Exam 6: Lipids, membranes, and the First Cells

The text states that ribonucleotides can diffuse through some types of liposomes.It's likely that the lipids present early in chemical evolution had short chains.Would liposomes formed from these types of lipids be more or less permeable to ribonucleotides than if early cells formed from long-chained lipids?

What most distinguishes lipids from other biomolecules is _____.

If you mechanically shook a mixture of amphipathic lipids and water,what would you expect to see when you observe the solution using an electron microscope?

Cooking oil and gasoline (a hydrocarbon)are not amphipathic molecules.Why?

What preserves the structural integrity of phospholipid bilayers?

Use the following information when answering the corresponding question(s). Rhodopsins are light-sensitive molecules composed of a protein (opsin)and retinal (derivative of vitamin A).Opsin is a membrane protein with several α-helical segments that loop back and forth through the plasma membrane.There are two classes of rhodopsins.According to Oded Beje,one class has relatively slow dynamics (a photocycle of approximately 0.5 second)and is well suited for light detection.The second class has faster dynamics (a photocycle of approximately 0.02 seconds)and is well suited for chemiosmosis pumping of protons or chloride ions across cell membranes.Oded Beje was the first,in September 2000,to report on a rhodopsin (proteorhodopsin)found in the domain Bacteria.[Source: O.Beje et al. ,Science 289 (2000): 1902.] -Sodium-potassium pumps _____.

What region of a steroid is hydrophilic?

Which of the following functions do lipids provide in a cell?

What type of functional group results when the alcohol group on glycerol reacts with the carboxylic acid group on a fatty acid?

Which of the following increases the strength of the hydrophobic interactions in lipid bilayers and thus makes them less permeable to polar molecules?

Gramicidin is an antibiotic that increases the permeability of bacterial cell walls to inorganic ions.What is the most likely mode of action of gramicidin?

Why do lipid bilayers form spontaneously?

Under what circumstances does membrane transport always require energy?

What will happen to a red blood cell (RBC),which has an internal ion concentration of about 0.9 percent,if it is placed into a beaker of pure water?

Integral membrane proteins stay in membranes because of _____.

Use the following information when answering the corresponding question(s). Rhodopsins are light-sensitive molecules composed of a protein (opsin)and retinal (derivative of vitamin A).Opsin is a membrane protein with several α-helical segments that loop back and forth through the plasma membrane.There are two classes of rhodopsins.According to Oded Beje,one class has relatively slow dynamics (a photocycle of approximately 0.5 second)and is well suited for light detection.The second class has faster dynamics (a photocycle of approximately 0.02 seconds)and is well suited for chemiosmosis pumping of protons or chloride ions across cell membranes.Oded Beje was the first,in September 2000,to report on a rhodopsin (proteorhodopsin)found in the domain Bacteria.[Source: O.Beje et al. ,Science 289 (2000): 1902.] -Cystic fibrosis (CF)is a membrane-transport disease that is caused by an allele found primarily in Caucasian populations.What mechanism fails in CF patients?

Which aspect of phospholipids is most important to the formation of bilayers?

What do phospholipids and triglycerides have in common?

You make a phospholipid bilayer with short,saturated hydrocarbon tails.You measure the permeability of this membrane to oxygen.You then double the length of the hydrocarbon tails,and remeasure membrane permeability.You then double the length of the hydrocarbon tails again,and make a third measurement of membrane permeability.You graph membrane permeability as a function of hydrocarbon tail length.Which of the graphs below best represents the data you expect?

What is the most important factor in explaining why diffusion occurs spontaneously?