Download Organelles to function of cell (pgs 191-200)

Organelles to function of cell (pgs 191-200)
Multiple Choice
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1. Which organelle converts sugars into energy?
a. lysosome
b. mitochondrion
c.
d.
nucleus
ribosome
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2. Cilia and flagella are used to move cells through watery environments. What role do these cell parts play on stationary
cells?
a. They hold neighboring cells in a fixed position.
b. They move substances along the surface of the cell.
c. They protect the cell by whipping at harmful cells.
d. They transmit waste materials away from the cell.
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3. A scientist at the polar ice cap was studying an ice sample from hundred of meters below the surface. While examining the
ice, the scientist found some cells from many years ago. Using an electron microscope, the scientist identified these cell
structures: a cytoskeleton, mitochondrion, nucleus, cell wall, and ribosomes. What kind of organism did the scientist find?
a. animal
c. plant
b. bacteria
d. He did not have enough information.
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4. Chloroplasts are organelles that convert light energy to sugars. These organelles are found only in plants. Which organelles
are found only in animals?
a. golgi apparatus
c. mitochondria
b. lysosomes
d. ribosomes
Short Answer
5. In plants, cells that transport water against the force of gravity are found to contain many more mitochondria than do some
other plant cells. What is the reason for this?
6. Folded membranes have important uses in the cell. Describe at least four of these uses.
7. Between which cell types is the difference greater—plant and animal cells or prokaryotic and eukaryotic cells? Give
reasons for your answer.
For many years, scientists thought of the nucleus as "a bag of chromatin floating in a sea of cytoplasm." Using electron
microscopes, scientists saw that the nucleus was much more complex. The nuclear envelope was two layered and covered
with pores.
Scientists began further research. Scientist S punched small holes in the nuclear envelope, allowing the contents to
pour out. He observed that the nucleus retained its spherical shape. From this, scientist S hypothesized that the nucleus had
some other structural framework, beyond the membrane itself. The next experiment performed by scientist S revealed that
the nucleus indeed had a fibrous protein framework, now called the nuclear matrix.
Three other scientists repeated this experiment, but each changed one part of it. Scientist X used detergents and salt to
remove the nuclear contents. Scientist Y used chemicals, and scientist Z used enzymes. All three observed that a nuclear
matrix remained.
Further electron microscopy revealed that the chromatin strands were anchored to a fibrous layer that lines the inner layer
of the nuclear envelope.
8. Describe a procedure to determine whether the attachment of the chromatin to the nuclear envelope is necessary for the
chromatin to become chromosomes.
9. Why did scientists X, Y, and Z use different substances to remove the nuclear contents?
10. What was the variable in the experiments by scientists X, Y, and Z?
11. Why did scientists X, Y, and Z carry out their experiments?
12. What observation from scientist S's second experiment supported the original hypothesis?
13. What was the hypothesis of scientist S in his first experiment?
14. Why is it important that some proteins extend all the way through the bilayer of a plasma membrane?
15. Compare the importance of the plasma membrane and the other cell structures it contains. Decide which structure you
believe is the most important to a cell.
16. Endoplasmic reticulum can be smooth or rough. What are the differences between the two types of ER?
17. A scientist examined a cell with a high-powered microscope. The scientist concluded that the cell was an animal cell. How
did the scientist know that the cell was from an animal?
18. Plant cells have cell walls. Animal cells do not have this structure. Create a hypothesis that might explain this differences
between plant and animal cells.
19. What is the relationship between exocytosis and the Golgi apparatus?
20. Describe how organelles move within the eukaryotic cell.
Problem
In the 1890s, E. Overton performed experiments to determine the structure of the plasma membrane. After many years and
various procedures, he determined that large, uncharged molecules enter a cell at a rate proportional to their solubility in
lipids. This observation was the first indication that the plasma membrane is probably made up of lipids. Many scientists
began to pursue the question of how the lipids were arranged.
In 1925, two Dutch scientists determined that the area covered by the lipids from a single red blood cell is twice the
area of the surface of the cell. From this, they reasoned that the cell is covered by a double layer of lipid molecules. Based
on this work, various scientists hypothesized that the membrane was like a "fat sandwich" with two outer layers of protein
on the surface of the lipid layer.
None of the ideas seemed a satisfactory explanation until microscopic studies of membranes prepared by a new
technique of "freeze-fracture" revealed that the proteins are actually embedded in the lipid layer. In 1972, on the basis on
these results and other evidence, two American scientists proposed the fluid-mosaic model.
21. What inference did the Dutch scientists make to reach their conclusion?