Chapter 11 (Membranes)- MCAT Prep Questions

*Which of the following molecules would not require a transport protein to cross the plasma membrane.* A. Sodium ion B. Potassium ion C. Glucose D. Citrate E. Carbon Dioxide

Carbon Dioxide

*Which fatty acid tail would contribute most to the stability of the cell membrane of a thermophilic bacterium?* A. B. C. D.

A.

*The sodium potassium pump helps to maintain electrolyte gradients through the use of ATP. Which of the following best describes this type of transport?* A. Diffusion B. Facilitated Diffusion C. Filtration D. Active Transport E. Osmosis

Active Transport

*Which statement best describes how cholesterol affects cell membrane fluidity?* A. Cholesterol increases fluidity at high temperatures and decreases fluidity at low temperatures. B. Cholesterol decreases fluidity at high temperatures and decreases fluidity at low temperatures. C. Cholesterol increases fluidity at high temperatures and increases fluidity at low temperatures. D. Cholesterol decreases fluidity at high temperatures and increases fluidity at low temperatures.

Cholesterol decreases fluidity at high temperatures and increases fluidity at low temperatures. **

*Which molecule diffuses through a membrane most quickly?* A. Ethylene B. Urea C. Benzene D. Glucose

Ethylene

*Glucose typically enters the cell through which mechanism?* A. Pinocytosis through a channel protein B. Simple diffusion through the cell membrane C. Facilitated diffusion through a carrier protein D. Active transport by a glucose transport protein

Facilitated diffusion through a carrier protein

*The rate of osmosis across a cell membrane depends upon which of the following?* I: Intracellular solute concentration II: Extracellular solute concentration III: Polarity of solutes IV: Molecular weight of solutes V: The presence of aquaporins A. I, II, and V B. I and II C. I, III, and IV D. I, II, III, IV, and V

I, II, and V

*The fluidity of plasma membranes___________.* A. Increases as the percent of unsaturated fatty acids increases B. Increases as the length of the fatty acid increases C. Is independent of the nature of fatty acids D. Increases as the percent of unsaturated fatty acids decreases E. Increases as the percent of saturated fatty acids increases

Increases as the percent of unsaturated fatty acids increases

*Which of the following are true about sodium-potassium pump.* A. It is a symporter because it transport sodium ions to the inside of the cell and potassium ions to the outside of the cell. B. It is an antiporter because it transport sodium ions to the outside of the cell and potassium ions to the inside of the cell. C. It is a symporter because it transport sodium ions to the outside of the cell and potassium ions to the inside of the cell. D. It is an antiporter because it transport sodium ions to the inside of the cell and potassium ions to the outside of the cell.

It is an antiporter because it transport sodium ions to the outside of the cell and potassium ions to the inside of the cell.

*Which intermolecular process primarily drives the formation of a bilayer when phospholipids are added to water?* A. The ordered arrangement of a bilayer is more favorable than the disordered state of individual free-floating phospholipids. B. Lipids cause water to arrange in an ordered, unfavorable cage-like structure. Forcing lipids into a bilayer reduces this effect. C. A bilayer arrangement maximizes the strength of Van der Waals forces among phospholipids. D. Phospholipids self-assemble into a bilayer due to the strong affinity they have for each other.

Lipids cause water to arrange in an ordered, unfavorable cage-like structure. Forcing lipids into a bilayer reduces this effect.

*Soap bubbles form because fatty acids salts organize into:* A. Lysosomes B. Micelles C. Phospholipid bilayers D. Hydrogen bonds

Micelles

*Which type of membrane protein is most likely to be a hormone?* A. Integral protein B. Lipid-bound protein C. Peripheral protein D. Steroid

Peripheral protein

*Which of the following best describes the composition of the plasma membrane of an animal cell?* A. Cholesteryl esters, proteins, and small but significant amount of triglycerides. B. A lipid bilayer formed mainly from cholesterol with proteins attached to both sides. C. Phosphoproteins and cholesterol. D. Phospholipids, sphingolipids, cholesterol and protein, with some carbohydrates. E. Lipoproteins in which triglycerides are a major component.

Phospholipids, sphingolipids, cholesterol and protein, with some carbohydrates.

*Which of the following is true of an electrochemical gradient?* A. Proton Motive force in the mitochondria is generated from a type of electrochemical gradient. B. To maintain the gradient, it is essential to have equal concentrations of a molecule on the intracellular sides of a membrane. C. Electrochemical gradients are only created by neutral molecules. D. Electrochemical gradients drive the movement of molecules in active transport.

Proton Motive force in the mitochondria is generated from a type of electrochemical gradient.

*Cholera affects millions of people around the world. It causes diarrhea, which can lead to dehydration and even death. Cholera toxin affects a chloride transporter that secretes chloride ion into the lumen of the small intestine. How does cholera toxin lead to dehydration?* A. The toxin turns off the transporter, so the negatively charged chloride pushes water into the lumen B. The toxin turns off the transporter, so water is no longer exchanged for chloride ion C. The toxin turns on the transporter, and water follows the ion due to osmosis D. The toxin turns on the transporter, and water is actively transported with the ion

The toxin turns on the transporter, and water follows the ion due to osmosis

*Assume that there are thirty sodium ions outside the cell and twenty potassium ions inside the cell. What will happen after one cycle of the sodium potassium pump?* A. There will be 33 sodium ions outside the cell and 22 potassium ions inside the cell. B. There will be 28 sodium ions outside the cell and 17 potassium ions inside the cell. C. There will be 27 sodium ions outside the cell and 18 potassium ions inside the cell. D. There will be 32 sodium ions outside the cell and 23 potassium ions inside the cell.

There will be 33 sodium ions outside the cell and 22 potassium ions inside the cell.Active Transport

*In nerve cells, sodium-potassium pumps exchange two K+ for three Na+ across the cell membrane. What is the primary purpose of this exchange?* A. To increase the concentration of K+ outside the cell B. To store electrical and chemical potential energy C. To propagate an action potential D. To increase the concentration of Na+ inside the cell

To store electrical and chemical potential energy

*Which statement represents a notable difference between simple diffusion and facilitated diffusion?* A. Unlike simple diffusion, the rate of facilitated diffusion is limited by the number of transport proteins in the membrane. B. Unlike simple diffusion, facilitated diffusion can occur in any type of cell. C. Unlike simple diffusion, facilitated diffusion requires energy in the form of ATP. D. Unlike simple diffusion, facilitated diffusion can transport ligands against a concentration gradient.

Unlike simple diffusion, the rate of facilitated diffusion is limited by the number of transport proteins in the membrane.

*Compared to a typical animal cell, the cell membranes on the paw of a polar bear would most likely have an increased concentration of which macromolecule?* A. Potassium channel proteins B. Unsaturated phospholipids C. Saturated phospholipids D. Aquaporin proteins

Unsaturated phospholipids

*How do potassium ions travel as they move into the cell?* A. Down the concentration gradient and down the membrane potential B. Up the concentration gradient and down the membrane potential C. Up the concentration gradient and up the membrane potential D. Down the concentration gradient and up the membrane potential

Up the concentration gradient and down the membrane potential