LIFE 102 1st Edition Lecture 10 Outline of Last Lecture I. Other structures in Eukaryotic cellsII. Cytoskeleton: Network of protein fibers throughout the cellIII. Extracellular components and connections between all cells help coordinate cellular activities IV. The cell: a living unit greater than the sum of its partsOutline of Current Lecture (CH. 7: MEMBRANE TRANSPORT PROCESSES)Current LectureI. Cell membranes are fluid mosaics of lipids and proteinsII. Transport of molecules over membranesIII. Membrane transport of proteinsIV. Membrane transport of most macromoleculesCell membranes are fluid mosaics of lipids and proteinsI. The cell and it’s organelles are surrounded by one or more membranesA. Functions of membranes:a. To separate compartments and to control traffic of molecules in/out of compartmentsB. Membrane structure:a. Phospholipid bilayer with proteins imbeddedb. Membrane components can more freely though the membrane in lateral direction (fluid mosaic model)c. Membrane Proteins:i. Can be integral (inserted in membrane)ii. Or they can be peripheral (attached to surface)iii. Functions: 1. Transport of molecules over membranes2. Receptor for extracellular signals3. Recognition of other cellsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.4. Forming intercellular junctures (anchors)5. Anchoring cytoskeleton to extracellular matrix6. Catalyzing enzymatic reactions d. They are bifacial: each membrane has a cytoplasmic side and a non-cytoplasmic sidei. This is because the orientation of the membrane proteins is crucial, aswell as some lipids. ii. Example: the outside of the plasma membrane contains oligosaccharides. These can be coupled to lipids (glycolipids) or to proteins (glycoproteins) and function in cell-cell recognition.Transport of molecules over membranesI. Membranes are selectively permeable: some substances can cross easily, others cantA. Small, uncharged molecules slip through the lipid bilayer easilyB. Large, hydrophobic molecules get through easily as well (they dissolve in the hydrophobic lipids)C. Charged large molecules do not pass easily. They need carriers (transporter membrane proteins)a. Carrier proteins are substrate-specific, and can be inhibited by compounds similar to the substrate.II. 2 types of transport over membranes: passive and activeA. Passive transport: driven by diffusion, no energy required, follows the concentrationgradient (goes from high to low concentration)a. Special types of passive transport:i. Facilitated diffusion: diffusion across membranes with help of carrier protein. Substance moves down the concentration gradientii. Osmosis: diffusion of water across membranes towards the side with lowest water concentration1. Occurs when two solutions on either side of a membrane havedifferent total solute concentrations. Water diffuses towards the highest solute concentration B. Hypertonic solution: the solution with the relatively higher total solute concentrationC. Hypotonic solution: the solution with the relatively lower total solute concentrationD. Isotonic solutions: solutions with the same total solute concentrationE. Active transport: Energy-requiring process where a transport protein pumps a molecule/ion across a membrane, often against its concentration gradienta. Example: Proton pumpi. Pumps H+ over membrane, using ATPb. Example: Sodium/potassium pump:i. Pumps Na+ away from cytoplasm and K+ towards cytoplasm using ATPc. Ion pumps maintain membrane potential i. Membrane potential: unequal distribution of charged ions on two sides of a membrane, caused by pumping of ions across membraneMembrane transport of proteinsI. Proteins are the only macromolecules that can cross membrane bilayers. A. They can only cross: a. From cytosol to ERb. From cytosol to peroxisomesc. From cytosol to chloroplastsd. From cytosol to mitochondriaMembrane transport of most macromoleculesI. Most macromolecules move between different compartments of the endomembrane system through vesicle transport: substance carrying vesicles can bud off one membrane and fuse with anotherA. Special forms of vesicle transport in/out of cells: a. Exocytosis: substances leave the cells as a vesicle fuses with plasma membraneb. Endocytosis: substances enter cells in a vesicle, formed by plasma