Download Science Review pack - Cells 2.1.1 Cell Theory: 1. All living things

Science Review pack - Cells
2.1.1 Cell Theory:
1.
2.
3.
All living things are made of cells
Cells are the smallest units of life
Cell come only from preexistent cells
2.1.2 Discuss the evidence for the cell Theory.
Evidence:
1.
2.
3.
Microscope
No smaller unit has been discovered
No living entity that has less than one cell
Louis Pasteur
Limitations:
1.
Amoebae is made of a single cell. Therefore is it possible to say “made of
cells”?
2. Are viruses alive or not, since they need a host cell?
3. Muscle tissue has many nuclei
2.1.3
Unicellular organisms carry out all the functions of life.
Unicellular organisms have:
 metabolism
 response
 homeostasis
 growth
 reproduction
 Nutrition
2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses,
bacteria, organelles and cells, using the appropriate SI unit.
From smallest to biggest:
1. molecules (1 nm)
2. thickness of membranes (10 nm)
3. viruses (100 nm)
4. bacteria (1 μm)
5. organelles (up to 10 μm)
6. and most cells (up to 100 μm)
The three-dimensional nature/shape of cells should be emphasized.
2.1.5 Calculate the linear magnification of drawings and the actual size of
specimens in images of known magnification.
Magnification= Scale bar measure / Scale bar label
Actual size= Measured length / Magnification
1
Units of measurement:
Unit of measurement
Kilometer
Meter
Centimeter
Millimeter
Micrometer
Nanometer
Abbr.
Km
M
Cm
Mm
Um
nm
Metric Equivalent
1000m
1m
0.01m
0.001m
0.000001m
0.000000001m
10^-3m
-10^-2m
10^-3m
10^-6m
10^-9m
http://www.box.net/shared/plq23bqjmy <-- Exam style measuring questions
2.1.6 Explain the importance of the surface area to volume ratio as a factor
limiting cell size.
The concept that the rate of heat production/waste production/resource
consumption of a cell is a function of its volume, whereas the rate of exchange of
materials and energy (heat) is a function of its surface area.
1
Volume
27
6 A larger SA: V ratio means
SA
54
6:1that the cell can act more
SA:V ratio
2:1
efficiently. For every unit of
volume that requires
nutrients or produces
waste, there is more
membrane to serve it.
3x3
cm
Short diffusion distance
Long diffusion distance
1 x 1 cm
Explain the importance:
The SA:V ratio is the factor that effectively limits cell size
In the cell the rate of heat and waste production and the rate of resource
consumption depend on the cell’s volume. Size affects the rate of these reactions
that occur in the interior of the cell. The surface of the cell (membrane) controls
exchange of material in and out of the cell. The more membrane (surface area) a
cell has the more substances can be moved in and out.
If a cell grows wider the surface area increases but at a much smaller pace than
the volume. This means that a large cell has relatively less membrane to bring in
needed materials and to rid the waste.
2
2.1.7 State that multicellular organisms show emergent properties. Emergent
properties arise from the interaction of component parts: the whole is greater
than the sum of its parts.
2.1.8 Explain that cells in multicellular organisms differentiate to carry out
specialized functions by expressing some of their genes but not others.
Multicellular organisms usually start out as a single cell after sexual reproduction.
This single cell reproduces at a very high speed and the resulting cells go through
a process called differentiation. This way a multicellular organism produces all
cell types that are necessary. The number of different cell types is huge.
Differentiation is the result of activation of specific genes but not others. Each cell
of a multicellular organism contains all the genetic information to produce an
entire organism. In the process of differentiation some cells can even lose the
ability to reproduce (nerve and muscle cells).
(Gene is a segment of DNA on a chromosome)
2.1.9
State that Stem cells:
 Retain the ability to divide
 Are able to differentiate along different pathways
1.1.10
The therapeutic use of stem cells is an area of constant development. For
example in the treatment of lymphoma, the bone marrow is destroyed in chemo
or radio-therapy. Therefore, cells are taken from the bone marrow and stored.
After the therapy, the cells can be used to replace the damaged bone marrow
and form healthy blood cells in the recovering patient.
Stem cells can be very helpful to the human kind in improving people’s state of
health. However, the use of stem cells includes certain ethical issues. For
instance, the use of embryonic stem cells involves their early death.
Nevertheless, if therapeutic cloning is successfully developed, the suffering of a
variety of patients could be reduced.
2.2-Prokaryotes
2.2.1 Draw and label:
3