Download Unit 2 pairs test answer key True/False 1. T 2. T 3. F

Unit 2 pairs test answer key
True/False
1. T
2. T
3. F
4. T
5. T
6. T
7. F
8. F
9. F
Modified True/False
1. T Sister chromatids are held together by the centromere\
2. F, cytokinesis. Telophase is the end of mitosis, cytokinesis involves the division into two cells.
3. F, binary fission. Prokaryotes divide by a process very different from mitosis, called binary
fission
Multiple Choice
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
D
There are 12 carbon, 22 hydrogen, and 11 oxygen atoms.
A
The electron has a charge of negative 1.
C
The neutron is neutral and is located in the nucleus.
C
The first level has 2, and the second has 5.
C
Ionic bonds form between two oppositely charged atoms or groups of atoms.
C
There are two covalent bonds, each one is between O and H.
B
A single covalent bond forms when two atoms share two electrons.
D
The reactants have more energy than the products, which means energy is lost to the
environment.
B
By lowering the activation energy, an enzyme increases the rate of the reaction.
D
Starch digestion would proceed most quickly in the presence of amylase at body
temperature.
C
Hydrogen bonds form between hydrogen and either oxygen, nitrogen, or fluorine.
A
Adhesion is caused by hydrogen bonds between water and some surface.
D
Water is polar while oil is nonpolar.
C
The pH decreases as the H+ increases.
A
Carbohydrate is the key substance for energy metabolism. Fat is used for storage but
not typically as a direct energy source.
16. D
Amino acids are the building block of protein.
17. A
DNA is the genetic material of the cell.
18. D
The nonpolar tails of the phospholipids repel water. The polar heads face the
environment inside and outside of the membrane. The nonpolar tails are in the middle, at
position E.
19. D
The earliest microscopes did not have very high resolution. Scientists could not observe
very small substances such as atoms and molecules.
20. C
All the statements are true, but only statement C is of the cell theory.
21. B
All bacteria are prokaryotes. Although they do contain genetic material, it is not located
in a nucleus.
22. D
All cells have cell membranes, chromosomes, and DNA. Eukaryotes have a nucleus.
23. C
The organism could not have been a bacterium because it had a nucleus, not an animal
because it had a cell wall. The organism was a plant.
24. B
Lysosomes are found only in animals.
25. D
As the solution becomes more concentrated, it will become increasingly hypertonic.
26. C
The illustration shows diffusion, doesn’t require energy
27. A
Choloroplasts are organelles found in plant cells and eukaryotic algae that conduct
photosynthesis.
28. D
In prophase, the cell’s chromatin tightens into chromosomes. Near the end of this
stage, the nuclear envelope breaks down and disappears. Finally, the spindle starts to form.
29. C
If a cell continues to grow, the ratio of surface area to volume will decrease will
decrease and have difficulty supplying nutrients and expelling waste.
30. B
“Synthesis” of DNA
31. D
By the end of prophase the nuclear membrane has disintegrated.
32. B
During metaphase, the spindle apparatus aligns the sister chromatids in the center, or
equator, of the cell.
33. D
In telophase, the chromosomes arrive at the poles and begin to relax, or decondense.
34. C
During mitosis, the cell’s replicated genetic material separates and the cell prepares to
divide into two cells.
35. D
Cancer cells spend less time in interphase than do normal cells.
36. B
The mutations that might lead to cancer occur relatively frequently but DNA repair
systems correct them. Cancer often is a result of a mutation in the DNA repair system itself that
prevents it from fixing other mutations.
37. B
During the second stage of interphase, called synthesis, a cell copies its DNA in
preparation for cell division.
38. C
Metaphase is one of the shortest stages of mitosis, but when completed successfully, it
ensures that new cells have accurate copies of the chromosomes.
39. C
Mitosis is the division of the nucleus. Without cytokinesis, mitosis alone will lead to a
multinucleate cell.
40. B
The decondensed chromosomes are so long and diffuse that they could not be
disentanled when they are dragged to the poles of the dividing cell.
41. A
The normal growth of the cell occurs in G1 before the chromosomes are replicated.
42. B
A stem cell’s usefulness lies in the fact that it is unspecialized and therefore has the
potential to develop into cells of different kinds that might be used to repair damaged tissue.
Completion
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Atom
Covalent
Chemical reaction
Catalyst
Polar
Hydrogen
A nucleus
Prophase
Cytoplasm
Checkpoints
Cancer
Stem cells
Short answer
1. Polarity allows water to dissolve many materials but not react with them chemically in the
process.
2. Sodium (Na) atoms each lose one electron. Chlorine (Cl) atoms each gain one electron. When
sodium chloride (NaCl) is formed by ionic bonding, the resulting molecule is stable.
3. Magnesium
4. Two
5. An acid
6. Tube 1 is the control because it contains the egg white but none of the experimental
substances. It is important to observe what would happen to the egg white without any of the
experimental substances.
7. Mitochondria are organelles that produce energy for cell reactions, active cells usually have
more mitochondria than do less active cells. It would be reasonable to conclude that the
number of mitochondria is in direct relation to the amount of work done by the cells.
8. Scientist would classify this bacterium as a prokaryote because it has no membrane-bound
internal structures and it does not have a distinct nucleus, even though it does contain a
nucleoid with DNA.
9. Membranes are useful for providing a surface for cell reactions. Efficiency of the cell processes
is increases by folded membranes. Folded membranes can be used to make compartments.
They also can be used to make canals for transport of substances.
10. The difference between prokaryotic and eukaryotic cells is greater because these two types of
cells differ in basic cell organization. Eukaryotic cells are characterized by membrane-bound
organelles. Prokaryotic cells do not have membrane-bound organelles and must carry on all
essential life processes without them.
11. To demonstrate that the nuclear matrix did not result from any chemical reactions but actually
existed as an independent structure
12. The variable was the method and substance used to remove the contents of the nucleus. Each
scientist used a different substance.
13. A fibrous protein network was observed to be present in the nucleus.
14. A compound light microscope can magnify objects about 1000 times. Because these
microscopes use light, the higher the magnification, the more the light that reaches the eye is
scattered. The wavelenths of visible light limit the resolution power of the visible light
microscope.
15. Prokaryotic cells do not have specialized internal structures and are therefore less complex than
eukaryotic cells. Prokaryotes are single-celled organisms. Because the first organisms on Earth
were unicellular, scientists believe that the first cells were prokaryotic.
16. Eukaryotic organelles allow cell processes to occur in specific areas in the cell. Prokaryotic cells
do not have organelles and this suggests that cell processes occur throughout the cell, rather
than in specific lotion.
17. Harmful substances might get trapped inside the cell or be allowed inside. Substances necessary
for the cell to survive might not be able to get inside the cell.
18. Both the inside and outside of the cell contain watery environments. Water molecules are polar
and are repelled by nonpolar molecules. Therefore, the nonpolar middle of the phospholipid
bilayer repels the polar molecules and separates the material inside and outside of the cells.
19. Both protect the structures that are contained inside. However, the cell membrane allows
materials to move in and out of the cell, while the case of the waterproof watch prevents fluids
from moving inside.
20. The different substances in the membrane move around. The movement is similar to
substances floating in water or another fluid, and the positions of the substances form a mosaic,
or pattern.
21. Proteins on the outer surface of the membrane transmit signals to the inside of the cell. Other
proteins at the inner surface support the cell’s structure and give it shape. Transport proteins
move materials in and out of the cell through the membrane.
22. You may argue that the cell cannot exist without the membrane protecting it. Some may argue
that al l the structures are equally important or argue that argue that a different structure, such
as the mitochondrion, is the most important structure of a cell.
23. Rough ER has large amounts of surface area where ribosomes are attached and proteins are
produced. Smooth ER has no attached ribosomes, but is the site where many complex
carbohydrates and lipids are created.
24. Animal and plant cells share some cell structures and other structures are unique to animals or
plants. Lysosomes and centrioles=animal cells, chloroplasts and cell walls=plant cells
25. Plants need rigid cells to stand at various heights and resist breakage. Therefore, it is an
advantage for plants to have cell walls. Animals have other systems for support, and they need
flexible cells for rapid movements.
26. Both osmosis and facilitated diffusion take advantage of the natural tendency for substances to
move from areas of high concentration to areas of low concentration. This means that the
action is passive and requires little or no added energy. In active transport, substances move
from a region of low concentration to one of high concentration. Energy is required to activate
processes that do not follow the follow the normal direction of diffusion.
27. In both situations, a portion of the plasma membrane surrounds large particles. However, the
plasma membrane never breaks apart or forms a hole. These processes demonstrate that the
plasma membrane is very fluid and is capable of reforming as parts break off.
28. The rate of diffusion is affected by concentration, temperature, and pressure. The scientist
used the same concentration for both experiments. However, the temperature was lower for
the second experiment. Also, at higher altitudes, air pressure is lower. Both lower
temperatures and decreased pressures slow down the rate of diffusion. Therefore, the rate of
diffusion for the second experiment would have been slower than for the first experiment.
29. Because the bromothymol in the control was still yellow, the CO2 did not leak out of the test
tubes. Therefore, in the other two test tubes, the Elodea must have taken in the CO2.
30. He could have exposed one test tube to white light and left another in complete darkness. He
could have used a test tube without a piece of algae.
31. The different colors of light
32. Prophase
33. A smaller cell can more efficiently transport substances. In addition, wastes will be expelled
more effectively and will be easier to obtain nutrients. For the cytoskeleton to be an efficient
transportation mechanism, the cell must be small.
34. Curing G1, a cell is growing, carrying out normal functions, and preparing to replicate its DNA.
During synthesis, the cell copies its DNA in preparation for mitosis. Finally, G2 is the stage in
which the cell prepares for division of the nucleus.