Ch 3: Carbon and the Molecular Diversity of Life

Question 1

Single sugar molecules are called __________.
These molecules generally have molecular formulas that are some multiple of the unit ___.

Answer 1

monosaccharides

CH₂O

Question 2

In the structure of glucose, we can see the trademarks of a sugar: the molecule has a ________ group, and multiple hydroxyl (-OH) groups.

Answer 2

carbonyl

Question 3

A carbonyl group is called a ______ if the carbonyl group is within a carbon skeleton, and an ________ if the carbonyl group is at the end of a carbon skeleton.

Answer 3

ketone

aldehyde

Question 4

The carbon skeleton of a monosaccharide ranges from _ to _ carbons long.

Answer 4

3 to 7

Question 5

In aqueous solutions, glucose and other 5- and 6- carbon sugars form _____, which is the most ______ form of these under physiological conditions.

Answer 5

rings

stable

Question 6

The valences of carbon and its most frequent partners (_______, ______, and ________) are the building code for the architecture of living molecules.

Answer 6

hydrogen, oxygen, and nitrogen

Question 7

Valence, the number of covalent bonds an atom can form, is generally equal to the # of electrons needed to complete the valence shell. What are the valences of these major elements of organic molecules?

hydrogen?

carbon?

nitrogen?

oxygen?

Answer 7

1

4

3

2

Question 8

What are isomers?

Answer 8

compounds with the same molecular formula, but different structures, and therefore, properties

Question 9

What are cis-trans isomers?

Answer 9

isomers which differ in their arrangement about a double bond

Question 10

Enantiomers are mirror images of one another. They differ in their spatial arrangement around an ________ carbon. They are designated by L- and D- meaning “levo” or “dextro”. In Latin, levo means left, and dextro means right.

Answer 10

asymmetric

Question 11

Which drug has two isomers that can be interconverted within the body and caused many birth defects 50 years ago?

Answer 11

thalidomide

Question 12

The FDA has approved thalidomide for treatment of what condition?

Answer 12

multiple myeloma

Question 13

What other factors besides arrangement of the carbon skeleton are important for determining molecular function?

Answer 13

functional groups

(e.g. estradiol vs testosterone; the only difference is testosterone has an extra methyl group, and a carbonyl group in place of a hydroxyl group)

Question 14

Peptide bonds are formed by _________ reactions, which link the carboxyl group of one amino acid to the amino group of the next.

Answer 14

dehydration

Question 15

Why is the term polypeptide not synonymous with the term ‘protein’?

Answer 15

Even for a protein consisting of a single polypeptide, the relationship is somewhat analogous to that between a long strand of yarn and a sweater of particular size and shape that can be knitted from the yarn. A functional protein is not just a polypeptide chain, but one or more polypeptides precisely twisted, folded, and coiled into a molecule of unique shape, which can be shown in several different types of models. And it is the amino acid sequence of each polypeptide that determines what three-dimensional structure the protein will have under normal cellular conditions.

Question 16

If you had a polypeptide chain 127 amino acids long, how many possible configurations exist if left to chance?

Answer 16

20¹²⁷

Question 17

What protein accounts for 40% of the protein in the human body?

Answer 17

collagen

Question 18

For instance, sickle-cell disease, an inherited blood disorder, is caused by the substitution of one amino acid (______) for the normal one (_______ ____) at the position of the sixth amino acid in the primary structure of hemoglobin, the protein that carries oxygen in red blood cells.

Answer 18

valine

glutamic acid

Question 19

What method is most commonly used to determine the 3-D shape of a protein?

Answer 19

X-ray crystallography (depends on the diffraction of an X-ray beam by the atoms of a crystallized molecule)

Question 20

What exactly are intrinsically disordered proteins?

Answer 20

Proteins which do not have specific 3-D shape until they interact with a target protein or other molecule. This indefinite structure gives them flexibility.

Question 21

There are 9 amino acids with hydrophobic (nonpolar) side chains. Name them.

Answer 21

GAVLIMP-TP

glycine, alanine, valine,

leucine, isoleucine, methionine, phenylalanine, tryptophan, proline

Question 22

What are nucleic acids?

Answer 22

Polymers made of monomers called nucleotides.

Question 23

What is the name of the process during which a bond between two monomers is broken?

This process is the opposite of what reaction?

Answer 23

Hydrolysis is the opposite of a condensation reaction. During hydrolysis, a water molecule is used up in the breaking of a bond between two monomers. An H is added to one monomer, and an OH is added to the other.

Question 24

Which chemical group is most likely to be responsible for an organic molecule behaving as a base?

a. hydroxyl
b. carbonyl
c. amino
d. phosphate

Answer 24

c. amino

(from Concept 2.5, p. 39: “A substance that reduces the hydrogen ion concentration of a solution is called a base. Some bases reduce the H⁺ concentration directly by accepting hydrogen ions. Ammonia (NH₃) for instance, acts as a base when the unshared electron pair in nitrogen valence shell attracts a hydrogen ion from the solution, resulting in an ammonium ion (NH₄⁺).

Question 25

Which of the following terms is a category which includes all others on the list?

a. disaccharide
b. starch
c. carbohydrate
d. polysaccharide

Answer 25

c. carbohydrate

Question 26

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

a. The two strands of the double helix would separate.
b. The phosphodiester linkages of the polynucleotide backbone would be broken.
c. The pyrimidines would be separated from the deoxyribose sugars.
d. All bases would be separated from the deoxyribose sugars.

Answer 26

b. the phosphodiester linkages of the polynucleotide backbone would be broken

Question 27

In a polynucleotide, adjacent nucleotides are joined by a phosphodiester linkage. In this linkage, what type of bond exists between the phosphate group and the sugars of two nucleotides?

Answer 27

a covalent bond

p. 67

Question 28

alpha-helices and beta-strands or pleated sheets are formed by ________ ______.

Answer 28

hydrogen bonds

Question 29

Starch (including amylose & amylopectin), glycogen, and cellulose, are all polysaccharides composed entirely of _______ monomers.

Glycogen is extensively branched, but _______ is unbranched; ________ (also unbranched) forms very straight chains held close together like strands by hydrogen bonds.

Amylopectin is somewhat branched.

Answer 29

glucose

amylose

cellulose

Question 30

Why are lipids not true polymers?

Answer 30

They are not made up of chains of monomers in the same way that proteins and carbohydrates are. They vary more in form. They also do not covalently link like other polymers.

They are generally not big enough to be considered macromolecules.

Question 31

Not all proteins have ____________ structure.

Answer 31

quaternary

Question 32

Tertiary structure is formed by R-group interactions, including ________ bonds, ionic bonds, and hydrophobic interactions. Strong ________ bonds called disulfide bridges may reinforce the protein’s structure.

Answer 32

hydrogen

covalent

Question 33

Temperature, __, salts present, can alter the shape and function of proteins.

Answer 33

pH

Question 34

A given ____ along a DNA molecule can direct synthesis of a type of RNA called messenger RNA (mRNA). The mRNA molecule interacts with the cell’s protein-synthesizing machinery to direct production of a __________, which folds into all or part of a protein.

Answer 34

gene

polypeptide

Question 35

Which nitrogenous bases are considered pyrimidines?

Answer 35

cytosine, thymine (found in DNA), uracil (found in RNA)

Question 36

Which nitrogenous bases are called the purines?

Answer 36

adenine and guanine

Question 37

Name the components of a nucleotide?

Which part(s) are considered the ‘nucleoside’?

Answer 37

phosphate group + pentose sugar + nitrogenous base

A nucleoside is a nitrogenous base linked to a pentose sugar molecule. (Essentially, it’s the nucleotide minus the phosphate group.)

Question 38

Identify this amino acid.

Answer 38

glycine (Gly or G)

Question 39

Name this amino acid.

Answer 39

alanine

(Ala or A)

Question 40

Name this amino acid.

Answer 40

valine

(Val or V)

Question 41

Name this amino acid.

Answer 41

Leucine

(Leu or L)

Question 42

Name this amino acid.

Answer 42

Isoleucine

(Ile or I)

Question 43

Name this amino acid.

Answer 43

methionine (Met or M)

Question 44

Name this amino acid.

Answer 44

phenylalanine (Phe or F)

Question 45

Name this amino acid.

Answer 45

Tryptophan (Trp or W)

Question 46

Name this amino acid.

Answer 46

Proline (Pro or P)

Question 47

Name this amino acid.

Answer 47

Serine (Ser or S)

Question 48

Name this amino acid.

Answer 48

Threonine (Thr or T)

Question 49

Name this amino acid.

Answer 49

Cysteine (Cys or C)

Question 50

Name this amino acid.

Answer 50

Tyrosine (Tyr or Y)

Question 51

Name this amino acid.

Answer 51

Asparagine (Asn or N)

Question 52

Name this amino acid.

Answer 52

Glutamine (Gln or Q)

Question 53

Name this amino acid.

Answer 53

Aspartic acid (Asp or D)

(a.k.a. aspartate - refers to the anionic or deprotonated form)

Question 54

Name this amino acid.

Answer 54

Glutamic acid (Glu or E)

(a.k.a. glutamate - refers to the anionic or deprotonated form)

Question 55

Name this amino acid.

Answer 55

Lysine (Lys or K)

Question 56

Name this amino acid.

Answer 56

Arginine (Arg or R)

Question 57

Name this amino acid.

Answer 57

Histidine (His or H)