Coursehero >> Ohio >> Toledo >> BIOL 2180

Course Hero has millions of student submitted documents similar to the one below including study guides, homework solutions, papers, exam answer keys and textbook solutions.

Five Chapter Cellular Membranes 1) Membranes a) Regulate traffic in and out of the cell b) Lipids i) Create an impermeable barrier to water-soluble molecules ii) Establish the physical integrity of the membrane iii) Lipids are like the water of a lake in which proteins "float" c) Proteins are embedded in the membrane d) Carbohydrates are attached to lipid or protein moecules i) On the outside of the plasma membrane 2) Fluid Mosaic Model 3) Lipids a) Make up the bulk of the membrane b) Mostly phospholipids c) Organized into a bilayer d) Hydrophilic regions face the outside of the cell and the cytoplasm e) Hydrophobic regions face each other f) Interior of the membrane is fluid i) Allows some molecules to move laterally within the plane of the membrane ii) Lipid molecules can move laterally as well iii) A phospholipid molecule rarely flip-flops in the membrane (1) This requires help from special proteins 4) Membranes a) All biological membranes have similar structures b) Some have different lipid and protein composition c) Some have 25% cholesterol i) Important in membrane integrity ii) Can either increase or decrease membrane fluidity 5) Effects of Cholesterol depends on... a) The fatty acid composition of other lipids b) Membrane fluidity decreases with decreases in temperature i) Decline in membrane function ii) Organisms change the lipid composition of membranes under cold conditions 6) Membrane Proteins a) Asymmetrical distribution b) Usually 1 protein for every 25 phospholipids i) Mitochondrial membrane 1 protein for every 15 phospholipids ii) In myelin 1 protein for every 70 phospholipids c) many proteins have both hydrophilic and hydrophobic regions i) form noncovalent interactions with lipids in the membrane d) Integral membrane proteins i) Have long stretches of hydrophobic amino acids ii) Completely crosses the bilayer iii) Form an alpha-helical region that interacts only with the hydrophobic core iv) Hydrophilic ends extend into the aqueous environment 7) Transmembrane Proteins a) Extend from the membrane on both sides b) Have a specific orientation i) Outside of the cell = shaped like a receptor ii) Inside portion changes shape in response to signal binding 8) Peripheral Proteins a) Lack hydrophobic regions b) Interact with exposed regions of integral proteins or phospholipids 9) The Membrane is Fluid a) Many proteins are free to move around in the membrane b) Some proteins are anchored to a specific region of the membrane i) Cytoskeleton ii) Lipid rafts groups of lipids in a semisolid state iii) Extracellular matrix 10) Membrane Carbohydrates a) Glycolipids i) Carbohydrate + lipid ii) Serve as recognition signals for cell-cell interactions iii) Can change when a cell becomes cancerous b) Glycoproteins i) Carbohydrate + protein ii) Cell recognition iii) Use an "alphabet" of single sugars to create a diverse set of messages 11) Similar cells group together a) Recognition i) One cell specifically binds to another cell of a specific type b) Adhesion i) The relationship between two cells is "Cemented" c) Tissue-specific and species-specific aggregation occur because of PM recognition proteins 12) Cell Adhesion a) Sponges b) If a sponge is disaggregated it can reaggregate to form another sponge c) Only cells from the same species adhere to one another d) Species-specific cell adhesion molecules fit together to form the tissues of the sponge 13) Recognition Proteins a) Proteins on the cell's surface i) In sponges it is a huge membrane glycoprotein ii) Recognition part is exposed to the envirionment b) Homotypic i) The same molecule sticks out of both cells c) Heterotypic i) Binding between cells with different proteins 14) Specialized Cell Junctions a) Specific cells adhere to one another forming tissues b) Epithelial tissues line body cavities and cover body surfaces c) Three types of junctions: i) Tight junctions (1) Seal tissues and prevent leaks (2) Functions: (a) Prevent the movement of substances through the intercellular spaces (b) Restrict the migration of membrane proteins and phospholipids (3) Polarize and stabilize the cell ii) Desmosomes (1) Hold cells together, acting like spot welds (2) Plaque dense cytoplasmic structure (a) Plaque proteins (b) Attached to fibers in the cytoplasm iii) Gap junctions (1) Facilitate communication between cells (2) Made up of specialized protein channels (3) Dissolved molecules, electrical signals 15) Selective Permeability a) Membrane Transport i) Passive Transport (1) Does not require the input of any outside energy (2) Energy is in the substances themselves (3) Diffusion ii) Active Transport (1) Requires the input of chemical energy (2) Does not use concentration gradients 16) Diffusion a) The process of random movement toward a state of equilibrium b) Movement of molecules from areas of higher concentration to areas of lower concentration c) Does diffusion lead to uniform distribution of solutes? d) Solutes distribute themselves by diffusion, uniformly and independently of each other 17) Diffusion Rate a) The of rate diffusion is dependent on: i) Temperature ii) The physical size of the solute iii) Electrical charge of the solute iv) The concentration gradient b) Very fast over short distances i) Not adequate to distribute substances over long distances 18) Diffusion across the Bilayer a) Diffusion rate is influenced by membrane permeability i) Steroids diffuse easily across the membrane ii) A protein of similar size will have a slower diffusion rate b) Generally impermeable to hydrophilic molecules i) Except water 19) Osmosis a) The diffusion of water across a membrane i) Net movement b) Completely passive process c) Water channels called aquaporins d) Molecules diffuse from an area of higher concentration to an area of lower concentration i) Water diffuses from an area of its higher concentration (lower solute concentration) to an area of its lower concentration (high solute concentration) 20) Types of Solutions a) Isotonic i) Two solutions of equal solute concentration b) Hypertonic i) A solution that has a higher solute concentration than the solution it is being compared to c) Hypotonic i) A solution that has a lower solute concentration than the solution it is being compared to d) The integrity of cells depends on the maintenance of a constant solute concentration i) Ex. RBCs in plasma 21) Facilitated Diffusion a) Polar substances such as amino acids and sugars cannot diffuse freely across the PM b) Involves proteins embedded in the membrane i) Channel proteins (1) Proteins that form channels through the membrane (2) Have polar amino acids and water inside the channel pore (3) Ion channels (a) Gated only open when bound to a specific molecule or when signaled to do so (b) Once open, millions of ions can rush through per second (c) Direction of diffusion is dependent on the concentration gradient (d) Specific for one type of ion ii) Carrier proteins (1) Involves the actual binding of a transported substance to a membrane protein (2) Sugars and amino acids (3) Diffusion is dependent on the concentration gradient (a) The concentration gradient can be maintained by metabolizing the transported substance (i) Glucose (b) Saturation limits the number of molecules that can be transported 22) The Glucose Transporter a) Carrier proteins allow glucose to enter a cell at a faster rate than would be possible by simple diffusion across the membrane barrier 23) Active Transport a) Ions or molecules move across the membrane from an area of lower concentration to an area of higher concentration i) Against the concentration gradient b) Requires the input of chemical energy i) energy comes from ATP hydrolysis c) Transporter Proteins i) Uniport (1) Move one type of molecule, like Ca2+, in one direction ii) Symport (1) Moves two different molecules in the same direction (2) Amino acids iii) Antiport (1) Moves two different molecules in opposite direction (2) Na+-K+ pump d) Primary Active Transport i) Uses the energy from ATP hydrolysis directly to pump ions across the membrane ii) Sodium potassium pump e) Secondary Active Transport i) Uses the energy of ATP indirectly ii) Energy is supplied by an ion concentration gradient iii) Concentration gradient is established by primary active transport iv) Flow of Na+ down its concentration gradient supplies the energy for glucose transport 24) Endocytosis a) Bring macromolecules, large particles, small molecules, and other cells into cells b) Molecules are too large and/or charged to cross the plasma membrane c) Three types i) Phagocytosis (1) Large molecules and whole cells (2) Used as a feeding process by unicellular protists (3) White blood cells defend the body against invading foreign cells ii) Pinocytosis (1) Brings small dissolved substances and fluids into the cell (2) Endothelium quickly gets fluids from the blood (3) Non-specific iii) Receptor-mediated endocytosis (1) Highly specific (2) Receptor proteins are exposed on the surface fo the cell in coated pits (3) Clathrin molecules form the coat of the pits (4) The coated pit invanginates once a receptor binds to its macromolecule forming a coated vesicle (5) Cholesterol uptake (a) Lipoproteins = cholesterol + triglycerides + proteins (b) Low density lipoproteins (LDLs) are recycled in the liver (c) Uptake of LDLs is mediated by receptor mediated endocytosis (d) The LDL is digested by a lysosome and the cholesterol is used by the cell (e) Familial hypercholesterolemia 25) Exocytosis a) Removing materials from cells i) Undigested materials, digestive enzymes, neurotransmitters b) A protein on the secretory vesicle binds to a protein on the plasma membrane c) Membranes merge and create an opening to the outside d) Other cell membrane functions i) Information processing ii) Energy transformation iii) Organizing chemical reactions 26) Chapter Summary a) Membranes consist of lipids, proteins, and carbohydrates b) Cell-cell junctions c) Passive membrane transport i) Diffusion ii) Facilitated diffusion d) Active transport i) Primary ii) Secondary e) Endocytosis and exocytosis

Find millions of documents here - Study Guides, Homework Solutions, Papers, Exam Answer Keys and more. Course Hero has millions of course related materials that will enable you to learn better, faster and get an A in all your courses.
Below is a small sample set of documents: