Cells - Human Anatomy & Physiology CELLS I. Timothy P....

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Timothy P. Scott, Ph.D. CELLS I. INTRODUCTION - Cells are the smallest units of life - Cells made of carbon, nitrogen, hydrogen, oxygen, and other trace elements - Average size is 10 μ m (ranges from 2 μ m to 1 m) II. CELL MEMBRANE AND ASSOCIATED STRUCTURES - Also known as the fluid mosaic model, bilipid layer & plasmalemma. - The plasma membrane (P.M.) is the boundary of every cell o It guards what goes in and what goes out - Everything from the P.M. to the nucleus is the cytoplasm o The cytoplasm has organelles and is an aquatic environment A. Lipids 1. Hydrophilic Heads (polar) - exterior boundaries – water loving 2. Hydrophobic Tails (nonpolar) - interior region – water hating a. Fatty acid tail hates water and is sandwiched in the middle of the bilipid membrane B. Proteins - Integral protein – goes all the way through the P.M. - Peripheral protein – on one side of the P.M. or the other (mostly on external side) - Cholesterol stabilizes the membrane and sugars are used for cell-cell recognition (ex. White blood cell recognizing virus as foreign) 1. Transport – protein channels 3. Immune system/hormonal activity 2. Structural support 4. Enzymes A. Carbohydrates – sugars (used for recognition) 1. Glycocalyx - from proteins 2. Glycolipid - from lipids a. Blood type d. Age of cells – older cells have worn our sugars b. Docking site for foreign particles e. Immunity - cancer c. Sperm-egg recognition f. Embryological adhesions (sticky – helps pull cells together B. Junctions – (each cell can have more than one type of junction) 1. Tight Junctions – impermeable; (like solid strip glued down); the P.M.’s CELLS Page 1 of 5
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are fused together. Examples: cells in the stomach keep acid out 2. Desmosomes – offers strength and flexibility; permeable; (like rivets) Examples: Skin, heart, uterus (they all need to be able to change shape but still remain strong) 3. Gap Junctions – special connection that allows messages to flow between cells unhindered (called connexons) - Hole in the center - For communication Examples: Muscles, G.I. system (peristalsis), heart C. Specialization - Microvilli Formation – used to increase surface area of a
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Cells - Human Anatomy & Physiology CELLS I. Timothy P....

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