Cell Theory Overview

Cell Theory

• The cell theory is a fundamental scientific theory explaining how life on Earth functions.
• All living organisms are made up of cells.
• This theory replaced the theory of spontaneous generation, which proposed living organisms could arise from inanimate objects.
• Robert Hooke first observed cells in 1665 while examining cork.
• He named them "cells" due to their resemblance to small compartments.
• Matthias Schleiden, Theodor Schwann, and Rudolf Virchow largely formulated the cell theory in 1839.

Tenants of Cell Theory

• All living organisms are composed of one or more cells.
• This includes everything from bacteria to whales.
• Cells are the fundamental structural and functional units of life.
• They are the smallest units performing all life's processes.
• New cells originate from pre-existing cells through cell division.

Cell Structure

• Cells are enclosed by a semi-permeable membrane composed of phospholipids.
• The membrane surrounds the cytosol, a watery solution containing salts and other molecules within the cell.
• Specialized organelles within the cytosol perform various functions, including energy production, protein synthesis, and waste removal.
• All cells contain DNA, the genetic material carrying instructions for life processes.

Cell Division

• Cells divide via mitosis, creating identical copies of the parent cell.
• Mitosis is crucial for growth, development, and replacing damaged cells.
• Multicellular organisms begin as a single cell, growing through mitosis and cell differentiation.
• Cell differentiation is the process where cells specialize for specific functions.
• Cells form tissues, tissues form organs, organs form organ systems, and organ systems form organisms.

Viruses

• Some scientists classify viruses as non-living due to their inability to reproduce independently.
• Viruses can only replicate inside a host organism's cells.

Explore the fundamental concepts of cell theory, including its formulation and main tenets. Learn about the significance of cells in all living organisms and how this theory replaced earlier misconceptions about the origins of life. Perfect for students studying biology and the foundational principles of life science.