ur mom's biol 215 e4

Not all signaling molecules act through PM receptors. Some bind to receptors found in the cytoplasm. Others bind to nuclear receptors. What type of signal could enter the cell by simple diffusion to activate a cytoplasmic receptor?

a. glucose
b. testosterone (steroid)
c. insulin (hydrophilic protein)
d. ATP
e. all of the above

Testosterone (steroid)

The ligand-binding domain of a GPCR was initially extending into the [ ] as it was transported to the PM in a transport vesicle.

a. cytoplasm
b. vesicle lumen
c. extracellular space
d. nucleus
e. not enough information given

Vesicle lumen

A GPCR is a type of [ ] membrane protein.

a. single-pass integral
b. monotopic integral
c. multi-subunit integral
d. peripheral
e. multipass integral

Multipass integral

Glycogenolysis involves...

a. glucose synthesis from non-carbohydrate sources
b. oxidation of glucose
c. hydrolysis of glycogen to release glucose-1-phosphate
d. phosphorolysis of glycoegn to release glucose-1-phosphate
e. reduction of CO2 to form carbohydrates

Phosphorolysis of glycoegn to release glucose-1-phosphate

The target of glycogen phosphorylase is the glycogen. What reaction will glycogen phosphorylase catalyze involving glycogen?

a. It will remove phosphate from glycogen.
b. It will transfer phosphate to glycogen, using ATP as a phosphate source.
c. It will transfer phosphate to glycogen using Pi as a phosphate source.
d. It will hydrolyze glycogen
e. It will hydrogenate glycogen

It will transfer phosphate to glycogen using Pi as a phosphate source.

Glycogen phosphorylase will be activated by a [ ] and deactivated by a [ ].

a. Kinase; phosphatase
b. Phosphatase; phosphorylase
c. Phosphorylase; kinase
d. Phosphorylase; phosphatase
e. Kinase; phosphorylase

Kinase; phosphatase

Glycogen synthase catalyzes which reaction?

a. Glycolysis
b. Gluconeogenesis
c. Glycogenolysis
d. Glycogenesis
e. Glyconeolysis

Glycogenesis

PKA also phosphorylates glycogen synthase. The phosphorylation will [ ] glycogen synthase.

a. activate
b. inactivate
c. not enough information given

Inactivate

Where is most of the Ca2+ stored in cells?

a. cytoplasm
b. Golgi
c. mitochondria
d. nucleus
e. smooth ER

Smooth ER

Is the [Ca2+]EC higher or lower than the cytoplasm?

a. higher
b. lower

Higher

Is the [Ca2+]ER higher or lower than the cytoplasm?

a. higher
b. lower

Higher

All of the following are considered secondary messengers except...

a. DAG
b. epinephrine
c. Ca2+
d. cAMP
e. IP3
f. All of the above are secondary messengers

Epinephrine

What type of signal could enter the cell by simple diffusion to activate a cytoplasmic receptor?

a. glucose
b. testosterone
c. insulin
d. ATP
e. All of the above

Testosterone

All of the following are examples of local-signaling pathways except...

a. paracine
b. cell-cell contact
c. gap junctions
d. endocrine
e. synpase

Endocrine

GPCRs directly interact with which type of signaling molecules?

a. G proteins
b. adenylyl cyclase
c. phospholipase C
d. primary messengers
e. Both A and D

Both A and D

The ligand-binding domain of a GPCR was initially extending into the [ ] as it was transported to the PM in a transport vesicle.

a. nucleus
b. vesicle lumen
c. extracellular space
d. cytoplasm
e. not enough information given

Vesicle lumen

How many membrane-spanning segments do all GPCRs contain?

a. 1
b. 3
c. 7
d. 12
e. It's variable

7

IP3 is released from...

a. smooth ER
b. PIP2 in the plasma membrane
c. adenylyl cyclase
d. GPCR
e. G-alpha

PIP2 in the plasma membrane

As common targets of kinases, what do serine, threonine, and tyrosine all have in common?

a. They are all basic
b. They are all acidic
c. They are all proteins
d. They all have hydroxyl groups
e. More than one of the above

They all have hydroxyl groups

What reaction does glycogen synthase catalyze?

a. glycogenesis
b. gluconeogenesis
c. glycolysis
d. glycogenolysis
e. glycogen decarboxylation

Glycogenesis

Glycogenesis will be [ ] regulated by the insulin signal transduction pathway.

a. positively
b. negatively

Positively

Diabetes is a result of chronically [ ] blood glucose levels.

a. High
b. Low

High

One treatment of type II diabetes involves reducing the activity of the liver. Reduction in which of the following pathways would help alleviate type II diabetes?

a. glycolysis
b. glycogenolysis
c. glycogenesis

Glycogenolysis

Where do we find the cytoskeleton in our cells?

a. In the cytoplasm
b. In the nucleus
c. Outside of the plasma membrane, forming the extracellular matrix
d. All of the above
e. Both A and B

Both A and B

Which of the following is NOT a role of the cytoskeleton in the cell?

a. Provides cells with mechanical strength
b. Organize internal contents
c. Cell division
d. Cell motility
e. All of the above are roles of the cytoskeleton

All of the above are roles of the cytoskeleton

If the [free tubulin]cyt \= 3 uM, what will happen to that concentration as MT growth occurs?

The [free tubulin]cyt will...

a. Increase
b. Decrease
c. Stay the same

Decrease

As growth occurs and the [free tubulin]cyt decreases, growth will stop first at which end of the MT?

a. Minus end
b. Plus end
c. Could be either

Minus end

A plasma membrane protein begins with a large hydrophilic regulatory domain. This is followed by six hydrophobic regions of 20+ amino acids, with short hydrophilic regions in between. Finally, a large hydrophilic domain, called domain A, is at the end of the polypeptide. The first signaling sequence of this protein is an N-terminal signal sequence.

If all six hydrophobic domains cross the membrane one time each, then it is possible that...

a. the regulatory domain and domain A will be on the same side of the membrane
b. the regulatory domain and domain A will both be intracellular
c. the regulatory domain is intracellular and domain A is extracellular
d. the regulatory domain and domain A are transmembrane domains
e. Choices A and B are both possible

The regulatory domain and domain A will be on the same side of the membrane

If a protein contains only an internal start-transfer sequence, where would the C terminus be found?

a. RER lumen
b. cytoplasm
c. extracellular space
d. Golgi membrane
e. Not enough information given

Extracellular space

Which amino acid(s) would you expect to predominate the membrane-spanning segments?

a. alanine
b. aspartate
c. glutamine
d. leucine
e. both A and D

Both A and D

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Choose the items that are involved in reception.

a. adenylyl cyclase
b. G-protein coupled receptor
c. protein synthesis
d. second messenger
e. signaling molecule
f. IP3
g. Ca2+
h. cAMP
i. phosphorylation cascade
j. receptor tyrosine kinase

G-protein coupled receptor; signaling molecule; receptor tyrosine kinase

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Choose the items that are involved in transduction.

a. adenylyl cyclase
b. G-protein coupled receptor
c. protein synthesis
d. second messenger
e. signaling molecule
f. IP3
g. Ca2+
h. cAMP
i. phosphorylation cascade
j. receptor tyrosine kinase

Adenylyl cyclase; second messenger; IP3; Ca2+; cAMP; phosphorylation cascade

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Choose the items that are involved in response.

a. adenylyl cyclase
b. G-protein coupled receptor
c. protein synthesis
d. second messenger
e. signaling molecule
f. IP3
g. Ca2+
h. cAMP
i. phosphorylation cascade
j. receptor tyrosine kinase

Protein synthesis

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine.

Put the following labels in order to show the process of histamine signal transduction from the H1 receptor. Not all labels will be used.

a. Calcium ions flow through the ligand-gated ion channel.
b. Phosphorylation cascade leads to the activation of a cellular response.
c. Calcium ion concentration increases in the cytosol.
d. Enzyme cleaves PIP2, forming DAG and IP3.
e. IP3 binds to a ligand-gated ion channel in the ER membrane.
f. Calcium ions activate a protein, leading to a cellular response.

1. Enzyme cleaves PIP2, forming DAG and IP3.
2. IP3 binds to a ligand-gated ion channel in the ER membrane.
3. Calcium ions flow through the ligand-gated ion channel.
4. Calcium ion concentration increases in the cytosol.
5. Calcium ions activate a protein, leading to a cellular response.

The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes).

Which of the following could account for the different cellular responses to histamine? Select all that apply.

a. the enzyme that is activated by the G protein associated with the receptor
b. the type of signaling molecule
c. the cell type in which the histamine receptor is located
d. the types of relay molecules within the cell
e. the type of second messengers involved in the signal transduction pathway

The enzyme that is activated by the G protein associated with the receptor
The cell type in which the histamine receptor is located
The types of relay molecules within the cell
The type of second messengers involved in the signal transduction pathway

What happens during glycogenolysis?

a. CO2 is reduced to form carbohydrates
b. glycogen is phosphorolyzed to release glucose-1-phosphate
c. glycogen is hydrolyzed to release glucose-1-phosphate
d. glucose is oxidized, producing ATP by oxidative phosphorylation
e. glucose is synthesized from non-carbohydrate sources

Glycogen is phosphorolyzed to release glucose-1-phosphate

Which enzyme catalyzes glycogenolysis?

a. glycogen phosphorylase
b. phosphorylase phosphatase
c. protein kinase A
d. phosphorylase kinase
e. glycogen synthase

Glycogen phosphorylase

Glycogen phosphorylase will be deactivated by a [ ] and activated by a [ ].

a. kinase; phosphatase
b. phosphorylase; kinase
c. phosphorylase; phosphatase
d. phosphatase; kinase
e. kinase; phosphorylase

Phosphatase; kinase

Comparing the mitochondrion and the chloroplast, which compartment in the mitochondria is most like the stroma in the chloroplast, in terms of function?

a. thylakoid lumen
b. matrix
c. mitochondrial stroma
d. intermembrane space
e. thylakoid membrane

Matrix

During the Calvin cycle, the intermediate molecules are [ ] to form triose phosphates.

a. reduced by ATP
b. oxidized by ATP
c. reduced and phosphorylated by NADPH
d. oxidized by NADPH
e. reduced by NADPH

Reduced by NADPH

COX4 is a nuclear-encoded protein that resides in the mitochondrial matrix. Which of the following statements regarding targeting of the COX4 protein is true?

a. COX4 is transcribed and translated in mitochondria
b. COX4 is co-translationally imported
c. COX4 would contain a signaling sequence that first targeted it to the RER before it eventually makes its way to the mitochondria
d. None of the above are true
e. both A and B are true

None of the above are true

\[ ] are the most heterogeneous type of cytoskeletal element.

a. microtubules
b. intermediate filaments
c. microfilaments
d. all of the elements are heterogeneous
e. none of the elements are heterogeneous

Intermediate filaments

Which of the following is NOT a function of the cytoskeleton?

a. cell shape
b. vesicle transport
c. cell division
d. cell locomotion
e. all of the above involves the cytoskeleton

All of the above involves the cytoskeleton

Microtubules are involved in all of the following except...

a. transport of vesicles between organelles of the endomembrane system
b. the formation of the spindle apparatus during cell division
c. the extension of the lamellopodium of a white blood cell during cell locomotion
d. the formation of flagella used by sperm cells to swim
e. microtubules are involved in all of the above

The extension of the lamellopodium of a white blood cell during cell locomotion

Flow of transport vesicles from the ER to the Golgi involves all of the following except...

a. kinesin
b. microtubules
c. ATP
d. dynein
e. All of the above are required

Kinesin

(MTOC is located on trans face of Golgi)

Which of the following is involved in propelling mucus across the epithelial layer of the trachea?

a. flagella
b. cilia
c. microfilaments
d. all of the above
e. both B and C

Cilia

True or false? In animal cells, microfilaments are organized by the centrosome.

False

Which cellular molecule will have an antagonistic action to the effects of adenylyl cyclase?

a. glycogen phosphorylase
b. cAMP
c. phosphodiesterase
d. Galpha-GTP
e. none of the above

Phosphodiesterase

What exactly is the role of phosphodiesterase in signal transduction?

a. it acts as a non-competitive inhibitor, binding to adenylyl cyclase to inhibit its action
b. it hydrolyzes phospholipids found in cellular membranes
c. it hydrolyzes the GTP on the Ga-GTP, inactivating the G protein
d. it is released upon cleavage of PIP2 in the plasma membrane, where it will diffuse and activate cellular targets
e. it degrades cAMP by cleaving the phosphodiester bond, resulting in the formation of AMP

It degrades cAMP by cleaving the phosphodiester bond, resulting in the formation of AMP

True or false? AMP cannot propagate a signal transduction cascade mediated by cAMP.

True

The cleavage of glycogen by glycogen phosphorylase releases...

a. cellulose
b. galactose-1-phosphate
c. glucose-1-phosphate
d. fructose-1-phosphate
e. nothing; glycogen phosphorylase cannot glycogen

Glucose-1-phosphate

Epinephrine acts as a signal molecule that attaches to [ ] proteins.

a. ion-channel receptor
b. nuclear receptor
c. receptor tyrosine kinase
d. intracellular receptor
e. G-protein linked receptor

G-protein linked receptor

A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to [ ] receptors.

a. intracellular
b. G-protein linked
c. ion-channel
d. steroid
e. receptor tyrosine kinase

G-protein linked

True or false? GPCRs contain 12 membrane-spanning domains.

False

GPCRs are considered...

a. multi-subunit integral membrane proteins
b. multi-pass integral membrane proteins
c. peripheral membrane proteins
d. lipid-anchored membrane proteins
e. single-pass integral membrane proteins
f. integral monotopic proteins
g. more than one of the above

Multi-pass integral membrane proteins

True or false? GPCRs directly interact with primary messengers.

True

True or false? The ligand-binding domain of a GPCR was initially extending into the cytoplasm as it was transported to the PM in a transport vesicle.

False

Which of the following is TRUE about GPCRs? Select all statements that apply.

a. The first membrane-spanning segment is an internal stop-transfer sequence
b. The last membrane spanning segment is a start-transfer sequence
c. The segment interacting with the G protein is extracellular.
d. The N-terminus is extracellular and the C-terminus is intracellular.
e. The C-terminus interacts with the G-protein
f. They contain 5 membrane-spanning segments

The first membrane-spanning segment is an internal stop-transfer sequence
The N-terminus is extracellular and the C-terminus is intracellular

True or false? A GPCR is involved in the vasodilation pathway.

True

Select all of the following that apply to cAMP.

a. is part of the signal transduction cascade resulting in vasodilation
b. allosterically activates protein kinase A
c. acts as a non-competitive inhibitor of protein kinase A
d. is a type of secondary messenger
e. inhibits protein kinase A
f. is part of the fight or flight signal transduction cascade
g. is produced by protein kinase A

Allosterically activates protein kinase A
Is a type of secondary messenger
Is part of the fight or flight signal transduction cascade

Colchicine is a cellular toxin known to bind to beta-tubulin, preventing its ability to interact with alpha-tubulin. Cytochalasin is a toxin that binds to G-actin, preventing its ability to polymerize. If a cell process is disrupted by colchicine, but not by cytochalasin, one can conclude that the cell process requires...

a. F-actin
b. the assembly of intermediate filaments
c. the assembly of microtubules
d. depolymerization of microtubules
e. Both A and D

The assembly of microtubules

You are studying microtubules (MTs) in vitro and have isolated MTs and their subunits in a test tube. If the critical concentration of tubulin dimers in the last tube is above the critical concentration for the plus end but below the critical concentration for the minus end, what will you observe in this in vitro system?

a. the MTs will not change in size
b. the cell would not be able to crawl
c. the MTs would get shorter
d. treadmilling will occur (i.e. simultaneous assembly and disassembly)
e. the MTs will continue to grow at both ends

Treadmilling will occur (i.e. simultaneous assembly and disassembly)

What could you add to an in vitro system to stop MTs from treadmilling?

a. tubulin-GTP dimers
b. tubulin-GDP dimers
c. GDP
d. could add either A or B

Tubulin-GTP dimers

True or false? Treadmilling is not observed as frequently in vivo as it is in vitro because the minus ends of most MTs are anchored in the y-tubulin ring complexes of the MTOCs inside the cell.

True

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound...

a. that mimics epinephrine and can bind to the epinephrine receptor
b. that increases phosphodiesterase activity
c. to stimulate G protein activity in liver cells
d. that stimulates cAMP production in liver cells
e. that does any of the above

That increases phosphodiesterase activity

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

a. phosphodiesterase
b. serine/threonine kinase
c. adenylyl cyclase
d. tyrosine kinases
e. phospholipase C

Phospholipase C

Which of the following is a correct association?

a. phosphodiesterase activity and the removal of phosphate groups
b. phosphorylase activity and the catabolism of glucose
c. kinase activity and the addition of a tyrosine
d. GTPase activity and the hydrolysis of GTP to GDP
e. adenylyl cyclase activity and the conversion of cAMP to AMP

GTPase activity and the hydrolysis of GTP to GDP

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

a. Estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding
b. Estrogen is produced in very large concentration and therefore diffuses widely
c. Estrogen is kept away from the surface of any cells not able to bind it at the surface
d. The subcomponents of estrogen, when metabolized, can influence cell response
e. Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding

Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding

What explains increased concentrations of Ca2+ in the ER?

a. Calcium levels in the blood or other body fluids are extremely low
b. Calcium ions are actively imported from the cytoplasm into the ER
c. The calcium ions are recycled from other molecules in the ER
d. Calcium cannot enter the plasma membrane through ion channels
e. Calcium concentration is kept low in the cytoplasm because of its high usage levels

Calcium ions are actively imported from the cytoplasm into the ER

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

a. It could only activate the epinephrine system
b. It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane
c. It would employ a transduction pathway directly from an external messenger
d. It would be able to carry out reception and transduction but would not be able to respond to a signal
e. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane

It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

a. G-protein coupled receptors
b. ligand-gated ion channels
c. receptor tyrosine kinases
d. steroid receptors

Receptor tyrosine kinases

When nitric oxide is used in the dilation of smooth muscle cells, which of the following would interfere with the relaxation of the smooth muscle cells? Inhibitors of...

a. calmodulin
b. guanylyl cyclase
c. calcium release by the ER
d. nitric oxide
e. all of the above

All of the above

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of...

a. adenylyl cyclase
b. phosphorylated proteins
c. cAMP
d. activated G proteins
e. GTP

cAMP

Which is an example of endocrine signaling?

a. A peptide made in the liver promotes uptake of amino acids from the blood throughout the body
b. A steroid causes adjacent cells to become pigmented
c. A derivative of tryptophan diffuses to neighboring cells to trigger signs of inflammation
d. both A and B
e. both A and C

A peptide made in the liver promotes uptake of amino acids from the blood throughout the body

True or false? Plants do not utilize long-distance signaling.

False

True or false? The fight or flight response involves endocrine signaling.

True

What is a hepatocyte?

a. A cell from a horse
b. A stem cell that gives rise to blood cells
c. A cell infected with the hepatitis A virus
d. a type of helper T cell
e. a liver cell

A liver cell

A defective hepatocyte was isolated from a liver cancer patient. This hepatocyte contains approximated 75+ active protein kinase A (PKA) molecules, even in the absence of epinephrine. What is a plausible explanation?

a. The cell's phosphorylase kinase gene has a mutation that makes the kinase active all of the time.
b. The cell's adenylate cyclase gene has a mutation that makes the cyclase active all of the time.
c. The cell's glycogen phosphorylase gene has a mutation that makes the phosphorylase active all of the time.
d. The cell's adenylate cyclase gene has a mutation that makes the cyclase inactive all of the time.
e. None of the above

The cell's adenylate cyclase gene has a mutation that makes the cyclase active all of the time.

What is the role of a kinase?

a. catalyze the hydrolytic remove of phosphate groups from target molecules
b. catalyze the addition of phosphate groups to target molecules, involving ATP
c. catalyze the addition of phosphate groups to target molecules, involving inorganic phosphate (Pi)
d. catalyze the breakdown of nucleic acids
e. catalyze the hydrolysis of target molecules

Catalyze the addition of phosphate groups to target molecules, involving ATP

Why is the consequence of epinephrine signaling so different for cardiac cells and hepatocytes?

a. The epinephrine receptors are more abundant on the surface of cardiac cells.
b. Different amounts of epinephrine reach each different type of target cell.
c. The downstream signaling components stimulated by the activated epinephrine receptor are different in cardiac cells and hepatocytes.
d. The epinephrine receptors on the surface of their target cells are different.
e. There is no difference in the responses of these cell types to epinephrine.

The downstream signaling components stimulated by the activated epinephrine receptor are different in cardiac cells and hepatocytes.

Where is epinephrine synthesized in our bodies?

a. pituitary gland
b. hypothalamus
c. red blood cells
d. adrenal gland
e. kidney tubules

Adrenal gland

Epinephrine is considered what type of signaling molecule?

a. GPCR
b. paracrine hormone
c. G-protein ligand
d. endocrine hormone
e. neurotransmitter

Endocrine hormone

Which of these statements accurately describes an MTOC in the cytoplasm of an undifferentiated cell?

a. MTOCs bind and stabilize the minus ends of most of the microtubules.
b. MTOCs bind and stabilize the minus ends of most of the microfilaments.
c. MTOCs bind and stabilize the plus ends of most of the microfilaments.
d. MTOCs bind and stabilize the plus ends of most of the microtubules.

MTOCs bind and stabilize the minus ends of most of the microtubules.

True or false? The minus end of microtubules and microfilaments is so named because subunits are lost and never added there.

False

The critical concentration of GTP-tubulin heterodimers in vitro has been measured and found to be 200 nM and 1000 nM for the plus and minus ends, respectively. Which of the following GTP-tubulin heterodimer concentrations would favor treadmilling?

a. 1 pM
b. 1 nM
c. 650 uM
d. 650 nM
e. 1200 nM

650 nM

During oxidative phosphorylation, ADP and Pi are combined in the...

a. stroma
b. matrix
c. intermembrane space
d. thylakoid lumen
e. cytoplasm

Matrix

True or false? The production of ATP during aerobic respiration is called photophosphorylation.

False

True or false? During photophosphorylation, ADP and Pi are combined in the thylakoid lumen.

False

During the day, the pH of the stroma is [ ] the thylakoid lumen.

a. the same as
b. higher than
c. lower than

Higher than

True or false? During the Cori cycle, glucose is converted into lactate in the liver.

False

Yogurt production involves all of the following EXCEPT...

a. lactate fermentation
b. increasing pH of the milk
c. glycolysis
d. lactose catabolism
e. all of the above are involved in yogurt production

Increasing pH of the milk

True or false? If the concentration of ATP inside a cell increases, the TCA cycle will be activated.

False

Glycogenesis is catalyzed by which enzyme?

a. glycogen phosphorylase
b. phosphorylase phosphatase
c. glycogen synthase
d. protein kinase A
e. phosphorylase kinase

Glycogen synthase

Protein kinase A will [ ] glycogen synthase.

a. deactivate
b. activate

Deactivate

PKA targets phosphorylase kinase. The action of PKA on phosphorylase kinase then leads to the [ ] of the [ ] pathway.

a. activation; glycogenolysis
b. deactivation; glycogenolysis
c. activation; glycogenesis
d. deactivation; glycogenesis
e. Both A and D

Activation; glycogenolysis

What causes catastrophe of the microtubule in vitro?

a. the lack of tubulin heterodimers
b. non-motor microtubule associated proteins (MAPs)
c. mutation of the β-tubulin
d. GTP hydrolysis

GTP hydrolysis

What is the role of GTP in microtubule polymerization?

a. GTP is a second messenger that signals the need for polymerization/de-polymerization.
b. GTP stabilizes the tip of the microtubule, allowing more monomers to be added.
c. GTP hydrolysis provides the energy for the polymerization of the microtubule.
d. GTP binds the alpha and beta tubulin subunits together to form the tubulin monomer.

GTP stabilizes the tip of the microtubule, allowing more monomers to be added.

What would happen in the treadmilling experiment if a non-hydrolyzable analogue of GTP were used?

a. The monomers would be unable to add to the plus end, and the microtubules would shrink until they disappeared.
b. The microtubule would treadmill until the new tubulin, with non-hydrolyzable GTP, reached the minus end, and then it would only extend at the plus end.
c. The non-hydrolyzable GTP would stabilize both ends, causing treadmilling to stop.
d. The microtubule would add monomers at both the plus and minus ends, growing in both directions.

The microtubule would treadmill until the new tubulin, with non-hydrolyzable GTP, reached the minus end, and then it would only extend at the plus end.

What is the difference between the plus and minus ends of the microtubule in in vitro experiments?

a. Polymerization occurs at the plus end.
b. The beta subunit of the tubulin is exposed on the minus end.
c. The plus end has a lower critical concentration for tubulin heterodimers.
d. Catastrophe occurs at the minus end.

The plus end has a lower critical concentration for tubulin heterodimers.

How would the drug taxol affect the in vitro dynamic instability and treadmilling experiments?

a. Taxol would stabilize the microtubules in both experiments, leading to polymerization without catastrophe.
b. Taxol would block catastrophe at the plus end in the dynamic instability experiment but not depolymerization at the minus end in the treadmilling experiment.
c. Taxol would block depolymerization at the minus end in the treadmilling experiment but not catastrophe at the plus end in the dynamic instability experiment.
d. Taxol would block the addition of tubulin in both experiments, leading to a destruction of the microtubules.

Taxol would stabilize the microtubules in both experiments, leading to polymerization without catastrophe.