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Physiology 1021
Beth Mac Dougall- Shackleton

MODULE 3: HUMAN CELL Basic Cell Organelles  Nucleolus: produces RNA found in ribosomes  Nucleus: location of all cell’s DNA  Endoplasmic Reticulum: site for protein synthesis  Mitochondrion: powerhouse (produces ATP)  Centriole: direct DNA movement in cell division  Lysosomes: digestive system of cell  Secretory Vesicle: transport proteins out of cell  Golgi apparatus: packages proteins into vesicles  Free Ribosomes: manufacturing proteins from amino acids under control of DNA The Cell Membrane  Selectively permeable: some items can cross very easily, while others cross with difficulty and some items cant cross at all  Lipid or fatty acid region: creates the “barrier” to water-soluble molecules such as ions (Na+, K+ Cl-, water)  Proteins are found in the cell membrane and perform a variety of functions; act as membrane transport mechanisms Cell Membrane Structure  Made of proteins that form channels and pores, carbohydrate molecules for cell recognition, cholesterol for stability  Phospholipid Molecules: are the most abundant components; double layer make up cell membrane; fat soluble substances can dissolve through lipid (a) Hydrophilic Head: “like water”; POLAR; face out into the water base solutions inside and outside of cell (b)Hydrophobic Tail: “dislike water”; NONPOLAR; oriented away from aqueous, extra and intracellular solutions in to the cell; fat soluble substances can dissolve through lipid region of membrane; water soluble substances cannot pass through lipid region of membrane  Cholesterol molecule: found inserted into nonpolar lipid layer of membrane; helps make membrane impermeable to some water soluble molecules & also helps keep membrane flexible over a wider temperature range  Associated Protein: can be attached to either the intracellular or extracellular surface of membrane;  Carbohydrate Molecule: groups of carb molecules can be could associated with extracellular membrane proteins or lipids; form a protein layer called glycocalyx which plays a key role in immune response of cell and in recognition of other cells in body  Membrane Spanning Proteins: embedded in phospholipid bilayer so they span entire width of membrane; act as gates/channels that control movement of certain substances in/out of cell (a) Receptors (for attachment of chemical hormones and neurotransmitters) (b)Enzymes (that help with chemical reactions or breakdown molecules) (c) ion channels/pores (allow water-soluble substances, like ions, into cell (d)membrane-transport carriers (transport molecules across membrane) (e) cell-identity markers (foreign particles that can stimulate the immune system Membrane Transport Mechanisms Simple Simple Facilitated Active Diffusion (A) Diffusion (B) Diffusion Transport Active/ Passive Down conc Down conc Down conc Against con gradient gradient gradient gradient (active) (passive) (passive) (passive) Mechanism Via lipid bilayer;Via protein-lined Via carriers Via pump fat soluble; pores; polar requiring ATP nonpolar molecules molecules Factors -con lg=fast -conc gradient -chemically -inc temp= fast -size of molecule specific -SA lg=fast -# of pores -completely -size mol sm= -charge inhibited by fast (specificity) structurally -vis less= fast similar molecules Examples 02, CO2, fatty Na+
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