Cell Organisation

Cell Organisation: Basic Principles

• Cells are basic units of life, which can share many common features yet also differentiate remarkably depending on their function in a multicellular organism.
• An organism’s shape, function, and adaptive features are determined to a significant extent by the properties of its cellular components and their specific arrangements.

Cell Specialisation

• Cell specialisation or differentiation involves a cell changing its structure and function to perform a specific role.
• This process is controlled by genes which are expressed or silenced leading to the production of different proteins and hence cell characteristics.
• Examples include nerve cells with long extensions for transmitting electrical impulses, and red blood cells which lack a nucleus to accommodate more haemoglobin.

Cellular Organisation in Tissues

• A tissue consists of a group of specialised cells working together to perform a common function.
• Examples include vascular tissues in plants (xylem and phloem) and nervous tissue in animals.
• Study of tissue types and their overall organisation within organs can be facilitated using techniques like histology, which involves the microscopic examination of thin tissue sections.

Structural Organisation: Organs & Organ Systems

• Organs are structures consisting of several tissue types assembled together to perform a specific set of functions. Examples include the heart, liver, or leaves in plants.
• An organ system is a group of organs working together to perform major functions for the organism. For instance, the digestive system involves organs like the stomach and intestines to break down and absorb food.

Role of Cell Junctions

• Specialised areas of the plasma membrane known as cell junctions aid in connecting cells and enable communication and transport between them.
• Gap junctions enable direct metabolic and electrical communication between cells, whereas tight junctions form a waterproof barrier, and anchoring junctions (desmosomes) provide mechanical stability.

From single-cell to multicellular life

• The evolution from unicellular to multicellular organisms involved cells becoming specialised and cooperating with each other, increasing survival and reproductive success.
• Colonial organisms like Volvox represent an important step in this transition, with cells exhibiting both independent and coordinated behaviours.

Understanding the bigger picture of cellular organisation is enormously beneficial. Remember the complexity and deeply interconnected nature of life while exploring individual cell components.