Quiz 2

Polymers that contain sugars ... (a) may store hereditary information. (b) may store energy. (c) may protect cells. Both (b) and (c). (a), (b), and (c).

(a), (b), and (c).

The unequal sharing of electrons within a water molecule makes the water molecule _____. hydrophobic polar ionic change easily from a liquid to gaseous form have a low surface tension

polar

Chemists assign atoms to chemical elements by counting their ________. electrons isotopes protons neutrons

protons

Each water molecule is joined to _____ other water molecules by ____ bonds. four ... polar covalent three ... ionic four ... hydrogen two ... hydrogen two ... polar covalent

four ... hydrogen

In fat synthesis,________and fatty acids combine to make fats plus________. esters; water esters; phosphate glycerol; water phosphate; glycerol glucose; phosphate

glycerol; water

In the reaction that builds a fat,________ groups react with ________ groups. carboxyl; amino hydroxyl; carboxyl hydroxyl; phosphate sulfhydryl; carboxyl phosphate; amino

hydroxyl; carboxyl

Which of the following helps most to explain why water has a high specific heat? (a) A water molecule can make 4 hydrogen bonds. (b) The water molecule has exceptionally strong covalent bonds. (c) Water temperature is exceptionally sensitive to heat. Both (a) and (b). Both (b) and (c).

(a) A water molecule can make 4 hydrogen bonds.

The open spaces in water's crystal structure make it possible for ... (a) aquatic life to exist at the North Pole. (b) water to have a low boiling point. (c) life to occur in hot springs. Both (b) and (c). (a), (b), and (c).

(a) aquatic life to exist at the North Pole.

A food company hydrogenated a barrel of fat. The treatment ... (a) made the fat less fluid. (b) made the fat less saturated. (c) lengthened the fat tails. (d) put more bends (kinks) in the fat tails. Both (a) and (d).

(a) made the fat less fluid.

Which statement is true of water's tensile strength? (a) It results from hydrogen bonding. (b) It helps to pull water through plants. (c) It involves both cohesion and adhesion. Both (a) and (b). (a), (b), and (c).

(a), (b), and (c).

A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH? (a) HA dissociates and releases H+ and A- into solution. (b) A- reacts with H+ to become HA. (c) As the solution loses H+, HA replaces the lost H+. Both (a) and (c). None of the above.

(b) A- reacts with H+ to become HA.

What do fats, steroids, and waxes have in common? (a) Moderate polarity. (b) Low solubility in water. (c) They occur in membranes. Both (a) and (c). Both (b) and (c).

(b) Low solubility in water.

Why doesn't oil mix with water? (a) Nonpolar molecules repel water molecules. (b) Polar molecules repel nonpolar molecules. (c) Polar molecules attract one another. (d) Nonpolar molecules attract one another. Both (a) and (d).

(c) Polar molecules attract one another.

Which statement is true of pH buffers? (a) They consist of strong acids and strong bases. (b) They keep the pH of the blood constant. (c) They consist of weak acids and weak bases. Both (a) and (b). Both (b) and (c).

(c) They consist of weak acids and weak bases.

To make a buffer, you need to ... (a) combine equal amounts of a strong acid and a strong base in water. (b) put either a strong acid or a strong base in water. (c) adjust the pH to 7.0. (d) have a weak acid or a weak base half ionized in water. Both (a) and (c).

(d) have a weak acid or a weak base half ionized in water.

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ... 10 neutrons. 9 protons. mass number 16, atomic number 7. 7 electrons. All of the above.

10 neutrons.

The mass number of an atom is 15, and its atomic number is 7. The atom probably has... about as much mass in electrons as in protons. at least 15 electrons. 7 units of negative charge in the nucleus. 8 neutrons in the nucleus. 7 electrons in the nucleus.

8 neutrons in the nucleus.

Which answer helps to explain why all living cells need pH buffers? ATP will not deliver energy if it is ionized. Hydrogen bonds only form at medium pH values. Amino acid side chains have many carboxyl and amino groups. Nucleic acids must have positive charges to form double helices.

Amino acid side chains have many carboxyl and amino groups.

Water is a source of ______________ for chemical reactions in cells. (a) hydrogen atoms (b) oxygen atoms (c) energy Both (a) and (b) (a), (b), and (c).

Both (a) and (b)

The presence of many C-C and C-H bonds causes fats to be ... (a) rich in energy. (b) insoluble in water. (c) low in energy. Both (a) and (b). Both (b) and (c).

Both (a) and (b).

Which factor is important in making it possible to cool yourself by sweating? (a) Molecules collide with varied angles and speeds. (b) Hydrogen bonds are relatively weak. (c) Water has more energy at the body surface. Both (a) and (b). (a), (b), and (c).

Both (a) and (b).

Which statement helps to explain why ice is less dense than liquid water? (a) Water molecules make hydrogen bonds at definite angles. (b) Cold molecules move less than warm molecules. (c) Hydrogen bonds lengthen in the cold. All of the above. Both (a) and (b).

Both (a) and (b).

Triglycerides vary with respect to the number of ... (a) hydrocarbon tails. (b) C atoms in the tails. (c) double bonds in the tails. Both (b) and (c). All of the above.

Both (b) and (c).

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________. C; it has 6 electrons. N; it has 6 protons. O; its mass number is 12. C; it has 6 protons. N; it has 6 electrons.

C; it has 6 protons.

Which statement is true of atoms? Protons repel electrons. Electrons determine the atom's size. Protons attract other protons. Most of an atom's volume is filled with matter. All of the above.

Electrons determine the atom's size.

How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base? In one case it adds H+; in the other case it adds OH-. The same buffer can't work for both acid and base. In one case the buffer is strong; in the other case it's weak. It's the same reaction running backward or forward.

It's the same reaction running backward or forward.

which statement must be mentioned in explaining why amphipathic molecules line up at a water surface? Nonpolar groups repel water. Polar groups repel water. Polar groups attract one another. Nonpolar groups attract one another. All of the above.

Polar groups attract one another.

Why is combination drug therapy for HIV/AIDS less likely to lead to resistance than single drug therapy? The drugs improve the immune system so that it is better able to find and remove virus particles. In the presence of multiple drugs, the mutation rate of HIV decreases. The likelihood of one virus spontaneously mutating to be resistant to several different drugs at the same time is extremely small. There are fewer side effects associated with combination drug therapy, and the appearance of resistance is directly related to the severity of side effects.

The likelihood of one virus spontaneously mutating to be resistant to several different drugs at the same time is extremely small.

Which statement is true of the energy levels of electrons in shells? Electrons must lose energy to move from the first to the second shell. The valence shell has higher energy than other occupied shells. All the electrons in an atom have similar amounts of energy. All of the above. None of the above.

The valence shell has higher energy than other occupied shells.

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say? Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids. Not so. Fats are small enough to travel easily without help. You have it backwards. Fats help phospholipids to travel. Right. Fats are too polar to travel alone in water. Yes. Nonpolar molecules aren't compatible with water.

Yes. Nonpolar molecules aren't compatible with water.

Which of the following statements about viruses is FALSE? The widespread use of antibiotics has led to resistant strains of viruses. Vaccines are available to prevent several diseases caused by viruses. People can get colds and flus again because the viruses are constantly mutating. If a virus mutates, the immune system may not recognize the virus.

The widespread use of antibiotics has led to resistant strains of viruses.

What do DNA, proteins, and fats have in common? They contain carbonyl groups. They are polymers. They contain phosphorus. They are polar. They contain nitrogen.

They contain carbonyl groups.

Which of the following can be found in bacteria, but not viruses? nucleic acids genetic material proteins a cell membrane

a cell membrane

dissolving is best described as ... a mingling of molecules and/or ions. breaking covalent bonds. molecules breaking into ions. a separation of molecules into neutral atoms. a change from a solid to a liquid.

a mingling of molecules and/or ions.

Suppose you were in charge of sending an unmanned space probe to a new planet in search of life. The probe would be able to collect and test samples and make observations, but the planet is too far away for the probe to be able to bring samples back to Earth. The probe is small and would only be able to run a few tests, so you want to pick a test for evidence of life that is broad enough to incorporate all forms of life as we know it. Which one of the following tests would be the best to use in this situation? a test for the presence of soil suitable for growing plants a test for the presence of things that change size quickly, since it would be an indication of growth and development a test for the presence of large organisms capable of movement a test for the presence of cells that contain DNA

a test for the presence of cells that contain DNA

Homeostasis is a living organism's ability to maintain constant internal conditions even when environmental conditions change. attempt to carry out photosynthesis even when there is no sunlight present. ability to pump blood through the body. ability to hibernate during cold times of the year. attempt to cool off, even when it is cold outside.

ability to maintain constant internal conditions even when environmental conditions change.

Buffers work best when ... the ratio of H+ to OH- is close to 1.0.nearly all of the buffer molecules are undissociated. about half of the buffer molecules are dissociated. nearly all of the buffer molecules are dissociated. the pH is nearly neutral.

about half of the buffer molecules are dissociated.

Radioactive decay is likely to occur when ... an electron hits the nucleus. protons break into neutrons and electrons. an atom has too many electrons. atoms collide with one another. an atom has too many neutrons.

an atom has too many neutrons.

Which of the following is NOT a characteristic of living things? being capable of reproduction having DNA as a genetic code exhibiting complex organization creating energy responding to stimuli

creating energy

The tendency of an atom to pull electrons toward itself is referred to as its _____. electronegativity covalency polarity tonicity ionic potential

electronegativity

Water has surface tension because ... molecules at the surface make more hydrogen bonds. water tends to evaporate from the surface. hydrogen bonds between surface water molecules resist being stretched. cohesion forces are weaker at the surface. there is positive pressure inside the water mass.

hydrogen bonds between surface water molecules resist being stretched.

Though you add heat, the temperature of boiling water remains constant because ... it takes energy to circulate water. it takes energy to break hydrogen bonds. water has a constant boiling temperature. it takes energy to break covalent bonds. None of the above. The temperature rises during boiling.

it takes energy to break hydrogen bonds.

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ... the first shell shouldn't have 3 electrons. the second shell should have 8 electrons. the first shell must fill before the second shell can have electrons. no shell can hold more than 2 electrons. the second shell can't have 4 electrons.

the first shell shouldn't have 3 electrons.

The most unsaturated fats have ... the fewest double bonds. the shortest hydrocarbon tails. the highest ratio of H to C. the most double bonds. the longest hydrocarbon tails.

the most double bonds.

Two atoms always represent the same element if they have ... the same mass number. the same number of electrons.the same number of shells. the same number of particles in the nucleus. the same number of protons.

the same number of protons.