Which of the following statements regarding the demonstration of the etiology of disease is FALSE?
A) The suspect agent must be present in all cases of disease.
B) The suspect agent must cause the disease under investigation when introduced into a susceptible host organism.
C) The suspect agent must be isolated and cultured in the laboratory.
D) It must be possible to reisolate the suspect agent from the infected experimental host.
E) The suspect agent must be the only potential pathogen present in disease cases.
E
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In muscle tissue, if there is not enough oxygen for aerobic respiration to occur, the muscle cell
A. can produce ATP by fermentation. B. cannot make ATP. C. uses creatine phosphate instead of ATP for energy. D. can produce ATP from fats. E. depletes its reserves of lactic acid.
Which of the following is NOT true of spindles?
a. They are permanent cell structures. b. Centrosomes act as microtubule originating centers for spindles. c. Some of their microtubules overlap at the cell equator. d. Tubulin is the main component. e. They are bipolar in their configuration
Which statement is NOT true about DNA replication?
A. It occurs more rapidly in bacteria than in eukaryotes. B. One strand of new DNA is replicated faster than the other strand at the replication fork. C. DNA replication is considered semiconservative because there is always an old strand acting as a template for a new strand. D. It proceeds in a 5'-to-3' direction only. E. DNA can only replicate at one point on a chromosome at one time.
Vasopressin is a hormone that is primarily released when the body is low on water. Release of vasopressin causes the kidneys to conserve water by concentrating urine and decreasing urine output. However, vasopressin also has additional functions in other tissues such as the brain and blood vessels, which are not directly involved in urine production. How could it be possible for vasopressin to trigger different responses in different tissues?
A. The kidneys have a receptor for vasopressin, but cells in the brain and blood vessels do not have a receptor for vasopressin. B. Vasopressin can be released at different times to result in different effects. C. Vasopressin can bind to, and act on, different receptor subtypes, leading to different cellular responses in different tissues. D. Vasopressin binds to the same exact receptor in different tissues, but causes a different conformational change to the receptor in each tissue.