Biology Test ch 2-5 Biochemistry

Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?

a)

What results from an unequal sharing of electrons between atoms? a) a polar covalent bond b) a nonpolar covalent bond c) a hydrogen bond d) an ionic bond

a) a polar covalent bond

Glycogen is primarily for ___ in ___ while starch is primarily for ___ in ___. a) energy storage; animals; energy storage; plants b) genetic information; animals; energy storage; plants c) energy storage; plants; energy storage; animals d) enzyme activity; animals; energy storage; plants

a) energy storage; animals; energy storage; plants

Choose the pair of terms that correctly completes this sentence. Nucleotides are to ____ as ___ are to proteins. a) nucleic acids; amino acids b) glycosidic linkages; polypeptide linkages c) amino acids; polypeptides d) polymers; polypeptides

a) nucleic acids; amino acids

A covalent bond is one which a) outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer-electron shells of both atoms. b) outer-shell electrons of one atom are transferred to the outer electron shells of another atom and a bond between the two atoms is formed. c) electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged. d) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms.

a) outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer-electron shells of both atoms.

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 expect a) the HCO3- to act as a base and remove excess H+ with the formation of H2CO3 b) the concentration of hydroxide ion (OH-) to increase c) a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3- d) the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3

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

The figure above in question 10, illustrates a ___ reaction that produces two ___ and a ___. a) condensation; hydroxyls; polymer b) condensation; water; polymer c) cleavage; water molecules; monomer d) rearrangement; water molecules; polymer

b) condensation; water; polymer

Which of the following explains most specifically the attraction of water molecules to one another? a) polar covalent bond b) hydrogen bond c) nonpolar covalent bond d) hydrophobic interaction

b) hydrogen bond

Hydrophobic substances such as vegetable oil are a) nonpolar substances that have an attraction for water molecules b) nonpolar substances that repel water molecules c) charged molecules that hydrogen-bond with water molecules d) polar substances that repel water molecules

b) nonpolar substances that repel water molecules

which of the following statements is true about buffer solutions? a) they maintain a constant pH when bases are added to them but not when acids are added to them b) they maintain a relatively constant pH when either acids or bases are added to them c) they maintain a constant pH when acids are added to them but not when bases are added to them d) they maintain.a constant pH of exactly 7 in all living cells and biological fluids

b) they maintain a relatively constant pH when either acids or bases are added to them

lipids are major constituents of ___; typical fats have ___ fatty acid chains while phospholipids have ___ chains. a) proteins, 3, 2 b) cell membranes, 2, 3 c) cell membranes, 3, 2 d) proteins, 2, 3

c) cell membranes, 3, 2

Why does ice float in liquid water? a) ice always has air bubbles that keep it afloat b) the crystalline lattice of ice causes it to be denser than liquid water c) hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water d) the ionic bonds between the molecules in ice prevent the ice from sinking

c) hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter? a) oxygen, hydrogen, calcium, sodium b) carbon, sodium, chlorine, nitrogen c) oxygen, hydrogen, nitrogen, carbon d) carbon, oxygen, sulfur, calcium

c) oxygen, hydrogen, nitrogen, carbon

Atoms whose outer electron shells contain eight electrons tend to a) be isotopes and very radioactive b) form ionic bonds in aqueous solutions c) be unstable and chemically very reactive d) be stable and chemically nonreactive, or inert

d) be stable and chemically nonreactive, or inert

an -OH groups is a(n) ___ groups while a -NH2 group is a(n) ___ group. a) carboxyl, hydroxyl b) amine, carboxyl c) hydroxyl, carboxyl d) hydroxyl, amino

d) hydroxyl, amino

Which of the following is most directly responsible for water's unique properties? a) it contains oxygen atoms and forms ionic bonds b) it contains hydrogen atoms that bond to other hydrogen atoms c) it is nonpolar and forms hydrogen bonds d) it forms hydrogen bonds and has polarity

d) it forms hydrogen bonds and has polarity

Based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely a) without charge b) negatively charged c) nonpolar d) positively charged

d) positively charged