1. Give two reasons why cells divide.
- As a cell becomes larger, the cell puts more demands on its DNA. A larger cell has difficulty moving nutrients and wastes across the cell membrane.
2. How is a cell's DNA like the books in a library?
- The more people there are going to the library, the more of a demand there is for books. A cell's DNA is like the books because the larger the cell gets, the more demand there is for the DNA.
3. What is the solution to the problems caused by cell growth?
- The solution to the problems caused be cell growth is cell division.
4. As a cell increases in size, which increases more rapidly, its surface area or its volume?
- As the cell increases in size, the volume increases more rapidly than the surface area.
5. Calculate the surface area, volume, and ratio of an imaginary cubic cell with a length of 4cm.
- Surface Area = 4cm x 4cm x 6 = 96cm^2
- Volume = 4cm x 4cm x 4cm = 64cm^3
- Ratio = 96/64 = 3:2
p.249 1-6
1.Name the main events of the cell cycle.
- The main events of the cell cycle are the cell growing, replicates DNA, and divides into two daughter cells.
- In prophase the chormatin condenses into chromosomes and the centrioles separate. A spindle begins to form. Then the nuclear membrane breaks down.
- In metaphase the chromosomes are lined up across the center of the cell. Then a spindle fiber is connected to each chromosome at its centromere.
- In anaphase the sister chromatids are moved apart, separating into individual chromosomes.
- In telophase the chromosomes come together at opposite ends of the cell and two new nuclear membranes form.
- During interphase, the cell grows and replicates its DNA and centrioles.
- Chromosomes are made up of proteins and DNA.
- The process of cell division in prokaryotic cells requires the cell contents to be separated in to two parts.
- The cytoplasm in divided into two during cytokinesis in both animal and plant cells. In animal cells the cell membrane pinches inward to divide the cytoplasm, but in plant cells a cell plate is formed between the divided nuclei and becomes a separating membrane.
p.252 1-5
1. What chemicals regulate the cell cycle? How do they work?
- The chemicals that regulate the cell cycle are called cyclins. They trigger cell division.
2. What happens when cells do not respond to the signals that normally regulate their growth?
- When cells do not respond to the signals that normally regulate their growth, tumors (masses of cells) are formed and may damage surrounding tissues.
3. How do cells respond to contact with other cells?
- Cells respond to contact with other cells by not growing.
- Cancer can be considered a disease of the cell cycle because the cell cycle fails to respond to regulators and cells continue to grow, forming tumors.
5. Write a hypothesis about what you think would happen if cyclin were injected into a cell that was in mitosis.
- If cyclin is injected into a cell that is already in mitosis, then the cell will continue going through mitosis without any change because the cell cycle is already triggered.
p.257 1-10
1. The rate at which materials enter and leave through the cell membrane depends on the cell's surface area. (d)
2.The process of cell division results in two daughter cells. (c)
3.Pairs of identical chromatids are attached to each other at an area called the centromere. (b)
4.If a cell has 12 chromosomes, how many chromosomes will each of its daughter cells have after mitosis? 12 chromosomes (c)
5. At the beginning of cell division, a chromosome consists of two centrioles. (b)
6.The phase of mitosis during which chromosomes become visible and the centrioles separate from one another is prophase. (a)
7.Metaphase is best illustrated in which figure? figure b.
8.The timing of the cell cycle in eukaryotic cells is controlled by a group of closely related proteins known as cyclins. (b)
9. In the cell cycle, external regulators direct cells to speed up or slow down the cycle. (a)
10.Uncontrolled cell division occurs in cancer. (a)
