Chap 3 NotesF10 - Biol 121 Anatomy Physiology I Cells The...

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Biol 121 Anatomy & Physiology I Dr. M.K. Hopper Cells: The Living Units A. Cell Theory 1. The cell is the basic structural and functional unit of living organisms; defining the properties of a cell is defining the properties of life. 2. Human body is comprised of trillions of these tiny building blocks. Primarily C, H, N and O take on the special characteristics of life. B. Cell Characteristics - are very diverse 1. Cell Size length ranges from 2 um to a meter or more Width - usually 10-100 um 2. Cell Shape Spherical -fat Disk - Red blood cell Branching - Nerve Cuboidal - kidney Flat - epithelium C. Composite Cell - All cells differ, but have common structural and functional features which include the plasma membrane, cytoplasm, and the nucleus. 1. Plasma (or Cell) Membrane a) flexible - fluid mosaic model Phospholipid bilayer hydrophilic portions interact with water outside and inside the cell. Hydrophobic ends meet in the center and form a lipid bilayer that exhibits selective permeability. b) Proteins included in or on the membrane serve as enzymes, receptors for hormones, transport vehicles, channels or pores, etc. c) Cholesterol is an integral part of membranes, give stability d) glycolipid and glycoproteins sugar coat, unique to each cell type. EX: Blood typing A, B, O
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e) Specialization's of the cell membrane Microvilli - finger like extensions that increase the surface area (intestinal cells) Cilia - short, hair like projections that sweep particles across the cells surface (respiratory tract) Flagella - longer tail, whip like actions propels the cell (sperm) 2. Junctions of the Plasma Membrane Blood cells, sperm cells and some phagocytic cells are free within the body. Most other cells join together with nearby cells. Types of junctions: a) Tight Junctions Protein molecules in adjacent plasma membranes fuse together tightly like a zipper forming an impermeable junction that encircles the cell. Tight junctions prevent molecules from passing through the extra-cellular space between adjacent cells. Ex: Tight junctions in GI tract keep digestive enzymes and microorganisms in the intestine from entering the blood. b) Desmosomes Adjacent cells do not actually touch but are held together by thin linker proteins. Mechanical couplings are also scattered like rivets along the sides of abutting cells. Prevent separation. Abundant in tissues subjected to great mechanical stress, such as skin, heart and uterus. c) Gap Junctions Adjacent plasma membranes are very close and the cells are connected by hollow cylinders. Ions, sugars and other small molecules pass through these water filled channels between cells. Exist in heart and smooth muscle where electrical message spread from cell to
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Chap 3 NotesF10 - Biol 121 Anatomy Physiology I Cells The...

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