AP BIOLOGY POGIL - The Cell Cycle Questions with Answers

AP BIOLOGY POGIL - The Cell Cycle The Cell Cycle What controls the life and development of a cell? why? An old piece of poetry says "to everything there is a season... a time to be born, a time to die." For cells, the line might say "a time to divide and a time to grow." In multicellular organisms, different types of cells have different roles and need to complete specific tasks. For example, a cell that isn't large enough is not useful for storing nutrients for later, but a cell that is too large will not be useful for transportation through a tiny capillary. In this activity, you will learn about the seasons of a cell's life, and in turn better understand how organisms function. Model 1 - The cell cycle 1. How many phases are in the cell cycle as shown in the diagram in Model 1? Four. 2. Starting at the starred cell, what is the order of the stages of a cell's life? 1' 2' 3. During which phase does the size of the cell increase? 4. During which phase does the number of cells increase? M. 5. Considering your answer to Questions 3 and 4, identify two ways that the growth of an organism can be accomplished through the events of the cell cycle. Growth can happen when cells increase in size or when the number ofcells in an organism increases (this takes place during Gl and M, respectively). The Cell Cycle 113 STOP 6. Cancer, the uncontrolled growth of cells, often results in a tumor, or mass of abnormal cells. Some cancerous tumors consist of many cells that are much smaller than normal. According to Model l, what part(s) of the cell cycle is (are) most likely being affected? Gl may be affected, not allowing the cells to fully grow. 7. In Model l, if the length of the arrow represents time, then for those cancerous cells, what happens to the time that is necessary for the cell cycle? What implication might this have for doctors who are treating cancer patients? The time decreases because the time necessary for Gl is reduced. Doctors need to start treatment quickly and use a drug that is absorbed by the system rapidly since the cancer cells reproduce at a faster rate than normal cells. Model 2 — Cell Cycle Data Phase Key Process Time Interval (hours) Sets of DNA present in each cell at end of phase Number of organelles in each cell at end of phase Gap I Cells getting larger and making more organelles. 1 1 1 560 Synthesis DNA replication 8 2 570 Gap2 Protein and organelle synthesis 4 2 600 Mitosis Cell and nuclear splitting 1 300 Total time: 24 8. Model 2 presents cell cycle data for a typical human cell in culture. Use the phase names in Model 2 to label the G, M, and S phases in Model 1. See Model 1. 9. Looking at the third column of Model 2, compare the time spent in mitosis with the time spent in gapl in human cells and describe any difference. Much more time is spent in gap than mitosis. 10. Imagine 100 cells were chosen randomly from a tissue sample and examined under a microscope. In which phase of the cell cycle would you expect to find the largest number of cells? Explain. More cells would be in the longer-lasting gam phase, because ifcells don't spend much time in a phase, they are less likely to be in it at any given time. STOP l l. Look again at Model 2. Compare the amount of DNA at the beginning and end of synthesis. Why did the amount of DNA change? POGIEM Activities for High School Biology The cell is preparing to divide, so there is double the amount ofDNA at the end ofsynthesis than at the beginning. 12. Fill in the "Key Process" column for synthesis phase in Model 2. See Model 2. 13. Cyto = cell, kinesis = cutting. What do you think takes place during cytokinesis? The cell (cytoplasm) is split in two. 14. Other than cytokinesis, what else occurs during the mitosis phase? Hint: Consider the sets of DNA in each cell. Nuclear division; the DNA is evenly divided, creating two separate nuclei. 15. Look carefully at information given to you in Model 1 and Model 2. Fill in the key process column in the table for gam. See Model 2. 16. If a culture in the lab starts with one human cell, how many cells will there be after 24 hours? Two cells. 17. The total time for the phases listed in Model 2 is 24 hours. How many human cells will be in the culture after another 24 hours? Explain. Four each one ofthe cellsfrom thefirst round ofthe cell cycle goes through it again. 18. Is the original cell "dead" or does it disappear after mitosis? Explain your answer. No, the original cell is divided into two new cells. Each cell has exactly the same DNA as the original cell, which duplicated its DNA before it divided. Therefore, each new cell has a complete set ofchromosomes (DNA) as well as halfthe organellesfrom the originalparent cell. 19. If a starfish sustains damage to a limb, it often grows a new one. If a human adult sustains damage to his or her spinal cord, mobility is often impaired. If a gecko loses its tail, it may grow a new one. Which type of cell is less likely to go through the cell cycle after being damaged— starfish limb, human spinal cord, or gecko tail? Support your answer. Human spinal cord cells, because that injury can't be repaired. 20. Occasionally cells stop dividing and enter another phase, G . If you damage your liver, new liver cells can be produced to replace up to 75% of the liver. However, if you sustain brain damage, your body does not produce new brain cells. Explain this observation using what you have learned about the cell cycle. The brain cells are in Go and do not reproduce, but the liver cells will reproduce to make new ones. 21. Keeping in mind the events of each part of the cell cycle, mark with a double arrow on Model I where those cells might (either temporarily or permanently) exit the cell cycle to G . Label this as G . Why did you choose this location for G ? Hint: Think of a place in the cell cycle where the cell is functioning normally, but not preparing to divide. It should be depicted coming offofgapr It can't be mitosis as the cell would be in the process ofdividing; it can't be synthesis or the DNA would be only partially copied; and it can't be gap2 or the cell would have too much DNA.