How does the presence of the poorly hydrolyzable GTP analogue GTP gamma
S affect cAMP production by adenylate cyclase?
If the GTP analogue can't be hydrolyzed, G-alpha remains active. Analog
binding to G(s) increases cAMP production. Analog binding to G(i) decreases
cAMP production.
Predict the effect of an overdose of insulin on brain function in a normal person.
Overdose of insulin in the brain would decrease blood glucose. A decrease in
blood glucose would decrease brain function. (death)
Pancreatic beta cells express a receptor for fatty acids. Fatty acid binding to this
protein appears to stimulate insulin secretion.(a) Does this phenomenon make
metabolic sense?
Fatty acids are similar to glucose as a metabolic fuel, the signal of an abundant
fuel would stimulate the release of insulin.
-
(b) Fatty acids appear to stimulate insulin secretion to a much greater extent
when glucose is also present. Why is this significant?
Extended fast = elevated levels of fatty acids. When glucose is no longer
available, insulin release would be inappropriate during this condition. A
combination of fatty acids and glucose would indicate a "fed state", triggering
insulin release.
,-
Explain why insulin is required for adipocytes to synthesize triacylglycerols
from fatty acids.
Insulin is required for adipocytes to synthesize triacylglycerols from fatty acids
by increasing GLUT4 receptors on the surface of adipocytes. Also supplies the
backbone of triacyglycerols from (glycerol-3-phosphate).
-
Experienced runners know that it is poor practice to ingest large amounts of
glucose immediately before running a marathon. What is the metabolic basis for
this apparent paradox?
Large amounts of Glucose = metabolism to rest and digest. Stimulates muscle,
liver and adipose tissue to synthesize fat, protein, and glycogen.
-
If the circulatory system of an ob/ob mouse is surgically joined to that of a
normal mouse, what will be the effect on the appetite and weight of the ob/ob
mouse?
Being that the ob/ob mouse doesn't make leptin, if the ob mouse were surgically
joined to a normal mouse, a decrease in appetite and weight would result.
-
, Discuss, in terms of AMPK activity and GLUT4, how physical inactivity might
lead to insulin resistance.
Physical inactivity = Less ATP, Less ATP = decreased ratio of AMP:ATP,
which decreases AMPK activity, which is positively associated with glucose
uptake by cells due to increase in GLUT4 activity. Decrease of AMPK =
decrease in GLUT4 activity, making insulin's job more difficult.
-
A diploid organism with a 45,000 kb haploid genome has 21% G residues.
Calculate the number of A, C, G, and T resides in each cell.
Explain why increasing the NaCl concentration increases the temperature at
which two strands of DNA "melt" apart.
At higher NaCl concentrations, there are more sodium ions to shield the
negatively charged DNA backbones, thus reducing electrostatic repulsions and
requiring more energy to separate the strands.
-
You have discovered an enzyme secreted by a particularly virulent bacterium
that cleaves the C2-C3 bond in the deoxyribose residues of duplex DNA. What
is the effect of this enzyme on supercoiled DNA?
The enzyme has no effect on the super coiling of DNA since cleaving the c2'-c3'
bond of ribose does not sever the sugar-phosphate of DNA
A closed circular duplex DNA has a 100-bp segment of alternating C and G
residues. On transfer to a high salt solution, the segment undergoes a transition
S affect cAMP production by adenylate cyclase?
If the GTP analogue can't be hydrolyzed, G-alpha remains active. Analog
binding to G(s) increases cAMP production. Analog binding to G(i) decreases
cAMP production.
Predict the effect of an overdose of insulin on brain function in a normal person.
Overdose of insulin in the brain would decrease blood glucose. A decrease in
blood glucose would decrease brain function. (death)
Pancreatic beta cells express a receptor for fatty acids. Fatty acid binding to this
protein appears to stimulate insulin secretion.(a) Does this phenomenon make
metabolic sense?
Fatty acids are similar to glucose as a metabolic fuel, the signal of an abundant
fuel would stimulate the release of insulin.
-
(b) Fatty acids appear to stimulate insulin secretion to a much greater extent
when glucose is also present. Why is this significant?
Extended fast = elevated levels of fatty acids. When glucose is no longer
available, insulin release would be inappropriate during this condition. A
combination of fatty acids and glucose would indicate a "fed state", triggering
insulin release.
,-
Explain why insulin is required for adipocytes to synthesize triacylglycerols
from fatty acids.
Insulin is required for adipocytes to synthesize triacylglycerols from fatty acids
by increasing GLUT4 receptors on the surface of adipocytes. Also supplies the
backbone of triacyglycerols from (glycerol-3-phosphate).
-
Experienced runners know that it is poor practice to ingest large amounts of
glucose immediately before running a marathon. What is the metabolic basis for
this apparent paradox?
Large amounts of Glucose = metabolism to rest and digest. Stimulates muscle,
liver and adipose tissue to synthesize fat, protein, and glycogen.
-
If the circulatory system of an ob/ob mouse is surgically joined to that of a
normal mouse, what will be the effect on the appetite and weight of the ob/ob
mouse?
Being that the ob/ob mouse doesn't make leptin, if the ob mouse were surgically
joined to a normal mouse, a decrease in appetite and weight would result.
-
, Discuss, in terms of AMPK activity and GLUT4, how physical inactivity might
lead to insulin resistance.
Physical inactivity = Less ATP, Less ATP = decreased ratio of AMP:ATP,
which decreases AMPK activity, which is positively associated with glucose
uptake by cells due to increase in GLUT4 activity. Decrease of AMPK =
decrease in GLUT4 activity, making insulin's job more difficult.
-
A diploid organism with a 45,000 kb haploid genome has 21% G residues.
Calculate the number of A, C, G, and T resides in each cell.
Explain why increasing the NaCl concentration increases the temperature at
which two strands of DNA "melt" apart.
At higher NaCl concentrations, there are more sodium ions to shield the
negatively charged DNA backbones, thus reducing electrostatic repulsions and
requiring more energy to separate the strands.
-
You have discovered an enzyme secreted by a particularly virulent bacterium
that cleaves the C2-C3 bond in the deoxyribose residues of duplex DNA. What
is the effect of this enzyme on supercoiled DNA?
The enzyme has no effect on the super coiling of DNA since cleaving the c2'-c3'
bond of ribose does not sever the sugar-phosphate of DNA
A closed circular duplex DNA has a 100-bp segment of alternating C and G
residues. On transfer to a high salt solution, the segment undergoes a transition
