Cell Organelles and Cell Theory | Agriculture Optional Notes for UPSC PDF Download

Cell Organelles

Cells are composed of various cell organelles that perform certain specific functions to carry out life’s processes.
The different cell organelles, along with its principal functions, are as follows:

• Nucleolus: The nucleolus is responsible for the synthesis of ribosomes and plays a role in regulating cellular activities and reproduction.
• Nuclear membrane: The nuclear membrane acts as a protective boundary that separates the nucleus from other cell organelles.
• Chromosomes: Chromosomes have a vital function in determining an individual's sex, with each human cell containing 23 pairs of chromosomes.
• Endoplasmic reticulum: The endoplasmic reticulum is engaged in the transport of substances within the cell and plays a key role in carbohydrate metabolism, as well as the synthesis of lipids, steroids, and proteins.
• Golgi Bodies: Golgi bodies serve as the cell's transportation system, facilitating the movement of materials within the cell.
• Ribosome: Ribosomes function as the cellular protein synthesis machinery.
• Mitochondria: Mitochondria are often referred to as "the powerhouse of the cell" because they generate ATP, the cell's energy currency.
• Lysosomes: Lysosomes contribute to cell protection by engulfing foreign bodies entering the cell and participating in cell renewal. They are commonly known as the cell's "suicide bags."
• Chloroplast: Chloroplasts are the primary organelles responsible for photosynthesis and contain the pigment chlorophyll.
• Vacuoles: Vacuoles store food, water, and various waste materials within the cell.

Cell Theory

Cell Theory was introduced by German scientists, Theodor Schwann, Matthias Schleiden, and Rudolf Virchow.
This theory outlines the following principles:

• Every living organism on Earth is made up of cells.
• Cells are the fundamental building blocks of life.
• All cells originate from pre-existing cells.

A contemporary rendition of the cell theory has been developed, encompassing these tenets:

• Energy is transported within cells.
• Genetic information is transmitted from one cell to another.
• The chemical composition of all cells is uniform.

Functions of Cell

Cells serve crucial roles in the growth and development of organisms.
Here are the essential functions of cells:

• Structural Support: Cells are the building blocks of all organisms, providing the foundational structure. The cell wall and cell membrane offer support. For instance, skin comprises numerous cells, and plant xylem cells provide structural support.
• Growth Facilitation through Mitosis: Cells undergo mitosis, a process in which parent cells divide into daughter cells, promoting an organism's growth by multiplication.
• Transport of Substances: Cells import essential nutrients to execute various chemical processes. Waste generated from these processes is expelled from the cells through active and passive transport. Smaller molecules like oxygen, carbon dioxide, and ethanol passively move across the cell membrane following concentration gradients. Active transport is utilized for larger molecules, demanding substantial energy for substance transportation.
• Energy Production: Cells require energy for their diverse chemical processes. In plants, energy is generated through photosynthesis, while animals use respiration to produce energy.
• Reproduction Assistance: Cells play a role in reproduction through mitosis and meiosis. Mitosis is a form of asexual reproduction in which parent cells divide to create daughter cells. Meiosis results in genetically distinct daughter cells.

In summary, cells are appropriately referred to as the fundamental structural and functional units of life because they provide structural support to organisms and perform a variety of functions vital for life processes.