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CELL ORGANNELS 1. Nucleus a. Nucleus Pores Large protein complexes that cross the nuclear envelope Proteins that make up the nuclear pore complex are known as nucleoporins About on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate cell, but it varies depending on cell type and throughout the life cycle Nuclear pores allow the transport of water-soluble molecules across the nuclear envelopeus The entire nuclear pore complex (NPC) has a diameter of about 120 nm The diameter of the opening (functional diameter) is about 9 nm wide and its "depth" is about 200 nm b. Nucleus Membrane (Nucleus Envelope) Encloses the genetic material in eukaryotic cells and serves as the physical barrier, separating the contents of the nucleus (DNA) from the cystol (cytoplasm) The nuclear envelope has two membranes, each with the typical unit membrane structure Each of the two membranes is made up of a lipid bilayer. The outer membrane is continuous with the rough endoplasmic reticulum (ER) and has ribosomes attached The inner nuclear membrane is connected to the nuclear lamina, a network of intermediate filaments composed of various lamin Lamina acts as a site of attachment for chromosomes and provides structural stability to the nucleus Numerous nuclear pores are inserted in the nuclear envelope and facilitate and regulate the exchange of materials (proteins such as transcription factors, and RNA) between the nucleus and the cytoplasm The outer and inner nuclear membrane are fused at the site of nuclear pore complex insertion 2. Cell Membrane also called plasma membrane or phospholipid bilayer contains a wide variety of biological molecules, primarily proteins and lipids, that are involved in a lot of cellular processes such as cell adhesion, ion channel conductance and cell signaling also serves as the attachment point for both the intracellular cytoskeleton and, if present, the extracellular cell wall Function Surrounds the cytoplasm of a cell and separates the intracellular components from the extracellular environment Plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix to help group cells together in the formation of tissues Movement of substances across the membrane can either be passive, occurring without the input of cellular energy, or active, requiring the cell to expend energy in moving it Structure Is made up mainly of ampthipathic phospholipids which spontaneously arrange so that the hydrophobic "tail" regions are shielded from the surrounding polar fluid, causing the more hydrophilic "head" regions to associate with the cytosolic and extracellular faces of the resulting bilayer. This forms a continuous, spherical lipid bilayer Arrangement of hydrophilic heads and hydrophobic tails of the lipid bilayer prevent polar solutes (e.g. amino acids, nucleic acids, carbohydrates, proteins, and ions) from diffusing across the membrane, but generally allows for the passive diffusion of hydrophobic molecules 3. Cell Walls Located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism Major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell They are found in plants, bacteria, fungi, algae, and some archaea. Animals and protozoa do not have cell walls In plants, the strongest component of the complex cell wall is cellulose, which is a polymer of glucose. In bacteria, peptidoglycan forms the cell wall. In this diagram, the cell wall is the outer green lining. 4. Ribosomes are complexes of RNA and protein that are found in all cells Function Protein biosythesis, which is the process of decoding RNA into protein 5. Endoplasmic Reticulum an eukaryotic organelle that forms an interconnected network of tubules, vesicles (small ball of liquid in a cell), and cisternae within cells Function protein translation (process in which cells build proteins) folding and transport of proteins to be used in the cell membrane (e.g. transmembrane receptors and other integral membrane proteins) production and storage of glycogen, steroids, and other macromolecules Structure an extensive membrane network of cisternae (sac-like structures) held together by the cytoskeleton Rough Endoplasmic Reticulum studded with ribosome giving it a "rough" appearance is known as RER membrane of the RER is continuous with the outer layer of the nuclear envelope Smoth Endoplasmic Reticulum synthesis of lipids and steroids, metabolism of carbohydrates, regulation of calcium concentration, drug detoxification, attachment of receptors on cell membrane proteins, and steroid metabolism 6. Golgi Body (Golgi Apparatus) Structure composed of membrane-bound stacks known as cisternae cisternae stack contains five functional regions which are the cisGolgi network, cis-Golgi, medial-Golgi, trans-Golgi, and trans-Golgi network each region contains different enzymes which carefully go over the contents depending on where they are supposed to be Function main function is to process and package the marcomolecules such as proteins and lipids that are synthesized by the cell it is a major site of carbohydrate synthesis 7. Lysosomes organelles that contain digestive enzymes some biologists say that they are only found in animal cells sometimes call "suicide-bags" or "suicide-sacs" because of what they do with autolysis which is destruction of a cell through the action of its own enzymes Functions the digestion of marcromolecules from phagoctosis (ingestion of other dying cells or larger extracellular material, like foreign invading microbes), endocytosis (where receptor proteins are recycled from the cell surface), and autophagy (wherein old organelles or proteins, or microbes that have invaded the cytoplasm are delivered to the lysosome) digesting foreign bacteria 8. Mitochondria are membrane-enclosed organelles found in most eukaryotic cells ange from 0.5–10 micrometers in diameter described as "cellular power plants" because they generate most of the cell's supply of ATP, used as a source of chemical energy Structure contains outer and inner membranes composed of phospholipid bilayers and proteins o Outer Membrane encloses the organelles has a protein-to - phospholipid ratio similar to that of the eukaryotic plasma membrane (about 1:1 by weight) contains large numbers of integral proteins called porins o Inner Membrane contains four types of proteins: (1) Those that perform the redox reactions of oxidative phosphorylation (2) ATP synthase, which generates ATP in the matrix (3) Specific transport proteins that regulate metabolite passage into and out of the matrix (4) Protein import machinery. 9. Chloroplast are organells found in plant cells and other eukaryotic organisms that conduct photosynthesis capture light energy to conserve free energy in the form of ATP Structure contained by an envelope that consists of an inner and an outer phospholipid membrane between these two layers is the intermembrane space material within the chloroplast is called the stroma also contains ribosomes, although most of its proteins are encoded by genes contained in the host cell nucleus, with the protein products transported to the chloroplast 10. Amyloplast are non - pigmented organelles found in plant cells responsible for the storage of amylopectin, a form of starch, through the polymerization of glucose also convert this starch into sugar, for when the plant needs energy found in underground storage tissues of some plants 11. Vacuole membrane-bound organelle which is present in all eukaryotic cells enclosed compartments which are filled with fluid such as water or different enzymes, though sometimes they may contain solids majority of vacuoles are formed through the fusion of multiple membrane vesicles Functions "Isolating materials that might be harmful or a threat to the cell Containing waste products Maintaining internal hydrostatic pressure or turgor within the cell Maintaining an acidic internal pH Containing small molecules Exporting unwanted substances from the cell" The vacuole is located in the center. 12. Transport Vesicle could be any vesicle that transports material around the cell transport vesicles are usually refered to those vesicles that transport material from the Endoplasmic Reticulum to the Golgi apparatus or from one part of the Golgi to another 13. Plasmodesmata are microscopic channels which traverse the cells walls of plant cells and enable transport and communication between them Structure typical plant cell may have between 103 and 105 plasmodesmata connecting it with adjacent cells are approximately 50-60nm in diameter at the mid-point and are constructed of three main layers, the plasma membrane, the cytoplasmic sleeve, and the desmotubule similar in structure to the cellular phospholipid bilayers 14. Tight Junction are the closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier to fluid Structure made up of a branching network of sealing strands, each strand acting independently from the others Functions they hold cells together they block the movement of intergral membrane proteins between the apical and basolateral surfaces of the cell which allows the specialized functions of each surface to be preserved they prevent the passage of molecules and ions through the space between cells 15. Peptoglycans polymer consisting to sugars and amino acids that make up the cell wall peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer common mistake people make is that peptidoglycan gives the cell its shape; however, the peptidoglycan helps maintain the structure of the cell, it is actually the MreB protein (protein found in bacteria that has been identified as a homologue of actin) that directs cell shape Function "main purpose of peptidoglycan is to maintain bacterial shape and to counteract the internal pressure of the bacterial cell" Structure peptidoglycan layer in the bacterial cell wall is a crystal lattice structure formed from linear chains of two alternating amino sugars 16. Glycoproteins proteins that contain oligosaccharide chains covalently attached to their polypeptide side-chains process is known as glycosylation 17. Cytoskeleton cellular "skeleton" contained in the cytoplasm in eukaryotic cells (animal and plant) Function maintains cell shape, protects the cell, enables cellular motion (using structures such as flagella, cilia, and lamellipodia), and plays important roles in both intracellular transport (the movement of vesicles and organelles, for example) and cellular division o Microtubules hollow cylinders about 25 nm in diameter, usually made up of 13 protofilaments 18. Cilia and Flagella Function to move a cell or group of cells or to help transport fluid or materials past them respiratory tract in humans is lined with cilia that keep inhaled dust, smog, and potentially harmful microorganisms from entering the lungs generate water currents to carry food and oxygen past the gills of clams and transport food through the digestive systems of snails