How many layers does the plasma membrane have?
a. One
b. Two
c. Three
d. Four
b. Two
The plasma membrane has two layers, made of several components—including phospholipids, cholesterol, proteins, and carbohydrates—that are able to flow and change position while keeping the basic integrity and shape of the membrane layers.
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How does the production efficiency of ectotherms and endotherms compare?
A. Usually higher in ecotherms than in endotherms. B. Usually lower in ecotherms than in endotherms. C. Approximately equal in ectotherms and endotherms. D. Usually negative in ectothems and positive in endotherms. E. Usually positive in ectothems and negative in endotherms.
What vulnerability is introduced by cell-surface signaling receptors?
a. They can cause a hole to form in the plasma membrane. b. They can introduce cells into the wrong areas of the body during development. c. They provide highly specific binding sites for viruses and other pathogens. d. They can result in non-specific binding foreign cells.
If houseplants must be left unattended for a length of time, some people recommend placing plastic bags over them. What is the reasoning behind this?
a. Water tension will decrease. b. The plants won't freeze. c. Photosynthesis will increase because of trapped carbon dioxide. d. Transpiration will be slowed and more water will be retained in the soil. e. The bag will trap oxygen.
Which of the following best describes sex-linked genes?
a. They are located on the X chromosome. b. They are linked to the sex-determining gene. c. They are expressed differently based on the sex of an individual. d. They are determinants of the sex of an individual.