CHEM 3070 Exam #3 Chp. 4, 16, 18

A drug is a chemical substance that affects the functioning of living things by A) attacking certain biological systems. B) protecting active sites. C) being a pain-reliever only. D) using its chemical shape and polarity.

A

Drugs that block the action of other substances are called A) analgesics. B) agonists. C) addictives. D) antagonists.

A

Hydrogen is a diatomic molecule, H2. The bond holding the hydrogen atoms together is A) polar covalent. B) nonpolar covalent. C) metallic. D) ionic.

A

If two atoms from the same element share three pairs of electrons in forming a molecule the bond is called a A) triple covalent bond. B) single covalent bond. C) double covalent bond. D) coordinate covalent bond.

A

Morphine has its activity when A) it fits into a receptor that has a cation site site and a double ring site. B) activating an enzyme when it hydrogen bonds. C) it fits into a receptor that has an anionic site, a ring site and a two carbon"hole". D) activating a receptor site when it hydrogen bonds

A

The action of an enzyme is dependent on A) molecular shape only B) molecular shape and polarity C) polarity only. D) hydrogen bonding only.

A

The attraction of an atom for a pair of shared electrons is called its A) covalence. B) valence. C) electronegativity. D) polarity

A

The substance that is changed by an enzyme in a reaction is called the A) substrate. B) reaction reagent. C) subject D) action site material.

A

Watson and Crick proposed that DNA exists as a(n) A) double helix. B) pleated sheet. C) beta sheet. D) alpha helix

A

When a silicon atom combines with hydrogen to form a molecule, how many bonds are formed? A) 4 B) 3 C) 2 D) 1

A

Which of the following pairs of atoms will form a polar covalent bond? A) C and S B) F and Na C) Ar and Cl D) K and Cl

A

An electron-dot structure is a convenient method of representing A) the complete electron configuration of the atom. B) valence electrons of an atom. C) all electrons of the atom. D) core electrons of an atom.

B

Arrange the following in order of increasing boiling point. CH3CH2OH (I) CH3CH2CH3 (II) H3C-O-CH3 (III) CH3CH2NH2 (IV) A) II < III < I < IV B) II < III < IV < I C) I < IV < III < II D) IV < III < II < I

B

In the hydrogen chloride molecule, HCl, the chlorine end of the molecule is more negative than the hydrogen end because A) hydrogen transfers an electron to chlorine. B) hydrogen is more electronegative than chlorine. C) hydrogen and chlorine have the same electronegativity. D) chlorine is more electronegative than hydrogen.

B

The individual strands of DNA are held together by: A) ester linkages B) hydrogen bonds C) peptide bonds D) covalent bonds E) none of the above

B

The most important feature that distinguishes one DNA molecule from another is (are) A) the type of sugar in each molecule. B) the order of the bases attached to the sugar phosphate backbone. C) the type of phosphate bonds. D) all of the above features

B

The repeating units in DNA are called A) nucleic acids. B) nucleotides. C) monomers. D) amino acids.

B

The structure of formaldehyde, CH2O, has A) a triple covalent bond between carbon and oxygen. B) a double covalent bond between carbon and oxygen. C) all single covalent bonds. D) all ionic bonds.

B

What is the backbone of the nucleic acid constructed of? A) amine bases B) alternating sugar phosphate groups C) glucose polymers D) polyamides

B

When ions arrange themselves in an orderly structure, that structure is known as a A) dipole. B) crystal. C) molecule. D) tetrahedron

B

Which of the following bases pairs with adenine in DNA? A) cytosine B) thymine C) guanine D) uracil

B

Which of the following compounds is NOT polar? A) CH2F2 B) NH2F C) CF4 D) NF3

B

Which of the following compounds will have the highest melting point? A) CO2 B) CaCl2 C) SCl6 D) N2H4

B

Which of the following molecules does not have a dipole moment? A) HCl B) CH2=CH2 C) CH3NH2 D) NH3

B

A nonpolar covalent bond will form between atoms that have an electronegativity difference of A) < 0.5 B) between 0.5 and 1.5 C) > 2.0 D) between 1.0 and 2.0

C

An organic molecule that must bind to an enzyme to make it function properly is a(n) A) apoenzyme. B) extremophile. C) coenzyme. D) isomerase.

C

Base pairing in DNA occurs through A) an interaction that is not well understood. B) covalent bonds between complementary bases on nucleic acid chains. C) hydrogen bonds between complementary bases on nucleic acid chains. D) salt bonds between complementary bases on nucleic acid chains.

C

Curare, the blow dart poison of Amazonian Indians, disrupts the acetylcholine cycle by blocking ___________. This is a common mechanism for drug action. A) the breakdown of the reactant. B) the release of the reactant. C) receptors. D) the formation of the reactant.

C

Enzymes are A) nucleic acids. B) structural material C) catalysts. D) genetic material.

C

In liquid methanol, CH3OH which intermolecular forces are present? A) Only dispersion and dipole=dipole forces are present. B) Only dipole=dipole and ion=dipole forces are present. C) Dispersion, hydrogen bonding and dipole=dipole forces are present. D) Only hydrogen bonding forces are present

C

The information in DNA is carried by the A) sugar molecules. B) base sequence. C) length of the nucleic acid chain. D) phosphate bonds.

C

The substance that can stop an enzyme from catalyzing a reaction is called A) a stopping agent. B) active site plug. C) an inhibitor D) an antiagent

C

Which drawing best represents hydrogen bonding? A) drawing 1 B) drawing 2 C) drawing 3 D) drawing 4

C

Which of the following compounds exhibits hydrogen bonding? A) H3C-O-CH3 B) HI C) NH3 D) CH3Cl

C

Which of the following compounds has the highest boiling point? A) H2S B) NH3 C) H2O D) HCl

C

Which of the following elements has the highest electronegativity? A) N B) B C) F D) Li

C

Which of the following is NOT a property of an ionic compound? Ionic compounds generally A) form solutions that conduct electricity well. B) dissolve in water. C) have melting points lower than those of molecular compounds. D) require more energy to change from the liquid to the gaseous state.

C

Which of the following statements about molecules is correct? A) A compound that contains only polar bonds must be polar. B) A compound that contains both polar and nonpolar bonds must be nonpolar. C) A compound that contains only polar bonds can be nonpolar. D) A compound that contains only nonpolar bonds can be polar

C

Which one of the following has the LOWEST electronegativity? A) chlorine B) oxygen C) sodium D) fluorine

C

Which substance has covalent bonds? A) NaCl B) MgBr2 C) CO2 D) LiCl

C

A class of molecules that works at very low concentrations in mediating hormonal activity has been studied and used to treat a variety of problems, including blood pressure, heart disease, and asthma. It is also responsible for the perception of pain. This group of compounds is known as the A) nucleic acids. B) fatty acids. C) prostaglandin. D) hormones.

D

In a Lewis formula, the dots represent A) whatever number of electrons are needed to satisfy the octet rule. B) only the electrons that are being transferred or shared. C) all the electrons in the atoms. D) the valence electrons in all the atoms

D

In a molecule of nitrogen, N2, the nitrogen atoms are bonded to each other by A) a double covalent bond. B) an ionic bond. C) a single covalent bond. D) a triple covalent bond.

D

In a nonpolar covalent bond, electrons are A) shared equally. B) uncharged. C) transferred. D) shared unequally.

D

Ionic compounds have strong forces between particles. This means that generally ionic compounds are ________ at room temperature. A) liquids B) covalently bonded C) gases D) solids

D

Nucleotides in nucleic acids are joined by links through the A) sugar groups. B) peptide bonds. C) base groups. D) phosphate groups.

D

The phrase "ïnduced fit" model means that A) the active site changes to accomodate the substrate B) the active site uses dipole-dipole interactions to change the substrate. C) the substrate does not initially fit in the active site D) all of the above happen.

D

The portion of an enzyme where the substrate "fits" during the reaction is called the A) action site. B) reaction site. C) substrate site. D) active site

D

When a fluorine atom reacts with a chlorine atom, the bond that forms between them should be A) nonpolar covalent. B) ionic covalent. C) ionic. D) polar covalent.

D

Which drawing best accounts for the polarity of water, H2O, and the bond polarities that make a major contribution to the overall molecular polarity? A.) drawing 1 B) drawing 2 C) drawing 3 D) drawing 4

D

Which of the following compounds has the highest boiling point? A) CH3CH2OH B) CH3CH2CH2CH3 C) H3C-O-CH3 D) HOCH2CH2OH

D

Which of the following elements can form four bonds with other atoms? A) F B) N C) O D) C

D

Which of the following should have the largest dipole moment? A) CO2(g) B) CH3F(g) C) H2(g) D) KCl(g)

D

Which of the following statements BEST describes the action of enzymes in living systems? A specific enzyme generally catalyzes A) a group of similar reactions. B) one specific reaction. C) many different reactions. D) either one specific reaction or a group of similar reactions.

D

Which one of the following compounds does NOT obey the "octet rule"? A) H2O B) NH3 C) CH4 D) SF6

D

Which substance has nonpolar covalent bonds? A) CO B) O2 C) NO2 D) NaCl

D

Which substance has polar covalent bonds? A) N2 B) Cl2 C) CaO D) SO2

D

Which term fits this definition? A measure of the tendency of an atom in a molecule to attract a shared pair of electrons to itself. A) polar B) nonbonding C) ionization D) electronegativity

D