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Section 5.1 Study Guide
Vocabulary
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Cell cycle
Mitosis (called M Phase)
Cytokinesis (also part of M Phase)
Interphase
Gap 1 (G1)
Gap 2 (G2)
Synthesis (S Phase)
Review Questions
1. What are the 4 stages of the cell cycle? What happens in each phase?
Gap 1, S-Phase (Synthesis), Gap 2 and M-Phase (mitosis and cytokinesis) make up the cell cycle. In
Gap 1 and Gap 2 the cell carries out its normal functions (such as protein synthesis, growth,
organelle production, making of hormones, propagation of action potentials in nerve cells, etc.); in
S-Phase the cell makes a duplicate of its nuclear DNA; and in M-Phase the cell undergoes division
(both of its nuclear DNA – mitosis – and cytoplasm – cytokinesis).
2. What parts of the cell cycle make up Interphase? What is the cell doing during interphase?
Interphase is made up of Gap 1, S-Phase (Synthesis), and Gap 2. During interphase the cell grows,
carries out normal functions such as protein synthesis, replicates its organelles, and duplicates
(synthesizes) its DNA during S-Phase.
3. What are the two processes that make up M-Phase? What are their functions?
The two processes are mitosis and cytokinesis. Mitosis is the division of the cell nucleus and its
contents, which are duplicated DNA chromosomes. Cytokinesis is the process that divides the cell
cytoplasm.
4. In which phase does the cell spend most of its time? What can you infer about the relative amount
of time a cell spends in each stage? Explain your answer.
A cell spends most of its time in Gap 1. The time a cell spends in Gap 1 varies greatly and is an
indication of the purpose of the cell. The cells of internal organs and smooth muscle spend more
time in Gap 1 than skin cells and other cells that receive a lot of wear and tear.
5. During G2, what might happen if the cell’s nutrition was not adequate? What might happen (or not
happen) to the cell? Explain.
Cells may not grow properly during Gap 1, the cell’s DNA my not synthesize correctly (or at all),
and the cell may not divide properly or at all.
6. Do you think a skin cell would have a long or short G1 stage? Explain why.
A skin cell would have a short G1. Skin cells undergo a lot of wear and tear because they are
exposed on the outside of the body. Therefore, they are replaced quickly.
7. During which stage of the cell cycle is DNA copied?
During S-Phase (referred to also as Synthesis)
8. Which stages of the cell cycle generally require about the same amount of time in all human cells?
M-phase (mitosis and cytokinesis), S-Phase when DNA is synthesized, and Gap 2. Gap 1 is the
highly variable phase in terms of how long it lasts.
9. What limits the maximum size of a cell? What can larger cells do to increase their surface area?
The ratio of cell surface area to volume – cells need sufficient surface area to provide the cell with
oxygen and other nutrients that must move across its cell membrane. Larger cells can increase
their surface area by being long and thin (like a neuron) or folded in some way to increase surface
area.
10. Suppose you treat cells with chemicals that block cytokinesis. Describe what you think the daughter
cells that result would look like.
The cells would probably look large and have two nuclei located at opposite sides of the cell. In
other words, the nucleus with the DNA would divide but the two daughter cells would not form
because there is no division of the cytoplasm. The cell would not be viable.
11. Predict how the rate of cell division would differ among skin cells, cardiac (heart) cells, and brain
cells (neurons)? Why might it take longer to recover from some injuries than others?
The skin cells would divide most frequently because of how much wear and tear they receive.
Cardiac cells divide only rarely in response to injury or cell death. Neurons do not divide at all.
The frequency of cell division affects how quickly an individual can recover from an injury.
Therefore, cardiac cells take longer than skin cells.
12. (Challenge Question) Predict how the rate of cell division would differ between single-celled algae
living in a sunny, nutrient rich pond versus algae living in a shady, nutrient-poor pond. Explain your
answer.
It is likely that the algae in the sunny pond would have a faster rate of cell division than the algae
in the shady pond. Any feasible way of testing the prediction is acceptable. One possibility could
be to gather algae from the two ponds and evaluate what percentages of the samples were in
each stage of the cell cycle. A higher percentage of the algae in the sunny pond would be in mphase than in the shady pond.
Make sure you know the stages of the cell cycle and what happens during each stage. It would help if
you were to draw this out and label it.