PHR 3200 Exam 4

When secreted in the human body, the hormone glucagon causes rapid degradation of glycogen in liver cells. This mobilization of glycogen is accomplished though a signaling pathway. What is the proper temporal sequence of the following steps in this reaction cascade?

1. glucagons binds to a specific, transmembrane receptor 2. displacement of GDP and GTP on the alpha subunit of the G proteins 3. formation of cyclic AMP by adrenylyl cyclase 4. dissociation of the regulatory subunits activates protein kinase A 5. phosphorylation of glycogen phosporylase 6. phosphorolysis of glycogen

Which C atom is the anomeric carbon?

1st C

Which C atom determines the D-L stereochemical designation?

4th C

Activity of the Ras protein is analogous to the _____ in terms of its ability to bind GTP.

G protein alpha subunit

What two amino acid residues are the targets of protein kinase A?

Thr and Ser

Which of the following would REDUCE a hormone signal mediated via the G protein signal transduction system? a. addition of a substance that activates protein phosphatases b. addition of a substance that inhibits phosphodiesterase c. addition of a substance that activates adenylate cyclase d. A and C

a. addition of a substance that activates protein phosphatases

Which of the following is not an accurate description of an event in a G protein signaling system? a. adenylate cyclase is activated by phosphorylation b. cAMP binds to protein kinase A causing its catalytic and regulatory subunits to dissociate c. the G protein dissociates into alpha and beta-gamma subunits d. the intracellular domain of the receptor undergoes a conformational change in response to ligand binding

a. adenylate cyclase is activated by phosphorylation

Which of the following is secreted from the pancreas when blood glucose levels are low? a. glucagon b. epinephrine c. glucose d. insulin

a. glucagon

Which of the following terms is used to describe the breakdown of triacylglycerols into free fatty acids and glycerol? a. lipolysis b. lipgenesis c. beta oxidation d. both A and B are correct e. both A and C are correct

a. lipolysis

Which of the following best describes the flux of metabolites through a highly exergonic step? a. the rate of the forward step is much greater than that of the reverse step b. the rate of the reverse step is much greater than that of the forward step c. the rates of the forward and the reverse steps are both very high d. the rates of the forward and the reverse steps are approximately equal

a. the rate of the forward step is much greater than that of the reverse step

Insulin signaling leads to the _____ of glycogen synthase and _____ of glycogen phosphorylase.

activation inactivation

What enzyme is activated by association with an active G protein?

adenylate cyclase

The bulk of triacylglycerols in the human body are stored in _____.

adipocytes

Where are triacylglycerols stored in humans under normal conditions?

adipocytes

What type of group is D-glucose?

aldohexose

What type of group is D-ribose?

aldopentose

Which family of hexose monosaccharides does the sugar shown belong to?

aldose and pyranose

Amylopectin contains primarily _____ glycosidic bonds with _____ glycosidic bonds as branch points.

alpha (1-->4) alpha (1-->6)

Tetrahydrocannabinol (THC), the active ingredient in marijuana, binds to a receptor in the brain. The natural ligand for the receptor is anandamide. Anandamide has a short half-life because it is rapidly broken down by a hydrolase. One product is ethanolamine. Name the other product of anandamide breakdown

arachidonic acid

Which of the following statements is false regarding diacylglycerol? a. many variants of diacylglycerol are possible depending on the fatty acids attached at either the C1 or C2 positions b. DAG activates protein kinase A c. DAG is converted to phosphatidic acid by diacylglycerol kinase d. DAG is a product of the hydrolysis of phophatidylinositol-4,5-biphosphate

b. DAG activates protein kinase A

Which of the following compounds does NOT contain a nucleotide as part of its structure? a. acetyl-CoA b. cytosine c. ATP d. FADH2, acetyl coA, cytosine and ATP all contain a nucleotide as part of their structure e. FADH2

b. cytosine

Which one of the following compounds is/are NOT used to synthesize ATP via a substrate-level phosphorylation reaction? a. 1,3-biphosphoglycerate b. glucose-6-phosphate c. phosphoenolpyruvate d. 3-phosphoglycerate e. phosphocreatine

b. glucose-6-phosphate d. 3-phosphoglycerate

Which of the following metabolic pathways is carried out only in the liver? a. glycogen storage b. ketogenesis c. fatty acid and synthesis d. tricylglyerol synthesis e. pentose phosphate pathway

b. ketogenesis

Which of the following is TRUE regarding receptor tyrosine kinases? a. the insulin receptor has two insulin binding sites, one on each beta subunit b. ligand binding to the receptor triggers autophosphorylation c. following ligand binding and dimerization the receptor moves to the nucleus d. An and B

b. ligand binding to the receptor triggers autophosphorylation

Lactase, the enzyme responsible for breaking lactose into its monomers is a ____ enzyme.

beta galactosidase

The active portion of the penicillin molecule is the ___ ring.

beta lactam

After several days of fasting, the liver begins producing relatively large amounts of ketone bodies. Which type of tissue is highly dependent upon this as its sole source of energy in the absence of glucose?

brain

Which of the following is NOT a high energy intermediate of metabolism? a. thioesters b. NADPH c. AMP d. ATP e. all of the above are high energy intermediates

c. AMP

The initial addition of oligosaccharides of N-glycosylated proteins occurs in the _____. A) lysosome B) golgi apparatus C) endoplasmic reticulum D) vacuole E) cytoplasm

c. endoplasmic reticulum

Which of the following vitamins is correctly paired with the disease that is caused by its deficiency? a. biotin, scurvy b. pantothenic acid, beriberi c. nicotinamide, pellagra d. thiamine, anemia e. folic acid, rickets

c. nicotinamide, pellagra

Which of the following is a ligand of the 2-adrenergic receptor? a. tyrosine b. serotonin c. norepinephrine d. caffeine e. adenosine

c. norepinephrine

The second messenger _____ is produced by the enzyme _____.

cAMP adenylate cyclase

Mutant Ras proteins have been found in various types of cancers. These mutants Ras proteins are typically able to bind but not hydrolyze GTP, which indicates that Ras ___ be inactivated and that cell signaling will ____.

cannot continue

What is(are) the major metabolic fuel(s) in mammals?

carbohydrates fats proteins

After a hormone binds to a cell-surface receptor, the receptor changes its ___.

conformation

Which of the following would diminish a hormone signal mediated via a G protein signal transduction system? a. addition of a substance which inhibits the GTPase activity of the G protein b. addition of a substance such as caffeine, which inhibits phosphodiesterase c. greater than normal expression of the receptor in the cell membrane d. addition of a substance which inhibits adenylate cyclase

d. addition of a substance which inhibits adenylate cyclase

Which of the following correctly describes a catabolic pathway? a. catabolic pathways may require an input of energy b. catabolic pathways may reduce NAD c. catabolic pathways synthesize larger molecules from smaller precursors d. both A and B are correct e. both B and C are correct

d. both A and B are correct

Which of the following does not accurately describe glycosylation sites of proteins? a. in loops or turns b. on the surfaces of proteins c. Asn, Ser, or Thr residues d. buried residues inside proteins

d. buried residues inside proteins

Which of the following is a second messenger? a. cortisol b. epinephrine c. ghrelin d. cyclic AMP e. none of the above

d. cyclic AMP

Which of the following would be positively charged at physiological pH? a. glucuronic acid b. fructose-6-phosphate c. xylitol d. glycosamine e. all of the above

d. glycosamine

Which of the following is used to move lipids around the bloodstream? a. micelles b. liposomes c. liposuctions d. lipoproteins e. cholestrol esters

d. lipoproteins

Which one of the following steps found in N-linked glycosylation is also part of O-linked glycosylation? a. a 14 unit oligosaccharide is attached to the protein b. some of the sugars are removed during processing c. a 3-residue sequence pattern in the protein determines the sites of glycosylation d. monosaccharides are added while the protein is in the golgi appratus

d. monosaccharides are added while the protein is in the golgi appratus

Which of the following statements concerning receptors is FALSE? a. receptors bind the first messenger at a specific binding site on the extracellular side of the cell membrane b. receptors are integral membrane proteins with a portion of their structure exposed outside the lipid bilayer on both sides of the membrane c. upon binding the first messenger, receptors undergo a conformational change d. receptors bind signal molecules specifically and irreversibly

d. receptors bind signal molecules specifically and irreversibly

Which of the following statements is NOT true about energy metabolism and the liver? a. the liver maintains suitable levels of fuel molecules in the blood for use by other tissues b. the liver maintains a glycogen store that is replenished after a meal c. the liver provides glucose in the blood in response to a glucagon signal d. the liver releases fatty acids for other tissues to use as fuel

d. the liver releases fatty acids for other tissues to use as fuel

Which of the following statements concerning ATP is FALSE? a. phosphate groups within ATP experience less resonance stabilization than free phosphate groups b. the hydrolysis of phosphoanhydride bonds in ATP releases large amounts of free energy c. the cleavage of phosphoanhydride bonds in ATP relieves electrostatic repulsion d. the phosphoanhydride bonds in ATP are "high energy bonds" that are different from other covalent bonds

d. the phosphoanhydride bonds in ATP are "high energy bonds" that are different from other covalent bonds

An Asp --> Glu mutation would likely ___ the affinity of ligand binding since Glu is 1 carbon ___ than Asp.

decrease longer

How might an Asp --> Asn mutation would likely ___ the affinity of ligand binding since Asn ___ form a non-covalent bond with the ligand

decrease would not

When a receptor loses its ability to transmit a signal following continuous exposure to a ligand, the receptor is said to be _____.

desensitized

The action of phospholipase C on phosphatidylinositol-4,5-bisphosphate generates two important signalling molecules. What are they?

diacyl glycerol inositol 1,4,5 triphosphate

Before a G protein can activate adenylate cyclase, it ___ into two parts

dissociates

Which of the following is correct regarding metabolic pathways? a. most pathways are isolated from other pathways b. the activity of most pathways is not regulated c. all cells within a multi-cellular organism contain the same pathways d. anabolic pathways never occur at the same time as catabolic pathways e. none of the above are correct

e. none of the above are correct

Which one of the following is NOT a type of metabolic "fuel" molecule that can be used by mammalian cells? a. glucose b. ketone bodies c. fatty acids d. amino acids e. options A-D are all metabolic fuel molecules

e. options A-D are all metabolic fuel molecules

Which of the following has the most spontaneous hydrolysis? a. 1,3-biphosphoglycerate b. phosphocreatine c. glucose-1-phosphate d. pyrophosphate e. phosphoenolpyruvate

e. phosphoenolpyruvate

Which of the following statements regarding G proteins is TRUE? a. hydrolysis of GTP is necessary for G protein subunits to seperate b. GTP is bound to the G protein in the inactive state c. G proteins bind the appropriate hormone at the cell surface d. G proteins are heterodimers of alpha and beta subunits e. when activated, the alpha subunit can cause adenylate cyclase to synthesize cAMP

e. when activated, the alpha subunit can cause adenylate cyclase to synthesize cAMP

Glucose and galactose are ___ of each other. a. epimers b. enantiomers c. diastereomers d. anomers

epimers

True or False: In N-linked oligosaccharides, N-acetylglucosamine can be linked to Asn, Gln, or His

false

True or False: delta G and delta G omega

false

What are the two major types of fuel store in mammals?

fat glycogen

Ketone bodies are produced from _____ in the _____.

fatty acids liver

In a well-fed state, brain cells use which one of the following compounds circulating in the blood stream almost exclusively as an energy source?

glucose

Adipose tissue requires _____ to synthesize triacylglycerols.

glucose fatty acids

Muscle cells can use _____ as metabolic fuel.

glucose fatty acids ketone bodies

During starvation, the liver supplies ______ to other tissues.

glucose ketone bodies

Which of the following phosphorylated compounds would be considered a "low-energy" intermediate in metabolism, relative to the others?

glucose-6-phosphate

Adipocytes convert glucose into fatty acids and _____.

glycerol

The storage polysaccharide in animals

glycogen

What is the major difference between glycogen and amylopectin?

glycogen contains about twice the number of branch points as amylopectin

Digestion of food utilizes enzymes that catalyze _____ reactions.

hydrolysis

For the following process, indicate whether it is activated (A) or inhibited (B) during FASTING. Lipolysis in adipocytes

inhibited

The second messenger _____ opens Ca2+ channels in the endoplasmic reticulum.

inositol triphosphate

The _____ receptor is a receptor tyrosine kinase.

insulin

The type of interaction between this amino acid on the receptor and epinephrine

ion pair

Why is acetyl-CoA considered a high energy molecule?

it contains a thioester bond

What characterizes the rate-determining step of a metabolic pathway?

it functions far from equilibrium and it has a large negative free energy change

The ∆G0' for the phosphorylation of creatine by ATP is +12.6 kJ/mol. How does this reaction proceed inside the cell?

it proceeds because of the enzyme creatine kinase, and because the concentrations of the reactants and products makes delta G omega approximately zero

In a G protein signal-transduction system, what role does the G protein play?

it transmits the signal from the receptor to other components of the signaling system

What type of group is D-erythrulose?

ketotetrose

What type of group is dihydroxyacetone?

ketotriose

Where are the two major sites of glucose storage in humans?

liver muscles

Where are the ultimate targets of the Ras-dependent signaling cascade located within the cell?

nucleus

How is ATP produced in mammalian cells under aerobic conditions?

oxidative phosphorylation substrate level phosphorylation

Insulin is produced by _____ in response to _____.

pancreas increasing blood glucose

Bacterial cell walls are made of ___.

peptidoglycan

Ligand binding to a receptor tyrosine kinase causes _____ of the receptor which then _____ the next protein in the signaling pathway.

phosphorylation phosphorylates

In a G protein signaling pathway, what would happen if phosphodiesterase were inactivated?

protein kinase A would remain active

Hormones bind to _____ with _____ affinity.

receptors high

How does insulin cause an increase in the rate of glucose transport into cells?

recruits glucose transporters from intracellular vesicles to the cell membrane

Any sugar that has a free aldehyde group is called a(n) _____.

reducing sugar

O-linked oligosaccharides are covalently attached to proteins through the side chain, O atom of ___ or threonine

serine

ATP can be generated directly by coupling its synthesis to a more highly exergonic reaction, in a process called ___.

substrate level phosphorylation

At equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes the solution?

the beta anomer predominates over the alpha anomer by a ratio of approximately 2:1

In the liver, both glucagon and epinephrine bind to different members of the G protein-coupled receptor family, yet binding of each of these ligands results in the same response- glycogen breakdown. These observations indicate that glucagon and epinephrine activate the synthesis of ___ secondary messengers and activate glycogen breakdown using ___ signaling pathways.

the same the same

O-linked oligosaccharides are commonly attached to the oxygen of _____.

threonine

During starvation, protein utilization dramatically decreases from a rate of 75 to 20 g/day as the fast increases in duration. Which body fuels are utilized during a prolonged fast in order to conserve body protein?

triacylglycerols

True or False: A glycosidic bond connects an anomeric carbon of one sugar to an alcohol oxygen of another sugar

true

True or False: A ΔG value of zero indicates that the reactions or processes are at equilibrium.

true

True or False: Compounds whose phosphoryl group-transfer potentials are greater than that of ATP include acetyl-phosphate and creatine phosphate.

true

What type of receptor is the insulin receptor?

tyrosine kinase receptor