Unit 3

1.

1 point

Which two functional groups are always found in amino acids?

ketone and adehyde

carbonyl and carboxyl

carboxyl and amino

phosphate and sulfhdryl

hydroxyl and aldehyde

2.

1 point

What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids

The primary structure of the protein would be changed.

The tertiary structure of the protein might be changed.

The biological activity or function of the protein might be altered.

Only A and C are correct.

A,B, and C are correct.

3.

1 point

For this pair of items, choose the option that best describes their relationship. (A) The number of purines in the DNA strand 5'-AAGAGGAGAAA-3' (B) The number of pyrimidines in the DNA strand 5"-AAGAGGAGAAA-3'

item (A) is greater than item (B)

item (A) is less than item (b)

item (A) is exactly or very approximately equal to item (B)

item (A) may stand in more than one of the above relations to item (B)

none of the above

4.

1 point

There are 20 different amino acids. What makes one amino acid different from another?

different carboxyl groups attached to an alpha carbon

different amino groups attached to an alpha carbon

different side chains (R groups) attached to an alpha carbon

different alpha carbons

different asymmetric carbons

5.

1 point

Enzymes are

carbohydrates

lipids

proteins

nucleic acids

all of these

6.

1 point

Which of the following is an example of hydrolysis?

the reaction of two monosacchardies, forming a disaccharide with the release f water

the synthesis of two amino acids, forming a peptide with the release of water

the reaction of a fat, forming glycerol and fatty acids with the release of water

the reaction of a fat, forming glycerol and fatty acids with the utilization of water

the synthesis of a nucleotide from a phosphate, a pentose sugar, and a nitrogenous base with the production of water

7.

1 point

What gives rise to the cohesiveness of water molecules?

hydrophobic interactions

nonpolar covalent bonds

ionic bonds

hydrogen bonds

both A and C

8.

1 point

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be compose of

120 adenine and 120 uracil uracil molecules

120 thymine and 120 adenine molecules

120 cytosine and 120 thymine molecules

240 adenine and 240 cytosine molecules

240 guanine and 240 thymine molecules

9.

1 point

At which level of protein structure are interactions between the side chains (R groups) most important?

primary

secondary

tertiary

quaternary

all of the above

10.

1 point

Testosterone and estradiol are

nucleic acid

carbohydrates

proteins

pospholipids

steriods

11.

1 point

Which of the following statements is false for the class of biological molecules known as lipids?

They are soluble in water

They are important constituent of cell membranes

They contain more energy than proteins and carbohydrates

They are not true polymers

They contain waxes and steroids

12.

1 point

Why are hydrocarbons insoluble in water?

The majority of their bonds are polar covalent carbon-to-hydrogen linkages.

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

They are hydrophilic.

They exhibit considerable molecular complexity and diversity.

They are lighter than water.

13.

1 point

An example of a hydrogen bond is the bond between

C and H in methane (CH4).

the H of one water molecule and the O of another water molecule.

Na+ and Cl- in salt.

the two hydrogen atoms in a molecule of hydrogen gas (H2).

Mg+ and Cl- in MgCl2.

14.

1 point

Which bonds are created during the formation of the primary structure of a protein?

peptide bonds

hydrogen bonds

disulfide bonds

phosphodiester bonds

A, B, and C

15.

1 point

A molecule with the chemical formula C6H12O6 is probably a

carboyhydrate

lipid

monosaccharide

carbohydrate and lipid only

carbohydrate and monosaccharide only

16.

1 point

What is the difference between covalent bonds and ionic bonds?

Covalent bonds involve the sharing of protons between atoms, and ionic bonds involve the sharing of electrons between atoms.

Covalent bonds involve the sharing of neutrons between atoms, and ionic bonds involve the sharing of electrons between atoms.

Covalent bonds involve the sharing of electrons between atoms, and ionic bonds involve the electrical attraction between atoms.

Covalent bonds involve the sharing of protons between atoms, and ionic bonds involve the sharing of neutrons between atoms.

Covalent bonds involve the transfer of electrons between atoms, and ionic bonds involve the sharing of neutrons between atoms.

17.

1 point

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers

Macromolecular synthesis occurs through the removal of water and digestion occurs through the addition of water

dehydration reactions can occur only after hydrolysis

hydrolysis creates monomers, and dehydration reactions break down polymers

A and B are correct

18.

1 point

Which of the following best describes the flow of information in eukaryotic cells?

DNA->RNA->proteins

RNA->proteins->DNA

proteins->DNA->RNA

RNA->DNA->proteins

DNA->proteins->RNA

19.

1 point

The a helix and the B pleated sheet are both common polypeptide forms found in which level of protein structure?

primary

secondary

tertiary

quaternary

all of the above

20.

1 point

How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?

12

11

10

9

8

21.

1 point

Humans can digest starch but no cellulose because

the monomer of starch is glucose, while the monomer of cellulose is glactose

humans have enzymes that can hydrolyze the beta glycosidic linkages of starch but no the alpha glycosidic linkages of cellulose

humans have enzymes that can hydrolyze the alpha glycosidic linkages of starch but not the beta glycosidic linkages of cellulose

humans harbor starch-digesting bacteria in the digestive tract

the monomer of starch is glucose, while the monomer of cellulose is maltose

22.

1 point

Which of the following statements is true about buffer solutions?

They maintain a constant pH when bases are added to them but not when acids are added to them.

They maintain a constant pH when acids are added to them but not when bases are added to them.

They maintain a constant pH of exactly 7 in all living cells and biological fluids.

They maintain a relatively constant pH when either acids or bases are added to them.

They are found only in living systems and biological fluids.

23.

1 point

Which of the following descriptions best fits the class of molecules known as nucleotides?

a nitrogenous base and a phosphate group

a nitrogenous base and a pentose sugar

a nitrogenous base, a phosphate group, and a pentose sugar

a phosphate group and an adenine or uracil

a pentose sugar and a purine or pyrimidine

24.

1 point

Evolution is biology's core theme that ties together all the other thems. This is because evolution explains

the unity and diversity of life

how organisms become adapted to their environment through the differential reproductive success of varying individuals

why distantly related organisms sometimes resemble each other

explains why some organisms have traits in common

all of the above

25.

1 point

Amino acids are acids because they always possess which functional group?

amino

carbonyl

carboxyl

sulfhydryl

aldehyde

26.

1 point

WHich of the following effects is produced by the high surface tension of water?

Lakes don't freeze solid in winter, despite low temperatures.

A water strider can walk across the surface of a small pond.

Organisms resist temperature changes, although they give off heat due to chemical reactions.

The pH of water remains exactly neutral.

None of the above

27.

1 point

Three or four of the following statements are true and correct. Which one, if any, is false?

Carbon, hydrogen, oxygen, and nitrogen make up approximately 96% of living matter.

The trace element iodine is required only in very small quantities by vertebrates.

Virtually all organisms require the same elements in the same quantities.

Iron is an example of an element needed by all organisms.

None of the above

28.

1 point

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?

C18H36O18

C18H32O16

C6H10O5

C18H10O15

C3H5O3

29.

1 point

Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one glactose molecule. How is lactose classified?

as a pentose

as a hexose

as a monosaccharide

as a disaccharide

as a polysaccharide

30.

1 point

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

is more closely related to humans than to frogs

is more closely related to frogs than to humans

may have evolved from gibbons but not rats

is more closely related to humans than to rats

may have evolved from rats but not from humans and gibbons

31.

1 point

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus, H2CO3<-> HCO3-+H+ If the pH of the blood drops, one would except

a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-.

the concentration of hydroxide ion (OH-) to increase.

the concentration of bicarbonate ion (HCO3-) to increase.

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

the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3.

32.

1 point

Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?

101

100

99

98

97

33.

1 point

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

the change in density when it condenses to form a liquid or solid

reactions with other atmospheric compounds

the release of heat by the formation of hydrogen bonds

the release of heat by the breaking of hydrogen bonds

the high surface tension of water

34.

1 point

Collecting data based on observation is an example of _____; analyzing this data to reach a conclusion is an example of _____ reasoning.

descriptive science; deductive

discovery science; inductive

hypothesis-based science; inductive

hypothesis-based science; deductive

the process of science; deductive

35.

1 point

Which of the following statements best describes the carbon atoms present in a seed-eating bird?

They were incorporated into organic molecules by plants.

They were processed into sugars through photosynthesis.

They are ultimately derived from carbon dioxide.

Only A and C are correct.

A, B, and C are correct.

36.

1 point

Which type of interaction stabilizes the alpha helix and the beta pleated sheet structures of proteins?

hydrophobic interactions

nonpolar covalent bonds

ionic bonds

hydrogen bonds

peptide bonds

37.

1 point

When blood glucose level rises, the pancreas secretes insulin, and as a result blood glucose level declines. When blood glucose level is low, the pancreas secretes glucagon, and as a result blood glucose level rises. Such regulation of blood glucose level is the result of

catalytic feedback

positive feedback

negative feedback

bioinformatic regulation

protein-protein interactions