Biolgoy Sect 1

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Section 51-1
1. Target cells are the specific cells that are affected
by a hormone.
2. A second messenger is an intracellular molecule
that amplifies the signal of a first messenger.
3. A prostaglandin is a lipid that regulates the activity
of cells that are in close proximity to its site
of production.
4. Hormones are molecules that are secreted in small
amounts, circulate in the bloodstream, and affect
distant target cells.
1. d 2. c 3. a 4. c 5. c
1. A first messenger binds to cell surface receptors
and stimulates production of a second messenger
that is located within the target cell.
2. Hormones are transported in the bloodstream.
3. No; they have ducts and secrete sweat, not
4. It depends on the enzymes and other proteins that
c-AMP activates to change the function of the cell.
1. Anti-C antibody prevents the hormone’s action.
2. No; the fact that three of the antibodies do not
alter the hormone’s action is evidence that it is
not simply the binding of an antibody that disrupts
the action of the hormone.
3. Segment C is probably the receptor binding portion
of the hormone.
Section 51-2
1. Hypothyroidism results from a thyroid-hormone
deficiency, but hypoglycemia results from excessive
2. Epinephrine and norepinephrine are both secreted
from the medulla of the adrenal glands.
3. Releasing hormones are produced by the hypothalamus
and control the secretion of luteinizing
4. Neurosecretory cells of the hypothalamus produce
oxytocin and antidiuretic hormone.
5. Estrogen, progesterone, and testosterone are all
steroid sex hormones secreted by the gonads.
1. d 2. a 3. c 4. d 5. b
1. No; the hypothalamus is a structure of the nervous
system that regulates the pituitary gland.
2. The thyroid glands secrete calcitonin, which lowers
blood levels of calcium, and the parathyroid
glands secrete parathyroid hormone, which raises
blood levels of calcium.
3. The thymus gland aids the immune system by contributing
to the development of T cells.
4. Oxytocin and antidiuretic hormone (ADH), are produced
in the hypothalamus by neurosecretory
cells. Oxytocin stimulates uterine contractions
during childbirth, and ADH stimulates water reabsorption
in the kidneys.
5. Insulin hormone deficiency causes Type I diabetes
mellitus. Type I can be differentiated from Type II
diabetes mellitus by an injection of insulin; the
symptoms of Type I will be relieved, while the
insulin injection will have no effect on the symptoms
of Type II.
1. D 2. A 3. E 4. F 5. B 6. C
Section 51-3
1. Antagonistic hormones are hormones that have
opposite effects on the concentrations of substances
that they regulate.
HRW material copyrighted under notice appearing earlier in this work. Modern Biology Study Guide Answer Key
2. A feedback mechanism is a series of events in
which the last step controls the first step.
3. In negative feedback, the last step inhibits the
first step.
4. In positive feedback, the last step stimulates the
first step.
1. d 2. a 3. c 4. c 5. b
1. Based on the information provided, the defective
organ would be the testis because excessive LH
was being secreted. The negative feedback mechanism
was attempting to increase the low level of
testosterone. Therefore, the LH concentration was
above normal.
2. Hormone concentrations would increase steadily
and without inhibition.
3. The TSH level should be above normal because
the negative feedback mechanism would attempt
to normalize the thyroid hormone levels by
increasing stimulation.
1. In Situation 1, the receptors of Cell M are defective.
There is no Cell M secretion, indicating that
hormone secreted by Cell D is required to stimulate
Cell M. Cell D secretion...
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