Download Science Focus 10 Chapter 7 Review KEY

TR 7-28
MHR • Unit 3 Cycling of Matter in Living Systems
CHECK YOUR UNDERSTANDING ANSWERS
10. Thinking Critically
1
Student Book Page 284
1.Chloroplasts, a cell wall, and sometimes a central vacuole are present in plant, but not animal cells.
2. Ribosomes on the endoplasmic reticulum carry out
protein synthesis.
3. The Golgi apparatus receives vesicles from the
endoplasmic reticulum and packages proteins into
vesicles for transport to the cell membrane (secretion) or to the lysosomes within the cell, much like
a post office receives and then redistributes mail.
4. Having separate compartments allows various
chemical reactions to be kept separate from one
another, which prevents these reactions from interfering with each other or damaging the cell, and
allows for greater efficiency of cell activities. Also,
having separate compartments (i.e., organelles) permits the organelles to have specialized functions
within a cell.
5. In plant cells, vacuoles give added internal support
to the plant cell. As well, they may provide storage
space for water and other substances, including toxins that make the cell (and thus the plant) taste bad
to animals.
6. Mitochondria and chloroplasts have their own
DNA, and probably evolved from bacteria that were
living symbiotically within other cells.
7. Thinking Critically Lysosomal contents leaking
into the cell would effectively digest the cell and
destroy it from the inside out.
8. Thinking Critically Because red blood cells have
no nuclei to direct their activities, the cells die
when their cell structures become worn out. Thus,
red blood cells would be expected to have a shorter
life span compared to cells that can repair themselves. (Students may be interested to know that red
blood cells have nuclei during the early stage of the
cells’ development. The nuclei are lost before the
cells enter the blood stream. Red blood cells live for
about 120 days before they break down and are
removed as waste.)
9. Thinking Critically The instructions for making
proteins are carried on DNA molecules, found in
the cell’s nucleus. The DNA is transcribed into a
messenger molecule, which is read and used to
make proteins in the ER. Since protein production
is dependent on the instructions encoded in the
genetic material, it is efficient to have the ER close
to the nucleus.
ER
*
*
lysosome
Golgi apparatus
*
energy
2
mitochondria
*
vesicles
*
*
cell membrane
CHAPTER AT A GLANCE
Student Book Page 285
(a) Hooke was the first to see that a plant was made of
numerous cells. Van Leeuwenhoek developed a single-lens microscope and was the first person to
describe single-celled micro-organisms. Schleiden
looked at hundreds of plant specimens and concluded that all plants are composed of cells. Schwann
recognized that the nucleus was common to almost
all cells and after viewing numerous specimens, he
concluded that animals were also composed of cells.
(b) The concept of spontaneous generation is that life
forms can arise from non-living matter. The theory
of biogenesis says that living organisms can come
only from other living organisms.
(c) Pasteur’s experiment supported the theory of biogenesis because when he prevented micro-organisms in the air from reaching the broth, growth did
not occur in the flask. In broth exposed to particulate matter in the air, micro-organisms were able to
enter and grow. Thus, Pasteur showed that these
micro-organisms arose from other micro-organisms, not by spontaneous generation.
(d) (i) Living cells: compound light microscope since
no preparation is needed.
(i) Shape of a molecule: STM since it allows visualization of structures as small as molecules.
(ii) Shape of a large or thick specimen: compound
light microscope would allow one to see the outline of the specimen; whereas an SEM would
allow one to see the superficial three-dimensional view of the specimen; a CLSM would also
produce a three-dimensional view of the specimen.
(e) Computers can save the microscope image.
Researchers can then retrieve, manipulate, and
study the image long after they create it.
Chapter 7 The Basis of Life• MHR
Computers can also be used to operate microscopes
and adjust specimens. Computers result in more
precise and often, better-quality images.
(f) Since most cells are transparent, stains are used to
make cells visible under a microscope. Stains bind
to and colour cellular structures, making cells more
visible.
(g) Cancer-causing genes are sequenced to determine
how they differ from healthy genes. Determining
the gene sequence helps researchers learn how the
gene affects cell activity and, hopefully, how it
changes healthy cells into cancer cells. Cell lines
from cancerous cells are also developed to help
researchers have a supply of cells. Cancer cells can
grow indefinitely in the laboratory whereas normal
cells cannot.
(h) Stem cells are able to produce other specialized
cells, unlike most cells, which can only divide to
produce cells like themselves. Scientists hope to use
this ability of stem cells to develop treatments and
cures for a variety of diseases or even to grow new
tissues or organs for transplants.
(i) Organelles are the specific internal parts of cells,
such as ribosomes or chloroplasts. Except for ribosomes, organelles are separated by membranes or
boundaries that compartmentalize the organelles,
enabling them to perform specific cell functions.
The compartments allow specific chemical reactions
to proceed unhindered by other cellular constituents.
(j) Plant cells have rigid cells walls, chloroplasts, and a
large central vacuole, while animal cells do not. The
difference in their structures relates to the differing
functions of plant and animal cells.
(k) (i) nucleus: storage of genetic information; directs
cell activities
(ii) endoplasmic reticulum: synthesis and/or modification of proteins, lipids, and other substances,
and transport of proteins via vesicles
(iii) cell membrane: defines the cell boundary, and
regulates the passage of molecules in and out of
cell
(iv) mitochondria: cellular respiration; provides
energy for cell
nucleus
rough endoplasmic
reticulum
smooth
endoplasmic
reticulum
cell
membrane
mitochondrion
TR 7-29
Prepare Your Own Summary
• Students’ timelines should include the events shown
in the following example:
Hooke observes cork cells
under microscope (mid 1600s).
Redi shows that maggots on
rotting meat develop from flies’ eggs,
not via spontaneous generation (1668).
Van Leeuwenhoek observes
single-celled organisms (1674).
Scheiden states that all plants are
composed of cells. Extending this idea,
Schwann states that all organisms are
composed of one or more cells (1839).
Virchow suggests theory
of biogenesis (1858).
Pasteur’s experiments provide
supporting evidence for biogenesis (1800s).
• Student charts could resemble:
Microscope
Explanation
Maximum magnification
- light used to illuminate
simple
specimens viewed
(light)
microscope through a single lens
- about 200×
compound - light used to illuminate
specimens viewed
light
microscope through two or more
stacked lenses
- 2000×
transmission - beam of electrons is
shone through thinly
electron
microscope sliced specimen to
create image
- over 1 million× (less
than 100 000× usually
more useful)
- beam of electrons
scanning
reflected off surface of
electron
microscope specimen to create
three-dimensional
image
- 300 000× (most
specimens viewed more
easily at 10 000× or
less)
- laser beam directed at
confocal
series of planes in a
laser
specimen; resulting
scanning
microscope “optical slices” are
stacked to create three
dimensional image
- not given in student
book (students may
suggest about
300 000×, same as a
scanning electron
microscope)
- electrons flow between
scanning
a probe and atoms on
tunnelling
microscope specimen’s surface;
computer generates
three-dimensional
image from the
information
- not given in student
book (students may
suggest that this
microscope is powerful
enough to obtain
images of atoms)
TR 7-30
MHR • Unit 3 Cycling of Matter in Living Systems
• Some possible answers:
– obtaining energy: mitochondria (transforms energy in food molecules), chloroplasts (fixes carbon
dioxide for food)
– producing wastes: vacuoles, vesicles, lysosomes,
endoplasmic reticulum (smooth)
– responding and adapting to the environment:
nucleus, cell membrane, vacuole
– reproduction: nucleus, cell membrane
– growing: nucleus, cell membrane, cell wall, endoplasmic reticulum (rough), Golgi apparatus
CHAPTER 7 REVIEW ANSWERS
Student Book Pages 286–287
Understanding Key Concepts
1. Redi was an Italian physician who used a controlled
experiment to test the idea of spontaneous generation. He demonstrated that maggots did not spontaneously generate from rotting meat, thus furthering support for the concept of biogenesis (life from
life).
2. Microscope improvements include: development of
different-shaped lenses; use of multiple lenses; use
of electrons instead of light; using laser beams and
computer imaging and interpretation. Different
types of microscopes give a variety of options to
view cells in two dimensions or three dimensions as
well as to view internal structures of live cells.
Microscopes were revolutionary because they
allowed scientists to view organisms and parts of
organisms that were previously not visible to the
naked eye.
3. Plants need chloroplasts because they are the structures in which the process of photosynthesis takes
place. Animal cells do not photosynthesize.
4. The development of microscopes allowed
researchers to finally observe individual microorganisms. Advances in microscopy, staining techniques, cell culture, and gene sequencing are all
technologies that have helped develop and promote
the understanding of cells. For example, gene replication techniques have allowed researchers to study
cancer cells. Advances in microscopes have allowed
researchers to obtain incredibly detailed images
even of DNA itself.
5. Both Virchow and Pasteur believed that cells did
not generate from non-living material, but rather
that cells came from pre-existing cells. The experiments of both scientists supported the theory of
biogenesis. Redi’s fly experiment and Pasteur’s
swan-necked flask experiment both included controls against which to compare the effects of the
manipulated variable. As well, both experiments
involved preventing organisms from entering into a
nutrient-rich medium, with the effect that these
same organisms did not grow in the meat or broth.
6. Stem cells have the ability to differentiate into
other cell types. As adults, people retain a limited
amount of stem cells. Embryonic stem cells are
thought to be able to differentiate into any cell
type, while adult stem cells can differentiate into a
limited number of cell types.
7. This is a plant cell because it has a rigid cell wall,
chloroplasts, and a large central vacuole.
8. Vesicles transport materials around the cell.
Vacuoles are membrane-bound spaces inside cells,
which are used for temporary storage. They can
store food, enzymes, and other materials, including
waste products. Lysosomes are a type of vacuole
created by the Golgi apparatus. They contain digestive enzymes and digest worn out organelles, food
particles, viruses, or bacteria. Lysosomes can fuse
with other vacuoles carry particles to be digested.
9. Many cancers may be caused by genes with mistakes or mutations; therefore, genes are the focus of
a good deal of cancer research.
10. Gene sequencing, cell culture (the development of
cell lines), and sequencing projects, such as the
Human Genome Project, all contribute information
on the links between genes and cancer.
11. The cell wall is found in plant cells, fungi, and most
bacteria. It is a rigid structure outside of the cell, or
plasma, membrane that provides support and protection. The cell membrane is semi-permeable and
is the more flexible boundary of a cell. The cell wall
is porous and allows molecules to pass through;
however, it does not regulate the passage of materials across itself as does the cell membrane.
12. (a) ribosome (iii) makes proteins
(b) mitochondrion (ii) converts energy in food
molecules into a form that cells can use
(c) vacuole (v) stores water in plants cells
(d) vesicle (i) transports materials from ER and
throughout the cell
Developing Skills
13. (a) Answers may vary. One option would be: Collect
water from a fish tank. Sterilize half the water
using a filter and put the water in a clean fish
tank. Put the rest of the water in a separate clean
tank. Cover both tanks. Monitor the fish tanks
for the growth of algae over a period of two
weeks. Growth of algae in the unfiltered water
with no growth of algae in the filtered water
would support the theory of biogenesis.
(b) If spontaneous generation were a better explanation for the development of algae in fish tanks,
one would expect to see algae in both the filtered and unfiltered water.
Chapter 7 The Basis of Life• MHR
14.
H2O
15. (a) The organelle is 927.5 nm long.
(b) The organelle is 4000 nm long.
(c)
500 nm
Problem Solving/Applying
16. One could begin viewing the mitochondria at a low
power. After focussing on the specimen, one could
turn to a higher microscope objective to view more
detail. Methylene blue could be used to make the
mitochondria more visible. Also, using a TEM,
which is capable of much greater magnification
than a light microscope, could be helpful.
17. The student could take a small sample from each
tube and grow the cells in cell culture. She would
have to monitor the cells from time to time under
the microscope. The samples in which the cells
began to change form or differentiate would probably be the stem cells.
18. Examine sections from the tissue under the microscope, and examine the cells. Look for a central
vacuole, chloroplasts, and cell walls, which would
indicate that the cells were plant cells.
19. Staining the cells with methylene blue would make
the nuclei more visible.
20. One possibility would be to use stem cells to grow
new pancreatic cells for diabetic patients.
21. If the ribosome could no longer function as a result
of the genetic mutation, the cell may not be able to
produce proteins. Or, the ribosome may be altered
in such a way that it puts together proteins improperly.
Critical Thinking
22. Red blood cells do not have readily available energy
stores and as a result, would not be expected to live
as long as other cells that have mitochondria.
TR 7-31
23. Hooke only saw cells in one plant (cork) and these
cells were dead. At the time, Hooke did not realize
the significance of his observation and thought the
cells were unique to cork. Thus, he did not realize
that the cells were common to all organisms as the
cell theory now states. Observations of cells in
other organisms were needed before scientists could
develop the cell theory.
24. Cell theory states that all cells come from pre-existing cells. Scientists studying diseases learn a lot
about unhealthy, infected, or diseased cells by
watching them replicate and comparing them with
healthy cells. In addition, stem cells may one day be
used in disease treatment.
25. Students may speculate that it would have taken
longer for scientists to develop the cell theory had
van Leeuwenhoek not published his results, because
his work would not have sparked an interest in the
microscopic world. By pooling information, scientists often come up with new ideas or see old data in
a new light; an example would be the conversations
of Schwann and Schleiden, which led them to propose the cell theory.
26. Answers will vary. It is the nature of science to continue to revise explanations for natural phenomena.
It is important to separate facts from theories. In
science, a theory is not a guess; it is a well-thought
out argument based on a set of verifiable facts. For
example, the theory of gravity may be “adjusted” in
its details from time-to-time, but it is a fact that
objects on Earth continue to fall to the ground.
If students have difficulty answering any
of the Focussing Questions, direct them
back to relevant sections in the textbook.