Download Chapter 1 Review Answers

Key Concept Review
1. (a) A plant cell
(b) (1) endoplasmic reticulum, (2) Golgi apparatus, (3)
mitochondrion, (4) vacuole, (5) cytoplasm, (6) chloroplast, (7)
ribosome, (8) cell membrane, (9) cell wall, (10) nucleus
(c) (2) The Golgi apparatus modifies, sorts, and packages proteins
from the endoplasmic reticulum. (3) The mitochondria supply
energy for the cell (convert the chemical energy in sugar into
usable energy). (6) The chloroplasts contain a green pigment
called chlorophyll that uses energy from the Sun to convert
carbon dioxide and water into sugar and oxygen in a process
called photosynthesis. (10) The nucleus is the control centre of
the cell. It also contains most of the cell’s DNA.
2. The cell cycle is a series of events. The cell is in interphase when it
is growing. During the first phase, G 1 , the cell grows, and produces
new proteins and organelles. In the second phase, S, the cell makes
an entire copy of the DNA in the cell as well as key proteins
associated with chromosomes. During the last phase of interphase,
G 2 , the cell produces organelles and structures needed for cell
division. The cell then goes into mitosis in which it divides the
genetic information into two portions and forms two daughter
cells.
3. During interphase, the cell grows, produces new proteins and
organelles, makes an entire copy of the DNA in the cell as well as
key proteins associated with chromosomes, and produces
organelles and structures needed for cell division.
4. There are four phases in mitosis. During prophase, the
chromosomes condense, the nuclear envelope disintegrates, the
mitotic spindles form and attach to the centromere, which connects
the sister chromatids (see diagram on page 30 of the student book).
During metaphase, the chromosomes completely condense and
move toward the centre of the cell (see diagram on page 30 of the
student book). During anaphase, the sister chromatids are pulled
apart into separate chromosomes and move to the opposite ends of
the cell (see diagram on page 31 of the student book). During
telophase, the cell divides the cytoplasm into two portions by
cytokinesis, the nucleus forms in each new cell, the mitotic
spindles disappear, and the cells enter interphase (see diagram on
page 31 of the student book).
5. Factors that affect the rate of mitosis include environmental
conditions (altitude, amount of sunlight) and antibiotics.
6. Apoptosis is the regulated or controlled death of cells. Apoptosis
helps remove cells that are no longer useful or that are not
functioning properly.
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Unit A: Tissues, Organs, and Systems of Living Things 63
7. Embryonic stem cells are unspecialized cells that are able to
undergo differentiation to form a variety of cells that look different
from one another and perform different functions. Adult stem cells
result from differentiated embryonic stem cells and have a limited
ability to create a variety of cell types. Most adult stem cells are
involved in the replacement of damaged tissues, such as skin and
blood.
8. Cells specialize to perform specific functions or tasks more
efficiently. For example, brain cells are responsible for the storage
of information and transmission of signals. The neural cells have
branches to make connections and to provide fast signal transfers.
9. Cancer cells remain unspecialized; they do not stop reproducing
and do not stick to other cells; they behave independently, and they
can move to another location in the body.
10. Four types of animal tissues are epithelial tissue, connective tissue,
muscle tissue, and nervous tissue.
11. Meristematic tissue is unspecialized tissue that is capable of
dividing by mitosis. It is found in several locations in the plant and
is responsible for growing new parts of the plant. Meristematic
tissue forms all the different plant tissues (epidermal, vascular, and
ground).
Connect Your Understanding
12. Magnification refers to how many times bigger an image appears
compared to the actual size of object. The higher the
magnification, the larger the image appears. Resolution is the
ability to clearly see details in the image. Contrast is the ability to
see the cell and its parts compared with each other and the
background. Cells are very small and need to be magnified to see
detail. It is often difficult to see cell parts, as they are often pale or
transparent, and they blend in with the background. Adjusting the
amount of light and using stains or dyes help increase contrast.
Since the unaided eye can resolve images that are 0.1 mm or
larger, a microscope is often necessary to see things smaller than
0.1 mm.
13. Plant and animal cells have some of the same organelles because
both types of cells have similar tasks that need to be completed in
the cell. Examples of common organelles include:
• mitochondria: powerhouses of the cell
• vacuoles: store water, nutrients, and wastes
• cell membrane: forms a protective layer around the cell that
controls materials moving in or out of the cell
• nucleus: control centre of the cell
• endoplasmic reticulum: carries materials through the cell
• cytoplasm: suspends the cell’s organelles in a jelly-like
substance that fills the interior of the cell
64 Unit A: Tissues, Organs, and Systems of Living Things
• Golgi apparatus: receives proteins from the endoplasmic
reticulum and modifies, sorts, and packages the proteins for
delivery in and out of the cell
• cytoskeleton: helps maintain the cell’s shape
14. Plant cells produce usable energy by converting light from the Sun
into energy through photosynthesis. Chloroplasts act as these solar
converters. Plant cells also have a large central vacuole that can fill
with water to help support its structure. In addition to a cell
membrane, plant cells have a cell wall, which helps maintain the
cell’s structure.
15. Students’ answers will vary but could include the idea that cell
membranes control the movement of materials entering and
leaving the cell through diffusion, where substances in high
concentration move across the membrane to areas of low
concentration. Concentration relates to how much of a substance is
dissolved in water.
16. The development of the microscope has allowed scientists to look
at and understand the cell since the cell is too small to see with the
unaided eye. As microscopes improved, the ability to distinguish
structures inside the cell led to discovering organelles. Observing
these structures helped to determine their functions.
17. Some materials move across the cell membrane using diffusion.
Some materials are kept in or out of the cell by the double layer of
lipids that makes up the cell membrane. Lipids are fat-like
molecules that do not dissolve in water.
18. Students’ answers will vary but could include:
• intake of nutrients: nutrients and gases move across the cell
membrane by diffusion; the nutrients may end up in the
cytoplasm or stored in vacuoles; the mitochondria and/or
chloroplasts convert the nutrients to usable forms of energy
• growth and reproduction: the nucleus directs growth; when the
cell is too large, the nucleus can direct the cell to undergo
mitosis
• waste removal: lysosomes contain digestive enzymes to break
down foreign materials; the waste is stored in vacuoles until it is
removed from the cell
19. There are a number of stages of the cell life cycle shown in this
photo. Many cells in the photo show interphase (nucleus is clearly
visible, distinct chromatids are not). The stages of mitosis that are
clearly visible include:
• prophase: nuclear membrane is not apparent and chromosomes
are visible as they condense
• metaphase: chromosomes are lined up in the middle of the cell
and mitotic spindles are visible
• telophase: cells are separating into two distinct cells with
chromosomes “clumped” in each separate cell
Unit A: Tissues, Organs, and Systems of Living Things 65
20. Cells are limited in growth and how large they can become. Once
they reach a particular size, the cells must divide to grow. Also, as
cells wear out or become damaged, they need to be replaced with
new cells of the same type. Both of these kinds of replacement are
accomplished through mitosis.
21. Tissues are groups of cells that work together to perform specific
functions or tasks. Cell specialization produces cells that are
capable of doing specific tasks very well, for example, skin or
muscle cells in animals, or xylem or phloem in the root or leaf.
22. Stem cells are unspecialized cells that can form specialized cells.
They are important to researchers for their ability to form
specialized cells that may lead to treatments to regrow, repair, or
regenerate tissues or organs; replace cancerous cells with healthy
cells; or replace damaged brain cells.
23. Students’ answers will vary but could include the process of using
stem cells to replace or regrow damaged or lost body parts.
24. Students’ answers will vary but could include:
• stem cells are unspecialized cells that undergo differentiation, a
process in which the cells become specialized
• embryonic stem cells differentiate into other types of cells that
perform different functions
• adult stem cells result from these specialized cell types dividing
and specializing further, resulting in cells with a limited ability
to create a variety of cell types
• cell specialization involves cells developing in different ways to
perform particular functions
25. Students’ answers will vary but could include:
• use of fluorescent substances added to cells that are placed
under ultraviolet light makes some structures become visible
where they might not have been seen before; this method can
also be used to watch certain functions as they occur in the cell
• transmission electron microscope (TEM) allows for a
magnification up to 1 500 000× of thin slices of a sample
• scanning electron microscope (SEM) provides magnification of
up to 300 000× and produces three-dimensional images of
surface features of a specimen
• scanning tunnelling microscope (STM) and atomic force
microscope (AFM) produce images of molecules within cells
that shed light on the structure and function of molecules within
the cell
26. Adult stem cells have a limited ability to create a variety of cell
types. They are found mostly in skin, blood, and neural tissue. For
example, in blood, adult stem cells could specialize to make red
blood cells or white blood cells, as needed. In research, scientists
have found that they can use adult stem cells from one organ to
help regenerate tissue from another organ. For example, adult
blood stem cells have regenerated liver, kidney, and brain cells.
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27. Vascular tissue called xylem transports nutrients, water, and
minerals from roots up the stem to the leaves. Vascular tissue
called phloem transports sugars from the leaves to other parts of
the plant. The stem generally does not perform photosynthesis, as
it tends to be shielded from light from the Sun by the leaves. Also,
the stem does not collect nutrients from