Chapter 10 assessment answers

1. a. Review Identify two reasons why a cell’s growth is limited. DNA can’t keep up with growth Plasma membrane doesn’t grow at same rate of volume and cannot provide enough food for cell or get enough waste out of cell.

1b. Explain As a cell’s size increases, what happens to the ratio of its surface area to its volume? The ratio between the two numbers decreases so that cell’s volume is growing faster than the surface area. Surface area represented by cell membrane. Cytoplasm represented by the cytoplasm or inner contents of cell.

1 c. Applying Concepts Why is a cell’s surface area-to- volume ratio important? Helps us understand why cells have to stay small. Diffusion is a slow process so if cell is too big, active and passive transport are not going to happen at the rate that they should for a bigger cell. Plasma membrane is not big enough to supply what the cell needs because volume increased faster than plasma membrane.

2. a. Review What is asexual reproduction? What is sexual reproduction? Asexual – involves 1 parent, each cell is genetically identical Sexual – involves 2 parents, each cell in not identical to either parent

2b. Explain What types of organisms reproduce sexually? Multicellular organisms like plants & animals And some single celled eukaryotic organisms

Asexual reproduction can produce large numbers of cells quickly 2c. Summarize What are the advantages and disadvantages of both asexual and sexual reproduction? Asexual reproduction can produce large numbers of cells quickly But are the cells are the same and in case of a change in environment, they do not have ability to adapt Sexual reproduction takes a longer period of time but offspring has genetic diversity that might allow them to have genes to adapt to a change in the environment.

3. The formula for finding the surface area of a sphere, such as a baseball or a basketball, is A = 4 TT r2, where r is the radius. The formula for finding the volume of a sphere is V = 4/3 TT r3. a. Calculate the surface area and the volume of the baseball and the basketball. Then, write the ratio of surface area to volume for each sphere. Basket ball r=12.2 Baseball r= 3.6

b. Infer If the baseball and basketball were cells, which would possess a larger ratio of area of cell membrane to cell volume? Baseball

10.2 1. a. Review What are chromosomes? DNA wrapped around histone proteins Carries genetic material

b. Compare and Contrast How does the structure of chromosomes differ in prokaryotes and eukaryotes? Prokaryotes have 1 chromosome in the shape of a circle Eukaryotes can have many chromosomes because the DNA is longer

2. a. Review What is the cell cycle? All the stages a cell must go through in order to grow and divide

b. Sequence During which phase of the cell cycle are chromosomes replicated S stage of interphase

3. a. Review What happens during each of the four phases of mitosis 3. a. Review What happens during each of the four phases of mitosis? Write one or two sentences for each phase. prophase: chromatin condenses and replicates; centrioles appear move to ends of cells while moving spindles across the middle of the cell , nucleus and nucleolus disappear; metaphase: sister chromatids line up in middle of cell anaphase: sister chromatids pulled apart to the opposite ends of the cell Telophase: nuclei reform around the chromatids that have separated into the opposite ends of the cell

b. Predict What do you predict would happen if the spindle fibers were disrupted during metaphase? The chromatids would not get moved to the middle of the cell; so the chromosomes could not be pulled apart during anaphase

4. a. Review What is cytokinesis and when does it occur? Division of the cytoplasm It occurs after sister chromatids have divided into two nuclei; after telophase

b. Compare and Contrast How does cytokinesis differ in animal and plant cells? Plant cells have a rigid cell wall which will not pinch inward. A cell plate forms first between two new nuclei. Then the cell wall for both cells will form on the other side of cell plate. Animal cells plasma membrane will simply pinch inward to form two new cells.

10.3 1. a. Review Name the two types of proteins that regulate the cell cycle. How do these proteins work? Internal Signals come from the inside of the cell. They allow cell cycle to proceed only after certain events occur External Signals come from outside the cell These signals speed up of slow down the cell cycle.

b. Form a Hypothesis Write a hypothesis about what you think would happen if cyclin were injected into a cell during mitosis. How could you test your hypothesis? Cyclins injected would cause the cell process of division to go faster To measure my hypothesis, I would need to count cells after I had injected the cyclin and compare them to cells that did not get any cyclin

2. a. Review Why is cancer considered a disease of the cell cycle? Because cancer is the overgrowth of cells Something went wrong with the controls that tell the cell to stop dividing

b. Compare and Contrast How are the growth of a tumor and the repair of a scrape on your knee similar? How are they different? The growth of cells both undergo all the processes in the cell cycle; interphase, mitosis, cytokinesis; they both involve rapid cell division The cancer cell will not stop dividing. The cells for the scrape on the knee will stop dividing after the skin has healed.