Question

section 10-3 regulating the cell cycle
(pages 250-252)
key concepts

• how is the cell cycle regulated?
• how are cancer cells different from other cells?

controls on cell division (page 250)

1. what happens to the cells at the edges of an injury when a cut in the skin or a break in a bone occurs?
2. what happens to the rapidly dividing cells when the healing process nears completion?

cell cycle regulators (page 251)

1. what do cyclins regulate?

1. what are internal regulators?
2. circle the letter of each sentence that is true about external regulators.

a. they direct cells to speed up or slow down the cell cycle.
b. they prevent the cell from entering anaphase until all its chromosomes are attached to the mitotic spindle.
c. they include growth factors.
d. they prevent excessive cell growth and keep the tissues of the body from disrupting one another.
uncontrolled cell growth (page 252)

1. what is cancer?

1. complete the flowchart about cancer.

cancer cells dont respond to signals that regulate ______.
↓
cancer cells form masses of cells called ______.
↓
cancer cells break loose and spread throughout the ______.

1. is the following sentence true or false? cancer is a disease of the cell cycle.

reading and study workbook 111

Explanation:

1. When there is an injury (like a cut in the skin or a bone break), cells at the edges of the injury divide rapidly. This is part of the body's natural healing process - new cells are needed to replace damaged or lost cells.
2. As the healing process nears completion, the rapidly - dividing cells receive signals to stop dividing. This is a regulatory mechanism to prevent over - growth of cells.
3. Cyclins are proteins that regulate the timing of the cell cycle. They bind to and activate cyclin - dependent kinases (CDKs), which then phosphorylate other proteins to drive the cell cycle forward.
4. Internal regulators are proteins that respond to events inside the cell. For example, they can ensure that the cell does not enter mitosis until its DNA has been replicated, or that it does not enter anaphase until all chromosomes are properly attached to the spindle fibers.

5.

• a. External regulators, such as growth factors, can direct cells to speed up or slow down the cell cycle. For example, platelet - derived growth factor (PDGF) stimulates the division of fibroblasts to help in wound healing (so a is true).
• b. The prevention of a cell from entering anaphase until all its chromosomes are attached to the mitotic spindle is a function of internal regulators (so b is false).
• c. Growth factors are a type of external regulator. They bind to receptors on the cell surface and trigger intracellular signaling pathways that affect the cell cycle (so c is true).
• d. External regulators, like some inhibitory factors, can prevent excessive cell growth and keep tissues from disrupting one another. For example, contact inhibition (where cells stop dividing when they come into contact with other cells) can be mediated by external signals (so d is true).

1. Cancer is a disorder in which body cells lose the ability to control cell growth. This can be due to mutations in genes that regulate the cell cycle, such as proto - oncogenes (which promote cell growth) and tumor suppressor genes (which inhibit cell growth).

7.

• Cancer cells don't respond to signals that regulate the cell cycle.
• Cancer cells form masses of cells called tumors. Benign tumors are non - invasive and do not spread, while malignant tumors are invasive and can metastasize.
• Cancer cells break loose and spread throughout the body. This process is called metastasis, and it allows cancer to spread from the original (primary) tumor to other parts of the body (secondary tumors).

1. Cancer is a disease of the cell cycle. Since cancer cells have defects in the mechanisms that control the cell cycle (such as mutations in cyclins, CDKs, or tumor suppressor genes), the statement “Cancer is a disease of the cell cycle” is true.

Answer:

1. The cells at the edges of an injury divide rapidly.
2. The rapidly dividing cells stop dividing.
3. Cyclins regulate the timing of the cell cycle.
4. Internal regulators are proteins that respond to events inside the cell.
5. a. True, c. True, d. True.
6. Cancer is a disorder in which body cells lose the ability to control cell growth.

7.

• the cell cycle
• tumors
• body

1. True.