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Chapter_2_The_Cell - Chapter 2 The Cell Basic Unit of...

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Chapter 2 The Cell: Basic Unit of Structure and Function I. Plasma (Cell) Membrane a. Plasma membrane aka cell membrane aka plasmalemma b. Thin outer border of cell c. Flexible layer that separates internal (intracellular) components of a cell from external environment and extracellular materials d. Vital, selective barrier that regulates passage of gases, nutrients, and waster b/t the internal and external environment e. Extracellular fluid aka interstitial fluid thin external layer of fluid that’s extensive enough to accommodate all required entry and exit movements f. Doesn’t increase as fast as cell’s volume so cell may reach point when there’s not enough membrane surface for transport –so cells remain small in order to get enough nutrients and dispose wastes g. Fluid mosaic model II. Composition and Structure of Membranes a. Lipids – materials insoluble in water i.e. fats, oils, steroids i. Phospholipids – polar; hydrophilic head and 2 hydrophobic tails and element phosphate ii. phospholipids bilayer – ensures that intracellular fluid (fluid w/in cell) and extracellular fluid (fluid outside cell) stay where they are iii. Cholesterol – steroid 1. HDL – high density lipoprotein 2. LDL – low density lipoprotein iv. Glycolipids – lipid w/ attached carb groups b. Proteins – complex, diverse molecules composed of amino acids c. Integral proteins embedded in and extend across bilayer; act as membrane channels and receptors d. In order for a drug to be therapeutic or toxic, it must penetrate the membrane or bind to these glycol-receptors aka the integral proteins III. General Functions of Plasma Membrane a. Communication – contains receptors that recognize and respond to molecular signals b. Intercellular connection – establishes a flexible boundary, protects cellular contents, and supports cell structure c. Physical barrier – phospholipid bilayer separates substances inside and outside cell d. Selective permeability – regulates entry and exit of ions, nutrients, and waste molecules though membrane IV. Protein-Specific Functions of Plasma Membrane a. Transport – sometimes requires ATP b. Intercellular attachment c. Anchorage for cytoskeleton d. Enzyme (catalytic) activity e. Cell-cell recognition f. Signal transduction V. Transport Across the Plasma Membrane a. Transport proteins aka carrier proteins – helps attract and assist specific in/external molecules to membrane b. Plasma membrane structure – allows water to diffuse and simple sugars to not c. Concentration gradient – substance that diffuses where it is more concentrated to where it is less concentrated d. Ionic charge – influences molecular movement across membrane e. Lipid solubility – lipid-soluble easily diffuse through bilayer f. Molecular size – small molecules can diffuse whereas large need transport VI. Passive Transport – along concentration gradient a.
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