Cell Bio Chapter 14

Which of the following lipids are distinctly enriched in lipid rafts? a. Cholesterol and sphingolipids b. Glycolipids and phosphatidylinositol c. Phosphatidylcholine and sphingomyelin d. Phosphatidylethanolamine and phosphatidylserine

a. Cholesterol and sphingolipids

Which of the following statements about ion channels is true? a. They are opened either by the binding of ligands or by changes in electric potential across the membrane. b. They require ATP. c. They are open most of the time. d. The rate of transport is slow compared to the rate of transport via carrier proteins.

a. They are opened either by the binding of ligands or by changes in electric potential across the membrane.

The pH of endosomes and lysosomes is a. acidic. b. alkaline. c. neutral. d. unknown.

a. acidic.

Mutations in the internalization signal of endocytic receptors prevent their interaction with a. adaptor proteins. b. caveolin. c. clathrin. d. dynamin.

a. adaptor proteins.

LDL uptake by cells is one of the functions of a. receptor-mediated endocytosis. b. phagocytosis. c. caveolae. d. ABC transporters.

a. receptor-mediated endocytosis.

Which of the following statements about ABC transporters is false? a. Each family member has an ATP-binding cassette. b. Each member of the family is a Cl- channel. c. They are the largest family of membrane transporters in humans. d. Each member of the family has shared domain structure features.

b. Each member of the family is a Cl- channel.

Which of the following statements about the relative concentrations of Na+ and K+ inside and outside of a typical mammalian cell is true? a. The concentration of Na+ and K+ outside the cell is about 30 times higher than inside the cell. b. The concentration of Na+ outside the cell is about 30 times higher than inside the cell, and the concentration of K+ inside the cell is 10 to 30 times higher than outside the cell. c. The concentration is the same for both ions, but there is a Cl- ion concentration gradient across the plasma membrane. d. The concentration of Na+ inside the cell is 30 times higher than outside the cell, and the concentration of K+ outside the cell is 10 times higher than inside the cell.

b. The concentration of Na+ outside the cell is about 30 times higher than inside the cell, and the concentration of K+ inside the cell is 10 to 30 times higher than outside the cell.

A feature common to most transmembrane proteins is a. a phosphorylated exterior domain. b. an α-helical region of about 20 to 25 hydrophobic amino acids. c. an amino acid sequence rich in acidic residues. d. a structure consisting almost exclusively of β-sheets.

b. an α-helical region of about 20 to 25 hydrophobic amino acids.

Two examples of membrane lipids that are present in small amounts are a. cholesterol and phosphatidylcholine. b. glycolipids and phosphatidylinositol. c. phosphatidylcholine and sphingomyelin. d. phosphatidylethanolamine and phosphatidylserine.

b. glycolipids and phosphatidylinositol.

Membrane proteins are able to move a. from the inner to the outer surface of a membrane. b. laterally within the plane of a membrane. c. from apical to basal surfaces of intestinal epithelial cells. d. only if attached to microtubules or microfilaments.

b. laterally within the plane of a membrane.

Which of the following are integral membrane proteins that do not contain a transmembrane α helix? a. Band 3 b. Glycophorins c. Glycosylphosphatidylinositol (GPI)-anchored proteins d. Spectrins

c. Glycosylphosphatidylinositol (GPI)-anchored proteins

The resting plasma membrane potential as described by the Nernst equation is the sum of the movement of many ions. However, in practice, the movement of _______, a single ion, is the major component determining membrane potential. a. Ca2+ b. Cl- c. K+ d. Na+

c. K+

Transport of glucose into the intestinal epithelium is driven by ion gradients established by the a. ATP pump. b. H+ pump. c. Na+-K+ pump. d. K+ channel.

c. Na+-K+ pump.

Active transport differs from facilitated diffusion in that a. ions are not transported via active transport, only by facilitated diffusion. b. active transport requires a protein component, whereas facilitated diffusion occurs by simple diffusion through the plasma membrane. c. active transport involves the transport of molecules up their concentration gradient. d. active transport involves a conformational change in the transport molecule.

c. active transport involves the transport of molecules up their concentration gradient.

The ingestion of large particles by cells is a form of endocytosis known as a. fluid phase endocytosis. b. pinocytosis. c. phagocytosis. d. transcytosis.

c. phagocytosis.

Which of the following statements about the glucose transporter is false? a. It transports glucose across the plasma membrane via a mechanism called "facilitated diffusion." b. It has 12 α-helical transmembrane segments. c. A conformational change in the transporter is involved in the transport process. d. Flow through it is unidirectional.

d. Flow through it is unidirectional.

Which of the following will not solubilize a typical peripheral membrane protein? a. Detergent b. Extreme pH c. High salt concentration d. Mildly hypertonic saline

d. Mildly hypertonic saline

Which of the following is not involved in receptor-mediated endocytosis? a. Clathrin b. Adaptor proteins c. Internalization signals d. Pseudopodia

d. Pseudopodia

What is the primary reason that mammalian red blood cells are used in the study of the plasma membrane? a. There are a lot of them and they are easily obtained. b. They contain larger plasma membranes than any other cell type. c. They are of particular interest because they are made up of a lipid monolayer. d. They lack nuclei and membrane-bounded organelles.

d. They lack nuclei and membrane-bounded organelles.

Although Na+ is smaller than K+, its passage through the K+ channel is blocked by the _______ filter. a. CO2 b. negativity c. positivity d. selectivity

d. selectivity