Chapter 2
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.
1
What is the maximum number of 100 amino acid long polypeptides that could be made?
20100
Which of the groups below is capable of only hydrophobic interactions?
C-C-C
Which interaction is most important in enhancing the solubility of macromolecules in water?
H bonds
The b pleated sheet is characterized by orientation of ______ the molecular axis.
H bonds perpendicular to
Which of the following tripeptides would be most likely to be soluble in an organic (hydrophobic) solvent like benzene?
N proline phenylalanine leucine C
The most electronegative atoms typically present in biological molecules are ____ and ____.
O, N
Which of the following groups is capable of only hydrophilic interactions?
O=C-OH
What is now thought to have been the genetic material in the first living organisms on Earth?
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?
Silicon is too large for its nucleus to attract the valence electrons of neighboring atoms enough to hold molecules together sufficiently.
How do amino acids like hydroxylysine and thyroxine, which are not among the 20 amino acids that are inserted into proteins, get into proteins?
They are the result of the alteration of R groups of the 20 amino acids after their incorporation into the polypeptide.
What bond is responsible for the branch points in glycogen and amylopectin?
a (1—>6) glycosidic linkages
A molecule that is capable of releasing or donating a hydrogen ion is termed a(n) _______.
acid
Which of the following is a nucleotide?
adenine + ribose + phosphate
What type of protein secondary structure is characterized as being highly extensible because of its coiled structure?
alpha-helix
Which polysaccharide bond cannot be broken by mammalian enzymes that normally digest polysaccharides?
b (1—>4) glycosidic linkages
Why do sugars tend to be highly water soluble?
because of their large numbers of hydroxyl groups
In a living organism, where are ionic bonds most likely to be found?
deep in a protein's core where water is excluded
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 semiindependent manner. These modules are called ______.
domains
The most stable atoms and thus those that are typically nonreactive are the atoms that have _______.
full outer shells
Which of the following is not a macromolecule formed by polymerization?
lipids
A release of hydrogen ions to a solution would most likely ____________.
lower pH
Which amino acid is most likely to be found in the core of a protein?
methionine
The lowmolecularweight building blocks of polymers are called _______.
monomers
What kind of bond results from an unequal sharing of electrons?
polar covalent bond
What level of structure in proteins is held together by intermolecular R group interactions?
quaternary structure
Tertiary structure in DNA is also known as ________.
supercoiling
Where are hydrophobic interactions most likely to occur?
the core of a watersoluble protein
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?
van der Waals forces
Under which circumstances would electrons be most likely to be shared equally?
when atoms of the same element are sharing them
