Test 1 Flashcards
1
Q
What is generally true about essential elements and living organisms?
A
Although all forms of life require iron, other elements are required only by certain species.
2
Q
If you were told that concentrations of trace elements above what is required by organisms generally have no effect on those organisms, what would you say?
A
False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.
3
Q
How would you respond to this reasoning? Oxygen is not a greenhouse gas; therefore, gases containing oxygen—such as ozone, nitrous oxide, and carbon dioxide—are not greenhouse gases either.
A
False. Compounds can have emergent properties that are very different from those of the elements that form them.
4
Q
There are __________ naturally occurring elements.
A
92
5
Q
Which of the following is a trace element?
A
Copper
6
Q
What are the four most abundant elements found in living systems?
A
Hydrogen, oxygen, nitrogen, and carbon
7
Q
Which of the following has negligible mass?
A
Electron
8
Q
Which of the following subatomic particles has appreciable mass but no charge?
A
Neutron
9
Q
The number of protons in an uncharged atom __________.
A
equals the number of electrons
10
Q
An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________.
A
8 and 17
11
Q
An uncharged atom of nitrogen (atomic number = 7) has __________.
A
seven protons and seven electrons
12
Q
In which of the following will isotopes of an element always differ?
A
Atomic mass
13
Q
A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective numbers of neutrons, protons, and electrons that this carbon isotope has are __________.
A
8, 6, and 6
14
Q
Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal).
A
three fewer neutrons
15
Q
The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?
A
An atom with 20 protons, 21 neutrons, and 20 electrons
16
Q
Why are radioactive isotopes useful in scientific research?
A
Because they can be used as tracers to follow particular atoms and molecules through metabolic pathways
17
Q
A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell.
A
8
18
Q
The chemical characteristics or reactivity of an element depend mostly on the __________.
A
number of electrons in its outermost shell
19
Q
Some groups of chemical elements react similarly to one another. For example, the chemistries of sodium and of lithium are similar, as are the chemistries of chlorine and of iodine. These similarities in chemistry result when different elements have similar __________.
A
numbers of outer-shell electrons
20
Q
How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
A
One electron
21
Q
For most atoms, when does the configuration of electrons make the atom unreactive?
A
When the atom has eight electrons in its outermost shell
22
Q
An atom that normally has __________ in its outer shell would not tend to form chemical bonds with other atoms.
A
eight electrons
23
Q
When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?
A
A covalent bond
24
Q
A covalent bond is likely to be polar if __________.
A
one of the atoms sharing electrons is much more electronegative than the other
25
When the proton number and electron number are unequal, the atom or molecule __________.
is an ion
26
Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?
The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge
27
The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?
-2
28
Ionic bonds form as a result of __________.
attraction between ions that have opposite charges
29
A hydrogen bond __________.
is a weak chemical bond
30
When do hydrogen bonds occur?
When partial opposite charges on molecules come close enough to attract each other
31
What is the role of van der Waals interactions in biological molecules?
Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules.
32
Which molecule has the shape of a completed tetrahedron?
Methane (CH4)
33
Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?
The molecule's shape
34
Which statement is true about chemical reactions?
They involve the making and breaking of chemical bonds.
35
Which statement describes a reversible reaction that has reached chemical equilibrium?
The rate of the reverse reaction equals the rate of the forward reaction.
36
Cells are surrounded by water, with which they are mostly filled. Which of the following occurs as a result?
All the above
37
Water is a polar molecule. What does this statement mean?
That atoms in the molecule have partial charges as a result of unequal sharing of electrons in a covalent bond
38
The partial charges on a water molecule occur because of __________.
the unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule
39
In a group of water molecules, hydrogen bonds form between which of the following?
The oxygen atom in one water molecule and a hydrogen atom in another water molecule
40
Which of the following accurately relates the emergent properties of water to the effects of global warming in the Arctic?
Ice floats because it is less dense than liquid water; floating ice insulates water below and provides a habitat for some species. The significant increase in Arctic air temperature over the past 50 years is causing a reduction in sea ice, compromising these beneficial effects of sea ice.
41
If water were not a polar molecule, how would the effects of climatic warming differ from those currently observed or predicted to occur in the future?
The effects would be drastically worse because the loss of the polar nature of water would greatly reduce its specific heat and its ability to moderate temperature.
42
The tendency of water molecules to stay close to each other as a result of hydrogen bonding __________.
is called cohesion, acts to moderate temperature, provides the surface tension that allows small animals to move across a water surface, and helps to keep water moving through the vessels in a tree trunk
43
What do cohesion, surface tension, and adhesion have in common with reference to water?
All are properties related to hydrogen bonding.
44
The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are __________.
both caused by water's partial charges
45
The phenomenon responsible for maintaining the upward movement of water through vessels in a tree is __________.
cohesion
46
Adhesion is best described as which of the following?
The clinging of one substance to another substance
47
You can fill a glass of water to just slightly above the rim without the water spilling over the glass. What property of water best explains this phenomenon?
Surface tension
48
Which action would involve the greatest transfer of heat?
Condensing 5 g of steam to liquid water
49
Imagine that organisms consisted of 70–95% alcohol instead of 70–95% water. Alcohol's specific heat is about half that of water. How would living things be different?
Systems for temperature regulation would have to be much more efficient.
50
The amount of heat required to change the temperature of 1 g of any substance by 1°C is defined as __________.
the specific heat of that substance
51
The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as __________.
the heat of vaporization of that substance
52
The reason that coastal climates are more moderate than inland climates primarily water's high
specific heat
53
Sweating has a cooling effect because of water's high __________.
heat of vaporization
54
Water has __________ than other liquids such as ethanol, reflecting its capacity to absorb large amounts of heat
a higher boiling point
55
Which of the following occurs because molecules of water are farther apart in ice than in liquid water?
Ice floats.
56
Water is a very versatile solvent because water molecules are __________.
polar
57
How does the polarity of water contribute to its ability to dissolve so many substances?
Because it is polar, water's negatively charged oxygen atoms and positively charged hydrogen atoms are attracted to positively and negatively charged ions and molecules.
58
Question 23:What are nonpolar molecules that cluster away from water molecules called?
Hydrophobic
59
A molecule that has all nonpolar covalent bonds would be __________.
hydrophobic
60
Why are cell membranes composed primarily of hydrophobic molecules?
n order to perform their function of separating the aqueous solutions outside cells from the aqueous solutions inside cells, cell membranes cannot be soluble in water.
61
Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, __________
stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5 L
62
A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution?
0.092 g
63
An acid is __________.
a compound that donates hydrogen ions to a solution
64
Adding acid tends to __________ of a solution.
increase the hydrogen ion concentration and lower the pH
65
Which of the following dissociations is that of an acid?
HF → H+ + F–
66
A glass of grapefruit juice, at pH 3, contains __________ H+ as a glass of tomato juice, at pH 4.
ten times as much
67
A solution at pH 6 contains __________ than the same amount of solution at pH 8.
100 times more H+
68
Adding a base tends to __________ of a solution
lower the hydrogen ion concentration and increase the pH
69
A substance that minimizes changes in the concentration of H+ and OH– in a solution is a __________.
buffer
70
Why is the increasing amount of carbon dioxide being taken up by the oceans a cause for concern?
More carbon dioxide causes an increase in carbonic acid (H2CO3), which leads to a decrease in the concentration of carbonate ion (CO32–).
71
The absorption of human-generated CO2 by the oceans __________.
increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for organisms that produce calcium carbonate shells
72
What is the process by which monomers are linked together to form polymers?
Dehydration reaction
73
In a hydrolysis reaction, __________, and in this process, water is __________.
a polymer is broken up into its constituent monomers; consumed
74
The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) __________ bond.
covalent
75
Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?
Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units.
76
In what polysaccharide form do plants store glucose to be available later as an energy source?
Starch
77
Which of the following molecules is a monosaccharide?
C6H12O6
78
At a conference, the speaker's grand finale was sautéing mealworms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide __________
chitin
79
Carbohydrates are used in our bodies mainly for __________
energy storage and release
80
The polysaccharide that you are most likely to have eaten recently is __________
starch
81
One characteristic shared by sucrose, lactose, and maltose is that __________.
they are all disaccharides
82
A polysaccharide that is used for storing energy in human muscle and liver cells is _
glycogen
83
Carbohydrates can function in which of the following ways?
Structural support and energy storage
84
Amylase is an enzyme that breaks down starch. Why can the same enzyme not break down cellulose?
The monosaccharide monomers in cellulose are bonded together differently than those in starch.
85
The subunits (monomers) in cellulose are linked together by _________
glycosidic linkages
86
Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least? (
Cellulose (in the lettuce)
87
Lipids differ from other large biological molecules in that they __________
are not truly polymers
88
Which of the following terms can be correctly used to describe compounds that do not mix with water?
hydrophobic
89
Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them?
For carbon skeletons of equal length, saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols do.
90
The lipids that form the main structural component of cell membranes are _________
phospholipids
91
If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules form a "ball of spaghetti" with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have _________
a charged or polar end and an uncharged or nonpolar end
92
Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)?
Phospholipid molecules have a distinctly polar "head" and a distinctly nonpolar "tail," whereas triacylglycerols are predominantly nonpolar.
93
The sex hormones estradiol and testosterone belong to which class of molecules
Lipids
94
High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place?
Cholesterol is the precursor for many important molecules such as sex hormones.
95
Manufacturers make vegetable oils solid or semisolid at room temperature by
adding hydrogen atoms to the fatty acid hydrocarbon chains, thereby converting carbon-carbon double bonds to single bonds
96
Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by __________.
ester linkages
97
The fatty acid tails of a phospholipid are __________ because they __________
hydrophobic; have no charges to which water molecules can adhere
98
The overall three-dimensional shape of a single polypeptide is called its _________
tertiary structure
99
When a protein is denatured, why does it lose its functionality?
Denaturation breaks the intramolecular bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.
100
Which of the following lists ranks these molecules in the correct order by size from smallest to largest?
Water, glucose, sucrose, protein
101
Which of the following represents a specific description of a polypeptide?
None of the listed responses is correct.
102
Enzyme molecules require a specific shape to perform their catalytic function. Which of the following might alter the shape of an enzymatic protein?
All of the listed responses are correct.
103
The α helix and β pleated sheet represent which level of protein structure?
Secondary structure
104
The peptide bond is __________.
a covalent bond joining amino acids together to form a polypeptide
105
Protein molecules are polymers (chains) of __________
amino acid molecules
106
The "primary structure" of a protein refers to _________
the sequence of amino acids along a polypeptide chain
107
What do Alzheimer's, Parkinson's, and mad cow disease have in common?
All are associated with the buildup of misfolded proteins in cells.
108
A glucose molecule is to starch as _________
a nucleotide is to a nucleic acid
109
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________
DNA
110
Based on complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________
adenine; thymine
111
Which of the following are pyrimidines found in the nucleic acid DNA
Thymine and cytosine
112
Which of the following describes a difference between DNA and RNA?
The first three listed responses correctly describe differences between DNA and RNA
113
Which of the following lists represents the chemical components of a nucleotide?
A nitrogenous base, a phosphate group, and a pentose sugar
114
Which of the following is true regarding complementary base pairing in DNA and RNA molecules?
Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules.
115
Which of the following is the simplest collection of matter that can live?
Cell
116
A researcher wants to film the movement of chromosomes during cell division. Which type of microscope should she choose, and why is it the best choice?
Light microscope because the specimen is alive
117
Which of the following statements is true about cell fractionation?
Cell fractionation separates cells into their component parts.
118
Consider two cells with the same volume but with very different surface areas due to differences in their shapes. The cell with the larger surface area is likely to __________
be involved in the rapid uptake of compounds from the cell's environment
119
Which of the following structures is found in eukaryotic but not prokaryotic cells?
Mitochondria
120
Which of the following is/are likely to limit the maximum size of a cell?
All of the choices are correct.
121
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
Phospholipids form a selectively permeable structure.
122
The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true?
The fluid aspect of the membrane is due to the mobility of phospholipids, and embedded proteins account for the mosaic aspect.
123
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?
On the outside (external) surface of the membrane
124
The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?
1.0 M
125
The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?
A hypertonic sucrose solution
126
Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?
A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis.
127
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?
Endocytosis
128
Which of the following correctly states the relationship between anabolic and catabolic pathways?
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
129
Which of the following states the relevance of the first law of thermodynamics to biology?
Energy can be freely transformed among different forms as long as the total energy is conserved.
130
Which part of the equation ΔG = ΔH – TΔS tells you if a process is spontaneous?
ΔG
131
Question 11:From the equation ΔG = ΔH – TΔS it is clear that __________
a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change
132
When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations
In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.
133
Which of the following is changed by the presence of an enzyme in a reaction
The activation energy
134
Which of the following statements correctly describe(s) the role or roles of heat in biological reactions?
The first and second choices are correct.
135
The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?
The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site
136
A molecule becomes more oxidized when it __________
loses an electron
137
Oxygen gas (O2) is one of the strongest oxidizing agents known. The explanation for this is that __________
the oxygen atom is very electronegative
138
Which of the following statements is the best explanation of what happens to the temperature and carbon dioxide concentration during a 1-hour class period in a classroom of 300 students if the heating and air-conditioning is turned off and all doors are kept closed?
Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration
139
A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to kill bacteria in people with infections. However, he cannot do this because __________
human cells must also perform glycolysis; the drug might also poison them
140
In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?
Pyruvate is oxidized, and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH.
141
The energy given up by electrons as they move through the electron transport chain is used in which of the following processes?
Pumping H+ across a membrane
142
Which of the following best describes the electron transport chain?
Electrons are passed from one carrier to another, releasing a little energy at each step.
143
If significant amounts of materials are removed from the citric acid cycle to produce amino acids for protein synthesis, which of the following will result?
The first three answers are correct.
144
