Nelson Biology 11

653 Pages·2002·30.356 MB·English

by  Bob Ritter, Christine Adam-Carr, Douglas Fraser

Unit
1
Cellular
Functions
A whole new field of science has opened up in the
area of nanotechnology. Nanotechnology involves
creating structures and machines of molecular dimen-
sions. Nano means one billionth (10–9). Researchers
have already produced tweezers made of DNA and a
motor containing just 56 atoms.
The scanning tunnelling microscope (STM) is a
miniscule electrical probe that creates topographical
images of objects at an atomic level. The STM has
revealed that the tremendous strength of an abalone
shell is due to the folded nature of an organic adhesive
in the shell. The idea of additional folds increasing the
strength of an adhesive is expected to be applied to
synthetic polymers.
Dr. Bob Wolkow speculates that
“this is only the start of combining
organic and inorganic materials,
and understanding them at an
atomic level. From here, I expect
an emergence of hybrid biology
and nanotechnology devices that
could be used as new medical
Dr. Bob Wolkow,
diagnostic tools.” Such tools
National Research
Council of Canada could be used to view our genes.
Overall Expectations
In this unit, you will be able to
• understand cell structure and function, including metabolism
and transport of substances across membranes;
• investigate the energy-converting activities of living
organisms;
• understand the relationship between cellular functions and
their applications in technology and the environment.
Unit
1
Cellular
Functions
A whole new field of science has opened up in the
area of nanotechnology. Nanotechnology involves
creating structures and machines of molecular dimen-
sions. Nano means one billionth (10–9). Researchers
have already produced tweezers made of DNA and a
motor containing just 56 atoms.
The scanning tunnelling microscope (STM) is a
miniscule electrical probe that creates topographical
images of objects at an atomic level. The STM has
revealed that the tremendous strength of an abalone
shell is due to the folded nature of an organic adhesive
in the shell. The idea of additional folds increasing the
strength of an adhesive is expected to be applied to
synthetic polymers.
Dr. Bob Wolkow speculates that
“this is only the start of combining
organic and inorganic materials,
and understanding them at an
atomic level. From here, I expect
an emergence of hybrid biology
and nanotechnology devices that
could be used as new medical
Dr. Bob Wolkow,
diagnostic tools.” Such tools
National Research
Council of Canada could be used to view our genes.
Overall Expectations
In this unit, you will be able to
• understand cell structure and function, including metabolism
and transport of substances across membranes;
• investigate the energy-converting activities of living
organisms;
• understand the relationship between cellular functions and
their applications in technology and the environment.
Unit
1 Are You Ready?
Knowledge and Understanding
1. Using the periodic table ofelements,in Appendix C,identify the elements
carbon,hydrogen,oxygen,and nitrogen.List everything you know about
these elements.
2. Use the terms molecule,ion,element,atom,or compound to describe each
substance:Mg2+,Na+,SO2,(cid:2)CH .
4 4
Cellular
3. Match each component ofthe compound light microscope (Figure 1) to its
correct name.
Functions
condenser lens stage revolving nosepiece
fine adjustment knob diaphragm objective lens
tube ocular lens coarse adjustment knob
(a)
(i) (b)
(d) (c)
(e)
(f)
(g)
(h)
Figure 1
Light microscope
4. Copy Table 1into your notebook.Match each part ofthe microscope in
Figure 1with the description ofits function in Table 1.
Table 1: Parts of a Microscope
Part Function
? directs light to the object or specimen
? moves tube up and down to focus on specimen
used with low-power objective lens
? moves tube up and down for sharp focus on specimen
? magnifies object, usually by 10 times
? supports the ocular lens
? changes objective lenses
? regulates amount of light reaching specimen
? enlarges image of specimen under three different magnifications
? supports the microscope slide
4 Unit 1
5.Figure 2shows a typical animal cell and plant cell.Prepare a table with the
headings Animal Cell and Plant Cell and list the structures that allow you
to distinguish between the two types ofcells.
Figure 2
animal cell plant cell Typical animal and plant cells
6. (a) Name the chemical process that occurs within the mitochondria ofall
plant and animal cells.
(b) Write a chemical (word) equation for this process.
Technical Skills and Safety
7. (a) Write the following steps for microscope use in the correct order.
• Using the coarse adjustment knob,focus the specimen.
• Using the fine adjustment knob,focus the specimen.
• Place the slide onto the stage and secure it with the clips.
• While looking through the ocular lens,centre the specimen within
the field ofview.
• Ensure that the low-power objective lens is in place.
• Once the specimen is centred and in focus,switch to a higher-power
objective lens.
(b) List the safety precautions that you should follow when using a
microscope.
8. Figure 3shows plant cells as viewed under a microscope.Draw a diagram
ofa cell.Label as many parts ofthe cell as you can.
Math Skills
Figure 3
9. Refer to question 8.Using an ocular lens with a magnification of15×,and
Plant cells
an objective lens magnification of50×,what is the total magnification?
Cellular Functions 5
Chapter
1 Cell Biology
A Window on the Invisible World
Inventions in one field ofscience often contribute to advancements in others.The
two greatest inventions ofthe 1600s,the telescope and the microscope (Figure 1),
changed the way people understood and explained the universe.No one scientist
was responsible for the development of the microscope.Like many other inven-
tions,the development of the microscope was an ongoing process that involved
In this chapter, you will be technological advances in glass making and lens polishing,along with refinements
able to to existing models.
The light microscope allowed scientists to view the contents of cells,and led
• describe how organelles and
to the realization that plants and animals share many common cellular features.
other cell components carry
out various cell processes, and Increasing the magnification eventually reached a point where resolution (clarity
explain how these processes ofthe image) became a major problem.
are related to organ functions; In 1938,James Hillier and Albert Prebus,graduate students at the University
• describe the structure of the cell of Toronto, produced the first functional electron microscope (Figure 2). The
membrane, and use this under-
main advantage of the electron microscope is in its greater resolution.This new
standing to explain how materials
microscope allows us to view viruses and subcellular parts, and together with
move into and out of cells;
biochemical evidence, assign functions to these structures. Since then, further
• explain the relationships between
important cellular processes in developments in the field ofmicroscopy have led to three types ofmicroscopes:
living cells; 1.Transmission Electron Microscope (TEM):The image is produced by a beam
• investigate factors affecting cellular
ofelectrons passing through a very thin slice ofthe specimen.The image
functions;
appears on a screen and is a flat,two-dimensional image (Figure 3).
• discuss research advances in
biotechnology and evaluate 2.Scanning Electron Microscope (SEM):The image is produced by a beam
their applications. of electrons which scans across the surface of the sample.As secondary
electrons are released by the sample,they form an image which is three-
dimensional in quality (Figure 4).
3.Scanning Tunnelling Microscope (STM):A miniscule electrical probe is
placed near the surface ofthe sample,and an image is created which can be
converted by computer to a topographical image.The images produced are
used for atomic-level imaging,and for manipulating molecules and atoms.
It is used in the field ofnanotechnology (Figure 5).
Reflect
onLearning
your
1. How have advances in technology allowed a greater understanding ofcellular
structures and functions?
2. How do the cells ofanimals differ from the cells ofplants?
3. (a) In your group,brainstorm a list ofsubstances you think must enter
and exit a cell.
(b) Make a separate list ofsubstances you think a cell would need to
keep out.
4. Write a short description ofhow you think substances enter and exit cells.
6 Chapter 1
Figure 3
Animal cell as seen through a transmission
electron microscope (10 000×)
Figure 1 Figure 2
The impact of the microscope was so The 1938 version of an electron micro-
great that most scholars of the 17th scope, made at the University of Toronto
century proudly displayed their micro- by James Hillier and Albert Prebus
scopes in full view.
Try This
Activity
Comparing Plant Cells
Figure 4
Scanning electron micrograph of a dust mite
(400×)
Figure 6 (400×) Figure 7 (12 000×)
• Refer to Appendix B to review the use of a microscope.
• Place a slide of a plant tissue (Elodea, Spirogyra,or other) under
your light microscope.
• Examine under low power, then medium power, and finally high
power.
(a) Compare what you see to the plant cells shown in Figures 6
and 7.
(b) Name any cell parts that you recognize.
Figure 5
(c) Which cell parts can be seen in all images?
Scanning tunnelling micrograph of double-
(d) Describe any structures that you can see only in the electron stranded DNA. The peaks represent the
micrograph (Figure 7). ridges of the helixes in the DNA molecule
(2 000 000×).
Cell Biology 7
1.1 The Cell Theory
The cell is the smallest living unit and is the basic building block oforganisms.It
has been estimated that the human body is made up of about 100 trillion cells.
Different cells in the body are specialized to perform various tasks.Muscle cells,
for example,are capable ofrapid contraction.Nerve cells transmit electrochem-
ical messages to the body about our environment and enable us to respond.
Vision, hearing, taste, smell, and touch all depend on nerves. The transport of
oxygen,defence against disease,and communication between different parts of
the body all depend on specialized body cells.
Most ofthe cells in your body are invisible to the naked eye.A colony ofsmall,
rod-shaped bacteria, called Escherichia coli (Figure 1), lives in your gut. These
microbes supply you with important vitamins and will likely be with you until the
end of your life.Plant spores and pollen may find their way into your lungs,and
a host of microbes and microscopic animal eggs may enter your body with the
food you consume.Your body is a living ecosystem.
Cells outside your body also play an important role in your life.For example,
a survey of your skin may reveal different types of fungi. Athlete’s foot is an
example of a fungus.Your skin also harbours a sphere-shaped bacterium called
Staphylococcus epidermis.
Other types ofcells have a variety offunctions that are useful to us.Yogurt is
a living community ofbacteria.A bacterium called Lactobacillus bulgaricuscauses
the milk in yogurt to sour,but a second bacterium,Streptococcus lactis,enhances
the taste.The processing ofcheese,beer,and wine depends on cells.Even the tan-
ning ofleather could not be accomplished ifit were not for cells.
In spite oftheir varied size,shape,appearance,and function,cells have some
things in common. All cells digest nutrients, excrete wastes, synthesize needed
chemicals,and reproduce.
Cells are the basic unit ofall living things.An understanding ofcell function
provides the basis for determining how tissues and organs work. This under-
standing arose from the observations and research of many scientists. In 1665,
Robert Hooke used the word cell to describe the repeated honeycomb structures
he observed while viewing a thin slice of cork with his primitive microscope.
Figure 1
Electron micrograph of
Escherichia coli. Large
numbers of bacteria live
in our intestines where
they help us digest food.
8 Chapter 1
1.1
Cork, the spongy tissue from cork oak trees, has few living cells; what Hooke
observed was the rigid cell walls that surround the once-living plant cells.In 1674,
Anton Van Leeuenhoek described living blood cells, bacteria, and single-celled
organisms in a drop of water.Around 1820,Robert Brown described the appear-
ance ofa tiny sphere in plant cells,which he called the nucleus.Nuclei were soon
discovered in animal cells.In 1838,a zoologist,Theodor Schwann,and a botanist,
Mathias Schleiden,concluded that plant and animal tissues are composed ofunits
called cells. It was the work of Louis Pasteur with microorganisms that led
Rudolph Virchow,in 1858,to theorize that all cells come from preexisting cells.
The cell theory states the following:
• All living things are composed ofone or more cells.
• The cell is the smallest entity that retains the properties oflife.
• New cells arise only from cells that already exist.
Try This
Activity
Making a Model of
Primitive Cells
Scientists believe that life began somewhere between 3.9 and 3.5 billion
years ago. One of the important steps in the process was the formation
of a cell membrane. One hypothesis for how the first cell membranes
formed points to tiny structures called microspheres (Figure 2), made
of protein and fats.
Materials:lab apron, safety goggles, latex gloves, medicine dropper,
10-mL graduated cylinder, water, large test tube, test-tube stopper,
10 mL of liquid vegetable fat or corn oil, Sudan IV indicator
Sudan IV is dissolved in alcohol and is flammable. Keep
covered before and after use. Keep away from a flame.
Avoid breathing the fumes. Keep away from your skin.
If it splashes in your eyes, wash with water for 15 min-
utes. You may have to seek medical attention.
Figure 2
Microspheres, tiny droplets of
fat, water, and protein, might have
given rise to cell membranes.
• Put on your lab apron, safety goggles, and gloves.
• Measure 6 mL of water. Pour the water into a large test tube.
• Using a medicine dropper, add 10 drops of vegetable fat and then
a single drop of Sudan IV indicator.
• Stopper the test tube and shake it vigorously with your index finger
firmly on the stopper, away from you and other students.
(a) Describe the microspheres.
(b) What happens when two microspheres touch?
(c) How is the barrier created by the microsphere similar to a cell
membrane?
Cell Biology 9
1.2 Overview of Cell Structure
Cells vary in size,shape,and function,but all plant cells and animal cells have many
cell membrane:a structure that surrounds common features (Figure 1).The cell membrane(or plasma membrane) forms the
the cytoplasm of the cell and regulates the outer boundary of the cell.All material inside the cell is called the protoplasm.
movement of materials in and out of the cell Inside the protoplasm,generally near the centre,is the nucleus.The fluid and other
materials between the cell membrane and the nuclear membrane or envelope,col-
protoplasm:the entire contents of a cell. lectively,are called the cytoplasm.
The protoplasm includes the nucleus, the
cytoplasm, and organelles.
cell membrane
nucleus:the control centre for the cell,
which contains hereditary information. The
nucleus is bound by a double membrane. nucleolus
nucleus
cytoplasm:a fluid that contains all cellular
parts enclosed inside the plasma membrane nuclear envelope
except the nucleus
cytoplasm
Figure 1
Basic structures common to plant and animal cells
Nucleus
The nucleus is the control centre of the cell, just like your brain is the control
eukaryotic:a type of cell that has a true centre ofyour body.A cell is classified as eukaryoticor prokaryotic,depending on
nucleus. The nuclear membrane surrounds whether or not it has a membrane-bound or true nucleus (see Figure 2).It directs
a well-defined nucleus. all of the cell’s activities.Inside the nucleus,hereditary or genetic information is
organized into threadlike structures called chromosomes. Each chromosome
prokaryotic: a type of cell that does contains a number of different characteristic-determining units,or genes.Each
not have its chromosomes surrounded by gene contains the instructions to produce protein. All chromosomes are com-
a nuclear membrane
posed ofnucleic acids and proteins.The nucleic acid in chromosomes is deoxyri-
bonucleic acid (DNA),the genetic material oflife.
chromosomes:long threads of genetic
The nucleus of every cell in your body contains DNA.The fascination that
material found in the nucleus of eukaryotic
scientists have for DNA arises from the fact that it is one of the few molecules
cells
genes:sections of a chromosome, each Types of cells
of which contains one set of instructions
deoxyribonucleic acid (DNA):a mole-
Prokaryotic cells Eukaryotic cells
cule that carries genetic information in cells
No true A true
nucleus nucleus
Bacteria Cyanobacteria Plant cells Animal cells
Figure 2
Classification of cells
10 Chapter 1