unit 2 hard questions (chemistry of life)

Which molecule shown above contains an amino functional group but is not an amino acid? 1. A 2. B 3. C 4. D 5. E

1. A

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2+H2O→H2CO3. Carbonic acid (H2CO3) is a weak acid. What will be the effect on pH of blood as that blood first comes in contact with respiring cells? 1. Blood pH will decrease slightly 2 Blood pH will increase slightly 3. Blood pH will remain unchanged

1. Blood pH will decrease slightly

Which bond or interaction would be difficult to disrupt when compounds are put into water? 1. covalent bonds 2. hydrogen bond 3. van der waals interaction 4. ionic bond 5. either covalent or ionic bonds

1. covalent bond

What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? 1. pH 2 2. pH 4 3. pH 10 4. pH 12 5. pH 14

1. pH 2

The R group or side chain of the amino acid serine is -CH2 -OH. The R group or side chain of the amino acid alanine is -CH3. Where would you expect to find these amino acids in globular protein in aqueous solution? 1. Serine would be in the interior, and serine would be on the exterior of the globular protein 2. Leucine would be in the interior, and serine would be on the exterior of the globular protein 3. Both serine and leucine would be in the interior of the globular protein 4. Both serine and leucine would be in the exterior of the globular protein

2. Leucine would be in the interior, and serine would be on the exterior of the globular protein

DNase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNase? 1. The two strands of the double helix would separate. 2. The phosphodiester bonds between deoxyribose sugars would be broken 3. The purines would be separated from the deoxyribose sugars. 4. The pyrimidines would be separated from the deoxyribose sugars. 5. All bases would be separated from the deoxyribose sugars.

2. The phosphodiester bonds between deoxyribose sugars would be broken

A new organism is discovered in the forests of costa rica. scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. these data suggest that the new organism 1. is more closely related to humans than to frogs 2. is more closely related to frogs than to humans 3. evolved at about the same time as frogs, which is much earlier than primate and mammals

2. is more closely related to frogs than to humans

How many different kinds of polypeptides, each composed of 12 amino acids, could be synthesized using the 20 common amino acids?

20^12

You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCl and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be 1. 2.0 2. 12.0 3. 7.0 4. 5.0 5. 9.0

3. 7.0

For the hydrolysis of ATP to ADP + Pi, the free-energy change is 7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products). In the cellular environment, however, the free-energy change is about 13 kcal/mol. What can we conclude about the free-energy change for the formation of ATP from ADP and i under cellular conditions? 1. It is +7.3 kcal/mol 2. It is less than +7.3 kcal/mol 3. It is about +13 kcal/mol 4. It is greater than +13 kcal/mol

3. It is about +13 kcal/mol

a given solution contains 0.0001 (10^-4) moles of hydrogen ions (H+) per liter. Which of the following best describes this solution? 1. acidic: will accept H+ from both strong and weak acids 2. basic: will accept H+ from both strong and weak acids 3. acidic: will give H+ to weak acids, but accepts H+ from strong acids 4. basic: will give H+ to weak acids, but accepts H+ from weak acids

3. acidic: will give H+ to weak acids, but accepts H+ from strong acids

How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity? 1. by changing the enzyme's stability 2. by changing the enzyme's location in the cell 3. by changing the shape of the protein 4. by changing the enzyme's pH optimum 5. An amino acid change away from the active site cannot alter the enzyme's substrate specificity.

3. by changing the shape of the protein

One of the buffers that contribute to pH stability in human blood is carbonic acid (H 2CO 3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO 3 -) and a hydrogen ion (H +), as noted below.h2co3 ---> hco3- + h+If the pH of blood increases, one would expect _____. 1. a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3- 2. the concentration of hydroxide ion (OH-) to increase 3. the concentration of bicarbonate ion (HCO3) to increase 4. The HCO3- to act as a base and remove excess H+ with the formation of H2CO3 5. The HCO3- to act as a acid and remove excess H+ with the formation of H2CO3

4. The HCO3- to act as a base and remove excess H+ with the formation of H2CO3

What is the difference (if any) between the structure of atp and the structure of the precursor of the a nucleotide in rna? 1. The sugar molecule is different 2. The nitrogen-containing base is different. 3. The number of phosphates is three instead of one 4. The number of phosphates is three instead of two 5. There is no difference

5. There is no difference

The complexity and variety of organic molecules is due to A) the chemical versatility of carbon atoms. B) the variety of rare elements in organic molecules. C) the fact that they can be synthesized only in living organisms D) their interaction with water. E) their tremendously large sizes.

A) the chemical versatility of carbon atoms.

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct? A) The 5' end has a hydroxyl group attached to the number 5 carbon of ribose. B) The 5' end has a phosphate group attached to the number 5 carbon of ribose. C) The 5' end has phosphate attached to the number 5 carbon of the nitrogenous base. D) The 5' end has a carboxyl group attached to the number 5 carbon of ribose. E) The 5' end is the fifth position on one of the nitrogenous bases.

B) The 5' end has a phosphate group attached to the number 5 carbon of ribose.

To attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur for the final attachment to occur? A) The ATP must first have to attach to the tRNA. B) The binding of the first two molecules must cause a 3-D change that opens another active site on the enzyme. C) The ATP must be hydrolyzed to allow the amino acid to bind to the synthetase. D) The tRNA molecule must alter its shape to be able to fit into the active site with the other two molecules. E) The 3' end of the tRNA must be cleaved before it can have an attached amino acid.

B) The binding of the first two molecules must cause a 3-D change that opens another active site on the enzyme.

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that A) have identical chemical formulas but differ in the branching of their carbon skeletons. B) are mirror images of one another. C) exist in either linear chain or ring forms. D) differ in the location of their double bonds. E) differ in the arrangement of atoms around their double bonds.

B) are mirror images of one another.

19) Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will A) be more flexible in structure. B) be more constrained in structure. C) be more polar. D) have more hydrogen atoms. E) have fewer structurally distinct isomers.

B) be more constrained in structure.

Testosterone and estradiol are A) soluble in water. B) structural isomers of each other. C) proteins. D) lipids. E) enantiomers of each other.

B) structural isomers of each other.

In animal metabolism, most of the monomers released by digestion of food macromolecules are metabolized to provide energy. Only a small portion of these monomers are used for synthesis of new macromolecules. The net result is that A) water is generated by animal metabolism. B) water is consumed by animal metabolism. C) the water consumed is exactly balanced by the water generated, to maintain homeostasis. D) water is consumed during homeostasis, but water is generated during periods of growth. E) water is generated during homeostasis, but water is consumed during periods of growth.

B) water is consumed by animal metabolism.

Which of the following statements describes enzyme cooperativity? A) A multienzyme complex contains all the enzymes of a metabolic pathway. B) A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway. C) A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits. D) Several substrate molecules can be catalyzed by the same enzyme. E) A substrate binds to an active site and inhibits cooperation between enzymes in a pathway

C) A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits.

A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone? A) a compound with the same number of carbon atoms as the hormone B) a compound with the same molecular mass (measured in daltons) as the hormone C) a compound with the same three-dimensional shape as part of the hormone D) a compound with the same number of orbital electrons as the hormone E) a compound with the same number of hydrogen and nitrogen atoms as the hormone

C) a compound with the same three-dimensional shape as part of the hormone

Amino acids are acids because they always possess which functional group? A) amino B) carbonyl C) carboxyl D) phosphate E) hydroxyl

C) carboxyl

Which two functional groups are always found in amino acids? A) ketone and methyl B) carbonyl and amino C) carboxyl and amino D) amino and sulfhydryl E) hydroxyl and carboxyl

C) carboxyl and amino

Which functional groups can act as acids? A) amino and sulfhydryl B) carbonyl and carboxyl C) carboxyl and phosphate D) hydroxyl and aldehyde E) ketone and amino

C) carboxyl and phosphate

Which of the following is a trace element? Nitrogen Hydrogen Copper Oxygen Carbon

Copper

Which of the following is a false statement concerning amino groups? A) They are basic in pH. B) They are found in amino acids. C) They contain nitrogen. D) They are nonpolar. E) They are components of urea

D) They are nonpolar.

A carbon skeleton is covalently bonded to both an amino group and a carboxyl group. When placed in water it A) would function only as an acid because of the carboxyl group. B) would function only as a base because of the amino group. C) would function as neither an acid nor a base. D) would function as both an acid and a base. E) is impossible to determine how it would function.

D) would function as both an acid and a base.

In a normal cellular protein, where would you expect to find a hydrophobic amino acid like valine? A.In the interior of the folded protein, away from water. B.On the exterior surface of the protein, interacting with water. C.In the transmembrane portion interacting with lipid fatty acid chains. D.In the interior of the folded protein, away from water, or in a transmembrane portion interacting with lipid fatty acid chains. E. Anywhere in the protein, with equal probability.

D. In the interior of the folded protein, away from water, or in a transmembrane portion interacting with lipid fatty acid chains.

Hermann Kolbe's synthesis of an organic compound, acetic acid, from inorganic substances that had been prepared directly from pure elements was a significant milestone for what reason? A) It solved an industrial shortage of acetic acid. B) It proved that organic compounds could be synthesized from inorganic compounds. C) It disproved the concept of vitalism. D) It showed that life originated from simple inorganic chemicals. E) It proved that organic compounds could be synthesized from inorganic compounds and disproved the concept of vitalism.

E) It proved that organic compounds could be synthesized from inorganic compounds and disproved the concept of vitalism.

Changing a single amino acid in a protein consisting of 325 amino acids would A) alter the primary structure of the protein, but not its tertiary structure or function. B) cause the tertiary structure of the protein to unfold. C) always alter the biological activity or function of the protein. D) always alter the primary structure of the protein and disrupt its biological activity. E) always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and affect its biological activity.

E) always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and affect its biological activity.

Organic molecules with only hydrogens and five carbon atoms can have different structures in all of the following ways except A) by branching of the carbon skeleton. B) by varying the number of double bonds between carbon atoms. C) by varying the position of double bonds between carbon atoms. D) by forming a ring. E) by forming enantiomers.

E) by forming enantiomers.

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics? a) Living organisms do not obey the second law of thermodynamics, which states that the entropy of an organism increases with each energy transformation. b) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe. c.) Living organisms do not follow the laws of thermodynamics d) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.

d) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.

Why does ice float in liquid water? a. The liquid water molecules have more kinetic energy and thus support the ice. b. The ionic bonds between the molecules in ice prevent the ice from sinking. c. Ice always has air bubbles that keep it afloat. d. Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water. e. The crystalline lattice of ice causes it to be denser than liquid water.

d. Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.

When two atoms are equally electronegative, they will interact to form 1. hydrogen bonds 2. van der waals interaction 3. polar covalent bonds 4. nonpolar covalent bonds e. ionic bonds

nonpolar covalent bonds