Download 1 - mrs. leinweber`s wiki

Science 10 Unit 3 Review
1. When Robert Hooke examined cork under his microscopes, he called the structures he saw “cells,” because they
reminded him of the small rooms in a monastery.
2. The particle model of matter states that all matter is made up of tiny particles, such as atoms and molecules, and
that these particles are in constant motion.
3. Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
Osmosis is the diffusion of water molecules across a membrane.
4. A concentration gradient is the difference in concentration of a particular kind of particle between two areas.
Diffusion occurs down a concentration gradient.
5. (a) Water, gases, glucose, and small ions are examples of materials transported by passive transport. Active
transport moves minerals, sodium ions, and other molecules against a concentration gradient.
(b) Passive transport can take place within the cell and across cell membranes, and includes diffusion, osmosis, and
facilitated diffusion. Some molecules can diffuse through the phospholipid bilayer. Channel proteins allow ions to
diffuse through the membrane. Carrier proteins enable other molecules to pass through the membrane via facilitated
diffusion. Active transport involves carrier proteins.
(c) Root cells use active transport to “pump” in minerals from the soil, against a concentration gradient. An example
of passive transport is osmosis into the phloem tissue cells.
6. (a) Gravitropism is the tropic response of plants to the force of gravity.
(b) Turgor pressure is the water pressure in plant cells.
(c) Sleep movements are the changes in the position of a plant’s leaves according to the time of day; controlled by
changes in turgor pressure.
(d) Cohesion is the tendency of like molecules (i.e.water) to be attracted to one another.
(e) Auxin is a plant hormone involved in plant responses, such as phototropism and gravitropism.
7. Phloem sap carries sugar, water, and nutrients from the leaves to the rest of the plant.
8. (a) Water, oxygen, carbon dioxide are three molecules that diffuse into the cell.
(b) These molecules are small, and uncharged.
9. (a) Phagocytosis transports organisms or large fragments of organic matter.
(b) Receptor-mediated endocytosis transports cholesterol and viruses.
(c) Diffusion transports water, and gases.
(d) Active transport moves minerals (in) and cell wastes (out) of a cell.
(e) Carrier proteins transport glucose.
10. In cell culture, cells are isolated and supplied with the nutrients they need for growth. Generations of cells result
from the growth and division of these cultures, and the resulting cell lines provide cells for research. This technique
is used in cancer research.
12. Schwann’s colleague, Schleiden, looked at hundreds of plants and concluded that all plants were composed of
cells. Schleiden suggested that the dark spot he could see in each cell (the nucleus) controlled the cell’s activities.
Schwann examined many animals and found that their tissues contained multiple structures, each containing a
nucleus. Thus Schwann concluded that animal tissues contained cells. Schwann went on to state that all organisms
are composed of cells—the first principle of the cell theory.
13. Channel proteins are a type of transport protein that forms tunnel-like pores in the cell membrane. The pores
created by channel proteins provide water filled passages through which small dissolved ions can diffuse.
14. Vascular tissue cells form a series of pipe-like tubes throughout the plant, from its roots, through its stem, and
through its leaves. Xylem and phloem make up these tubes.
15. With increases in cell size, the cell volume increases much faster than its surface area. Volume increases by a
factor of 3 (it is cubed); however, surface area only increases by a factor of 2 (it is squared). A cell’s size and shape
are closely related to its function. Smaller cells with a high surface area-to-volume ratio, such as those that are .at or
have many in foldings, efficiently absorb and transport substances through the cell membrane and through the
cytoplasm. Cells with low surface area-to-volume ratios, such as round cells, may be used for storage.
16. As a result of photosynthesis, plants cells consume carbon dioxide and produce oxygen. In plants, far greater
volumes of gases are produced during photosynthesis than are consumed by cellular respiration, resulting in an
overall net production of oxygen.
17. Cell membranes are composed of a double layer of phosopholipids. Proteins and other molecules are embedded
between and attached to the phospholipids. Each phospholipid molecule has a head end, which is hydrophilic, and a
tail end, which is hydrophobic. In the membrane, the phospholipid hydrophilic head points outward, toward water.
The hydrophobic tails are sandwiched in the middle of the membrane.
18. Minerals are actively transported into the root cells. Osmosis then brings water into the root cells. The increasing
water pressure pushes water up the xylem.
19. Peter Boysen-Jensen showed that the signal responsible for regulating phototropism in plants was a chemical
signal, capable of diffusing through gelatin.
20.
(b) Animal cells do not have central vacuoles, cell walls, or chloroplasts.
21.
22. (a) The apple juice was hypotonic to the inside of the raisin.
(b)
23. (a) Leaf coverage is the manipulated variable.
(b) Movement of water in the tube is the responding variable.
(c) D is the control because it rejects the movement of water when the plant is untouched.
(d) Water movement depends on the transpiration of water from the leaves. When water exits the plant due to
transpiration from the leaves, more water is pulled up the stem. If there are fewer leaves, there is less transpiration
and thus less movement of water in the tube. If there are no leaves, or if transpiration is prevented by submersing the
leaves in water, the movement of water in the stem is halted.
24. Refer to pages 306-307 of the Student Book for some examples of how semi-permeable membranes are used in
water purification, kidney dialysis, transdermal patches, and drug delivery by liposomes.
25. These series of images could be stacked to produce a three-dimensional image of the hand.
26. (a) Transpiration will be reduced in the plant that is misted, because the humidity around the leaf is high. When
the soil is watered, transpiration will continue as water .owing up through the xylem replaces water vapour lost
through transpiration.
(b) The plant that has its soil watered is more likely to survive as there is a continual supply of water coming from
the roots below. Once the water on the leaves evaporates (after being misted) there is no water to replace that being
lost through transpiration since the soil would be dry.
27. (a) Beaker B has the higher solute concentration.
(b) Osmosis will occur: water inside the dialysis tubing (which contains the solution from Beaker A)will move out
into Beaker B.
28. The active transport proteins are transporting materials across the cell membrane and out of thecell, against the
concentration gradient. As a result, the previously isotonic situation is upset and the concentration gradient changes,
causing fluid to move out of the cell and its volume to decrease.
29. (a) Transmission electron microscopes have enough magnifying power to reveal the structure of viruses and cell
membranes. A TEM could be used to study the interaction between a virus and a cell at different time periods during
the infection process.
(b) Some viruses “trick” cells into allowing the virus to enter by receptor-mediated endocytosis. A greater
understanding of this process could help scientists to understand how viruses infect cells.
(c) Answers will vary.
30. The concentration of Mg2+ is the same in each cell, so Mg2+ is not transported by CFTR. The normal
level of Na+ in the cytoplasm is very low. The defective CFTR may be unable to transport Na+ out of the cell. The
level of Cl– is negligible in the cytoplasm of the cell with the defective CFTR. This may be due to the defective
CFTR being unable to transport Cl– into the cell.
31. Some cancer cells do not respond to the signal for cell death by way of apoptosis. It is possible that knowing
more about the genes for apoptosis could help researchers to learn how to prevent continuous cell growth.
32. Students’ answers may vary; however, they may suggest asking the researcher how large her sample size was.
Not all differences in genes and gene sequences are the result of harmful mutations, as some variation is normal.
One way to test her hypothesis would be to see if a large proportion of patients with lung cancer have this particular
mutation. Their gene sequences could be compared to genes from patients without lung cancer. Students may
suggest running a tissue culture study to compare the growth of cells with the normal version of the gene and cells
with the mutated version of the gene.
33. The radioactive carbon dioxide would enter the leaf through the stomata. Here, photosynthetic cells of the leaf
would incorporate the radioactive carbon dioxide as raw material for photosynthesis. The sugar formed would then
be transported in the phloem vessels.
34. Multicellular organisms have cells specialized for obtaining or creating food, building cell structures, converting
food molecules into a readily useable form of energy, transporting needed materials and wastes, and storage, among
other functions. The smooth functioning of societies depends on people carrying out analogous roles.
35. Endoplasmic reticulum (rough), Golgi apparatus, and vesicles would be most numerous in cells specialized in
secreting proteins.
36. Closed systems do not permit the flow of matter between the cell and its environment. If cells were closed
systems, they would have to have all of the requirements for life within the cell without needing movement of
materials in or out of the cell. Cells would need some internal way of generating nutrients and getting rid of wastes
without transport across the cell membrane.
37. Both the cell wall and the cell membrane form boundaries around the cell and keep the cell contents together.
The cell membrane, unlike the cell wall, also acts as a selective filter. The cell wall provides structural support,
which the cell membrane does not. Plant cells need cell membranes to enclose the cytoplasm and regulate the
passage of molecules in and out of the cells. Plant cell walls prevent plant cells from bursting from turgor pressure.
38. A TEM must have been used to capture the first image, since the magnification is too high for a light
microscope, but reasonable for an electron microscope, and the image depicts a thin slice through the cell. A CLSM
would have been used to capture the second image, as the magnification would be reasonable for a CLSM, and the
image is three-dimensional.
39. A semi-permeable membrane would allow some materials through (e.g., the water or liquids) while restricting
the passage of others (e.g., milk solids). Dialysis tubing is semi-permeable and permits osmosis to occur, but not the
diffusion of larger molecules, such as sugar.
40. The higher the surface area-to-volume ratio, the more transport is possible across the cell membrane and the
faster it is for materials to reach their destinations within the cell. This results in an efficient transport of nutrients
and elimination of wastes in such cells. Cells specialized in transporting nutrients will usually be shaped in such a
way that they have a high surface area-to-volume ratio.
41. Cell membranes contain embedded proteins that help move substances across the membrane or carry out
chemical reactions. Some materials simply diffuse through the membrane. Cell membranes prevent many substances
from entering a cell and are selective in the materials that they allow to pass through. Particle size often limits
transport, and membrane proteins are also used to facilitate transport. Stomata allow the passage of gases in and out
of the cellular spaces in the leaves. The stomata are surrounded by guard cells, which change in size and regulate the
opening of the stomata. Stomata are not selective in regulating which gases enter or leave the leaf.
42. Water enters the plant via the roots. Root hairs have tips permeable to water, and water enters these cells by
osmosis. A solution of water and minerals-the xylem sap-accumulates in the root xylem; as water pressure in the
roots increases, water is pushed up the plant. Water is also pulled from above because of the process of transpiration.
As water evaporates from the leaves, water molecules move into place to replace the molecules that were lost to the
environment. The water properties of cohesion and adhesion allow for water to move throughout the plant. Water is
used in the chloroplasts during photosynthesis and exits as water vapour through the stomata in the leaves.
43. Without a cell membrane, a cell would have no control over what enters and exits the cell. Unless another
organelle assumes this role, the gathering of nutrients and expelling of wastes would be impossible. Furthermore, the
cell contents would not remain together, and biochemical reactions would not occur in an organized manner. Such
an “organism” would have no order; it could possibly resemble the precursors to life on Earth.
44. Such cells would only be able to survive in a very specific environment that, due to concentration gradients,
permitted the diffusion of wastes out of the cells, diffusion of nutrients into the cells, and little or no osmosis in
either direction.
45. Blocking of xylem sap would kill a plant as there would be no way for water and minerals to move from the
roots to the leaves. Water is required for photosynthesis. As well, the water keeps cells turgid and prevents wilting
(in smaller plants) and eventual death.
46. Students’ answers will vary. Virchow would have to have good examples or evidence of the existence of cells to
show Aristotle. In Aristotle’s time, the idea that living organisms came from non-living matter was widely believed.
Given the knowledge and technology of the day, this was a reasonable hypothesis. Virchow could demonstrate to
Aristotle, using a controlled experiment, his idea that cells divide to produce more cells. Looking at cells through a
microscope would probably also impress Aristotle.
47. The size of the stomata and the number of stomata influence a plant’s rate of transpiration. Also, the surface area
of the leaves and the presence or absence of a coating on the leaves influences the transpiration rate. A designer
plant with a low transpiration rate would likely have few and small stomata, all on the underside of the leaves, and
the leaves would be very small and covered with a protective coating. A designer plant with a high transpiration rate
might have many large stomata, with some on both sides of large, thin leaves.
48. Electron microscopes allowed researchers to see detailed representations of the cell surface and within cells at
extremely high magnifications. This technology would allow researchers to track the results of protein movement as
a result of the membrane’s fluidity. As well, images of proteins and carbohydrates on the membrane’s outer surface
could be obtained.
49. When salmon enter the sea from fresh water, water would move from their body cells towards the environment.
The opposite would occur when the salmon return to fresh water to spawn. The kidneys of salmon help them
regulate solute concentration. Salmon are able to change the amount of water they ingest in the different
environments, and also to produce urine with differing salt content in fresh or salt water. For example, in seawater, a
fish must get rid of excess salt so it pumps salts out of its gills. However, the fish also loses water through its gills
because its body fluids are less concentrated than is seawater. The fish also loses water in its urine. In the ocean, a
fish makes up for these losses by drinking seawater and excreting much of the salt through its gills by active
transport. Students would not be expected to have prior knowledge of homeostasis in salmon; students need only
speculate that active transport would be required and why.
50. Pores in the tubing must be the correct size so as to allow small dissolved waste molecules to diffuse out of the
patient’s blood, while retaining large proteins and blood cells. The dialysis tubing must be immersed in a solute
concentration that has a salt and water concentrate equal to that in the patient’s blood so that there is no net flow of
salt and water through the dialysis tubing in either direction.
51. A high mineral concentration in the soil could affect the water uptake in plant roots by upsetting the
concentration gradient. A high environmental mineral content may cause osmosis out of the roots; active transport of
minerals into the root cells might eventually reverse the concentration gradient, so that water would move into and
not out of the roots. Without a reverse in the concentration gradient, perhaps due to insufficient active transport of
minerals into the roots, water would not move into the root cells, and there would be no root pressure to force water
up the xylem. The pull of water from transpiration would also eventually cease due to the lack of water.
52. By having leaves that fall off during the summer, the palo verde tree conserves water during the hottest part of
the year. The small leaves also have a small surface area, which reduces water loss via transpiration. Since the stem
of the plant is capable of photosynthesis, glucose is still generated in the plant during the summer.
53. Palisade tissue cells are the main site of photosynthesis in the leaf; thus, it makes sense that these cells are
located close to the upper surface of the leaf, where they can receive adequate amounts of light. Less light reaches
the area closer to the lower side of the leaf.