Download Chapter 2: Cells

Chapter 2: Cells
Activity 2.1
1
A
B
C
D
E
F
G
Eyepiece or ocular lens
Objective lens
Stage
Mirror
Coarse focus
Fine focus
Body
2
a Eyepiece
Part of the microscope on which the specimen is
placed
Sharpens the focus on high power
b Coarse focus knob
Unit used to measure microscopic objects
c Stage
Equipment used to make a wet mount
d Objective lens
The object being studied using the microscope
e Micrometre
f Specimen
The lens of the microscope closest to the
specimen
The part of the microscope you look through
g Mirror
Used to reflect light through the specimen
h Fine focus knob
Used to focus the microscope on low power
i Slide and coverslip
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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Activity 2.2
1
a Cell wall
The skin that holds the cell together
b Cell membrane
A watery, jelly-like mixture that contains many
smaller parts where the work of the cell takes
place
The powerhouse of the cell where the energy we
need is released from the food we eat
The skeleton of a plant
c Nucleus
d Cytoplasm
e Vacuole
f Mitochondria
g Ribosome
h Endoplasmic reticulum
i Lysosome
j Chloroplast
2
The garbage disposal units that get rid of wastes
from the cell
Part of the cell where photosynthesis takes
place
Control centre of the cell
Contains wastes or chemicals that are being
moved around the cell
Microscopic factories that produce the proteins
we use to grow and repair our bodies
Pathways that allow materials to move quickly
and easily through the cell
From the top:
Cell membrane; nucleus; cytoplasm; chloroplast; vacuole; cell wall
Activity 2.3
1 a
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2
b
They would fall down into a heap.
c
They would remain on top of one another like a tower of bricks.
It would be very easy to burst the animal cell because it is only protected by a thin
cell membrane. The plant cell would be more difficult to burst because the cell
membrane is protected by the cell wall.
3 a
b
The animal cell is most easily able to change its shape.
4
The tree would collapse to the ground.
5
The runner would not be able to move as the muscles would all become rigid and
inflexible. The tissues of the joints would not be elastic.
6 a
List the advantages and disadvantages of having cells like animal cells.
Advantages
The shape can be changed—muscles can
stretch and relax.
The cells are elastic to some extent and
withstand some pressure without damage.
b
Disadvantages
The body needs some form of support.
The cells are easily damaged by sharp
objects and abrasion.
Many animals have skeletons that support the body—which may be internal
or external. Some animals such as humans have an internal skeleton to
support and protect our tissues and organs. Some animals have shells and
external skeletons to provide protection. Antennae and other sense organs
warn them of potential danger, allowing them to avoid it.
7 a
List the advantages and disadvantages of having cells like plant cells.
Advantages
The rigid outer surface provides both protection
for the internal contents and structure. There is
no need for a separate skeleton.
Disadvantages
The cells cannot change shape and
therefore movement is not possible.
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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b
Individual plants cannot move. However, the seeds of many plants are
adapted to move away from the parent plant.
Activity 2.4
1
cm
0.03
0.7
0.2
0.0045
0.03
0.013
0.004
0.0078
2
3
a
3 cm
b
30 µm
mm
0.3
7
2
0.045
0.3
0.13
0.04
0.078
µm
300
7000
2000
45
300
130
4
78
a
Question
What is the diameter of the
red blood cell?
What is the diameter of the
human cheek cell?
What is the length of the
cell from the leaf?
What is the width of the
cell from the leaf?
What is the length of the
onion skin cell?
What is the width of the
onion skin cell?
What is the length of the
body of the Vibrio
bacterium?
What is the diameter of the
body of the Vibrio
bacterium?
What is the length of the
tail of the Vibrio
bacterium?
What is the diameter of the
Streptococcus bacterium?
Measurement
(cm)
Scale
Calculation
Actual
size (µm)
1
1 cm = 5 µm
1 × 5 µm
5
2.5
1 cm = 20 µm
2.5 × 20 µm
50
5.5
1 cm = 10 µm
5.5 × 10 µm
55
1.3
1 cm = 10 µm
1.3 × 10 µm
13
5.3
1 cm = 20 µm
5.3 × 20 µm
106
2.7
1 cm = 20 µm
2.7 × 20 µm
54
2
1 cm = 1 µm
2 × 1 µm
2
0.5
1 cm = 1 µm
0.5 × 1 µm
0.5
3
1 cm = 1 µm
3 × 1 µm
3
0.5
1 cm = 1 µm
0.5 × 1 µm
0.5
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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b
50 ÷ 0.5 = 100
c
555 ÷ 5 = 11
Activity 2.5
1 a – Sunflower pollen
b – Paper
c – Eye of a fly
d – Salt crystals
e – Foot of a housefly
f – Cotton fibres
g – Tip of ballpoint pen
h – Rust on a rusty nail
2
It is difficult to know how to look at the image, to make the correct parts come
forward or go into the background as your brain creates the three dimensions.
You cannot tell which parts are important.
Early scientists did not know what was really there in a cell and what may be an
artefact created by the processing of the materials for the microscope.
When you look at something new you try to relate it to something familiar.
However, in some situations there is nothing familiar.
Activity 2.6
1 a
Human skin cell: The flat shape with cells overlapping means that the cells
can form a complete cover for the body with no gaps between the cells.
b
Nerve cell in brain: The many branching axons are able to make connections
between many cells of the brain.
c
Nerve cell in body: The long axons mean that the nerve message can travel
for long distances within the body.
d
Cell from small intestine: The cells have a large surface area through which
food can be absorbed.
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2 a
The cell wall has progressively become thicker and the cell has lost its
contents.
b
The thick cell wall would provide support for the plant as it became larger
and heavier.
3
Feature of cell
How the feature helps the cell do its job
a
Cells in the upper layers of
leaves have large numbers of
chloroplasts.
b
Muscle cells in the human
leg have large numbers of
mitochondria.
The upper layers are exposed to the Sun. The large
numbers of chloroplasts would use the Sun’s energy for
photosynthesis.
The muscles require energy for movement. The energy
would be supplied by the mitochondria.
c
The cells in plant stems
that carry water from the roots
have no cross walls so they form
a continuous tube like a drinking
straw.
d
Cells in bone can produce
a hard substance that completely
surrounds them.
The lack of cross walls means that the water can flow up
the stem with nothing to stop it.
The hard substance would add strength to the bone,
making the whole skeleton stronger to support the body.
Activity 2.7
1
Length of side
(cm)
2
1
0.5
a
b
c
e
24
6
1.5
g
Number of
cubes
1
8
64
Total surface
area (cm2)
24
48
96
The surface area doubles at each stage.
0.25
0.125
f
Surface area of
cube (cm2)
0.375
0.09375
512
4096
192
387
Four times faster because the total surface area of 64 0.5 cm cubes is 96
cm2, and the total surface area of one 2 cm cube is 24 cm2. 96 ÷ 24 = 4.
2
They have a larger surface area, so they can absorb more water.
3
The cells shown in Figure 2.7.2b have a large surface area, so the small intestine
is probably where absorption of food takes place.
4
Figure 2.7.3a would carry out gas exchange more efficiently because more of the
surface area of the cells is exposed to the air pockets.
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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Activity 2.8
1
Growing cells separately from the organism they came from.
2
Cultured cells are used to produce vaccines that protect you from diseases; to
produce anticancer agents; to produce new skin for grafting on to wounds; and to
produce new organs.
3
Muscle cells can only produce new muscle cells, whereas stem cells are able to
become different types of cells under special conditions.
4
The flow diagram should include the following steps: Extract cells from the
bladder and extract muscle cells → Grow cells in culture solution → Place cells
on the bladder-shaped shell (muscle cells to the outside; bladder cells to the
inside) → Continue to grow cells for 7 weeks → Stitch new bladder into position.
5. Without the shell the cells would not form an organ of the correct shape.
6
Cells from the bladder lining and muscle cells
7
The two types of cells have different functions, both of which are essential for the
functioning of the bladder.
Activity 2.9
Cells crossword
Answers
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The letters in the bolded column spell MICROSCOPE.
Definition of microscope: an instrument used to make very small things look bigger.
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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Cells wordfind
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Key term
Cell wall
Endoplasmic reticulum
Epithelium
Field of view
Image
Nerve cell
Nucleus
Ocular lens
Organ
Specimen
Tissue
Vacuole
Definition
The skeleton of the plant
Pathways along which materials move through the cell
Another name for skin
The amount of the specimen seen through a microscope
What is seen using the microscope
Cells that carry information in the body.
The control centre of the cell
The lens of the microscope that you look through
Structures that contains at least two different types of tissues that
work together to complete a task
The object being looked at through a microscope
Groups of cells that perform the same function in the body
Small structures in animal cells that may contain wastes or
chemicals.
Large sap-filled structures in plant cells that stores water, wastes
and nutrients
Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2
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