Quiz 3

Which of the following statements is true?

A) Fatty acids are synthesized by the stepwise addition of three carbon units. B) Unsaturated fatty acids are usually branched. C) Fatty acids with 24 carbons are most common. D) Saturated fatty acids have no double bonds between carbons.* E) Hormones are unsaturated fatty acids.

Which of the following accurately describes the structure of fibrous proteins?

A) Fibrous proteins usually contain a number of different domains with different structural motifs. B) Fibrous proteins are composed of an equal mixture of α helices and β sheets with interconnecting looped segments. C) Fibrous proteins have an extensive tertiary and quaternary structure that affects the strength and elasticity of each fiber. D) Fibrous proteins have a simple primary structure and very little secondary structure, resulting in long, thin fibers. E) Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure.*

Which of the following is true of glycolipids?

A) Glycolipids are usually found on the exterior surface of the plasma membrane.* B) Glycolipids are found in plastids and are used to store energy. C) Fructose and sucrose are often part of glycolipids. D) Glycolipids contain steroids. E) Usually more than 10 sugar units are attached to the glycolipid.

Which of the following is false?

A) Phospholipids are important in membrane structure. B) Serine is a molecule that may be part of a phosphoglyceride. C) Phosphatidic acid contains two fatty acids and a phosphate group. D) Sphingolipids are the predominant phospholipid in membranes.* E) Phospholipids are amphipathic.

Which of the following statements is false?

A) There are more than 60 different kinds of amino acids present in cells. B) The R group of amino acids differs from one amino acid to another. C) Only around 20 amino acids are used in protein synthesis. D) Equal amounts of D- and L-amino acids are found in cells.* E) An amino acid has an N-terminus, a C-terminus, and an R group.

The components of a nucleotide are

A) a carboxyl group, an amine group, and a variable R group. B) a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base.* C) a three-carbon alcohol with a hydroxyl group on each carbon and three fatty acids. D) two six-carbon sugars attached with an α(1→4) glycosidic bond. E) a six-carbon sugar, an ester linkage, and a four-ringed hydrocarbon.

Which of the following is not a polymer of numerous monomer units?

A) a phospholipid* B) a polypeptide C) an RNA molecule D) cellulose E) starch

Complementary relationships between purines and pyrimidines

A) allow adenine to form two hydrogen bonds with thymine (or uracil) and guanine to form three hydrogen bonds with cytosine to form double-stranded nucleic acids.* B) allow the interaction of the oppositely charged amino acids to form the tertiary structure of proteins. C) allow adjacent bases in a nucleotide chain to stack tightly, stabilizing the DNA double helix. D) provide highly ordered, repetitive bonding to form α helices and β sheets within proteins. E) Both A and C are correct.

Trans fats

A) are unsaturated fatty acids. B) resemble saturated fatty acids in shape. C) are associated with an increased risk of heart disease. D) are present in small amounts in meat and dairy products. E) All of these statements are true.*

Which of the following is a possible function of a terpene?

A) cell surface receptor B) vitamin * C) enzyme D) motility E) structure

The two strands of DNA are held together by ________; thus ________.

A) covalent bonds; double-stranded DNA is very stable at a range of temperatures B) ionic bonds; double-stranded DNA separates into two separate strands in water C) hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures* D) antiparallel bonds; double-stranded DNA is amphipathic E) hydrophobic interactions; double-stranded DNA separates into two separate strands when dissolved in a hydrocarbon (hydrophobic) solvent

Which of the following has the greatest number of glycosidic bonds?

A) glucose B) triacylglycerol C) amylose* D) DNA E) vitamin A

Which of the following is not a major functional class of proteins?

A) hereditary proteins* B) enzymes C) motility proteins D) regulatory proteins E) structural proteins

RNA and DNA differ

A) in that RNA contains ribose and DNA contains deoxyribose. B) in that RNA contains nucleosides and DNA contains nucleotides. C) in that RNA contains uracil and DNA contains thymine. D) both A and C.* E) All of these are correct.

A peptide bond

A) is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid.* B) is a covalent bond between the functional R groups of adjacent amino acids. C) is a covalent bond between the NH group of one polypeptide and the CO group of an adjacent polypeptide that holds together multimeric proteins. D) is a noncovalent bond that dictates the tertiary structure of a protein. E) is a covalent bond between adjacent glucose molecules in a peptide.

The primary structure of a protein

A) is important for determining the secondary and tertiary structure of a protein. B) is simply the order of amino acids from one end of the protein to another. C) is important both genetically and structurally. D) is the linear sequence of amino acids that are linked together by peptide bonds. E) All of these statements are true.*

Cellulose belongs to which of the following groups of macromolecules?

A) lipids B) carbohydrates* C) proteins D) nucleic acids E) none of these

Which of the following pairs correctly matches the monomer with its polymer?

A) peptides; proteins B) amino acids; polysaccharides C) glucose; proteins D) terpenes; nucleic acids E) nucleotides; nucleic acids*

The nucleoside triphosphate molecules in DNA are linked together in the 5'→3' by a(n) ________ bridge.

A) phosphate B) covalent C) phosphodiester* D) peptide E) phosphatidyl .

Disulfide bonds are often found to stabilize which of the following levels of protein structure?

A) primary B) secondary C) tertiary* D) primary, secondary, and tertiary E) None of these structures involve disulfide bonds.

Hydrogen bonding is most important in stabilizing the ________ structure of many proteins.

A) primary B) secondary* C) tertiary D) quaternary E) primary, secondary, tertiary, and quaternary

Fatty acids are ________; they function in the cell as ________.

A) short chains of double-bonded carbon molecules; storage lipids B) short chains of double-bonded carbon molecules; vitamins and cofactors C) four-ringed hydrocarbon molecules; key components of membranes D) long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids* E) short chains of double-bonded carbon molecules; vitamins, cofactors, and storage lipids

Which of the following is not one of the six classes of lipids?

A) steroids B) terpenes C) fatty acids D) triacylglycerols E) pectins*

Which of the following is not a steroid??

A) testosterone B) estradiol C) cortisol D) aldosterone E) phenylalanine*

A general trend in the structure of many biomolecules is

A) that the order and bonding of monomers form the basis for the secondary and tertiary structure of the polymer.* B) that they are all soluble in water independent of the size of the polymer. C) that each class of biomolecule forms one type of secondary structure independent of the order of the monomers in the polymer. D) that each class of biomolecule can form either fibrous or globular conformations depending on the chemical conditions inside the cell. E) that four different monomers form the basis for the functional and structural properties of each polymer.

Which of the following is found exclusively in RNA?

A) thymine B) guanine C) uracil* D) adenine E) cytosine

The function of triglycerides is

A) to store energy.* B) to form semipermeable membranes. C) to transport substances in and out of cells. D) store information. E) Both B and C are correct.

The term amphipathic describes the characteristic of some molecules that have

A) two polar regions. B) only a single polar region. C) both a polar and a nonpolar region.* D) no polar regions. E) two nonpolar regions.

What are the three general types of amino acids?

A) α helices, β sheets, and looped segments B) covalent, noncovalent, and van der Waals forces C) positive, negative, and noncharged D) hydrophobic, polar (noncharged), polar (charged)* E) acidic, basic, and neutral

the chemical nature of each amino acid is determined by which of the following groups ?

R

which is false

a. sphingolipids are the predominant*

which of the following has the greatest number of glycosidic bonds?

amylose

which is true of gylcolipids

glycolipids are usually found on the exterior surface of the plasma membrane

which of the following contributes to the stability of the dan double helix

hydrophobic interactions between aromatic bases at the center of the double helix

proline is referred to as the helix breakers because

it lacks the hydrogen atom needed for hydrogen bonding

the nucleoside triphosphate molecules in dan are linked in the 5'......3' by an _____ bridge

phosphodiester

two proteins associated with a rare neurodegenerative disorder have been sequenced. protein A contains many polar amino acids with small regions containing non polar, hydrophobic amino acids. protein B is rich in non polar, hydrophobic amino acids with only two small regions containing polar amino acids. what might this suggest about the two proteins?

protein A may be cytoplasmic protein and protein B may be a membrane associate protein

which is true

saturated fatty acids have no double bond between carbons

cholesterol is a _____ which ____

steroid, is a compound of eukaryotic membranes and is the basis for many animal and plant hormones

you are researching a cytoplasmic protein associated with a nerve disorder. the native form of the enzyme appears to be globular protein; however, when a sample of the purified protein is treated with a chemical that reduces disulfide bone, the enzymatic activity decreases dramatically and multiple globular proteins can be detected in the sample. What does this tell you about the protein?

the protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds

you are investigating the structure of the seeds of a newly discovered tropical plant. there is storage material inside the seed. you treat the seed with peptidase (an enzyme that breaks peptide bonds), glycoside hydrolyses (an enzyme that breaks B glycosidic bonds), and amylase (bang enzyme that breaks a glycosidic bonds). only the amylase appears to dissolve the storage material in the seed. what does this tell you about the identity of the storage material?

the seed contains starch to store carbon and energy

which of the following is not found in DNA under normal circumstances?

uracil