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Cells
Key facts
1. The cell theory states that living organisms are composed of cells, that cells are the smallest unit of life, and
that cells come from pre-existing cells.
2. Even unicellular organisms carry out the functions of life which include: metabolism, response, homeostasis,
growth, reproduction and nutrition.
3. A size hierarchy exists involving cells going from largest to smallest: cells (100 microns) – organelles (10
microns) – bacteria (1 micron) – viruses (100 nanometers) – membrane thickness (10 nanometers) – molecules
(1 nanometer).
4. Scale bars or stated magnifications allow one to determine the actual size of specimens.
5. It is essential that there be a high surface area to volume ratio if a cell is going to successfully exist. As a
cell increases in size, the volume increases much faster than the surface area thus decreasing the surface area to
volume ratio. This decreases the chances for the successful existence of the cell.
6. It is essential to note that cells show emergent properties. This means that the interaction of the parts of the
cell results in the fact that the whole is greater than the sum of its parts.
7. In multicellular organisms, cells differentiate to carry out specialized functions. This specialization occurs
as a result of differential expression of genes in multicellular organism’s genes.
8. Stem cells have yet to go through the differentiation process. Thus, they maintain the ability to differentiate
along different pathways. There appears to be stem cells in most major types of tissues.
9. Stem cells have many therapeutic uses including the replacement of damaged bone marrow cells in leukemia
patients. In the future it may be possible to treat conditions such as Alzheimer’s disease and Parkinson’s
disease with stem cells. There is even hope that some forms of diabetes may be treated with these
undifferentiated cells. Plants show large numbers of stem cells in meristematic (growth) areas.
10. Prokaryotic cells divide by binary fission.
11. Prokaryotic cells include ribosomes, a cell wall, a cell membrane, a nucleoid region, and, in most cases,
plasmids.
12. Some prokaryotic cells include an exterior layer of a complex sugar compound called a capsule.
13. Ribosomes carry out protein production, and they do not include an exterior membrane.
14. Bacteria are examples of prokaryotic cells and are between one and ten micrometers in size.
15. Flagella occur in some bacteria and they allow organism mobility.
16. The nucleoid region is composed of a circular thread of pure DNA.
17. The cell wall is made of a material called peptidoglycan.
18. Eukaryotic cells are up to 100 micrometers in size.
19. Membrane bound organelles are characteristic of eukaryotic cells.
20. Common organelles include: endoplasmic reticulum, ribosomes, lysosomes, Golgi apparatus, mitochondria,
nucleus, chloroplasts, centrosomes, and vacuoles.
21. Animals cells contain centrioles but plant cells do not. Plant cells contain chloroplasts, animal cells do not.
Plant cells have cell walls, animal cells do not. Plant cells have larger vacuoles than animal cells.
22. The extracellular matrix of the animal cell is produced by the secretion of glycoproteins. This matrix
functions in support, adhesion and movement.
23. The exterior of the plant cell involves the cell wall and it maintains cell shape, prevents excessive water
uptake, and holds the whole plant up against the force of gravity.
24. Cell membranes include phospholipids and proteins. These proteins may be classified as integral, transport
or peripheral proteins.
25. It is the hydrophobic and hydrophilic properties of phospholipids that maintain the structure of cell
membranes.
26. Functions of membrane proteins include hormone binding sites, enzyme activity (such as ATPase), cell
adhesion, cell-to-cell communication, channels for passive transport, and pumps for active transport (Na+K+).
27. Diffusion is the passive movement of particles along a concentration gradient.
28. Osmosis is the passive movement of water across a partially permeable membrane along a concentration
gradient.
29. Cells expend energy (ATP) during active transport. Passive transport does not involve the expenditure of
ATP by the cell.
30. Endocytosis and exocytosis are examples of active transport. It is essential that the membrane has a degree
of fluidity so that shape changes may occur to allow endocytosis and exocytosis to occur.
31. Integrated proteins are embedded in the phospholipid bilayer of the plasma membrane, whereas peripheral
proteins are attached to the surface.
32. Vesicles are used to transport materials within the cell between the rough endoplasmic reticulum, the Golgi
apparatus, and the plasma membrane.
33. The cell cycle includes 4 phases: G1, S, G2, and M.
34. Interphase of the cell cycle includes G1, S, and G2.
35. Tumours (cancers) are the result of uncontrolled cell division and they may occur in any organ or tissue.
36. Interphase is the phase in which the cell is carrying out its appointed activity or activities. Metabolic
activities such as protein synthesis, DNA replication and organelle reproduction occur in this phase.
37. The phases of mitosis can be remembered in their proper order by ‘I play music at the concert’. Interphase,
prophase, metaphase, anaphase, telophase; cytokinesis.
38. It is essential to know the important events of these phases of mitosis.
39. During prophase and metaphase the chromosome is actually two molecules of DNA attached together at the
centromere. Each molecule of DNA is called a chromatid.
40. When the chromatids of the chromosomes split during anaphase, two separate chromosomes appear and the
term chromatid is not used anymore.
41. The kinetochore of the centromere allows attachment to the spindle microtubules.
42. The microtubules are made of a protein called tubulin.
43. Mitosis produces two genetically identical nuclei. However, the cytoplasm splitting which occurs during
cytokinesis does not result in identical halves. One half may have more organelles of a particular type than the
other.
44. Growth, embryonic development, tissue repair and asexual reproduction involve mitosis.
45. The term plasma membrane, not cell surface membrane, should be used for the membrane surrounding the
cytoplasm.
Complete the following.
1. What happens to the relative rate of excretion of metabolic wastes from cells as the surface area to volume
ratio of the cell decreases? Explain why.
2. Complete the following statements:
a. One millimeter is a ___________ times smaller than a meter.
b. One micrometer (micron) is a __________ times smaller than a millimeter.
c. One nanometer is a ___________ times smaller than a micron.
3. What is a scale bar?
4. Order the following from largest to smallest:
paramecium, ribosome, adenine, water, E.coli, X chromosome, carbon, mitochondria
5. Calculate specimen size of the following:
SHOW work:
6. Discuss the evidence for the cell theory. (Give the 3 main statements and support for each.)
7. What is one example of an organism that defy’s the cell theory? Why?
8. What is a stem cell?
9. How are stem cells used to treat Stargardt’s disease?
10. What would prevent stem cells from other species being successful in humans?
11. Name the function of the following prokaryotic cell parts:
a. cell wall
b. plasma membrane
c. cytoplasm
d. pili
e. flagella
f. ribosomes
g. nucleoid
12. By what mechanism do prokaryotic cells divide?
13. How do ribosomes differ in prokaryotic and eukaryotic cells?
14. What is the endosymbiotic theory?
15. Name two organelles that are similar to prokaryotic cells.
16. Name three ways that animal and plant cells are different.
17. Why would muscle cells have large numbers of mitochondria?
18. What is the major component of plant cell walls?
19. Which major type of cell demonstrates compartmentalization?_________________ Why is this important?
20. In which organelle would one find cristae and matrix?
21. What is the route within a cell in which vesicles move cargo?
22. Name one function of lysosomes.
23. Compare the structure and function of rough and smooth endoplasmic reticulum.
24. Why would liver cells have a large amount of sER?
25. What are the major components of a phospholipid which occurs in cellular membranes?
26. Animal cell membranes contain cholesterol to maintain proper membrane fluidity. Since plant cell
membranes do not contain cholesterol, how do they maintain membrane fluidity?
27. Which end of a phospholipid is hydrophobic?_____________________
Which is hydrophilic?____________________
28. Name 3 general functions of cell membrane proteins.
29. Explain what membrane glycoproteins are.
30. Compare and contrast passive and active transport.
31. State two examples of passive transport.
32. How does facilitated diffusion compare to diffusion?
33. What substance moves in osmosis?
34. Compare a hyperosmotic (hypertonic) solution to a hypo-osmotic (hypotonic) solution.
35. When looking at a hyperosmotic solution on one side of a membrane and a hypo-osmotic solution on the
other side, which way will water passively flow?
36. At what point will passive transport end?
37. Complete the following statements:
a. Small and non-polar molecules cross membranes ___________.
b. Large and polar molecules cross membranes with _______________.
38. What two major factors affect whether a substance can move across a membrane?
39. What type of transport is the sodium-potassium pump an example of?
40. In the Na+-K+ pump, do sodium ions move in or out of the cell? Depolarization or repolarization?
41. In the Na+-K+ pump, do potassium ions move in or out of the cell? Depolarization or repolarization?
42. How does the Na+-K+ pump maintain membrane potential?
43. What is the overall result of mitosis?
44. What is the overall result of cytokinesis?
45. What is the role of interphase in the life of a cell?
46. Name the four phases of mitosis and briefly describe what happens in each.
47. Why are the two cells produced by mitosis called clones?
48. Explain what happens in the following phases of interphase:
a. G1
b. S
c. G2
49. Explain how cytokinesis differs in plant and animal cells.
50. If a parent cell has 12 chromosomes, how many chromatids would be present right after S?__________________
51. What phase of the cell cycle would be greatly decreased in time in a tumour cell?