plasma membrane, controls what enters and leaves the cell.
- The cytoplasm is the gel-like substance found within the cell membrane which contains all the cell's organelles.
- The nucleus controls cell activities and contains the cell's DNA.
- The mitochondria are known as the powerhouses of the cell and produce the cell's energy through a process called respiration.
- The ribosomes are involved in protein synthesis.
- The endoplasmic reticulum serves as a pathway for the transport of materials throughout the cell, and is involved in the synthesis of proteins and lipids.
- The golgi apparatus plays a key role in the modification, sorting, and packaging of proteins for delivery to targeted destinations.
Types of Cells
- Prokaryotic cells: These cells lack a defined nucleus and do not contain membrane-bound organelles. Examples include bacteria and archaea.
- Eukaryotic cells: These cells have a defined nucleus enclosed by a nuclear membrane and contain other membrane-bound organelles. Examples include cells of fungi, plants, and animals.
Specialisation of Cells
- In multicellular organisms, cells tend to be specialised to perform particular functions.
- There can be many types of specialised cells in an organism, including nerve cells, muscle cells, and red blood cells.
- Each type of cell has structural adaptions that allow it to perform its function efficiently.
Cell Division
- There are two main types of cell division, namely, mitosis and meiosis.
- Mitosis is used for growth and repair and results in two genetically identical cells.
- Meiosis is used for sexual reproduction and results in four genetically different cells.