molecular ch 2

In a living organism, where are ionic bonds most likely to be found? A) in the cytoplasm B) between DNA strands C) deep in a protein's core where water is excluded D) on the surface of a protein E) on the surface of a lipid

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Tertiary structure in DNA is also known as ________. A) primary structure B) supercoiling C) double helix D) -helix

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What level of structure in DNA would be disrupted by a reagent that breaks apart hydrogen bonds?

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Which of the following is a nucleotide? A) phosphate + ribose B) adenine + deoxyribose C) sugar + nitrogenous base D) adenine + ribose + phosphate

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Why are free ionic bonds of little importance and relatively unlikely to form in living organisms? 1) Cells are composed mostly of water, which interferes with ionic bonds between free ions. 2) Cells are largely hydrophobic. 3) They are crystals. A) 1 B) 2 C) 3 D) 1 and 2 E) 2 and 3

1

What is the maximum number of 100 amino acid long polypeptides that could be made? A) 100^20 B) 2,000 C) 20^100 D) 20^101 E) 20

20^100

What kind of noncovalent interaction is typified by interactions between two molecules that are so close together that they can experience weak attractive forces bonding them together? A) H bonds B) ionic bonds C) hydrophobic interactions D) polar covalent bonds E) van der Waals forces

H bonds

Which interaction is most important in enhancing the solubility of macromolecules in water? A) hydrophobic interactions B) nonpolar covalent bonds C) H bonds D) van der Waals forces E) Both hydrophobic interactions and nonpolar covalent bonds

H bonds

The -pleated sheet is characterized by orientation of ______ the molecular axis. A) H bonds parallel to B) H bonds perpendicular to C) ionic bonds parallel to D) ionic bonds perpendicular to E) peptide bonds perpendicular to

H bonds perpendicular to

The most electronegative atoms typically present in biological molecules are ____ and ____. A) O, C B) O, P C) O, N D) C, N E) C, Na

O, N

What is now thought to have been the genetic material in the first living organisms on Earth? A) RNA B) DNA C) protein D) polypeptides

RNA

Why is silicon not suitable for making covalent bonds stable and strong enough to form the basis of living organisms, even though it is just below carbon on the periodic table? A) Silicon is too large for its nucleus to attract the valence electrons of neighboring atoms enough to hold molecules together sufficiently. B) Silicon is too small for its nucleus to attract the valence electrons of neighboring atoms enough to hold molecules together sufficiently. C) Silicon is too large for its nucleus to attract the protons of neighboring atoms enough to hold molecules together. D) Silicon is too small for its nucleus to attract the protons of neighboring atoms enough to hold molecules together.

Silicon is too large for its nucleus to attract the valence electrons of neighboring atoms enough to hold molecules together sufficiently.

What bond is responsible for the branch points in glycogen and amylopectin? A) (1—>4) glycosidic linkages B) (1—>4) glycosidic linkages C) (1—>6) glycosidic linkages D) (1—>6) glycosidic linkages E) 3'-5' phosphodiester linkages

a(1—>6) glycosidic linkages

What type of protein secondary structure is characterized as being highly extensible because of its coiled structure? A) -pleated sheet B) double helix C) -helix D) supercoiling

a-helix

A molecule that is capable of releasing or donating a hydrogen ion is termed a(n) _______. A) base B) hydrion C) acid D) anachronism E) pain

acid

Why do sugars tend to be highly water soluble? A) because they have only a few hydroxyl groups B) because of their large numbers of hydroxyl groups C) because of their large numbers of sulfhydryl groups D) because of their large numbers of methyl groups E) because of their small molecular weights

because of their large numbers of hydroxyl groups

What bond is responsible for the branch points in glycogen and amylopectin? A) (1—>4) glycosidic linkages B) (1—>4) glycosidic linkages C) (1—>6) glycosidic linkages D) (1—>6) glycosidic linkages E) 3'-5' phosphodiester linkages

beta(1—>4) glycosidic linkages

Proteins are often composed of two or more distinct modules that fold up independently of one another. They often represent parts of a protein that function in a semi-independent manner. These modules are called ______. A) protein motifs B) functionals C) domains D) dominoes

domains

The most stable atoms and thus those that are typically nonreactive are the atoms that have _______. A) equal numbers of electrons and protons B) equal numbers of electrons and neutrons C) full inner shells D) full outer shells E) all covalent bonds

full outer shells

You are working with an enzyme altase that you denature in the presence of urea. If altase were denatured no further by the addition of mercaptoethanol, what would that suggest to you about the enzyme?

it doesnt have disulfide bonds

Which of the following is not a macromolecule formed by polymerization? A) proteins B) lipids C) polynucleotides D) polysaccharides E) DNA

lipids

A release of hydrogen ions to a solution would most likely ____________. A) raise pH B) lower pH C) buffer pH D) change salinity E) keep pH steady

lower pH

The low-molecular-weight building blocks of polymers are called _______. A) minipolymers B) monoblocks C) monomers D) portions E) octamers

monomers

What kind of bond results from an unequal sharing of electrons? A) ionic bond B) polar covalent bond C) H bond D) nonpolar covalent bond

polar covalent bond

What level of structure in proteins is held together by intermolecular R group interactions? A) primary structure B) secondary structure C) tertiary structure D) quaternary structure

quaternary structure

You treat a partially purified preparation of protein with a reagent that breaks bonds between sulfur atoms. Which level(s) of protein structure are likely to be affected the most?

tertiary

Where are hydrophobic interactions most likely to occur? A) on the surface of a water-soluble protein B) the core of a water-soluble protein C) in contact with water molecules D) between two charged molecules E) between two ions

the core of a water-soluble protein

Under which circumstances would electrons be most likely to be shared equally? A) when they are equidistant from nuclei B) when they are equidistant from each other C) when atoms of the same element are sharing them D) when the atoms sharing them are different

when atoms of the same element are sharing them