Cell Theory and Function

Cell Theory

• Cell theory is a fundamental concept in biology stating that all living organisms are composed of cells, cells are the basic units of structure and function in living organisms, and cells arise from pre-existing cells.
• The first description of cells was made by Robert Hooke in 1665.
• Anton van Leeuwenhoek observed single-celled organisms.
• Matthias Schleiden and Theodor Schwann formulated the cell theory in the mid-19th century.
• Rudolf Virchow completed the cell theory by adding the crucial component about cell genesis.

Cell Function

• Cells perform various functions necessary for life, including metabolism, reproduction, and response to stimuli.
• Metabolism encompasses all chemical reactions within a cell, including the breakdown and synthesis of molecules.
• Cells reproduce through cell division, ensuring growth and repair.
• Cells respond to internal and external stimuli, maintaining homeostasis.
• The specific functions vary greatly depending on the cell type (e.g., muscle cells contract, nerve cells transmit signals).
• Cells have specialized structures called organelles that perform specific tasks.

Tissues

• Tissues are groups of similar cells that work together to perform a specific function.
• Four main tissue types in animals: epithelial, connective, muscle, and nervous tissues.
• Epithelial tissue covers surfaces, lines body cavities, and forms glands.
• Connective tissue supports and connects other tissues, including bone, cartilage, and blood.
• Muscle tissue allows movement.
• Nervous tissue transmits nerve impulses.

Organs

• Organs are structures composed of two or more tissue types that work together to perform a specific function.
• Organs are highly specialized for their roles.
• Examples include the heart, lungs, liver, stomach, brain and kidneys.
• Organs work in coordination within organ systems to maintain the overall health and function of an organism.
• Organs have specialized regions and structures in order to facilitate the functions they carry out.
• Organs can be comprised of several types of tissues in varying amounts. For example, the stomach comprises layers of smooth muscle tissue for digestion and epithelial tissue lining the stomach.
• Specialized cells within organs work together with supporting tissues such as connective and other cell types contributing to organ function.