1.give two reasons why cells divide.
- The larger a cell becomes, the more demands the cell plaeces in its DNA and the more trouble the cell has moving enough nutrients and wastes across the cell membrane.
2. how is a cell's DNA like the books in a library?
- Cells DNA are like books in the library because a large cell would have to make greater demands on its available genetic "library," and then in comparison a library would have to provide more books for a town that contnues to grow.
3. what is the solution to the problems caused by cell growth?
-the solution to the problems caused by cell growth is, the replication of DNA.
4. as a cell increases in size, which increases more rapidly, its surface are or it's volume?
-The volume of a cell increases more rapidly than the surface area of a cell.
-The volume of a cell increases more rapidly than the surface area of a cell.
5. Calculate the suface area, volume and ratio of surface area to volume of an imaginary cubic cell with a length of 4 cm.
surface area: 4 cm * 4 cm * 6= 96 cm2
volume: 4 * 4 * 4= 64 cm3
ratio of surface area= 96/1= 96:1
volume: 4 * 4 * 4= 64 cm3
ratio of surface area= 96/1= 96:1
p. 249 questions 1-6
1. Name the main events of the cell cycle?
1. Name the main events of the cell cycle?
-3 main events of the cell cycle are cell growth, preparation for division, and division to form 2 daughter cells.
2. Describe what happens during each of the four phases of mitosis?
-four phases of mitosis:
prophase- the chromosomes become visible, condensed chromosomes become attached to fibers in the spindle at a point near the centromere of each chromotid. at the end of prophase, the chromosomes coil even more tightly then the nucleous disappears and the nucleur envelope breaks down.
metaphase- chromosomes line up across the center of the cell. microtubules connect the centromere of each chromosome to the poles of the spindle.
anaphase- the centromeres seperate allowing the sister chromatids to seperate and become individual chromosomes. they continue to seperate till they become two groups near the poles of the spindle. this process ends when the chromosomes stop moving.
telophase- the chromosomes begin to disperse into a tangle of dense material. a nucleur envelope reforms around the cluster of chromosomes. a spindle begins to break apart, and a nucleolus becomes visible in eahc daughter nucleus. mitosis is then complete , yet cell division stil has to occur.
3. describe what happens during interphase.
-Interphase refers to all stages of the cell cycle other than mitosis. During interphase, cellular organelles double in number, the DNA replicates, and protein synthesis occurs. The chromosomes are not visible and the DNA appears as uncoiled chromatin.
4. what are chromosomes made of?
-they are made up of DNA
5. how do prokaryotic cells divide?
-The chromosome is duplicated prior to division. The two copies of the chromosome attach to opposing sides of the cellular membrane. Cytokinesis, the physical separation of the cell, occurs immediately.
-The chromosome is duplicated prior to division. The two copies of the chromosome attach to opposing sides of the cellular membrane. Cytokinesis, the physical separation of the cell, occurs immediately.
6. how is cytokinesis in plant cells similiar to cytokinesis in animal cells? how is it different?
-they are similiar because they both contain its own nucleus .
-they are different because in an animal cell the cell membrane is drawn inward until the cytoplasm in pinched into two nearly equal parts. in a plant cell, the cell plates forms midway between the divided nuclei. The cell plate gradually develops into a seperating membrane. A cell wall then begins to apear in the cell plate.
p.252 questions 1-5
1. what chemicals regulate the cell cycle? how do they work?
-cyclins regulate the cell cycle. they do so in eukaryotic cells.
2. what happens when cells do not respond to the signals that normally regulate their growth?
-they form masses of cells called tumors that can damage the surrounding tissue.
3.how do cells respond to contact with other cells?
-they respond by not growing.
4. why can cancer be considered a disease of the cell cycle?
-because understanding and combating cancer remains a major scientific challenge.
http://www.stormingmedia.us/15/1566/A156683.html5. write a hypothesis about what you think would happen if cyclin were injected into a cell that was in mitosis.
If cyclin were injected into a cell that was in mitosis, the timing would be off and the process would then be messed up.
p.257 questions 1-10
1. the rate at which materials enter and leave through the cell membrane depends on the cell's volume
2. the process of cell division results in sister chromatides.
3. pairs of identical chromatids are attached to each other at an area called the spindle
4. if a cell has 12 chromosomes, how many chromosomes will each of its daughter cells have after mitosis 6
5. at the beginning of cell division, a chromosome consists of two chromatids.
6. the phase of mitosis during which chromosome become visible and the centrioles seperate from one another is telophase
7. metaphase is best illustrated in which figure? figure b
8. the timing og the cell cycle in eukaryotic cells is controlled by a group of closly related proteins known as cyclins.
9. in the cell cycle, external regulators direct cells to grow uncontrollably
10. uncontrolled cell division occurs in cyclin
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