BIOL 201 Chapter 5 notes
BIOL 201 Chapter 5 notes BIOL 201L 004
Popular in Introduction to Cell Biology and Genetics
BIOL 201L 004
verified elite notetaker
Popular in Biology
This 4 page Class Notes was uploaded by Kayla Wisotzkey on Sunday October 9, 2016. The Class Notes belongs to BIOL 201L 004 at Towson University taught by Dr. Sarah Texel in Fall 2015. Since its upload, it has received 19 views. For similar materials see Introduction to Cell Biology and Genetics in Biology at Towson University.
Reviews for BIOL 201 Chapter 5 notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/09/16
Chapter 5 Structure of membranes Fluid mosaic model: a. Integral membrane proteins: embedded in the membrane b. Peripheral proteins: associated with the surface of the membrane Cellular membranes are composed of 4 components: 1) Phospholipid bilayer: provides a flexible matrix, is selectively permeable (only lets certain molecules pass through) 2) Transmembrane proteins: a collection of proteins that float in the lipid bilayer. They function in transport and communication across the membrane… many integral proteins are not fixed in the membrane Carriers: transport molecules across the membrane Channels: passively transport molecules across the membrane Receptors: transmit information into the cell 3) Interior protein network: intracellular proteins that support the membrane and reinforce its shape. They control the lateral movement of key membrane proteins, anchoring them to sites Spectrins: determine the shape of the cell Clathrins: anchor proteins to certain sites 4) Cell surface markers: glycoproteins (aid in tissue recognition) and glycolipids (aid in selfrecognition) Electron microscopy: allows biologists to closely study the cell membrane Ways to prepare a specimen for viewing: 1) Embed the tissue in a matrix and cut it into “epoxy shavings” which are put into a grid. Beams of electrons are directed through the grid 2) Freezefracturing: the tissue is embedded in a medium and quick frozen with liquid nitrogen. The frozen tissue is tapped with a knife and a crack is formed, visibly revealing the membrane Phospholipids Three classes of lipids: glycerol phospholipids, sphingolipids, and sterols Glycerol phospholipids: most diverse, vary in length and composition of their fatty acid tail Sphingolipids: contain saturated hydrogen chains sterols: groups of naturally occurring unsaturated steroid alcohols Phospholipids spontaneously form bilayers because they are amphipathic (polar heads, nonpolar tails) The nonpolar interior of a lipid bilayer stops the passage of watersoluble substances through the bilayer The phospholipid bilayer is fluid and stable because water’s affinity for hydrogen bonding never stops The hydrogen bonding of water holds the membrane together Proteins 6 key classes of membrane proteins: 1) Transport: only certain solutes can enter the cell through channels or carriers composed of proteins 2) Enzymes: cells use enzymes attached to the membrane to carry out chemical reactions on the interior surface 3) Cellsurface receptors: surface receptor proteins detect important chemical messages 4) Cellsurface identity markers: identify the cell to other cells; different proteins in each cell 5) Celltocell adhesion proteins: act by forming temporary or permanent interactions to another cell 6) Attachments to the cytoskeleton: surface proteins that interact with other cells are anchored to the cytoskeleton by linking proteins Anchoring molecules: modified lipids that have nonpolar regions that insert into the internal portion of the lipid bilayer and chemical bonding domains that link directly to proteins; attach some membrane proteins to the membrane Transmembrane domain: a hydrophobic region of a transmembrane protein that anchors it in the protein composed of hydrophobic amino acids usually arranged into helices pores: nonpolar regions of the membrane with pleated sheets that form a polar environment on the inside of the sheet. This allows molecules to pass through. integral proteins: amphipathic, hydrophilic, regions span the protein peripheral proteins: found only on one membrane’s side, attached to integral proteins or lipids Passive transport: the movement of substances across a cell’s membrane without expending energy concentration gradient: a difference between the concentrations on the inside and outside of the membrane diffusion: the net movement of dissolved molecules from a region where they are more concentrated to where they are less concentrated this will continue until the concentration is the same in all regions… after that, movement in both directions still occurs, but no net change occurs facilitated diffusion: the diffusion of molecules or ions through carrier proteins or ion channels… no energy needed, but a concentration gradient is needed channel proteins: have hydrophilic interiors that provide an aqueous channel through which polar molecules can pass carrier proteins: bind to a specific molecule that cannot cross the membrane and help it cross the membrane… change shape during the transport process The cell membrane is selectively permeable… only some substances can pass through Ion channel: has a hydrated interior that spans the membrane; allows ions to pass through 3 conditions determine the movement of the ions: 1) The concentrations on both sides of the ions 2) The voltage difference across the membrane and for the gated channels 3) If the gate is open or closed osmosis: the net diffusion of water across a membrane towards a higher concentration osmotic concentration: the concentration of all solutes in the solution hypertonic: a solution with a higher concentration of solutes than the cell; the water will rush out of the cell and it will shrink isotonic: a solution with the same concentration of solutes as the cell; the cell is healthy and normal hypotonic: a solution with a lower concentration of solutes than the cell; the water will rush into the cell and it will swell and possibly burst aquaporin: a membrane channel that allows water to cross the membrane more easily than by diffusion osmotic pressure: the force needed to stop osmotic flow Maintaining osmotic balance: a. Extrusion: some singlecelled eukaryotes use a vacuole to rhythmically contract and pump out water b. Osmotic regulation: many terrestrial animals will circulate a fluid through their body that bathes the cells in an isotonic solution c. Turgor pressure: the internal pressure in plant cells that presses its cell membrane against the cell wall, carrying rigidity Active transport: moving substances up a concentration gradient; requires the expenditure of energy… enables a cell to move substances out of the cytoplasm and into the extracellular fluid protein carriers: 1) uniporters: transports a single type of molecule/ion 2) symporters: transports 2 molecules/ions in the same direction 3) antiporters: transports 2 molecules/ions in different directions sodiumpotassium pump: ▯ 1) Three Na+ bind to the cytoplasmic side of the protein, causing the protein to change its shape. ▯ 2) In its new shape, the protein binds a molecule of ATP and cleaves it into ADP and phosphate. ADP is released, but the phosphate group is covalently linked to the protein. The protein is now phosphorylated. ▯ 3) The phosphorylation of the protein induces a second shape change in the protein. This change translocates the three Na+ across the membrane, so they now face the outside. In this new shape, the protein has a low affinity for Na+, and the three bound Na+ break away from the protein and diffuse into the extracellular fluid. ▯ 4) The new shape has a high affinity for K+, 2 bind to the extracellular side of the protein as soon as it is free of the Na+. ▯ 5) The binding of the K+ causes another shape change in the protein, this time resulting in the hydrolysis of the bound phosphate group. 6) Freed of the phosphate group, the protein reverts to its original shape, exposing the two K+ to the cytoplasm. This shape has a low affinity for K+, so the two bound K+ dissociate from the protein and diffuse into the interior of the cell. The original shape has a high affinity for Na+. When these ions bind, they initiate another cycle. coupled transport: molecules are moved against their concentration gradient using the energy stored in the gradient of a different molecule Bulk transport Endocytosis: the uptake of material into cells 1) Phagocytosis: endocytosis of a solid molecule; the plasma membrane folds inwards around the particle and engulfs it to form a vacuole 2) Pinocytosis: the process of fluid uptake in a cell receptormediated endocytosis: process by which specific macromolecules are transported into eukaryotic cells at clathrincoated pits Exocytosis: the discharge of material from vesicles at the cell surface
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'