Exam 1
Magnesium has an atomic number of 12. What is the most stable charge for a magnesium ion?
+2 charge
Which functional group shown above is characteristic of alcohols?
--OH
How many neutrons are present in the nucleus of a phosphorus-32 ( 32P) atom (see the figure above)?
17
How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?
2
How many electron pairs does carbon share to complete its valence shell?
4
Which of the following produces and modifies polysaccharides that will be secreted?
Golgi apparatus
Which of the following are compounds?
H2O and CH4, but not O2
Why does ice float in liquid water?
Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur?
The cell will become turgid
Which of the following is a property of liquid water? Liquid water ________
has a heat of vaporization that is higher than that for most other substances
Which of the following can be attributed to water's high specific heat?
A lake heats up more slowly than the air around it
Which of the following effects can occur because of the high surface tension of water?
A raft spider can walk across the surface of a small pond
Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose
the cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell
Cell size is limited by
surface to volume ratios
Which of the following is the best description of an atom's physical structure?
Atoms are little bubbles of space with mass concentrated at the center of the bubble
Which of the structures illustrated above is an impossible covalently bonded molecule?
B
Prokaryotes are classified as belonging to two different domains. What are the domains?
Bacteria and Archaea
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?
C18H32O16
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
CO2
Which of the following is a major difference between prokaryotic cells and eukaryotic cells?
Eukaryotic cells have more intracellular organelles than prokaryotes.
Which of the following is true of osmosis?
In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
Which of the following takes place as an ice cube cools a drink?
Kinetic energy in the liquid water decreases
Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the
MITOCHONDRIA :D
The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?
MgCl2
You have two beakers. One contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen
NaCl crystals will dissolve readily in water but will not dissolve in methanol
Which functional group(s) shown above is (are) present in all amino acids?
O=C-O-H & -NH2
In living systems molecules involved in hydrogen bonding almost always contain either oxygen or nitrogen or both. How do you explain this phenomenon?
Oxygen and nitrogen are elements with very high attractions for their electrons
You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?
Permeability to glucose will increase
Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
Proteins secreted by prokaryotes are synthesized on ribosomes bound to the cytoplasmic surface of the plasma membrane
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life
Gaucher disease is the most common of lipid storage diseases in humans. It is caused by a deficiency of an enzyme necessary for lipid metabolism. This leads to a collection of fatty material in organs of the body including the spleen, liver, kidneys, lungs, brain, and bone marrow. Using your knowledge of the structure of eukaryotic cells, identify the statement below that best explains how internal membranes and the organelles of cells would be involved in Gaucher disease.
The lysosomes lack sufficient amounts of enzymes necessary for the metabolism of lipids.
H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell-cell interaction (cell junctions), and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain the results of Wilson's experiments?
The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge.
How do phospholipids interact with water molecules?
The polar heads interact with water, the nonpolar tails do not
How many electrons are involved in a double covalent bond?
four
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
gap junctions
Can the atomic mass of an element vary?
Yes. Adding or losing neutrons will change the atomic mass without forming a different element.
What results from the chemical reaction illustrated above? The reactants have no charge.
a cation with a net charge of +1 and an anion with a net charge of -1
Which of the following descriptions best fits the class of molecules known as nucleotides?
a nitrogenous base, a phosphate group, and a sugar
Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits
altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered
for a protein to be an integral membrane protein, it would have to be
amphipathic,with at least one hydrophobic region
Which of the following allows water to move much faster across cell membranes?
aquaporins
Lipids _____
are insoluble in water
Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At higher temperatures, these regions
are less fluid than the surrounding membrane
which of the following is NOT true? Both chloroplasts and mitochondria
are part of the endomembrane system
Saturated fatty acids
are the principal molecules in lard and butter
Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will
be more constrained in structure
According to the fluid mosaic model of cell membranes, phospholipids
can move laterally along the plane of the membrane
The element present in all organic molecules is
carbon
An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
cell-cell recognition
In what way do the membranes of a eukaryotic cell vary?
certain proteins are unique to each membrane
The complexity and variety of organic molecules is due to
chemical versatility of carbon atoms
Which polysaccharide is an important component in the structure of many animals and fungi?
chitin
What component of amino acid structure varies among different amino acids?
components of R-group
Familial hypercholesterolemia is characterized by
defective LDL receptors on the cell membranes
Van der Waals interactions may result when
electrons are not symmetrically distributed in a molecule
Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other? Testosterone and estradiol
have different functional groups attached to the same carbon skeleton
The molecule shown the accompanying figure is a _____.
hexose
The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?
hydrogen bond
Water molecules are attracted to one another by
hydrogen bonds
Which type of bond must be broken for water to vaporize?
hydrogen bonds
In a plant cell, DNA may be found
in the nucleus, mitochondria, and chloroplasts
The membranes of winter wheat are able to remain fluid when it is extremely cold by
increasing the percentage of unsaturated phospholipids in the membrane
Diffusion
is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. Hydrogenated vegetable oil _____.
is solid at room temp.
Which of these classes of biological molecules does NOT include polymers?
lipids
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
lysosomes
A molecule with the chemical formula C6H12O6 is probably a _____.
monosaccharide
Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubular tracks along which vesicles could be transported, and they added vesicles and ATP (because they knew the transport process requires energy). Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?
motor proteins
When the atoms involved in a covalent bond have the same electronegativity, what type of bond results?
non-polar covalent bond
In which of the structures illustrated above are the atoms bonded by ionic bonds?
none
Nucleic acids are polymers made up of which of the following monomers?
nucleotides
Knowing the atomic mass of an element allows inferences about which of the following?
number of protons plus neutrons in the element
Which of the following illustrations is NOT a structural isomer of an organic compound with the molecular formula C6H14? For clarity, only the carbon skeletons are shown; hydrogen atoms that would be attached to the carbons have been omitted.
one with double bond
Which of the following most accurately describes selective permeability?
only certain molecules can cross the cell membrane
Stanley Miller's 1953 experiments supported the hypothesis that
organic molecules can be synthesized abiotically under conditions that may have existed on early Earth
A covalent chemical bond is one in which
outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals
Which of the following processes includes all others?
passive transport
An organism with a cell wall would most likely be unable to take in materials through
phagocytosis
What results from an unequal sharing of electrons between atoms?
polar covalent bond
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds.
You disrupt all hydrogen bonds in a protein. What level of structure will be preserved?
primary structure
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
proteins
Which level of protein structure do the α-helix and the β-pleated sheet represent?
secondary
Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to _____.
separate chromosomes during cell division
A compound contains hydroxyl groups as its predominant functional group. Therefore, this compound
should dissolve in water
Refer to the figure above (first three rows of the periodic table). What element has properties most similar to carbon?
silicon
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
The liver is involved in the detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and, therefore, abundant in liver cells?
smooth ER
Rank, from low to high, the pH of blood, stomach acid, and urine.
stomach acid, urine, blood
The figure above shows the structures of glucose and fructose. These two molecules are
structural isomers
Rhodopsins are light-sensitive molecules composed of a protein (opsin) and retinal (a derivative of vitamin A). Opsin is a membrane protein with several α-helical segments that loop back and forth through the plasma membrane. There are two classes of rhodopsins. According to Oded Beje, one class has relatively slow dynamics (a photocycle of approximately 0.5 seconds) and is well suited for light detection. The second class has faster dynamics (a photocycle of approximately 0.02 seconds) and is well suited for chemiosmosis: pumping of protons or chloride ions across cell membranes. Oded Beje was the first, in September 2000, to report on a rhodopsin (proteorhodopsin) found in the domain Bacteria Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure found in this protein?
tertiary
The figure above shows the structures of glucose and fructose. These two molecules differ in
the arrangement of carbon, hydrogen, and oxygen atoms.
The force driving simple diffusion is _____, while the energy source for active transport is _____.
the concentration gradient; ATP
The partial negative charge in a molecule of water occurs because
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
In the fractionation of homogenized cells using centrifugation, the primary factor that determines whether a specific cellular component ends up in the supernatant or the pellet is the
the size and weight of the component
Ions diffuse across membranes through specific ion channels down
their electrochemical gradients
When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell?
there is a random movement of substances into & out of the cell
Differences among organisms are caused by differences in the
types and relative amounts of organic molecules synthesized by each organism
