The Cell: Basic Unit of Life
📌 All living beings are formed by tiny cells, mostly only visible through a microscope, which contain everything necessary for vital functions like nutrition, relation, and reproduction.
🦠 Organisms can be unicellular (like bacteria/amoebas) or pluricellular (like trees/whales, composed of billions of cells).
🧬 Cells contain DNA, the hereditary material responsible for offspring resembling their parents.

Discovery and The Cell Theory
🔬 Robert Hooke first used the term "cell" in 1665 after observing dead plant cells in cork, noting their resemblance to small honeycombs.
📜 The Cell Theory is summarized in four postulates: the cell is the structural, physiological, origin, and genetic unit of all living things.
🌟 The postulate on origin states that cells arise only from pre-existing cells (omnis cellula e cellula concept demonstrated by Virchow in 1855).

Cell Classification by Structure
🧬 Cells are primarily classified into prokaryotes (simple, no defined nucleus, genetic material in a nucleoid) and eukaryotes (complex, possess organelles, defined nucleus).
🧱 Common cellular components include the cell membrane (controls substance passage), cytoplasm (gelatinous filling), and genetic material (DNA).
🌳 Eukaryotes include protists, fungi, animals, and plants, while prokaryotes are found only in the Monera kingdom (eubacteria and archaeobacteria).

Prokaryotic Cell Components
🕸️ Prokaryotic structures include the capsule (mucous layer), cell wall (protection), plasma membrane, nucleoid (containing DNA), ribosomes, and the flagellum (for movement).

Eukaryotic Organelles (Shared & Animal Specific)
👑 The nucleus directs cell activities and houses DNA, while the cell/plasma membrane acts as a regulator for entry/exit.
⚡ The mitochondrion is the powerhouse, producing energy via cellular respiration.
🔄 The Golgi apparatus processes and distributes proteins, similar to a transport system.
🐶 Animal cells uniquely feature centrioles (organize microtubules/cell skeleton) and lysosomes (recycle/decompose cellular waste).

Eukaryotic Organelles (Plant Specific)
🛡️ Plant cells possess a rigid cell wall providing structure and protection beyond the membrane.
💧 A large central vacuole acts as a storage area for water, salts, and nutrients.
🌿 Chloroplasts contain chlorophyll, enabling photosynthesis for the plant to create its own food.

Cell Classification by Shape and Size
👁️ Cells can be macroscopic (visible to the naked eye, e.g., egg yolk) or microscopic (requiring a microscope, e.g., red blood cells).
🤸 Cell shape varies based on function: flat (epithelial cells), stellate (neurons), disc-shaped (red blood cells), or elongated (muscle cells).

Key Points & Insights
➡️ The core structure of all life lies in the cell, acting as the basic unit of structure, physiology, origin, and genetics.
➡️ Prokaryotic cells lack a membrane-bound nucleus, housing DNA in a nucleoid, while eukaryotic cells are structurally complex with various membrane-bound organelles.
➡️ Plant cells are distinguished by having a cell wall, chloroplasts, and a large central vacuole, features absent in typical animal cells (which have centrioles and lysosomes).

📸 Video summarized with SummaryTube.com on Nov 10, 2025, 13:52 UTC