Cell and Molecular Biology Exam 3

signaling by the steroid hormone estrogen is an example of _____ signaling

a. autocrine

b. endocrine

c. paracrine

d. direct cell-to-cell

b. Endocrine

Signaling by neurotransmitters is an example of _______ signaling.

a. autocrine

b. endocrine

c. paracrine

d. direct cell-to-cell

C. Paracrine

Signaling by cadherins is an example of _______ signaling.

a. autocrine

b. endocrine

c. paracrine

d. direct cell-to-cell

D. Direct cell-to-cell

Stimulation of T lymphocytes, leading to their synthesis of a growth factor resulting in T lymphocyte proliferation, is an example of _______ signaling.

a. autocrine

b. endocrine

c. paracrine

d. direct cell-to-cell

A. autocrine

Which signal molecule diffuses through the plasma membrane to ultimately bind nuclear receptors and influence transcription?

a. estrogen

b. nitric oxide

c. cadherins

d. nerve growth factor

A. Estrogen

Steroid hormones usually act via receptors that

a. are coupled to G proteins that activate adenylyl cyclase.

b. activate tyrosine kinases.

c. bind to DNA.

d. activate phospholipase C.

C. Bind to DNA

Statins, a class of drugs that are often administered to patients with high cholesterol, inhibit the biosynthesis of cholesterol. Statin drugs would not be expected to affect the biosynthetic pathway of which of the following signal molecules?

a. Thyroid hormone

b. Vitamin D3

c. Retinoic acid

d. Estrogen

C. Retinoic Acid

A glucocorticoid binding to its receptor stimulates

a. phosphorylation of a transcription factor protein that activates a gene.

b. formation of a receptor dimer that triggers an intracellular signal pathway.

c. formation of a receptor dimer that binds to and activates a gene.

d. binding of the receptor monomer to a gene.

C. Formation of a receptor dimer that binds to and activates a gene

Nitric oxide is a signal molecule that can

a. bind to surface receptors and activate second messengers.

b. bind to surface receptors and open ion channels.

c. diffuse across cell membranes and bind to receptors that regulate transcription.

d. diffuse across cell membranes and directly alter the activity of intracellular enzymes.

D. Diffuse across cell membranes and directly alter the activity of intracellular enzymes

Nitric oxide is considered a paracrine signal molecule because it

a. is slow to diffuse

b. is produced in very small quantities

c. is unstable, with a short half-life

d. binds to cell surface receptors that are very plentiful

C. Is unstable, with a short half-life

Neurotransmitters act by binding to receptors that are

a. ligand-gated ion channels.

b. located in the cytoplasm.

c. tyrosine-kinase receptors.

d. not coupled to G proteins.

A. Ligand-gated ion channels

The medical usage of nitroglycerine in heart disease is based on its

a. inhibition of adenylate cyclase and blood vessel contraction

b. conversion to NO which causes blood vessel dilation

c. activation of NO-synthase and muscle cell contraction

d. promotion of cyclooxygenase and prostaglandin synthesis

B. conversion to NO which causes blood vessel dilation

Enkephalins and endorphins bind to the same receptors in the brain as

a. nerve growth factor

b. aspirin

c. morphine

d. acetylcholine

c. morphine

In plants, cytokinins stimulate

a. cell division.

b. cell elongation.

c. cell enlargement.

d. fruit ripening.

A. cell division

In plant cells, which signaling molecule induces cell elongation?

a. Acetylcholine

b. gamma-aminobutyric acid (GABA)

c. Auxin

d. Retinoic acid

C. auxin

Which molecule stimulates fibroblasts to proliferate and thus heal a wound?

a. EGF

b. NGF

c. NO

d. PDGF

D. PDGF

Differentiation of blood cells and control of lymphocytes during the immune response is regulated by which type of signaling molecule?

a. Enkephalins

b. Fibroblast growth factor

c. Platelet derived growth factor

d. Cytokines

D. Cytokines

The G protein that activates adenylyl cyclase is a

a. monomeric G protein in the Ras family that binds GTP

b. dimeric G protein that separates into alpha and beta subunits

c. heterotrimeric G protein that separates into alpha and beta gamma subunits

d. heterotrimeric G protein that separates into alpha and beta and gamma subunits

C. heterotrimeric G proteins that separates into alpha and beta gamma subunits

In an active state of a G protein, the

a. alpha subunit binds to a target protein, and the beta gamma subunit remains bound to the receptor

b. alpha and beta gamma subunits both can bind to target proteins

c. alpha beta and gamma subunits both can bind to the target proteins

d. gamma subunit can bind to a target protein, and the alpha beta subunit remains bound to the receptor

b. alpha and beta gamma subunits both can bind to target proteins

The GTP on the G protein that is linked to adenylyl cyclase is split to GDP and Pi

a. in the inactive site

b. in the process of subunit separation

c. upon activation by the receptor

d. by the active alpha subunit

D. by the active alpha subunit

Cholera toxin inhibits the ability of the alpha subunit of Gs to split GTP. If you treated cells with cholera toxin, the resulting effect would be _______ of adenylyl cyclase

a. stimulation

b. inhibition

c. molecular degradation

d. increased synthesis

A. stimulation

A mutation that causes a G-protein to lose its ability to hydrolyze bound GTP would be expected to have constitutively

a. inactive betagamma subunits

b. bound alphabetagamma subunits

c. active alpha subunits

d. inactive alpha subunits

C. active alpha subunits

The alpha subunit of the G protein that is associated with the epinephrine receptor, Gs,

a. opens Ca2+ channels.

b. closes Na+ channels.

c. activates adenylate cyclase.

d. inhibits adenylate cyclase.

C. activates adenylate cyclase

The major function of cAMP in animal cells is to activate

a. adenylyl cyclase.

b. protein kinase A.

c. protein kinase C.

d. tyrosine kinases.

B. Protein kinase A

Protein kinase A is activated by

a. phosphorylation of its catalytic subunit.

b. phosphorylation of its regulatory subunits.

c. binding of cAMP to its catalytic subunits.

d. binding of cAMP to its regulatory subunits.

D. binding of cAMP to its regulatory subunits

Binding of cAMP to the _______ subunits of protein kinase A (PKA) leads to

_______ of that protein kinase.

a. catalytic; activation

b. catalytic; inactivation

c. regulatory; inactivation

d. regulatory; activation

D. regulatory; activation

Protein kinase A regulates glycogen metabolism by phosphorylating glycogen synthase and

a. phosphorylase kinase.

b. glycogen phosphatase.

c. glycogen phosphorylase.

d. glucokinase.

A. phosphorylase kinase

Protein kinase A regulates glycogen metabolism by _______ glycogen synthase and _______ glycogen phosphorylase.

a. activating; activating

b. inactivating; inactivating

c. activating; inactivating

d. inactivating; activating

D. Inactivating; activating

The action effected by protein kinase A is terminated by

a. inactivation of initial receptor

b. inaction of the stimulatory G protein

c. degradation of cAMP

d. dephosphorylation of phosphoproteins by protein phosphatase 1

D. dephosphorylation of phosphoproteins by proteins phosphatase 1

During the odorant response in the cilia of olfactory neurons, the second messenger ______, leads to the opening of ion channels in the plasma membrane of olfactory neurons and the production of a nerve impulse.

a. Ca2+

b. cAMP

c. cGMP

d. IP3

B. cAMP

Protein X is activated by protein kinase A. A mutation in protein X that replaces the protein's only serine residue with an arginine residue would be expected to

a. increase activation of protein X

b. eliminate activation of protein X

c. have no effect on activation of protein X

d. prevent inactivation of protein X

B. eliminate activation of protein X

CREB is activated by

a. cAMP binding in the nucleus.

b. phosphorylation by protein kinase A in the nucleus.

c. cAMP binding in the cytoplasm.

d. phosphorylation by protein kinase A in the cytoplasm.

B. phosphorylation by protein kinase A in the nucleus

Which statement correctly describes how protein kinase A can activate genes?

a. Nuclear protein kinase A is activated by cAMP to phosphorylate general transcription

factors.

b. Cytosolic protein kinase A is activated by cAMP to release the catalytic subunits,

which move into the nucleus and phosphorylate CREB.

c. Cytosolic protein kinase A is activated by cAMP to release the catalytic subunits,

which move into the nucleus and phosphorylate general transcription factors.

d. Nuclear protein kinase A is activated by cAMP to phosphorylate CREB.

B. cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate CREB

Activated CREB protein

a. phosphorylates protein phosphatase 1, leading to its activation

b. binds to specific DNA sequences and influences transcription of genes involved in growth and development

c. binds to ribosomal subunits and influences translation of proteins important in growth and development

d. phosphorylates protein kinase A in the cytoplasm

B. binds to specific DNA sequences and influences transcription of genes involved in growth and development

The first step in growth factor pathway activation is

a. receptor dimerization.

b. receptor phosphorylation.

c. Ras activation.

d. the binding of SH2-containing proteins.

A. receptor dimerization

MAP kinase is an abbreviation for _______ protein kinase.

a. microtubule-associated

b. mitogen-activated

c. mitosis-activating

d. mitosis-associated

B. mitogen-activated

A researcher generated a mutant SH2-containing protein such that it binds tyrosine

and phosphotyrosine with equal affinity. As a result, MEK activity would be expected to

a. increase with ligand binding-induced dimerization.

b. remain the same with receptor dimerization and autophosphorylation.

c. decrease due to changes in Raf activation.

d. decrease due to allosteric inhibition of SH2-domain binding.

B. remain the same with receptor dimerization and autophosphorylation

Binding of integrins to the extracellular matrix leads to integrin clustering and activation of the nonreceptor tyrosine kinase

a. CREB

b. FAK

c. PKA

d. Ca2+/calmodulin-dependent kinase

B. FAK

Mutated oncogenic Ras proteins usually

a. cleave GTP more rapidly than normal.

b. fail to bind Raf.

c. cleave GTP less rapidly than normal.

d. bind GAP more tightly than normal.

C. cleave GTP less rapidly than normal

Ras is a membrane-bound _______ when activated.

a. small monomeric G protein that binds GTP

b. dimeric G protein that separates into and subunits

c. heterotrimeric G protein that separates into and subunits

d. heterotrimeric G protein that separates into and subunits

A. small monomeric G protein that binds GTP

MAP kinase signal cascades are often organized into functional groups or cassettes by

a. scaffold proteins.

b. binding of SH2 domains to each other.

c. lipid rafts.

d. binding MAP kinase-responsive genes.

A. scaffold proteins

the RAS guanine nucleotide-binding protein is activated by

a. cAMP binding

b. serine phosphorylation by protein kinase A

c. GDP binding

d. GTP binding

D. GTP binding

MEK is a protein kinase that phosphorylates _______ residues.

a. threonine and tyrosine

b. tyrosine

c. histidine

d. arginine and lysine

A. threonine and tyrosine

Hydrolysis of PIP2 by phospholipase C is stimulated by

a. G protein-linked receptors.

b. protein-tyrosine kinase receptors.

c. serine-threonine kinase receptors.

d. both G protein-linked receptors and protein-tyrosine kinase receptors.

D. both G protein-linked receptors and protein-tyrosine kinase receptors

The second messenger, phosphatidylinositol 3,4,5-trisphosphate (PIP3) is generated by the action of the enzyme _______ on phosphatidylinositol 4,5-bisphosphate (PIP2).

a. protein kinase A

b. protein kinase C

c. phosphatidylinositide (PI) 3-kinase

d. mTOR kinase

C. phosphatidylinositide (PI) 30-kinase

The mTOR pathway is a central regulator of cell growth that couples the control of

a. protein synthesis to the availability of growth factors, nutrients, and energy.

b. DNA replication during mitosis and during meiosis.

c. transcription factors that regulate gene expression in the liver.

d. transcription factors that regulate gene expression in early embryonic development.

A. protein synthesis to the availability of growth factors, nutrients, and energy

NF-kB can activate genes during the immune response by a protein kinase that

a. phosphorylates the transcription factor NF-kB to activate it.

b. phosphorylates the inhibitory factor IkB, causing it to be degraded and to release NF-kB.

c. phosphorylates a MAP kinase to initiate its cascade.

d. activates a phosphorylase that removes an inhibiting phosphate from the NF-kB.

B. phosphorylates the inhibitory factor of IkB, causing it to be degraded and to release NF-kB

Which of the following would lead to a termination of Wnt signaling?

a. Phosphorylation of Disheveled

b. Inactivation of the destruction complex

c. Phosphorylation of β-catenin

d. Activation of Tcf

c. Phosphorylation of β-catenin

Phosphorylation of G protein-coupled receptors by GRK

a. turns off G protein signaling.

b. hyper sensitizes G protein signaling.

c. blocks the dissociation of the G protein from the receptor.

d. inhibits the GTPase activity of the alpha subunit of the G protein.

D. turns off protein signaling

How would inhibition of PI 3-kinase affect ERK activity in a growth factor-stimulated cell?

a. ERK activity would be inhibited

b. ERK activity would be unaffected

c. ERK activity would be upregulated

d. ERK protein would be targeted for destruction by proteolysis

a. ERK activity would be inhibited

mitochondria and chloroplast proteins are synthesized on

a. ER ribosomes

b. free cystolic ribosomes

c. the Golgi apparatus

d. peroxisomes

b. free cytosolic ribosomes

which of the following contain their own genomes?

a. Mitochondria, but not chloroplasts and peroxisomes

b. chloroplasts, but not mitochondria and peroxisomes

c. mitochondria and chloroplasts, but not peroxisomes

d. mitochondria, chloroplasts, and peroxisomes

c. mitochondria and chloroplasts, but not peroxisomes

Which statement about mitochondria is true?

a. They produce most of the ATP derived from the breakdown of lipids and carbohydrates.

b. They produce all of the ATP derived from the breakdown of fatty acids.

c. They produce all of the ATP derived from the breakdown of carbohydrates.

d. They produce about 10% of the ATP derived from the sunlight.

a. they produce most of the ATP derived from the breakdown of lipids and carbohydrates

The infoldings of the inner mitochondrial membrane are called

a. cisternae.

b. cristae.

c. laminae.

d. lamellae.

b. cristae

The inner compartment of mitochondria is called the

a. stroma.

b. intermembrane space.

c. inner membrane space.

d. matrix.

D. matrix

Which compound is a product of glycolysis that is transported into the mitochondria?

a. Pyruvate

b. Acetate as acetyl CoA

c. Lactic acid

d. Citric acid

a. pyruvate

The citric acid cycle consists of the oxidation of _______ to produce _______.

a. pyruvate; CO2, NADH, and FADH2

b. acetyl CoA; CO2, NADH, and FADH2

c. pyruvate; CO2

d. pyruvate; NADH and FADH2

b. acetyl CoA; CO2, NADH, and FADH2

Most small molecules are permeable across

a. both mitochondrial membranes.

b. the inner, but not the outer, mitochondrial membrane.

c. the outer, but not the inner, mitochondrial membrane.

d. neither mitochondrial membrane.

c. the outer, but not the inner, mitochondrial membrane

Mitochondria can

a. divide by fission.

b. fuse with one another.

c. be transported to areas of high energy use.

d. All of the above

D. all of the above (divide by fusion, fuse with one another, and be transported to areas of high energy use)

The mitochondrial outer membrane contains channels composed of proteins called

a. porins.

b. aquaporins.

c. connexins.

d. claudins.

a. porins

The outer mitochondrial membrane contains proteins that

a. synthesize ATP.

b. pump protons.

c. transport pyruvate and fatty acids.

d. direct translocation.

d. direct translocation

Electron transport occurs in the mitochondrial

a. outer membrane.

b. intermembrane space.

c. inner membrane.

d. matrix.

c. inner membrane

the process by which mitochondria are though to have arisen during evolution is called

a. symbiosis

b. phagocytosis

c. endosymbiosis

d. pinocytosis

c. endosymbiosis

Most mitochondrial genomes consist of

a. a single linear DNA molecule.

b. several linear DNA molecules.

c. several circular DNA molecules.

d. a single circular DNA molecule.

c. several circular DNA molecules

the organisms most similar to mitochondria are

a. progenotes

b. alpha-proteobacteria

c. cyanobacteria

d. purple sulfur bacteria

b. alpha-proteobacteria

Mitochondria contain

a. no genes of their own.

b. genes for mitochondrial proteins.

c. genes for mitochondrial proteins and rRNAs.

d. genes for mitochondrial proteins, rRNAs, and tRNAs.

d. genes for mitochondrial proteins, rRNAs, and tRNAs

In what way does the mitochondrial genetic code differ from the "universal" genetic code?

a. Some codons code for different amino acids.

b. There are no stop codons.

c. It accommodates less wobble.

d. All of the above

a. some codons code for different amino acids

The proteins encoded by the human mitochondrial genome function in

A. mitochondrial ribosomes

B. mitochondrial DNA polymerases

C. respiratory complexes and oxidative phosphorylation

D. helicases

c. respiratory complexes and oxidative phosphorylation

Mitochondrial DNA is inherited by means of

a. maternal transmission.

b. paternal transmission.

c. random assortment.

d. Mendelian genetics.

a. maternal transmission

Which of the following is a mitochondrial disease?

a. Lou Gehrig's disease

b. Retinoblastoma

c. Leber's hereditary optic neuropathy

d. Crohn's disease

c. Leber's hereditary optic neuropathy

Most mitochondrial proteins are synthesized on

a. mitochondrial ribosomes from nuclear mRNAs.

b. cytoplasmic ribosomes; they are imported co-translationally as they are being synthesized.

c. cytoplasmic ribosomes; they are imported after they are completely synthesized.

d. mitochondrial ribosomes from mitochondrial mRNAs.

c. cytoplasmic ribosomes; they are imported after they are completely synthesized

Mitochondrial targeting presequences usually consist of a

a. hydrophobic α helix.

b. hydrophobic random chain.

c. negatively charged α helix.

d. positively charged α helix.

d. positively charged alpha helix

Tim and Tom are

a. twin brothers with the same mitochondrial disease.

b. chaperones.

c. protein translocators in mitochondrial membranes.

d. transporters of small molecules across the mitochondrial membranes.

c. protein translocators in mitochondrial membranes

The mitochondrial protein presequence is cleaved off by a protease called

a. signal peptidase.

b. presequence protease.

c. ubiquitin-targeted protease.

d. matrix processing peptidase.

d. matrix processing peptidase

Mitochondrial inner membrane single-pass transmembrane proteins are inserted into the inner membrane

a. through a transporter called Oxa translocase.

b. through Tim.

c. through Tim and Tom.

d. directly from the matrix into the lipid bilayer.

a. through a transporter called Oxa translocase

Most mitochondrial phospholipids are synthesized in the

a. mitochondrial matrix.

b. mitochondrial intermembrane space.

c. ER.

d. Golgi apparatus.

c. ER

Which of the following is not involved in the initial transport of a protein across the mitochondrial outer membrane from the cytosol?

a. Hsp70

b. Tim23

c. Tom

d. ATP

b. Tim23

Which of the following is not involved in targeting a protein from the intermembrane space into the inner mitochondrial membrane?

a. Tim9

b. Tim10

c. Tim22

d. Tom

d. Tom

The import of mitochondrial matrix proteins from the cytoplasm requires

A. an electrochemical gradient across the inner membrane.

B. a potassium gradient across the inner membrane.

C. ATP and a proton gradient across the inner membrane.

D. ATP and a potassium gradient across the inner membrane.

c. ATP and a proton gradient across the inner membrane

the energy required to drive the transport of small molecules into and out of mitochondria is provided by the

a. chemiosmotic gradient

b. hydrolysis of ATP

c. electrochemical gradient

d. negative charge of small molecules

c. electrochemical gradient

Which of the following phospholipids contains four fatty acid chains and is associated with a restriction in proton flow?

a. Phosphatidylcholine

b. Cholesterol

c. Sphingolipid

d. Cardiolipin

d. cardiolipin

chloroplasts differ from mitochondria in that chloroplasts

a. do not generate ATP

b. do not originate by endosymbiosis

c. do not replicate by division

d. synthesize their own amino acids and fatty acids

d. synthesize their own amino acids and fatty acids

Chloroplasts are similar to mitochondria in that both

a. have a porous outer membrane.

b. contain light sensitive pigments.

c. require presequence amino acids on proteins for import.

d. require folded cristae as the site of electron transport.

a. have a porous outer membrane

Thylakoids are often arranged in stacks called

A. dictyosomes

B. grana

C. plastids

D. stroma

b. grana

chloroplasts synthesize

a. elaioplasts

b. amino acids

c. peroxisomes

d. catalase

b. amino acids

The chloroplast genome contains about _______ genes.

a. 20

b. 150

c. 1,500

d. 3,000

b. 150

Chloroplast tRNAs translate

a. all mRNA codons according to the universal code.

b. all the amino acids according to the universal code but have different stop codons.

c. some codons as amino acids that differ from the universal code but use the same stop codons.

d. some codons as amino acids that differ from the universal code and use some different stop codons.

a. all mRNA codons according to the universal code

Most chloroplast proteins are synthesized on

a. free ribosomes in the cytosol.

b. RER membranes in the cytoplasm.

c. ribosomes bound to the outer chloroplast membrane.

d. ribosomes in the chloroplast stroma.

a. free ribosomes in the cytosol

The most abundant protein on Earth is

a. cytochrome c.

b. rubisco.

c. ATP synthase.

d. glucose-6-phosphatase.

b. rubisco

the transport of proteins across the outer and inner chloroplast membranes occurs through complexes called

a. Tim and Tom

b. Tic and Toc

c. Sec and Tat

d. import complexes

b. Tic and Toc

many proteins incorporated into the thylakoid lumen are synthesized

a. in the thylakoid lumen

b. in the stroma and transported across the thylakoid membrane

c. on the outer chloroplast membrane and transported across the thylakoid membrane by way of its hydrophobic signal sequence

d. in the cytosol, imported into the stroma, and transported across the thylakoid membrane by way of a second signal sequence

d. in the cytosol, imported into the stroma, and transported across the thylakoid membrane by way of a second signal sequence

carotenoids are stored in

a. chloroplasts

b. chromoplasts

c. amyloplasts

d. elaioplasts

b. chromoplasts

all plastids, including chloroplasts, develop from

a. chromoplasts

b. etioplasts

c. elaioplasts

d. proplastids

d. proplastids

An amyloplast is a plastid that

a. stores starch.

b. stores lipid.

c. is arrested in chloroplast development by lack of light.

d. stores pigment.

a. stores starch

The major function of peroxisomes is to

a. oxidize certain organic molecules and degrade the H2O2 produced by these reactions.

b. produce hydrogen peroxide for cells.

c. digest old organelles.

d. digest macromolecules taken up by endocytosis.

a. oxidize certain organic molecules and degrade the h202 produced by these reactions

Peroxisomes contain the enzyme _______, which breaks down H2O2 into H2O and oxygen.

a. peroxidase

b. catalase

c. peroxigen

d. glyoxylate

b. catalase

Which of the following is the human disease caused by mutations in the proteins required for importing functional proteins into peroxisomes?

a. Turner's syndrome

b. Zellweger syndrome

c. I-cell disease

d. Leber's hereditary optic neuropathy

b. Zellweger syndrome

Most peroxisomal proteins are synthesized on

a. free ribosomes in the cytosol.

b. RER membranes in the cytoplasm.

c. ribosomes bound to the outer peroxisome membrane.

d. ribosomes inside the peroxisome.

a. free ribosomes in the cytosol

New peroxisomes form by

a. budding from the Golgi apparatus.

b. budding from preexisting peroxisomes.

c. de novo assembly from proteins synthesized in the cytosol.

d. budding of vesicles from the ER and growth and division of preexisting peroxisomes.

d. budding of vesicles from the ER and growth and division of preexisting peroxisomes

Actin filaments are approximately _______ in diameter.

a. 5 Å

b. 7 nm

c. 11 nm

d. 25 nm

b. 7 nm