Cells. Mitosis. DNA

Instructions: Read chapter 3 in your textbook and review the lecture notes and study resources provided by your instructor. Type your answer in the answer block provided for each question. Answer blocks should expand as you type. If you experience difficulty typing in the provided answer blocks, you may type your answers in a new document. Save a copy of the completed activity to your computer for your records. Although this activity is not graded, your instructor reserves the right to require students to submit their completed work at any time throughout the semester. Short Answer Questions

1. Explain why mitosis can be thought of as cellular immortality? Mitosis is a process in which cells replicate their DNA to create new cells that are genetically identical. The DNA is propagated throughout the new cells and the genetic information is “immortalized”. |

2. Contrast the roles of ER-bound ribosomes with those free in the cytosol. Free ribosomes synthesize soluble proteins that function in cytosol or other organelles.Membrane-bound ribosomes (forming rough ER) synthesize proteins to be incorporated into membranes, lysosomes, or exported from the cell.|

3. Cells lining the trachea have whip-like motile extensions on their free surfaces. What are these extensions, what is their source, and what is their function? The trachea’s free surface is covered with cilia. These ciliated cells propel mucus full of dust particles and bacteria upward away from the lungs. They help keep the respiratory system free of debris and potentially harmful bacteria.|

4. Name the three phases of interphase and describe an activity unique to each phase. 3 phases of Interphase: * G1 – the centrioles begin
replicating * S – DNA is replicated * G2 – final preparations for mitosis are completed and centrioles finish replicating.|

5. Differentiate clearly between primary and secondary active transport processes. * Primary transport is a type of active transport in which the energy needed to drive the transport process is provided directly by hydrolysis of ATP. * Secondary transport is a single ATP-powered pump that indirectly drives the secondary active transport, such as the Na+ -K+ pump|

Clinical Application Questions

1. A “red hot” bacterial infection of the intestinal tract irritates the intestinal cells and interferes with digestion. Such a condition is often accompanied by diarrhea, which causes loss of body water. On the basis of what you have learned about osmotic water flows, explain why diarrhea may occur. Diarrhea may occur because the cells within the intestinal tract have been damaged, affecting the mucous lining of the intestines. When these cells and mucous lining have been damaged, they are not able to absorb properly, which can lead to passive loss of nutrient-rich fluids and decreased ability to absorb the lost fluids. Osmosis to absorb these necessary liquids into our bodies cannot happen because the bacterial infection has damaged the cells that perform this very important task and cause diarrhea. Without proper cell function, osmosis cannot occur. |

2. Dynein is missing from the cilia and flagella of individuals with a specific inherited disorder. These individuals have severe respiratory problems and, if males, are sterile. What is the structural connection between these two symptoms? Dynein is a protein from the microtubules of cilia and flagella. It functions as an ATP-splitting enzyme and is essential to the motility of cilia and flagella. The cilia within the respiratory system cannot move and function properly to remove dust particles and bacteria to maintain a healthy respiratory system. Immobility of sperm causing sterility is due to the flagella of the sperm being unable to move the sperm within the female reproductive system to reach and fertilize an egg.|

3. Water is a precious natural resource in Florida and it is said that supplies are dwindling. Desalinization (removing salt from) ocean water has been recommended as a solution to the problem. Why shouldn’t we drink salt water? Explain. Salt water is toxic to our bodies because the body eventually fails when it has to try to get rid of the salt that enters our bodies if we were to drink salt water. The body normally gets rid of excess salt by the kidneys producing urine, but it needs regular water to dilute the salt in our body for our kidneys to work properly. Normally that is not a problem because we drink water and eat foods with water in them. Tissue in our bodies also contains water that can be used. But if there is too much salt in our bodies, our kidneys cannot get enough water to dilute the salt and our bodies will shut down due to kidney failure.

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