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Definition
| any oranic substance that does not dissolve in water, but dissolves well in nonpolar organic solvents. Lipids include fatty acids, fats, oils, waxes, steroids, and phospholipids |
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| Most lipids contain units of isoprene or... |
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Definition
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Definition
| a class of lipid with a characteristic four-ring hydrocarbon structure (ex: cholesterol). |
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| Describe the compostion of a fat molecule. |
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Definition
| Fats are nonpolar molecules composed of three fatty acids that are linked to a three-carbon molecule called glycerol |
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Term
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Definition
| the covalent bond formed by a condensation reaction between a carboxyl group and a hydroxyl group. Ester linkages join fatty acids to glycerol to form a fat or phospholipid |
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Term
| What are the four major components of a phospholipid? |
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Definition
-glycerol
-a phosphate group
-small organic molecule that is charged or polar
-two fatty acid tails (nonpolar, saturated/unsaturated) |
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Term
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Definition
| compounds that contain both hydrophilic and hydrophobic elements/regions. An example would be phospholipids |
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| If you add phospholipids (with two fatty acid chains) to a beaker of water, what structure will spontaneously form? Why? |
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Definition
| A lipid bilayer will occur because the hydrophilic heads interact with water while the hydrophobic tails interact with one antoher |
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| What structure will form if detergent molecules (with one fatty acid chain) are added to a beaker of water? Why? |
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Definition
| A micelle will form if detergen molecules are added to a beaker of water for the same reason, but there is less room so it forms the circle shape |
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Term
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Definition
| spherical, sealed lipid layer created (only from phospholipids) in lab; "artificial membrane" |
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| How are liposomes and planar bilayers used to study lipid bilayers? |
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Definition
| Liposomes and planar bilayers are used to study lipid bilayers by researching what happens when a known ion or molecule is added to one side of a lipid bilayer; also planar bilayers checks to see how rapidly different solutes can cross the membrane (if it all) when a) different types of phospholipids are used to make the membrane or b) if proteins or other molecules are added to the membrane |
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Term
| How permeable is the lipid bilayer to each of the following types of substances: large uncharged polar molecules, small uncharged polar molecules, ions, and hydrophobic molecules? |
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Definition
| Large uncharged polar molecules rarely cross; small uncharged polar molecules are able to cross generally; ions rarely, if ever, cross; hydrophobic molecules cross frequently |
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Term
| A lipid bilayer with _______ and ________ hydrocarbon (fatty acid) tails have a higher permeability and fluidity |
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Definition
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| A lipid bilayer with ______ and _______ hydrocarbon (fatty acid) tails have lower permeability and fluidity |
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Definition
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Term
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Definition
| all the carbon-carbon bonds are single bonds, meaning it holds the maximum amount of hydrogen |
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Definition
| at least one carbon-carbon is a double bond; double bonds produce kinks in hydrocarbon chains |
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Definition
| is a transconformation fat, meaning that there is a hydrogenation of unsaturated fats; not found in nature, only manufactured |
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Term
| How does temperature affect membrane permeability and fluidity? |
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Definition
| The higher the temperature the higher the fluidity and vice versa |
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Term
| At warm temperatures, increasing cholesterol will _______ fluidity |
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Definition
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| At cold temperatures, increasing cholesterol will ______ fluidity |
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Definition
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| What type of movement is common for phospholipids in cell membranes? How is this movement related to the fluidity of the membrane? What type of movement is very rare for a phospholipid in a cell membrane? |
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Definition
| Phospholipids are in constant lateral motion, but rarely flip to the other side of the bilayers. This is to increase fluidity |
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Term
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Definition
| the spontaneous movement of a substance from high concentration to low concentration |
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Definition
| high concentration to low concentration spontaneously |
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Definition
| high concentration to low concentration however it requires a protein |
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Definition
| diffusion of water (pure water); water moves until concentration of solute is equal OR water moves until pure water concentration is equal |
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Term
| In a ______ solution an animal cell will shrivel (water will move out of cell) |
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Definition
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Term
| In a ______ solution an animal cell will swell (or perhaps burst) because water moves into the cell |
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Definition
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Term
| In an _______ solution an animal cell will remain normal because concentrations are equal |
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Definition
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Term
| Do plant cells respond the same way as animal cells in these solutions? |
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Definition
| No, because of their cell wall, turgor pressure, and vacuole. |
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Term
| The ______ molecular weight, the _______ the rate of diffusion |
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Definition
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Term
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Definition
| hypothesis that the plasma membrane and organelle membranes consist of proteins embedded in a fluid phospholipid bilayer |
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Term
| Peripheral membrane protein |
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Definition
| proteins on one side or the other of the lipid bilayer (don't pass through); made up of entirely polar amino acids |
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Term
| Integral membrane protein |
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Definition
| proteins that pass through the lipid bilayer; are amphipathic (meaning they have polar/charged, hydrophilic amino acid residues on the outside and nonpolar hydrophobic residues on the inside) |
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Term
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Definition
| when a membrane protein transports a substance from low concentration to high concentration; it's up/against concentration gradient; requires input of energy and carrier protein |
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Term
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Definition
| transporter; conformational change on both sides; like a shuttle; distinct binding sites for molecules |
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Term
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Definition
| has open/closed state; like a tunnel |
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Term
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Definition
| the combined effect of an ion's concentration gradient and electrical (charge) gradient across a membrane that affects the diffusion of ions across the membrane |
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Term
| Describe the action of the sodium-potassium ATPase pump |
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Definition
-binding sites with a high affinity for sodium ions are available
-three sodium ions from the inside of the cell bind to these sites and activate the ATPase activity in the pump
-a phosphate group from ATP is transferred to the pump. When the phosphate group attaches, the pump changes its shape in a way that opens the ion-binding pocket to the external environment and reduces its affinity for sodium ions
-the sodium ions leave the protein and move to the exterior of the cell
-in this conformation, the pump has binding sites with a high affinity for potassium ions facing the external environment
-two potassium ions from the outside the cell bind to the pump
-when the potassium is bound, the phosphate group is cleaved from the protein and its structure changes in response--back to the original shape with ion-binding pocket facing the interior of the cell. Then the cycle repeats |
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Term
| With respect to a concentration gradient, explain what is meant by spontaneous movement versus nonspontaneous movement of molecules |
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Definition
-A spontaneous reaction (going down a concentration gradient) goes along with the order of the univers.
-A nonspontaneous doesn't go along with the order of the universe and requires energy to go up the concentration gradient |
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Term
| A defect in what transport (channel) protein is responsible for the human genetic disorder cystic fibrosis? What are the symptoms of this disease? Why do these symptoms occur? |
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Definition
| CFTR- cystic fibrosis transconductance regulator; symptoms of this disease is lung/breathing problems; these symptoms occur because water doesn't wash and lubricate the lumen of the lung, thus resulting in mucus build-up and thickening |
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Term
| How is the structure of saturated fats different from that of unsaturated fats? |
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Definition
| the hydrocarbon tails in a saturated fat have the maximum number of hydrogens possible |
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Term
| What distinguishes amphipathic liquids from other lipids? |
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Definition
| Amphipathic lipids have polar and nonpolar regions |
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Term
| If a solution surrounding a cell is hypertonic relative to the inside of the cell, how will the water move? |
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Definition
| It will move out of the cell via osmosis |
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Term
| When does a concentration gradient exist? |
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Definition
| When solute concentrations differ on the two sides of a membrane |
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Term
| In terms of structure, how do channel proteins differ from carrier proteins? |
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Definition
| Channel proteins form pores in the membrane and carrier proteins undergo conformational changes to shuttle molecules or ions across the membrane |
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Term
| Explain why phospholipids form a bilyer in solution, and why the process is spontaneous. |
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Definition
| Hydrophilic phosphate-containing head groups interact with water; hydrophobic hydrocarbon tails associate with each other; a bilayer is more stable than are independent phospholipids in solution |
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Term
| Ethanol (C2H5OH) is the active ingredient in alcoholic beverages. Would you predict that this molecule crosses lipid bilayers quickly, slowly, or not at all? Explain. |
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Definition
Ethanol's polar hydroxyl group reduces the speed at which it can cross a membrane, but its small size and lack of charge would allow it to slowly cross membranes
-between the rates of water and glucose transport |
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Term
| In an experiment, you create two groups of liposomes-one made from red blood cell membranes and the other from frog egg cell membranes. When placed in water, those made with red blood cell membranes burst more rapidly than those made from frog membranes. What is the best explanation for these results? |
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Definition
| The red blood cell liposomes contain aquaporins, which are not abundant in the frog cell liposomes |
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| Unicellular organisms live in a wide range of habitats, from the hot springs in Yellowstone National Park to the freezing temperatures of the Antarctic. Make a prediction about the saturation status of the membrane phospholipids in organisms that live in extremely cold environments versus those that live in extremely hot environments. Explain. |
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Definition
| Organisms that live in very cold environments are likely to have highly unsaturated phospholipids. The kinks in unsaturated hydrocarbon tails keep membranes fluid and permeable, even at low temperature. Organisms that live in very hot environments would likely have phospholipids with saturated tails, to prevent membranes from becoming too fluid and permeable |
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