MCB 181 1st Edition Lecture 8 Outline of Previous Lecture I. Building PolymersII. ProteinsIII. Protein Structuresa. Primary Structureb. Secondary Structurec. Tertiary Structured. Quaternary StructureIV. Clicker QuestionsOutline of Current Lecture I. LipidsII. Permeability of a Lipid BilayerIII. Clicker QuestionsCurrent LectureI. Lipidsa. The term lipids refers to carbon-containing compounds that are found in organisms and are largely nonpolar and hydrophobici. They will dissolve in liquids that are nonpolar organic compoundsb. Lipids (unlike amino acids, nucleotides, and carbohydrates) are defined by their properties and not by their chemical structure i. The structure of the lipids varies widelyc. Lipids do not dissolve in water because of their high hydrocarbon contentd. There are three types of lipids found in cellsi. Steroids – distinguished by four-ring structure / various steroids differ from one another by the functional groups or side groups attached to those ringsii. Fats (triglycerides) – joined by an ester linkage / are not polymersiii. Phospholipids – consist of a glycerol molecule that is linked to a phosphate groups and either two chains of isoprene or two fatty acid / in some cases thephosphate group is bonded another small organic molecule such as cholinee. Amphipathic molecules are molecules that contain both a hydrophobic side and a hydrophilic side are key in the creation of the phospholipid bilayer that surrounds all cellsi. Van der waals interaction keep stable the hydrophobic region in the lipid bilayerf. Liposomes are water bound vesicles that form from stray phospholipid bilayersII. Permeability of a Lipid Bilayera. Permeability – tendency of a structure to allow a given substance to pass across a lipid bilayer more readily than othersi. The internal environment of the vesicle can become different from the outsideb. Lipid bilayers are selectively permeable which means that some substances can crossthe membrane more easily than othersi. Small nonpolar molecules move across bilayers quickly which large moleculesand charged substances either cross slowly or not at allc. Unsaturated hydrocarbon – is the hydrocarbon that contain a double bond between two carbon atoms in a hydrocarbon chain / higher permeabilityd. Saturated hydrocarbon – is the one whose hydrocarbon chain does not contain any double bond / least permeablee. Polyunsaturated hydrocarbons – is the hydrocarbon that have many double covalentbonds / highest permeabilityf. How Molecules Move Across the Membranei. Solvent – substance in which the solute dissolves / usually the component greater in larger amountii. Solute – component in a solution which changes state upon dissolving / it is the component present in a smaller quantityiii. Concentration gradient – difference in solute concentrationiv. Diffusion – spontaneous movement of molecules from an area of high concentration to low concentration (i.e., down a concentration gradient)v. Osmosis – diffusion of water across a selectively permeable membrane from a region of high water concentration (low solute concentration) to a region oflow water concentration (high solute concentration)g. Effect of tonicity on the cell:i. Hypotonic – in comparing two solutions, referring to the one with the lower solute concentration (thus, higher water concentration)ii. Hypertonic – in comparing two solutions, referring to the one with the highersolute concentration (thus, lower water concentration)iii. Isotonic – having the same solute concentration (thus, same water concentration) as another solutionIII. Clicker QuestionsAssertion ReasonAfter pickling the vegetable will lose weightBecauseThe tonicity inside of the vegetables is hypotonic in comparison to the pickling solution.Assertion is true; Reason is true; reason is the correct explanation.Assertion ReasonVan der waals interactions areproduced in regions of the proteins that are hydrophobic.BecauseHydrophobic molecules force water molecules to interact with each other.Assertion is true; Reason is