Exam 2 Practice Questions Flashcards
Proteins have a variety of sizes and shapes, and include fibrous proteins, globular proteins, and membrane proteins. Which of the following is characteristic of membrane proteins?
a) hydrophilic amino acid side chains on the outside
b) hydrophobic side chains in the interior
c) hydrophobic side chains oriented toward the lipid bilayer
d) fibrous and water insoluble
e) composed of three polypeptide chains that intertwine
c) hydrophobic side chains oriented toward the lipid bilayer
T/F The alpha-helix structures of proteins are produced by hydrogen bonding interactions between the R side chains of the amino acid residues.
a) true
b) false
b) false
In addition to the alpha-helix, another important type of protein secondary structure is the beta-pleated sheet. What type of interactions hold together the polypeptide strands
in the beta-pleated sheet?
a) disulfide cross-bridges (S—S) between cysteine residues of different peptide chains
b) clustering of hydrophobic side chains away from solvent
c) ionic interactions involving acidic and basic residues
d) hydrogen bonding between carbonyl carbons (C==O) and amide hydrogens
(H—N) of different strands.
e) van der Waals interactions contributing to a favorable free energy of
association
d) hydrogen bonding between carbonyl carbons (C==O) and amide hydrogens
Which of the following is not one of the types of protein secondary or tertiary structure found in naturally occurring proteins?
a) left-handed alpha-helix
b) anti-parallel beta-sheet
c) right-handed alpha-helix
d) parallel beta-sheet
e) collagen triple helix
a) left-handed alpha-helix
In a bimolecular reaction, where two molecules (A + B) react to yield products
(P + Q), the velocity or rate of the reaction is given by v = k[A][B] and the overall reaction is said to be:
a) saturated
b) zero-order
c) first-order
d) 1⁄2 Vmax
e) second-order
e) second-order
Coenzymes are nonprotein components (cofactors) that are associated with enzymes and are required to carry out the catalytic activity of the enzymes. Which is incorrect about coenzymes?
a) include metal ions such as Fe2+ or Fe3+, Cu2+, Zn2+, Mg2+, and Mn2+
b) many are derived from water-soluble vitamins such as thiamine (vitamin B1), niacin, riboflavin (vitamin B2), pantothenic acid, and vitamin B12
c) often are intermediate carriers of functional groups in catalyzing the conversion of substrates to products
d) examples include NAD, FAD, coenzyme A, biocytin, and tetrahydrofolate
e) tightly bound coenzymes are known as prosthetic groups
a) include metal ions such as Fe2+ or Fe3+, Cu2+, Zn2+, Mg2+, and Mn2+
From the Michaelis-Menten equation, when the substrate concentration [S] is much
greater than Km, the Michaelis-Menten equation is approximated by:
a) v=Vmax
b) v=k[A]
c) v = (Vmax/Km)[S]
d) v = k[A][B]
e) v = k’[S]
a) v=Vmax
Insulin is a protein hormone that is generated by the proteolytic cleavage of a specific peptide from the middle of the proinsulin polypeptide chain. In this way, active insulin is made up of two, short chains, an A chain and a B chain. Which of the following is the major bond or interaction that holds the two chains together?
a) hydrogen bonds
b) hydrophobic interactions
c) disulfide bridges
d) ionic interactions
e) van der Waals forces
c) disulfide bridges
Chymotrypsin, an enzyme of the digestive tract that breaks down dietary proteins, is an example of an enzyme that is synthesized as an inactive precursor, called a proenzyme or zymogen. The inactive proenzyme, chymotrypsinogen, is converted to π-chymotrypsin by the action of the enzyme trypsin. π-chymotrypsin is then converted to the mature form of the protease, α-chymotrypsin, by the action of:
a) trypsin
b) chymotrypsinogen
c) π-chymotrypsin
d) pepsin
e) trypsinogen
c) π-chymotrypsin
Blood clot formation consists of a series of zymogen activation steps that lead to the conversion of fibrinogen to fibrin, which aggregates to produce a clot. All of the following are correct about the blood clotting process except:
a) the zymogens that are activated include the serine proteases Factor XII, Factor XI, Factor IX, Factor VII, and Factor X
b) the intrinsic pathway of blood clot formation is initiated by blood coming into contact with tissue surfaces damaged by injury
c) the extrinsic pathway of blood clot formation is initiated by tissue factors that are released by trauma to tissues
d) the intrinsic and extrinsic pathways converge at Factor X, and the final common pathway includes the conversion of fibrinogen to fibrin and the aggregation of fibrin
e) thrombin is a kinase enzyme that phosphorylates a specific serine residue of fibrinogen; the phosphorylated form of fibrinogen is known as fibrin
e) thrombin is a kinase enzyme that phosphorylates a specific serine residue of fibrinogen; the phosphorylated form of fibrinogen is known as fibrin
The molecule tristearoylglycerol is an example of:
a) mixed triacylglycerol
b) tricarboxylic acid
c) simple triacylglycerol
d) trioleoylglycerol
e) triterpene
c) simple triacylglycerol
Phosphatidic acid is the parent compound for which class of lipids?
a) steroids
b) glycerophospholipids
c) waxes
d) triacylglycerols
e) terpenes
b) glycerophospholipids
Lipids that result from combining two or more molecules of isoprene are:
a) steroids
b) cholesterol
c) sphingolipids
d) terpenes
e) bile acids
d) terpenes
Which steroid is a principal component of animal cell plasma membranes?
a) cortisol
b) mineralocorticoids
c) deoxycholic acid
d) cholesterol
e) estradiol
d) cholesterol
When added to water, phospholipids tend to form bilayer structures that resemble membranes. The bilayers form spontaneously and rapidly, and are stable structures. Which of the following is a type of bilayer structure formed by phospholipids in water?
a) micelles
b) Golgi apparatus
c) multilamellar vesicles
d) Gram-negative cell walls
e) inside-out micelles
c) multilamellar vesicles
