development of cell theory

• In 1838 and 1839, Matthias Jacob Schleiden and Theodore Schwann discovered that plants and animals are both made of cells
• In 1855, Rudolph Virchow collaborated with Schleiden and Schwann to develop the Cell Theory, which includes the principles that all living organisms are made up of one or more cells, cells are the most basic unit of life, and cells only come from the division of pre-existing cells
• Organisms may be Unicellular (composed of 1 cell) or Multicellular (made of many cells)
• All cells have in common a plasma (cell) membrane, which is a boundary that allows things into and out of the cell
• Eukaryotic cells have a membrane-bound nucleus and membrane-bound organelles, while Prokaryotic cells lack a membrane-bound nucleus and membrane-bound organelles
• Cell structures with specific functions surrounded by a membrane are found in eukaryotes only
• Prokaryotic cells are unicellular organisms like bacteria, while eukaryotic cells, found in animals, plants, protists, and fungi, have a membrane-bound nucleus and membrane-bound organelles
• The cell membrane regulates what enters and leaves the cell, separating it from its external environment
• The cytoplasm is the ground substance and the largest part of the cell where organelles and cellular inclusions are found
• The Endoplasmic Reticulum (ER) has two types: Rough ER plays a role in protein production, folding, quality control, and dispatch, while Smooth ER is involved in lipid manufacture and metabolism
• The Golgi apparatus sorts, modifies, and packages proteins and other materials from the ER for storage or secretion from the cell
• Mitochondria are the site of cellular respiration, known as the cell "powerhouse," where glucose is used to produce cell energy (ATP)
• Lysosomes contain enzymes that help digest food, bacteria, and worn-out cell parts, while peroxisomes contain enzymes specialized to digest toxic substances
• Ribosomes are where proteins are made, some free-floating and others attached to the endoplasmic reticulum
• Centrioles, found only in animal cells, are self-replicating structures made of bundles of microtubules that help in organizing cell division
• The cytoskeleton, a network of protein filaments, helps the cell move and maintain its shape, strength, and ability to move
• Microtubules form the cores of cilia and flagella in sperm cells and help maintain cell shape
• Microfilaments support the cell to maintain its structure and shape, providing resiliency against forces that can alter the shape
• The nucleus controls most cell processes, contains nearly all of the cell’s DNA, and serves as a site for the storage of hereditary factors
• The nuclear membrane is the two-layered outer limit of the nucleus separating it from the cytoplasm
• Chromatin is made up of DNA and proteins, forming chromosomes during cell division
• Plant cells have chloroplasts for photosynthesis, a cell wall for structure, and a large central vacuole for water storage, while animal cells usually have many small vacuoles
• Chloroplasts in plant cells contain chlorophyll for photosynthesis, chromoplasts synthesize and store pigments, and leucoplasts store food such as starches, lipids, and proteins