Chapter 3: 2 Types of Cells

Chapter 3 2 Types of Cells: ① sex cells (germ sells or reproductive cells) ↳ male sperm ↳ female oocytes ② Somatic cells ↳ all body cells other than sex cells Plasma Membrane Plasma membrane: the outer part of a cell, made of a phospholipid bilayer. Cholesterol is a steroid used to "stiffin" the membrane making it less fluid and permeable ↳ contains the cytoplasm (cytosol = intracellular fluid) and organelles Functions: · Physical isolation - a physical barrier separating the cytoplasm from extracellular fluid - · Regulation of exchange with the environment - controls what goes in and out of the cell · Sensitivity to the environment - recognizing and responding to changes · Structural Support Membrane Proteins: ① Integral proteins (transmembrane proteins) Types of membrane proteins: ② Peripheral proteins · Enzymes - ↳ Within the membrane ↳ bound to the inner or outer surface of membrane Membrane Carbohydrates - · proteoglycans, glycoproteins, and glycolipids ↳ extend outside cell membrane ↳ forms sticky "sugar coat" called glycocalyx · Functions of Glycocalyx: ↳ lubrication and protection ↳ anchoring and locomotion ↳ specificity in binding (function as receptors) ↳ Recognition (immune response) · Anchoring proteins · Recognition proteins · Receptor proteins · Carrier proteins · Channels Movement across the plasma membrane · Selective permeability · passive or active (ATP) · Passive Processes: ↳ Diffusion ↳ Osmosis ↳ Facilitated Diffusion · Active Processes: ↳ Active Transport ↳ Endocytosis ↳ Exocytosis Factors that influence rate of diffusion: Passive Transport · Distance an area of higher concentration to lower concentration · Temperature and low concentrations of a substance · Electrical Forces · The net movement of substances (molecules/ions) from · Ion and molecule size · Concentration Gradient: the difference between the high · Concentration Gradient · Molecules in continuous random motion tend to become more evenly distributed over time · Simple diffusion: alcohol, fatty acids, and steroids can enter cells easily because they can diffuse through the lipid portions of the membrane (lipophilic) · Channel-mediated diffusion: very small passages created by transmembrane proteins for things that cannot easily diffuse through the phospholipid bilayer (facilitated diffusion) · Osmosis: diffusion of water across a selectively permeable membrane ↳ osmosis is movement of water, diffusion is movement of solutes Osmotic Pressure: the force that water moves into a solution because of solute concentration Hydrostatic Pressure: the force applied to water to push it out somewhere Filtration: transport of water/molecules thru plasma membrane by force of hydrostatic pressure ↳ HP - pressure exerted by standing fluid on an object ↳ eg.) blood capillaries Aquaporins: water channels that help movement of water Osmolarity/Osmotic Concentration: total solute concentration in an aqueous solution Tonicity: how the solution effects the shape of a cell ↳ isotonic: no osmotic flow occurs and the cell is a normal size and shape ↳ hypotonic: water flows in the cell causing it to swell all big or burst (hemolysis) · more solutes in cell than outside ↳ hypertonic: water flows out of the cell causing it to shrivel (crenation) · more solutes outside cell than inside Assisted Membrane Transport · Large and/or poorly lipid-soluble molecules cannot cross membrane on their own ① Carrier-mediated transport ② Vesicular transport ① Carrier-mediated Transport · carrier proteins (integral proteins) bind to specific ions or substrates and carry them across the plasma membrane (can also change their shape so they can fit) · 3 important characteristics: ↳ specificity ↳ saturation ↳ regulation · Passive (facilitated diffusion) = with the gradient ↳ binds to receptor site, changes its shape and rides it into cell · Active (active transport) = against gradient ↳ requires ATP ↳ Primary Active Transport: energy from ATP directly (Na-K exchange pump) ↳ Secondary Active Transport: indirect energy from somewhere else ② Vesicular Transport · the transport of materials using membranous sacs (vesicles) that form at or fuse with the plasma membrane · requires energy expenditure by the cell 2 forms of vesicular transport: 1. Endocytosis: into the cell ↳ receptor-mediated endocytosis ↳ pinocytosis ↳ phagocytosis 2. Exocytosis: out of the cell ↳ transcytosis Sections 3-2, 3-3, and 3-8 will be in a separate “review” section as we will not be directly tested on them but need to know the anatomy and terms (on eclass supplementary)