:Cells Parts and Functions

• Cells are the basic building blocks of all living things, providing structure for the body, taking in nutrients from food, converting those nutrients into energy, and carrying out specialized functions.
• Cells contain the body’s hereditary material.
• Robert Hooke discovered cells in the mid-1600s when he observed a sliver of cork and saw "a row of empty boxes".
• Robert Hooke coined the term "cell".
• The major motor proteins are myosin, kinesin, and dynein.
• Cilia are short and are used to move substances outside human cells.
• Flagella are whip-like extensions found on sperm cells.
• Basal bodies like centrioles are found in cilia and flagella.
• Centrioles are short, barrel-shaped organelles composed of microtubules.
• Cell walls are found in plants, fungi, and many protists and surround the plasma membrane.
• Cell walls in plants are mostly cellulose, while in fungi they contain chitin.
• The extracellular matrix is a meshwork of fibrous proteins and polysaccharides in close association with the cell that produced them.
• Junctions between cells include plasmodesmata, adhesion junctions, tight junctions, and gap junctions.
• All living organisms are composed of cells, which may be unicellular or multicellular.
• The cell is the basic unit of life, and cells arise from pre-existing cells.
• Cells are highly complex and organized, possess a genetic program and the means to use it, are capable of producing more of themselves, acquire and utilize energy, and carry out a variety of chemical reactions.
• Prokaryotes are the first cell type on earth and are found in Bacteria and Archaea.
• Prokaryotic cells have no membrane-bound nucleus, a nucleoid region of DNA concentration, and organelles not bound by membranes.
• Eukaryotic cells have a nucleus bound by membrane, include fungi, protists, plant, and animal cells, and possess many organelles.
• Bacteria-like organelles are derived from symbiotic bacteria and are a result of an ancient association, as per the endosymbiotic theory.
• The plasma membrane acts as the boundary between the outside and inside of a cell, acts much like a gatekeeper, regulating the passage of molecules and ions into and out of the cell.
• The plasma membrane functions in compartmentalization, scaffolding for biochemical activities, providing a selectively permeable barrier, transporting solutes, responding to external stimuli, and intercellular interaction.
• Cytoplasm is a viscous fluid containing organelles, components of cytoplasm include interconnected filaments and fibers, fluid (cytosol), and organelles (not nucleus).
• The nucleus is the control center of the cell, it is a double membrane, and contains chromatin and a nucleolus.
• The nuclear envelope separates the nucleus from the rest of the cell, it is a double membrane, and has pores.
• The nucleolus is present in most cells, it directs the synthesis of RNA, and forms ribosomes.
• Ribosomes act as a workbench, and it is here that the information contained within the mRNA from the nucleus is used to synthesize a polypeptide chain.
• The endomembranous system consists of the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
• The endoplasmic reticulum helps move substances within cells, it is a network of interconnected membranes, and consists of two types: rough endoplasmic reticulum and smooth endoplasmic reticulum.
• Rough endoplasmic reticulum has ribosomes attached to its surface, it may modify proteins from ribosomes, and it is involved in manufacturing proteins.
• Smooth endoplasmic reticulum does not have attached ribosomes, it has enzymes that help build molecules, and it is involved in carbohydrate and lipid synthesis.
• The Golgi apparatus is involved in synthesis of plant cell wall, packaging and shipping of cell contents, and its mechanisms include molecules coming in vesicles, vesicles fusing with Golgi membrane, molecules may be modified by Golgi, molecules may be pinched off in separate vesicle, and vesicle leaves Golgi apparatus.
• Lysosomes contain digestive enzymes, they function in cell renewal, break down old cell parts, and digest invaders.
• Vacuoles are membrane-bound storage sacs, they are more common in plants than animals, and their contents include water, food, and wastes.
• Peroxisomes are simple, membrane-bound vesicles with a diameter of 0.1 to 1.0 m that may contain a dense, crystalline core of oxidative enzymes.
• Mitochondria have their own DNA, are bound by a double membrane, and are the powerhouse of the cell, responsible for ATP and cellular respiration.
• Chloroplasts are solar energy capturing organelles, they take place in the chloroplast, and make cellular food, glucose.
• Cytoskeleton and motor proteins associated with the cytoskeleton are instrumental in allowing cellular movements.