Biol 0280 Test Bank Lec 15 Metabolism and Hormones as Regulators

Describe three possible fates for glucose 6-phosphate in the liver.

(1) conversion to liver glycogen; (2) dephosphorylation and release of glucose into bloodstream; (3) oxidation via the pentose phosphate pathway; (4) oxidation via glycolysis and the citric acid cycle; (5) oxidation to acetyl-CoA, which then serves as precursor for synthesis of triacylglycerols, phospholipids, and cholesterol.

Glycogen synthase is activated with the addition of insulin. Describe the signaling pathway, clearly identifying at least four of the kinases, proteins, or lipids that participate AND how each is activated.

1) Insulin binds insulin receptor, turning on the receptor's tyrosine kinase activity which 2) Phsophorylates IRS1, 3) recruting and actvating PI3K by binding to its SH2 domain. 4) PI3K phosphorylates PIP2 to PIP3, 5) activating PKB by phosphorylation by PDK1. 6) PKB phosphorylates GSK3, inactivating it. 7) Glycogen synthase remains active in the absence of phosphorylation by GSK3.

What are the three ketone bodies that accumulate in the blood of a starving individual?

1. Acetone 2. Acetoacetate 3. b-Hydroxybutyrate

What are the five fates of Glucose-6-phosphate in the liver?

1. Glucose efflux 2. Glycogen storage 3. Oxidation for energy 4. Storage into lipids 5. Pentose Phosphate Pathway

What are the four fates of fatty acids in the liver?

1. Storage (TAG, PL), 2. Breakdown, beta-oxidation(Acetyl-CoA), 3. Secretion in lipoproteins (TAG, PL), 4. Transport in blood (Albumin)

Which one of the following statements is true? A) The brain prefers glucose as an energy source, but can use ketone bodies. B) Muscle cannot use fatty acids as an energy source. C) The brain exports ketone bodies as fuels for other tissues. D) Fatty acids cannot be used as an energy source in humans because humans lack the enzymes of the glyoxylate cycle. E) Heart muscle stores fuel as glycogen.

A) The brain prefers glucose as an energy source, but can use ketone bodies.

Nitric oxide is produced from which reaction?

A) arginine to citrulline

Select the statements from the right column that best describe the metabolism of each organ, tissue, or cell in the left column. Please indicate all correct answers. A) releases glycerol and fatty acids into the blood during periods of fasting B) in a normal nutritional state, utilizes glucose as the exclusive fuel C) synthesizes ketone bodies when the supply of acetyl CoA is high D) can release lactate into the blood E) can store glycogen but cannot release glucose into the blood F) can synthesize fatty acids, triacylglycerols, and VLDL when fuels are abundant Brain ____________ Muscle ____________ Adipose Tissue _____________ Liver ____________

A) releases glycerol and fatty acids into the blood during periods of fasting B) in a normal nutritional state, utilizes glucose as the exclusive fuel C) synthesizes ketone bodies when the supply of acetyl CoA is high D) can release lactate into the blood E) can store glycogen but cannot release glucose into the blood F) can synthesize fatty acids, triacylglycerols, and VLDL when fuels are abundant Brain _________B__________________ Muscle ____D,E______________________ Adipose Tissue ____A________________ Liver _________C, F_______________

For each of the following statements, indicate (by letters) which of the hormones (none, one, or more than one) listed below is/are appropriate: A. Epinephrine B. Glucagon C. Insulin It stimulates glycogen breakdown in the liver. It stimulates glycolysis in the liver. It stimulates glycogen synthesis in the liver. It stimulates gluconeogenesis in the liver. It stimulates glycogen synthesis in adipose tissue. It stimulates lipid synthesis in adipose tissue. It stimulates glycogen synthesis in muscle tissue. Its receptor is a serpentine (G protein-linked) receptor. Its receptor is a receptor-enzyme. Its receptor is located in the cell membrane.

A. Epinephrine B. Glucagon C. Insulin It stimulates glycogen breakdown in the liver. A, B It stimulates glycolysis in the liver. C It stimulates glycogen synthesis in the liver. C It stimulates gluconeogenesis in the liver. A,B It stimulates glycogen synthesis in adipose tissue. None It stimulates lipid synthesis in adipose tissue. C It stimulates glycogen synthesis in muscle tissue. C Its receptor is a serpentine (G protein-linked) receptor. A, (B) Its receptor is a receptor-enzyme. C, (B allowed) Its receptor is located in the cell membrane. A, B, C,

Describe the signal transduction associate with epinephrine: A. Where does the hormone bind? B. What is the name of the component responsible for the transmission of the first messenger and how does it get activated? C. What is the name of the enzyme that is activated by this component and what is the name of the second messenger that is generated? D. What is the name of the enzyme that is activated by the second messenger generated in C.?

A. On the extracellular domain of the GPCR (adrenergic receptor) B. The Gα subunit (of the heterotrimeric stimulatory G protein). Via conformational change at the cytosolic domain of the GPCR that leads to the release of GDP from the Gα subunit and the binding of GTP. C. Adenylate cyclase, cAMP D. Protein Kinase A (PKA)

Identify the metabolic effects of insulin from the list below (more than one answer may be correct). A. Stimulates glycogen synthesis B. Decreases gluconeogenesis C. Decreases glycogen synthesis D. Decreases glucose transport E. Increases gluconeogenesis F. Increases blood glucose levels

A. Stimulates glycogen synthesis B. Decreases gluconeogenesis

In skeletal muscle, phosphocreatine functions as:

B) a reservoir of high-energy of phosphate to replenish ATP.

Epinephrine triggers an increased rate of glycolysis in muscle by:

B) activation of phosphofructokinase-1.

Steroid hormones are carried on specific carrier proteins because the hormones:

B) cannot dissolve readily in the blood because they are too hydrophobic.

When blood glucose is abnormally low, the pancreas releases:

B) glucagon.

The ion channel that opens in response to acetylcholine is an example of a ____________ signal transduction system.

B) ligand-gated

Which of the following is not involved in signal transduction by the β-adrenergic receptor pathway? A) ATP B) Cyclic AMP C) Cyclic GMP D) GTP E) All of the above are involved.

C) Cyclic GMP

The effects of acetylcholine on the postsynaptic ion channel are mainly due to:

C) protein conformational changes.

The Cori cycle is:

C) the production of lactate from glucose in peripheral tissues with the resynthesis of glucose from lactate in liver.

Identify the metabolic effects of glucagon from the list below (more than one answer may be correct). A. Stimulates glycogen synthesis B. Decreases gluconeogenesis C. Decreases glycogen synthesis D. Decreases glucose transport E. Increases gluconeogenesis F. Decreases blood glucose levels

C. Decreases glycogen synthesis E. Increases gluconeogenesis

Describe the effect of cholera toxin on cellular signaling.

Cholera toxin disrupts G protein signaling by ADP-ribosylation of the Gsα subunit. The intrinsic GTPase activity is inactivated in the ADP-ribosylated Gsα subunit resulting in a constantly activated Gsα subunit, which constantly activates adenylyl cyclase.

Liver cells have the necessary enzymes to perform the following conversions except: A) alanine into palmitic acid B) palmitic acid into cholesterol C) glucose into stearic acid D) palmitic acid into glucose E) glucose into serine

D) palmitic acid into glucose

For use during bursts of heavy activity, muscle cells store "high-energy" phosphate as:

D) phosphocreatine

The biopolymers that humans use to store potential fuel molecules are glycogen, proteins, and triacylglycerols. What is the preferred order of use?

D. Glycogen > triacylglycerols > proteins

The relative concentrations of ATP and ADP control the cellular rates of: A) glycolysis. B) oxidative phosphorylation. C) pyruvate oxidation. D) the citric acid cycle. E) all of the above.

E) all of the above.

An elevated insulin level in the blood:

E) stimulates synthesis of fatty acids and triacylglycerols in the liver.

The largest energy store in a well-nourished human is:

E) triacylglycerols in adipose tissue.

T / F The brain can use fatty acids as fuel when glucose is not available T / F The Cori cycle is an inter-organ pathway transporting pyruvate and glucose between muscle and liver. T / F When blood glucose is abnormally high, the pancreas releases glucagon.

False False False

T / F Phosphocarnitine serves as 'stored ATP' to regenerate ATP during bursts of heavy activity. T / F The brain requires glucose as preferred energy source but can use ketone bodies and fatty acids when glucose is unavailable. T / F Glucagon and insulin act in opposition, in some cases on the same target enzyme. T / F Epinephrine regulates glucagon and insulin secretion.

False False True True

Some hormones trigger very rapid responses, whereas for others the response takes much longer to develop. What generalization about the mechanisms of action of these two types of hormones can explain the differences in response times?

Fast-acting hormones affect the activity of preexisting cellular enzymes. Slow-acting hormones alter gene expression, thereby changing the levels of active cellular components.

Briefly describe the self-inactivation mechanism of G proteins.

GTP bound to the activated Gα subunit is hydrolyzed by the protein's intrinsic GTPase activity, thereby turning itself off. The inactive α subunit then reassociates with the βγ subunit.

When blood glucose is high, the pancreas releases ____________________, when blood glucose is low, the pancreas releases ____________________.

Insulin glucagon

The insulin signaling pathway regulates the activity of glycogen synthase through GSK3 and PKB. Briefly explain how this regulation works. Your answer should include for all three enzymes whether phosphorylation activates or inactivates the enzyme and how they interact with each other.

Insulin pathway phosphorylates and activates PKB kinase which phosphorylates and inactivates GSK3. Active GSK3 phosphorylates and inactivates glycogen synthase. Active glycogen synthase produces glycogen. So when insulin is present, glycogen synthase is active.

In the space provided, name the energy sources (molecules) for muscle contraction during: Light activity or rest _____________ Bursts of heavy activity ______________

Light activity or rest: Fatty acids, ketone bodies, glucose Bursts of heavy activity: muscle glycogen, phosphocreatine

What does creatine look like?

NH2-C=NH2(+)-N(CH3)-CH2-COO(-)

G protein-coupled receptor

See Exam 2 2010 question 16

Receptor guanyl cyclase

See Exam 2 2010 question 16

Which class of hormones acts via nuclear receptors? Briefly describe the mode of action of these hormones.

Steroid hormones. Examples are the sex hormones testosterone and estradiol. They pass through the plasma membrane and interact with receptor proteins in the nucleus. The hormone receptor complex interacts with DNA and alters the expression of specific genes.

Briefly describe key elements of steroid hormone signal transduction in the cell. Where does the receptor bind the ligand, what is the biochemical activity of the activated receptor, and what is the biochemical result of receptor activation?

The steroid hormone enters the cell. The receptor binds the steroid hormone (ligand) in the nucleus. The activated receptor alters transcription of specific genes resulting in changes in the expression of these genes (changes in the amount of newly synthesized proteins).

List at least three factors affecting the activity of enzymes

binding of ligands/allosteric effectors/inhibitors post-translational modification (phosphorylation) binding of regulatory proteins enzyme sequestration enzyme degradation factors affecting enzyme synthesis (transcriptional regulation, mRNA lifetime/degradation, translation)

Metabolic fuel sources exported to other organs are ___________ from adipose tissue and ________ from brain.

fatty acids (+glycerol) none

Fill in the blank in the following statement: During prolonged fasting, fatty acids in the liver are converted to _______________ which is/are transported to the _________________ to be used as fuel.

ketone bodies, or Acetone or Acetoacetate or b-hydroxybutyrate. brain.

Spermidine and spermine are derived from the amino acids _________. A cofactor (not a precursor) that is involved in their synthesis is ___.

methionine and ornithine PL

Insulin is an example of a(n) ____________ hormone.

peptide