Cells

• Two major classes of cells: Prokaryotes and Eukaryotes
• Robert Hooke was the first person to use the term "cell" when referring to the small empty chambers in the structure of cork
• Theodor Schwann concluded that all animal tissues were composed of cells
• Rudolf Virchow proposed the theory of biogenesis where cells only arise from pre-existing cells
• Cell is the basic structural and functional unit of living organisms
• Water accounts for about 70-75% of the weight of the cell
• Organic compounds account for 25-30% of the cell height
• Eukaryotic cells have a membrane-bound nucleus and other membrane-bound organelles
• Plasma membrane is a phospholipid bilayer containing cholesterol and proteins, and some carbohydrates. It functions as a physical barrier to enclose cell contents
• Nucleus is enclosed within a double membrane and consists of DNA serving as genetic material
• Nuclear envelope contains nucleolus
• Nucleolus consists of RNA and proteins which function in ribosomal unit assembly
• Nucleoplasm surrounds the chromatin and nucleoli
• Cytoplasm is responsible for various cellular processes and is located between the plasma membrane and the nucleus
• Mitochondria are double-membrane-bound organelles containing a circular strand of DNA. They are responsible for the production of energy in the form of ATP
• Outer membrane of mitochondria is highly permeable to small molecules due to the presence of a pore-forming protein called porin
• Intermembrane of mitochondria contains many proteins that participate in oxidative phosphorylation
• Inner membrane of mitochondria has multiple folds projecting inwards, called cristae
• Lysosomes are spherical-shaped membrane-bound organelles formed from the Golgi apparatus. They contain digestive enzymes and function to digest microbes or materials by the cell
• Rough endoplasmic reticulum is an extensive interconnected membrane network involved in protein synthesis
• Ribosomes are involved in protein synthesis
• Smooth endoplasmic reticulum is an extensive interconnected membrane network lacking ribosomes
• Golgi apparatus is a series of several elongated, flattened sac-like membranous structures that modify, package, and sort materials
• Vesicles transport cellular material
• Secretory vesicle is the matured vesicles
• Peroxisomes are smaller, spherical membrane-bound organelles formed from the endoplasmic reticulum. They function to detoxify specific harmful substances
• Cytoskeleton is an organized network of protein filaments that maintain integral structural support and organization of cells
• Microfilaments maintain cell shape
• Intermediate filaments give mechanical support to structures like the nucleus and plasma membrane
• Microtubules provide structural support
• Prokaryotes (eubacteria and archaebacteria) are the most abundant organisms on earth
• Prokaryotic cells do not contain a membrane-bound nucleus and have no subcellular organelles, only infoldings of the plasma membrane called mesosomes
• The deoxyribonucleic acid (DNA) in prokaryotic cells is condensed within the cytosol to form the nucleoid
• Some prokaryotes have tail-like flagella
• Passive Transport Process: Diffusion is the movement of a substance from an area of higher concentration to an area of lower concentration
• Simple diffusion is the type of diffusion of dissolved solutes through the plasma membrane
• Facilitated Diffusion is the type of diffusion that requires a protein carrier
• Osmosis is the diffusion of water across a selectively permeable membrane
• Active Transport Process uses energy (ATP) provided by the cell
• Exocytosis refers to the bulk movement of substances out of the cell by fusion of secretory vesicles with the plasma membrane