1 10 12 The Cell Exam 1 Study Guide Cell the basis structural and functional unit of living organisms regardless of type all cells are composed of carbon hydrogen nitrogen oxygen and trace amounts of several other elements All cells have the same basic parts and some common functions generalized cell Because the human body has over 200 different cell types that vary in size shape an function cells are very diverse Three main parts of a cell 1 Plasma Membrane a fragile barrier the outer boundary of the cell 2 Nucleus controls cellular activity and lies in the center of the cell 3 Cytoplasm the intracellular fluid that is packed with organelles small structures that perform specific cell functions Cell identity marker glycoprotein distinguishes your cells from anyone else s Plasma Membrane Selective permeability small neutrally charged lipid soluble can freely pass Water is unique highly polar Hydrophobic tails Hydrophilic heads Fluid Mosaic Model depicts the plasma membrane as an exceedingly thin structure composed of a double layer or bilayer of lipid molecules within protein molecules dispersed in it The proteins which mostly float in the fluid lipid bilayer form a constantly changing mosaic pattern Integral proteins firmly inserted into bilayer Peripheral Proteins attach rather loosely to integral proteins or membrane lipids and are easily removed without disrupting the membrane Glycoproteins are membrane proteins with a carbohydrate group attached that protrude into the extracellular fluid The Gylococalyx is the entire sugary coating surrounding membrane made up of carbohydrate portions Plasma Membrane Specializations Microvilli minute fingerlike extensions of the plasma membrane that project from a free or exposed cell surface Increase plasma membrane surface area most often found in intestinal and kidney tubule cells Membrane Junctions 1 Glyocoproteins in the Glycocalyx act as an adhesive 2 Wavy contours of the membranes of adjacent cells fit together in a tongue and groove fashion 3 Special membrane junctions are formed a Tight junctions integral proteins in plasma membranes fuse together forming impermeable junction that encircles the cell b Desmosomes anchoring junctions c Gap Junctions communicating junction between adjacent cells Notes Ion channels allow specific ion to move through water filled pore Carrier integral carries specific substances across membrane by changing shape aka transporters Receptor integral recognize specific ligands Enzyme integral and peripheral catalyze reason inside or outside the cell Linker Integral and peripheral anchors filaments inside and outside plasma membrane providing structural ability and shape for cell may participate in movement or linking to other cells Passive Transport FROM HIGHER CONCENTRATION LOWER CONCENTRATION diffusion of solutes DIFFUSION IS AFFECTED BY AMOUNT AND STEEPNESS OF GRADIENT TEMPERATURE SURFACE AREA AND DIFFUSION DISTANCE osmosis 2 ways Through lipid bilayer simple diffusion Through aquaporins integral membrane proteins Tonicity concentration of salt solutions in blood and elsewhere o Isotonic soln normal cell o Hypertonic soln cell shrinks crenation o Hypotonic soln cell swells hemolysis facilitated diffusion requires a specific channel or a carrier molecule but no energy is used Channel mediated facilitated diffusion i e potassium channel no energy passive transport Carrier mediated facilitated diffusion i e glucose across membrane no energy passive transport filtration The process that forces water and solutes through a membrane or capillary wall by fluid or hydrostatic pressure The gradient for filtration is a pressure gradient that pushes solid containing fluid from a higher pressure area to a lower pressure area Active Transport REQUIRES ENERGY various types of transporters Energy required Antiporters carry 2 substances across membrane in opposite directions Symporters carry 2 substances across membrane in same direction ACTIVE TRANSPORT USES ENERGY TO PUSH AGAINST CONCENTRATION GRADIENT 2 types o Primary active transport o Secondary active transport Protein changes its conformation in such a manner that it pumps the bound solute across the membrane Best example of Active transport Na K pump 3NA 2K higher concentration of Na outside of cell Single Na K pump moves Na across membrane against concentration gradient the pump stores energy as the substance is pumped back across the gradient other substances are dragged along for example glucose see diagram below Vesicular Transport Vesicle small spherical sac formed by budding off from a membrane Endocytosis materials move into cell in vesicle o 3 types receptor mediated endocytosis phagocytosis relatively large or solid material is engulfed by the cell bulk phase endocytosis pinocytosis Exocytosis vesicles fuse w plasma membrane and release into extracellular fluid Transcytosis combo of both endo and exo Generating and Maintaining a Resting Membrane Potential Membrane potential voltage across the membrane Resting membrane potential 50 to 100 mV Maintaining Resting Membrane Potential 1 K diffuses along the concentration gradient out of the cell via leakage channels Loss of K results in a negative charge on the inner plasma membrane 2 As more K leaves the cell the negativity of the cell becomes great enough to attract K back into the cell Cell Environment Interactions Cells respond to extracellular chemicals such as hormones and neurotransmitters throughout the body Cell Adhesion Molecules o Cell adhesion molecules are found on almost every cell in the body Play a key role in embryonic development and wound repair o These sticky glycoproteins act as Molecular Velcro that cells use to anchor themselves to molecules in extracellular space as well as each other The arms that migrating cells use to haul themselves past one another SOS signals sticking out from the blood vessel lining that rally protective white blood cells to a nearby infected or injured area Mechanical sensor that respond to local tension at the cell surface by stimulating synthesis or degradation of adhesive membrane junctions Transmitters or intracellular signals that direct cell migration proliferation and specialization Role of Membrane Receptors Contact Signaling actual coming together and touching of cells the means by which cells recognize each other Chemical Signaling o A ligand is a molecule that binds w a receptor Neurotransmitters nervous system signals Hormones endocrine system
View Full Document
Unlocking...