BIO 1108 EXAM QUESTIONS AND
ANSWERS A+ GRADED
What are the benefits of endocrine signaling in comparison to neuronal signaling.
Endocrine Signaling: secretes hormones
that coordinate slower but longer-acting
responses including reproduction,
development, energy metabolism, growth, and
behavior; slow response, long-lasting, broad impact, difficult to reverse
The Nervous System: The nervous system conveys high-speed electrical signals along
specialized cells called
neurons; these signals regulate other cells
Distinguish between hormones and local regulators.
Hormones: secreted by endocrine cells and released in the extracellular fluid where
they travel down the bloodstream and triggering responses in target cells anywhere in
the body.
Local Regulators: molecules that act over short distances and reach their target cells
solely by diffusion.
(paracrine signaling - target cells lie near the secreting cell)
(autocrine signaling - target cell is the secreting cell)
Define and give an example of a neurohormone.
In neuroendocrine signaling, specialized neurons called neurosecretory cells secret
molecules that diffuse from nerve cell endings into the bloodstream. These molecules
which travel through the blood stream to taget cells, are a class of hormone called
neurohormone.
Ex. Antidiuretic hormone (vasopressin) which is a hormone essential for kidney function
and water balance.
What are pheremones?
Chemicals that are released into the external environment
List the three major classes of molecules that function as hormones.
(1) Polypeptides (Insulin)
-water-soluble
-cannot pass through the plasma membrane readily so they must bind to cell-surface
receptors that relay into to the nucleus through intracellular pathways
(2) Steroids (cortisol & ecdysteroid)
-lipid-soluble
-can pass through cell membrane readily
-receptors typically reside in cytoplasm or nucleus
(3) Amines (epinephrine & thyroxine)
-water-soluble (though thyroxine - large non polar hydrophobic molecule - is lipid-
soluble)
Explain the differences in the location of receptors in the target cells of
watersoluble and lipid-soluble hormones. Compare their roles in initiating
signaltransduction pathways, and describe the changes they are likely to trigger
, within the
target cell.
H20-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and
bind to cell-surface signal receptors. Binding of such hormones to receptors induces
changes in cytoplasmic molecules and sometimes alters gene transcription .
Lipid-soluble hormones diffuse out across the membranes of endocrine cells. Outside
the cell, they bind to transport proteins that keep them soluble in the aqueous
environment of the bloodstream. Upon leaving the bloodstream, they diffuse into target
cells, bind to intracellular signal receptors, and trigger changes in gene transcription.
Describe the pathway of water-soluble hormones
Binding of H2O-soluble hormone to a signal receptor protein triggers events at the
plasma membrane that result in a cellular response. In addition, cell surface receptors
cause proteins in the cytoplasm to move into the nucleus and alter transcription of
certain genes.
Describe the pathway of lipid-soluble hormones
Intracellular receptors for lipid-soluble hormones typically perform the entire task of
transducing a signal within a target cell.
For Example:
Steroid hormone receptors are located in the cytosol prior to binding to a hormone.
When a steroid hormone binds to its cytosolic receptor, a hormone-receptor complex is
formed and then moves into the nucleus. There, the receptor portion of the complex
alters transcription of particular genese by interacting with a specific DNA-binding
protein or response element in the DNA.
Discuss how and why different target cells exposed to the same hormone may
respond in diverse ways.
The different effects brought about by a particular hormone can vary if target cells differ
in the molecules that receive or produce the response to that hormone.
Example: Epinephrine.
-simultaneously triggers glycogen breakdown in the liver, increased blood flow to major
skeletal muscles, and decreased blood flow to the digestive tract.
Tissues vary in their response to epinephrine because they vary in their receptors or in
their signal transduction pathways.
(1) Liver cell vs. skeletel muscle blood vessel (same receptor, different signal
transduction pathway)
Target cell recognition of epinephrine involves G-protein-coupled receptors. Liver cells
have a B-type epinephrine receptor that activates the enzyme protein kinase A, which in
turn regulates enzymes in glycogen metabolism. In blood vessels supplying skeletal
muscle, the same kinase activated by the same epinephrine receptor inactivates a
muscle specific enzyme . The result is smooth muscle relaxation and hence increased
blood flow.
(2) Skeletel muscle blood vessel vs. intestinal blood vessel (different receptors for that
hormone)
In contrast, intestinal blood vessels have an alpha- type epinephrine receptor. Rather
than activate protein kinase A, the alpha receptor triggers a distinct signaling pathway
ANSWERS A+ GRADED
What are the benefits of endocrine signaling in comparison to neuronal signaling.
Endocrine Signaling: secretes hormones
that coordinate slower but longer-acting
responses including reproduction,
development, energy metabolism, growth, and
behavior; slow response, long-lasting, broad impact, difficult to reverse
The Nervous System: The nervous system conveys high-speed electrical signals along
specialized cells called
neurons; these signals regulate other cells
Distinguish between hormones and local regulators.
Hormones: secreted by endocrine cells and released in the extracellular fluid where
they travel down the bloodstream and triggering responses in target cells anywhere in
the body.
Local Regulators: molecules that act over short distances and reach their target cells
solely by diffusion.
(paracrine signaling - target cells lie near the secreting cell)
(autocrine signaling - target cell is the secreting cell)
Define and give an example of a neurohormone.
In neuroendocrine signaling, specialized neurons called neurosecretory cells secret
molecules that diffuse from nerve cell endings into the bloodstream. These molecules
which travel through the blood stream to taget cells, are a class of hormone called
neurohormone.
Ex. Antidiuretic hormone (vasopressin) which is a hormone essential for kidney function
and water balance.
What are pheremones?
Chemicals that are released into the external environment
List the three major classes of molecules that function as hormones.
(1) Polypeptides (Insulin)
-water-soluble
-cannot pass through the plasma membrane readily so they must bind to cell-surface
receptors that relay into to the nucleus through intracellular pathways
(2) Steroids (cortisol & ecdysteroid)
-lipid-soluble
-can pass through cell membrane readily
-receptors typically reside in cytoplasm or nucleus
(3) Amines (epinephrine & thyroxine)
-water-soluble (though thyroxine - large non polar hydrophobic molecule - is lipid-
soluble)
Explain the differences in the location of receptors in the target cells of
watersoluble and lipid-soluble hormones. Compare their roles in initiating
signaltransduction pathways, and describe the changes they are likely to trigger
, within the
target cell.
H20-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and
bind to cell-surface signal receptors. Binding of such hormones to receptors induces
changes in cytoplasmic molecules and sometimes alters gene transcription .
Lipid-soluble hormones diffuse out across the membranes of endocrine cells. Outside
the cell, they bind to transport proteins that keep them soluble in the aqueous
environment of the bloodstream. Upon leaving the bloodstream, they diffuse into target
cells, bind to intracellular signal receptors, and trigger changes in gene transcription.
Describe the pathway of water-soluble hormones
Binding of H2O-soluble hormone to a signal receptor protein triggers events at the
plasma membrane that result in a cellular response. In addition, cell surface receptors
cause proteins in the cytoplasm to move into the nucleus and alter transcription of
certain genes.
Describe the pathway of lipid-soluble hormones
Intracellular receptors for lipid-soluble hormones typically perform the entire task of
transducing a signal within a target cell.
For Example:
Steroid hormone receptors are located in the cytosol prior to binding to a hormone.
When a steroid hormone binds to its cytosolic receptor, a hormone-receptor complex is
formed and then moves into the nucleus. There, the receptor portion of the complex
alters transcription of particular genese by interacting with a specific DNA-binding
protein or response element in the DNA.
Discuss how and why different target cells exposed to the same hormone may
respond in diverse ways.
The different effects brought about by a particular hormone can vary if target cells differ
in the molecules that receive or produce the response to that hormone.
Example: Epinephrine.
-simultaneously triggers glycogen breakdown in the liver, increased blood flow to major
skeletal muscles, and decreased blood flow to the digestive tract.
Tissues vary in their response to epinephrine because they vary in their receptors or in
their signal transduction pathways.
(1) Liver cell vs. skeletel muscle blood vessel (same receptor, different signal
transduction pathway)
Target cell recognition of epinephrine involves G-protein-coupled receptors. Liver cells
have a B-type epinephrine receptor that activates the enzyme protein kinase A, which in
turn regulates enzymes in glycogen metabolism. In blood vessels supplying skeletal
muscle, the same kinase activated by the same epinephrine receptor inactivates a
muscle specific enzyme . The result is smooth muscle relaxation and hence increased
blood flow.
(2) Skeletel muscle blood vessel vs. intestinal blood vessel (different receptors for that
hormone)
In contrast, intestinal blood vessels have an alpha- type epinephrine receptor. Rather
than activate protein kinase A, the alpha receptor triggers a distinct signaling pathway
