The Cell - SS1 Biology Lesson Note

A cell is the basic structural and functional unit of all living organisms. It is the smallest independently functioning entity within an organism and is often referred to as the building block of life. Cells are enclosed by a plasma membrane, which separates the internal cellular components from the external environment. The plasma membrane is selectively permeable, allowing the passage of certain molecules in and out of the cell.

Inside the cell, various structures and organelles carry out specific functions. The nucleus, often referred to as the control center of the cell, contains the genetic material in the form of DNA (deoxyribonucleic acid). DNA carries the instructions for the cell's development, growth, and functioning.

Other organelles, such as mitochondria, are responsible for energy production through cellular respiration. Endoplasmic reticulum and Golgi apparatus are involved in protein synthesis, modification, and transport. Lysosomes contain digestive enzymes for breaking down waste materials and cellular components. The cytoskeleton provides structural support and allows cell movement, while the cytoplasm houses various metabolic reactions.

Figure 42 Image from rsscience.org

Cells are incredibly diverse, varying in size, shape, and specialized functions depending on the organism and tissue type. They can be categorized into two broad groups: prokaryotic and eukaryotic cells. Prokaryotic cells, found in bacteria and archaea, lack a nucleus and other membrane-bound organelles. Eukaryotic cells, found in plants, animals, fungi, and protists, have a nucleus and various membrane-bound organelles.

Cells can carry out essential life processes, such as growth, reproduction, responding to stimuli, and maintaining homeostasis. They are highly complex and dynamic entities, cooperating with each other to form tissues, organs, and entire organisms.