Questions
G11 Biology
2.1 Cell Theory
1. What are the functions of life, as demonstrated by all living organisms?
Nutrition, growth , response to stimuli, reproduction, homeostasis, movement, order
2. Define the following terms, with examples:
Unicellular: made of one cell
Multicellular: made of many cells
Acellular: not made of cells
3. Why are viruses often considered non-living?
Not composed of cells
Only carry out life processes whilst inside another cell
4. Outline the three fundamental statements of cell theory
i. All living things are made of cells
ii. All cells come from pre-existing cells
iii. Cells are the smallest structural unit that carries out the life processes
5. What is the significance of the discoveries made by Antonie van Leeuwenhoek and Robert
Hooke?
Leeuwenhoek – discovered protists (animalicules)
Hooke – named the cell
6. Some types of cell seem to break the laws of cell theory.
a. Give two examples of cells which are multinucleated
Fungal hyphae/muscle cells
b. Why are viruses often considered ‘acellular’ or even non-living?
Acellular – because not made of cells
Non- living – because only carry out the life processes whilst inside another cell
7. Complete this table of SI units of length:
Metric Equivalent
Whole
scientific notation
Unit
Abbreviation
kilometer
km
1 000 m
103 m
Meter
m
1m
-
centimeter
cm
0.1
10-2 m
Millimeter
mm
0.001 m
10-3 m
micrometer
μm
0.000 001 m
nanometer
nm
0.000 000 001
10
Mag = imagesize/actual size
Mag = 25mm/2µm
Mag = 25 000 µm/2µm = X 12 500
b. By which method (shown here) do bacteria
reproduce?
Binary fission
m
10-9 m
8. The diagram below shows the characteristic rod-shaped structure of E. coli bacteria.
a. What is the magnification of the image?
–6
9. What is the actual size of the structures delineated in yellow?
Actual size = image size/magnification
a.
b.
c.
d.
55mm/1000 = 0.055mm OR 55µm
75mm/5000 = 0.015mm OR 15µm
45mm/200 = 0.225mm OR 225µm
25mm/100 = 0.25mm OR 250µm
10. Calculate the magnification of these scale bars:
Mag = Image size (scale bar)/actual size
a.
b.
c.
d.
e.
f.
g.
17mm/2µm = 17000µm/2µm = X8500
17mm/67µm = 17000µm/67µm = X253
33mm/100nm = 33 000 000nm/100nm = X330,000
33mm/100µm = X330
20mm/50µm = X 400
20mm/50mm =X0.4
23mm/500m = X 0.000046
11. What is the magnification of these images?
a. Scale bar 10µm measures 40mm on the image.
Mag = Image/actual
Mag = 40mm/10µm = 40 000 µm/10µm = X4000
b. Scale bar 5µm measures 25mm on the image.
Mag = 25 000µm/5µm = X5000
12. A micrograph has a scale bar of 2µm, which measures 40mm on the image. Measuring the
maximum length of the cell in the image, the ruler reads 180mm. How long is the cell?
40mm = 2 µm
1mm = 2/40 = 0.05 µm
180 mm = 9µm
13. A student views an image of a cell magnified 350 times. The image is 250mm long. What is the
actual length of the sample in the image?
Actual size = image size/magnification
Actual size = 250mm/350 = 0.71mm OR 710µm
14. Compare the sizes of these structures. Use SI units.
Plant
cell
Animal
cell
nucleus
bacteria
Mitochondria
virus
ribosome
Membrane
thickness
molecules
40µm
20µm
5µm
0.5 – 1.0 µm
0.5 – 1.0 µm
10nm
20nm
10nm
1nm
15. As the volume of a cell increases, what happens to…? (increase/ decrease)
a. Production of waste products.
Increases
b. Usage of nutrients and oxygen.
Increases
c. The surface area: volume ratio.
Decreases
16. What are the advantages of maximizing the surface area: volume ratio in a cell?
More membrane per unit area of the cell/ cell can supply its needs more efficiently
17. What strategies do cells use to maintain an efficient SA:Vol?
Folding of membranes/ keep cells small/ compartments within the cell
18. What are some of the ways in which larger organisms maximize SA:Vol?
Elephants – large ears
19. How can a large SA:Vol be harmful or costly to smaller animal species?
Small animals will lose heat to their environment very quickly/they will need to eat all the time
in order to replace this lost energy
20. Unicellular organisms carry out all the functions of life, multi-cellular organisms differentiate
and show emergent properties.
a. What is meant by the term emergent properties?
Sum is more than its parts
Watch has complex parts but when it is put together it shows properties that were nto evident
previously
b. What are the advantages of cells differentiating to carry out specific functions?
Division of labour/ cells can specialize/ more efficient at one job
21. All cells in a living organism carry the same genetic information.
a. What is a stem cell?
An undifferentiated cell capable of differentiating and producing more stem cells
b. What are the following types of stem cells?
Pluripotent: can differentiate into any type of body cell
Multipotent: can differentiate into several types of body cells
Nullipotent: cannot divide
c. What type of cell can a liver stem cell become?
A liver cell
22. Outline the process of cell differentiation that leads from an uncommitted stem cell to a
specialized cell, including the role of gene expression. A flow chart might help.
Uncommitted stem cell  environmental signal (chemical)  key genes are activiated  cell differentiation  specialized cell
23. Give three examples of specialized cells in multicellular organisms. Describe how their structure
relates to their function.
i.
Nerves: elongated/myelinated/many dendrites
ii.
Retina: light sensitive
iii.
Muscle: large number of mitochondria to provide energy for contraction
24. Complete the table below to show how stem cells can be used in medicine.
Therapeutic cloning
Parkinson’s disease
Alzheimer’s
Used to treat
Diabetes
Skin
Brief method: Involves the culturing of stem cells
outside of the body. These can then be
used to replace damaged tissue.
Stem cell transplants
Bone marrow (leukemia)
Ethical Use of embryonic stem cells/sacrifice of
considerations one human life to save another.
Adult stem cells are used/not so
controversial
Stem cells can be harvested, bone
marrow destroyed. Stem cells can then
be used to replace the bone marrow
25. What are the objections of some groups to the use of embryonic stem cells?
Taking of human lives
Possible use in reproductive cloning
Cosmetic use