MCDB 1150 Clicker Questions Exam 2

If 10 glucose molecules (C6H12O6) were linked by condensation reactions, how many glycosidic bonds would be in the resulting polymer? A. 10 B. 20 C. 9 D. 18

C

If 10 glucose molecules (C6H12O6) were linked by condensation reactions, how many oxygen atoms would be found in this polymer? A. 60 B. 10 C. 51 D. 69

C

The peptide sequences below represent a SEGMENT of a membrane protein. (HYDROPHOBIC AMINO ACIDS ARE SHOWN IN BOLD TYPE): Which sequence is most likely to be found in the membrane spanning region of a channel? a. *LSSSLGALLLLLLALLFWLYIVMS*N*WTGG* b. PE*L*PDEK*L*KKDKEDPDDDDPEKPQ*L*NKPPD c. Neither

C

What would happen to a 1:1 mixture of a triglyceride and water if it were shaken and allowed to sit for a few minutes? (Note: this triglyceride has a low melting point so will be liquid at room temperature) a. you would see a clear solution with only one phase b. you would see tiny dispersed droplets within the water solution c. you would see two distinct and separate phases

C

Which of the following is NOT a function of lipids in the cell? a. structural component of cell b. energy storage c. information storage d. cell-cell communication

C

Which of the following lists of lipids is properly arranged according to amphipathicity (from lowest to highest)? a. phosphatidylcholine, cholesterol, triglyceride b. cholesterol, triglyceride, phoshpatidylcholine c. triglyceride, cholesterol, phosphatidylcholine

C

You have discovered a previously unstudied carbohydrate. You determine that it normally resides on the outside surface of the cell membrane. You also notice that it is often attached to a polypeptide. What hypothesis would be most consistent with these observations? a. This carbohydrate is likely to be an energy source. b. This carbohydrate is likely to be a cofactor for an enzyme that is involved in cell transport. c. This carbohydrate is likely to be acting as some sort of signal to other cells. d. This carbohydrate is likely to be helping to anchor some protein to the cell membrane.

C

Given what you know about ALL the chemical properties and structure of the lipid bilayer and proteins, which of the following proteins would you expect to find ASSOCIATED with the membrane? a. A globular protein with nonpolar amino acid chains folded into the interior of the protein and hydrophilic side chains exposed to water. b. A protein with a stretch of ~20-30 consecutive hydrophobic amino acids. c. A protein with multiple stretches of ~20-30 (consecutive) alternating hydrophilic and hydrophobic amino acids. d. All the above

D

If you were to grab the ends of any of the polysaccharides listed below, which would you be able to stretch the most? a. glycogen b. cellulose c. chitin d. amylose e. none

D

What do you predict would happen if you added a fatty acid and a hydrophobic substance to water in a beaker and mixed vigorously? a. The fatty acid forms a layer on top of the water and the hydrophobic substance forms a layer at the bottom of the beaker b. The fatty acid forms a layer at the the bottom of the beaker and the hydrophobic substance forms a layer on top of the water c. Both the fatty acid and the hydrophobic substance are insoluble in water a form layers at the top and bottom of the beaker d. The fatty acid interacts chemically with both the water and the hydrophobic substance, thereby solubilizing the hydrophobic substance

D

Which of the following polymers contain nitrogen? A) starch B) glycogen C) cellulose D) chitin E) none

D

Given what you know about the chemical properties of the lipid bilayer, which of the following proteins is LIKELY to associate with the membrane? a. A protein with one or more stretches of ~20-30 consecutive hydrophobic amino acids. b. A globular protein with nonpolar amino acid chains folded into the interior of the protein and hydrophilic side chains exposed to water. c. A protein consisting of ONLY hydrophilic amino acids (no hydrophobic amino acids). d. A protein with a 20-30 amino acid stretch of alternating polar and nonpolar amino acids. e. All of the above.

E

Adding hydrogen atoms to fatty acid tails of a triglyceride containing double bonds (C=C) would: a. increase the triglyceride's melting temperature b. decrease the triglyceride's melting temperature

A

Cell walls are used by many different organisms for protection from their environment and structural support. These cell walls must obviously be insoluble in water; otherwise, they would dissolve the first time an organism got wet. Which of the following carbohydrates would you expect to be most soluble in water? A) starch B) peptidoglycan C) cellulose D) chitin

A

Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical? A) The geometry of the bonds is different, and the shapes of enzyme active sites are highly specific. B) Starch is held together by hydrogen bonding, not covalent bonding. C) Cellulose molecules are highly branched, and enzymes are too bulky to fit. D) Starch is held together by peptide bonds, not glycosidic linkages.

A

"Selective" permeability refers to the property of the membrane that allows some types of molecules to move faster through the membrane than others. "Selective permeability" is determined by the fatty acid composition of the phospholipids and cholesterol content of the membrane. a. True b. False

B

Compare a membrane composed primarily of lipid molecules with saturated fatty acids to one with lipids having unsaturated fatty acid tails. Which type of membrane do you predict would be more fluid (less "gelled")? A. membrane composed mostly of lipids with saturated fatty acids B. membrane containing lipids with unsaturated fatty acids

B

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by condensation reactions? A. C18H36O18 B. C18H32O16 C. C6H10O5 D. C18H30O15 E. C3H6O3

B

The peptide sequences below represent a SEGMENT of a membrane protein. (HYDROPHOBIC AMINO ACIDS ARE SHOWN IN BOLD TYPE): Which sequence is most likely to be found in a lipid anchored protein? a. *LSSSLGALLLLLLALLFWLYIVMS*N*WTGG* b. PE*L*PDEK*L*KKDKEDPDDDDPEKPQ*L*NKPPD c. Neither

B

You are trying to design a drug to block this pore. What sort of molecule do you think would be most effective at blocking such a pore? a. A hydrophilic molecule b. A hydrophobic molecule

B