Biochem 10 Flashcards

A pharmacologist describes the cell membrane as allowing some solutes through while restricting others. Which property best matches this description?
A. Freely permeable barrier
B. Completely impermeable barrier
C. Selectively permeable barrier
D. Uniformly porous barrier

A toxin selectively disrupts smooth endoplasmic reticulum function. Which cellular process is most directly impaired?
A. DNA replication
B. Lipid synthesis
C. Ribosome assembly
D. Protein translation

A cell loses structural integrity after simultaneous disruption of its primary cytoskeletal systems. Which set best lists those systems?
A. Actin, keratin, dynein
B. Collagen, elastin, tubulin
C. Myosin, actin, spectrin
D. Actin, intermediate, tubulin

A pituitary signal enters the bloodstream to act at distant targets. In that system, the chemical messenger is termed a:
A. Neurotransmitter
B. Hormone
C. Cytokine
D. Retinoid

A macrophage secretes a protein that coordinates local immune activity. In that system, the messenger is termed a:
A. Hormone
B. Neurotransmitter
C. Cytokine
D. Growth factor

Which trio matches the listed nonspecific messengers?
A. Retinoids, eicosanoids, growth factors
B. Peptides, steroids, nucleotides
C. Amines, gases, electrolytes
D. Enzymes, antibodies, complement

A T cell requires direct membrane contact with an antigen-presenting cell to receive an activating signal. Which signaling mode is described?
A. Autocrine
B. Endocrine
C. Paracrine
D. Juxtacrine

A wound-healing mediator diffuses a short distance to alter gene expression in adjacent cells. Which signaling mode is described?
A. Paracrine
B. Juxtacrine
C. Endocrine
D. Synaptic

A review classifies receptors into two broad groups. Which pair matches the listed receptor classes?
A. Ion-channel, G-protein coupled
B. Plasma membrane, intracellular binding proteins
C. Tyrosine kinase, serine-threonine
D. Cytokine, growth factor

A student lists subclasses of plasma membrane receptors. Which option is NOT one of the listed plasma membrane subclasses?
A. Ion-channel receptors
B. G-protein coupled receptors
C. Intracellular binding proteins
D. Serine-threonine kinase receptors

A hormone receptor complex is found directly regulating transcription of a specific gene. Which description best matches most intracellular receptors?
A. Gene-specific transcription factors
B. Ligand-gated ion channels
C. Cell-surface adhesion proteins
D. Serine-threonine phosphatases

A signaling molecule binds an intracellular receptor that then localizes to the nucleus. What does this receptor class bind directly?
A. RNA polymerase
B. Plasma membrane lipids
C. Ribosomal subunits
D. DNA

A growth signal activates a receptor that increases its kinase activity through a specific chemical modification. What activates tyrosine kinases as listed?
A. Dephosphorylation
B. Phosphorylation
C. Ubiquitination
D. Proteolysis

A pathway diagram notes that ligand binding triggers a shape change in a signal transducer by binding to a specific domain. Which domain is listed?
A. Transmembrane domain
B. DNA-binding domain
C. SH2 domain
D. Catalytic domain

A question bank lists common second messengers. Which molecule is NOT included in the provided list?
A. DAG
B. IP3
C. cAMP
D. cGMP

A microbiology lab optimizes culture conditions for Vibrio cholerae. Which condition best supports growth as listed?
A. Alkaline conditions
B. Acidic conditions
C. Neutral conditions
D. Hyperosmotic conditions

A traveler develops profuse watery diarrhea from Vibrio cholerae infection. Activation of which epithelial channel is listed as the mechanism?
A. ENaC channel
B. CFTR channel
C. Aquaporin channel
D. Na⁺/K⁺ ATPase

A clinician wants an enzymatic uric acid level determination in a patient with suspected gout. Which enzyme activity is observed as listed?
A. Hexokinase
B. Xanthine oxidase
C. Uricase
D. Pyruvate kinase

A patient has recurrent gout. Based on the listed scheme, which pairing correctly matches “treatment” vs “prevention”?
A. Allopurinol / colchicine
B. Colchicine / uricase
C. Uricase / allopurinol
D. Colchicine / allopurinol

During prolonged fasting, one tissue synthesizes ketone bodies while another uses them. Which pairing matches the listed mitochondrial enzyme distribution?
A. Muscle synthesizes; liver uses
B. Liver synthesizes; muscle uses
C. Liver uses; liver synthesizes
D. Muscle uses; muscle synthesizes

A lecturer emphasizes membrane asymmetry and asks where glycoproteins and glycolipids are predominantly located. Which leaflet is correct as listed?
A. Outer leaflet
B. Inner leaflet
C. Both leaflets equally
D. Neither leaflet

A pathology question describes the carbohydrate layer (glycocalyx) on the outer cell surface. What is its listed function?
A. ATP synthesis platform
B. Ion transport reservoir
C. Cell recognition marker
D. Nuclear import signal

A membrane lipid is identified as the principal sphingolipid component. Which lipid is correct as listed?
A. Phosphatidylserine
B. Phosphatidylethanolamine
C. Phosphatidylcholine
D. Sphingomyelin

A drug flips membrane lipids and disrupts normal leaflet composition. Which pair is listed as typical for the outer leaflet?
A. Phosphatidylserine, phosphatidylinositol
B. Phosphatidylcholine, sphingomyelin
C. Phosphatidylethanolamine, phosphatidylserine
D. Phosphatidylinositol, phosphatidylcholine

A genetics vignette references inner leaflet signaling scaffolds and asks which set is typical for the inner leaflet as listed.
A. Phosphatidylcholine, sphingomyelin, phosphatidylethanolamine
B. Sphingomyelin, phosphatidylcholine, phosphatidylethanolamine
C. Phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine
D. Phosphatidylcholine, phosphatidylethanolamine

A physiology stem asks which lipid is specifically noted as contributing to membrane potential due to its net negative charge. Which lipid is correct as listed?
A. Phosphatidylserine
B. Phosphatidylcholine
C. Sphingomyelin
D. Phosphatidylethanolamine

Which outer-leaflet lipids are hydrolyzed by a key Clostridium perfringens toxin?
A. Cardiolipin and phosphatidylinositol
B. Phosphatidylserine and phosphatidylethanolamine
C. Phosphatidylcholine and sphingomyelin
D. Cholesterol and gangliosides

In gas gangrene, toxin-driven membrane lysis most directly benefits the bacteria by providing:
A. Nutrients for bacterial growth
B. Antibodies for immune evasion
C. ATP for host repair
D. Iron for hemoglobin synthesis

A lab increases membrane rigidity by altering lipid composition. Which pair is listed as determining membrane fluidity?
A. Sphingomyelin and glycolipids
B. Phosphatidylserine and actin
C. Integral proteins and spectrin
D. Cholesterol and unsaturated fatty acids

A patient with impaired CO₂ transport has a defective RBC “chloride shift.” Which RBC membrane protein normally exchanges bicarbonate and chloride?
A. Glycophorin sialoglycoprotein
B. Band 3 anion exchanger
C. Spectrin cytoskeletal scaffold
D. Protein 4.1 linker

In systemic capillaries, CO₂ entry into RBCs drives the “chloride shift.” Which direction best matches the listed exchange?
A. HCO3− in, Cl− out
B. Cl− in, HCO3− out
C. Na+ in, K+ out
D. K+ in, Na+ out

A hematology question asks which RBC membrane component provides an external negative charge that repels other cells.
A. Band 3 cytoplasmic tail
B. Ankyrin membrane adaptor
C. Spectrin heterotetramer
D. Glycophorin sialic acid coat

In hereditary spherocytosis, a mutation disrupts linkage between Band 3 and the cytoskeleton. Which adaptor connects Band 3 to spectrin?
A. Protein 4.1
B. Actin junctional complex
C. Ankyrin adaptor protein
D. Dystrophin-like complex

A distinct RBC membrane defect disrupts the glycophorin-based junctional complex. Glycophorin links to actin and spectrin through:
A. Ankyrin adaptor
B. Protein 4.1
C. Band 3 cytosolic domain
D. Clathrin coat

Which prominent peripheral protein provides mechanical support?
A. Spectrin peripheral scaffold
B. CFTR chloride channel
C. Glycophorin receptor
D. Aquaporin water channel

A neurologic vignette references CJD/mad-cow and notes the culprit prion protein is tethered to neuronal membranes by a:
A. Transmembrane alpha helix
B. Prenylated C-terminus
C. Myristoylated N-terminus
D. GPI anchor

A mutation broadly impairs lysosomal digestion. Which set matches the listed lysosomal digestive enzymes?
A. Kinases, ligases, isomerases, lyases
B. Nucleases, phosphatases, glycosidases, esterases, proteases
C. Oxidases, reductases, synthases, helicases
D. Polymerases, topoisomerases, transferases, dehydrogenases

The lysosomal enzymes are best categorized as:
A. Transferases
B. Lyases
C. Hydrolases
D. Isomerases

An experimental drug raises intralysosomal pH and causes substrate buildup. These enzymes normally function in an:
A. Acidic lumen
B. Neutral cytosol
C. Alkaline matrix
D. Hypotonic extracellular space

“Cystine proteases” in lysosomes are also called:
A. Caspases
B. Cathepsins
C. Calpains
D. Kallikreins

A biochem study finds peak lysosomal hydrolase activity at which listed pH?
A. pH 3.0
B. pH 4.5
C. pH 7.4
D. pH 5.5

A genetic defect prevents lysosomes from maintaining acidity. Which listed pump maintains the acidic lumen?
A. Na+/K+ ATPase
B. SERCA ATPase
C. V-ATPases proton pump
D. Na+/H+ exchanger

"Vesicular ATPases” maintain intralysosomal pH. They are best described as a(n):
A. Active proton pump
B. Passive chloride channel
C. Sodium-coupled symporter
D. ATP-independent antiporter

A population genetics stem asks about heterozygote advantage in cystic fibrosis. Heterozygotes are described as immune to:
A. Typhoid fever
B. Shigellosis
C. Rotavirus gastroenteritis
D. Cholera

Cholera toxin causes diarrheal fluid loss by making CFTR do which listed behavior in intestines?
A. Be internalized from membrane
B. Stay open in intestines
C. Reverse ion selectivity
D. Lose ATP-binding ability

The CFTR change above most directly produces:
A. Constipation from reduced secretion
B. Malabsorption from bile loss
C. Dehydration from secretory diarrhea
D. Bradycardia from vagal tone

In this mechanism, intestinal secretion increases which listed ions into the lumen?
A. Potassium and bicarbonate
B. Calcium and phosphate
C. Magnesium and sulfate
D. Chloride and sodium

The ion secretion above is followed by net loss of:
A. Water
B. Glucose
C. Urea
D. Bile salts

A lysosomal storage disease question asks what accumulates in Tay-Sachs, per the provided pairing.
A. Glycogen accumulation
B. Sphingomyelin accumulation
C. Ganglioside accumulation
D. Cholesterol ester accumulation

A second lysosomal storage disease asks what accumulates in Pompe, per the provided pairing.
A. Ganglioside accumulation
B. Glycogen accumulation
C. Mucopolysaccharide accumulation
D. Cerebroside accumulation

What is involved in oxidative reactions using molecular oxygen?
A. Peroxisome
B. Lysosome
C. Golgi
D. Ribosomes

Another listed peroxisomal role is to:
A. Generate urea from ammonia
B. Convert cholesterol to bile salts
C. Package proteins for secretion
D. Synthesize ATP via ETC

Peroxisomes synthesize ether lipids called:
A. Prostaglandins
B. Triacylglycerols
C. Plasmalogens ether lipids
D. Glycogen granules

Which statement about peroxisomes matches the provided material?
A. Contain no DNA
B. Contain circular DNA genome
C. Contain histones and chromatin
D. Replicate by mitosis

The largest subcellular organelle in animal cells is the:
A. Golgi apparatus
B. Mitochondrion
C. Peroxisome
D. Nucleus

A cell with increased ribosome production shows a prominent nuclear substructure. The nucleolus is the site of:
A. Splice pre-mRNA transcripts
B. rRNA transcription and ribosome assembly
C. Lipid synthesis and detoxification
D. Protein glycosylation and sorting

The nucleus is separated by the nuclear envelope and communicates with cytoplasm through:
A. Desmosomes
B. Tight junctions
C. Nuclear pores
D. Gap junctions

Electron microscopy shows the outer nuclear membrane blending directly into a ribosome-studded cisternal network. That membrane is continuous with:
A. Rough endoplasmic reticulum
B. Smooth endoplasmic reticulum
C. Golgi cis network
D. Inner nuclear lamina

A transcription factor enters the nucleus normally but cannot leave, causing nuclear accumulation. Which signal is most likely defective?
A. Nuclear localization signal
B. Nuclear export signal
C. Signal peptide
D. Lysosomal targeting signal

A hepatocyte shows extensive ER tubules without surface ribosomes. Which organelle is described?
A. Rough ER
B. Golgi complex
C. Smooth ER
D. Nucleolus

After chronic exposure to a toxic solvent, hepatocytes upregulate a smooth-ER enzyme class for xenobiotic metabolism. Which class is it?
A. Hydrolases
B. Glycosidases
C. Kinases
D. Cytochrome P450 enzymes

A path slide shows glycogen concentrated in cytoplasmic regions rich in which organelle?
A. Rough ER
B. Smooth ER
C. Golgi complex
D. Nucleus

A newly synthesized enzyme is destined for a membrane-bound organelle (e.g., lysosome). Where is it most likely synthesized?
A. Rough ER ribosomes
B. Free cytosolic ribosomes
C. Mitochondrial ribosomes
D. Nuclear ribosomes

A secreted protein is translated on ER-bound ribosomes. What is the next major trafficking station listed?
A. Proteasome
B. Peroxisome
C. Golgi complex
D. Nucleolus

A peptide hormone is synthesized on RER and processed through Golgi. Which listed fate is appropriate?
A. Remain in cytosol
B. Remain in nucleus
C. Insert into mitochondria
D. Secreted from the cell

A lab assay detects N-linked glycosylation on a nascent polypeptide. Where does this modification primarily occur?
A. Rough endoplasmic reticulum
B. Smooth endoplasmic reticulum
C. Cytosol
D. Nucleus

A cytosolic enzyme is translated on free ribosomes. Its posttranslational modification status is most consistent with:
A. Extensive N-linked glycosylation
B. Seldom modified
C. Frequent disulfide bonding
D. Routine lipid anchoring

A child with neurodegeneration has a peroxisomal disorder where membrane transport of fatty acids is reduced due to decreased transporter content. Which defect best matches?
A. Golgi sorting enzyme loss
B. SER ribosome detachment
C. Nuclear pore depletion
D. Peroxisomal fatty-acid transporter loss

A neonate has hypotonia and multisystem disease from failure to produce proteins required for peroxisome synthesis. Which disorder matches?
A. Adrenoleukodystrophy
B. Cystic fibrosis
C. Zellweger syndrome
D. Tay-Sachs disease

Which option correctly lists the three Golgi compartments provided?
A. Cis, medial, trans
B. Inner, outer, lamina
C. Matrix, cristae, IMS
D. Apical, basal, lateral

On EM, the convex Golgi face oriented toward the nucleus is the:
A. Trans Golgi network
B. Medial stacks
C. Secretory vesicle face
D. Cis Golgi network

A vesicle budding from the Golgi face nearest the plasma membrane most likely originates from the:
A. Cis Golgi network
B. Medial Golgi stacks
C. Trans Golgi network
D. Nuclear envelope

A motor protein moves vesicles and positions organelles along tracks composed of:
A. Tubulin microtubules
B. Actin microfilaments
C. Keratin intermediate filaments
D. Collagen fibers

A migrating fibroblast requires cytoskeletal elements for movement. Which pair is listed as involved?
A. Spectrin and ankyrin
B. Intermediate filaments only
C. Fibrous proteins only
D. Actin and tubulin

A patient’s cells show reduced tensile strength due to defects in fibrous cytoskeletal proteins. Which component is implicated?
A. Microtubules
B. Intermediate filaments
C. Actin microfilaments
D. Centrioles

The primary role of intermediate filaments in the cell is:
A. Second messenger generation
B. Organelle positioning
C. Structural support
D. Steroid synthesis

In the general signaling sequence, what is the first listed event after a stimulus occurs?
A. Messenger secreted
B. Receptor binds messenger
C. Response is produced
D. Signal terminates

In the general signaling sequence, which listed step represents termination?
A. Messenger diffuses to target
B. Signal ceases
C. Receptor binds messenger
D. Stimulus is sensed

The monomeric G-protein Arf belongs to which superfamily?
A. Ran superfamily
B. Rab superfamily
C. Ras superfamily
D. Rho superfamily

Arf is also known as:
A. Adenylate regulatory factor
B. Ankyrin-related factor
C. Acid resistance factor
D. ADP-ribosylation factor

In a cholera model, blocking Arf prevents entry of which toxin component into cells?
A. Cholera A toxin
B. Botulinum toxin
C. Tetanus toxin
D. Diphtheria toxin

Neurotransmitters are secreted from neurons in response to:
A. Hormone receptor dimerization
B. Cytokine binding
C. Second messenger diffusion
D. An action potential

At a cholinergic synapse, what directly triggers acetylcholine release into the cleft?
A. Na+ influx
B. Ca2+ influx
C. K+ efflux
D. Cl− influx

A protein found in the cytoplasm, peroxisomes, or nucleus is most likely synthesized on:
A. Golgi-bound ribosomes
B. RER-bound ribosomes
C. Free ribosomes
D. Lysosome-bound ribosomes

A secretory protein contains multiple disulfide bonds and a lipid anchor addition consistent with the listed site of these modifications. Where do they occur?
A. Cytosol
B. Smooth ER
C. Golgi lumen
D. Rough ER

A receptor translated on RER and sorted through Golgi ultimately becomes part of the cell surface. Which listed fate matches?
A. Embedded in plasma membrane
B. Remains in cytosol
C. Remains in nucleus
D. Inserted into peroxisome

A protein fails to enter the nucleus and accumulates in cytosol despite normal synthesis. Which signal most directly governs nuclear entry?
A. Nuclear export signal
B. Golgi retention signal
C. Nuclear localization signal
D. Lysosomal targeting signal

Steroid-producing cells show abundant smooth ER with P450 activity. Which process is most directly supported?
A. rRNA processing
B. Steroid hormone synthesis
C. N-linked glycosylation
D. Protein sorting

A boy develops progressive neurologic decline; testing reveals reduced peroxisomal membrane fatty-acid transporter content. Which disorder best matches?
A. Zellweger syndrome
B. Pompe disease
C. Tay-Sachs disease
D. Adrenoleukodystrophy

In the general signaling sequence, what is the earliest event that occurs after an initial stimulus?
A. Receptor binds messenger
B. Signal ceases, terminated
C. Messenger secreted
D. Response is elicited

A locally acting mediator is released and then reaches adjacent cells before binding its receptor. Which step best describes “reaches adjacent cells”?
A. Messenger diffuses/transported
B. Receptor binds messenger
C. Response is elicited
D. Signal terminates

A ligand has arrived at its target tissue but no downstream effect occurs because the receptor is blocked. Which step is directly prevented?
A. Messenger secreted
B. Messenger diffuses/transported
C. Receptor binds messenger
D. Signal ceases, terminated

A receptor binds its ligand normally, but a mutation prevents any intracellular change despite binding. Which step is specifically impaired?
A. Messenger diffuses/transported
B. Binding elicits response
C. Signal terminates
D. Messenger secreted

A signaling pathway remains “stuck on” due to impaired shutoff mechanisms. Which step is failing?
A. Receptor binds messenger
B. Messenger diffuses/transported
C. Binding elicits response
D. Signal ceases, terminated

A tyrosine kinase receptor example:
A. EGF receptor
B. Cytokine receptor
C. TGF-β receptor
D. Nicotinic receptor

A receptor class that uses JAK-STAT. Which receptor type fits?
A. EGF receptor
B. Cytokine receptor
C. GPCR heptahelical receptor
D. TGF-β receptor

A fibrotic signaling ligand activates a serine/threonine receptor kinase pathway. Which ligand-receptor pair best fits?
A. EGF receptor
B. Cytokine receptor
C. TGF-β receptor
D. Muscarinic receptor

Ligand binding to an RTK rapidly causes what key structural change enabling kinase activation?
A. Ion channel opening
B. STAT nuclear entry
C. SMAD dephosphorylation
D. Receptor dimerization

RTKs propagate signals by phosphorylating target proteins predominantly on which residue?
A. Serine
B. Tyrosine
C. Threonine
D. Histidine

In RTK signaling, which “second messenger” is listed as only rarely involved?
A. Phosphatidylinositol
B. Ras
C. MAP kinase
D. cAMP

In JAK-STAT signaling, activated JAK phosphorylates STAT, which then enters the nucleus to act as a:
A. Membrane ion transporter
B. Cytoskeletal motor protein
C. Second messenger lipid
D. Gene transcription factor

TGF-β signaling activates which nuclear-directed mediators to alter gene expression?
A. STAT proteins
B. Ras proteins
C. SMAD proteins
D. Grb2 proteins

In the RTK → Ras pathway, what immediately follows “binding and dimerization”?
A. Raf binds MAP kinase
B. Autophosphorylation
C. STAT phosphorylation
D. IP3 release

A mutation prevents GDP→GTP exchange on Ras after RTK activation. Which protein normally performs that exchange?
A. Raf
B. Grb2
C. SH2 domain
D. SOS (GEF)

A biopsy shows constitutively “on” Ras driving proliferation. Which nucleotide state defines activated Ras?
A. Ras–GDP bound
B. Ras phosphorylated
C. Ras–GTP bound
D. Ras deacetylated

A targeted therapy stabilizes inactive Ras. Which nucleotide state defines deactivated Ras?
A. Ras–GDP bound
B. Ras–GTP bound
C. Ras–ATP bound
D. Ras–CTP bound

A phosphotyrosine-binding adaptor is required to recruit SOS in RTK signaling. Grb2 is best described as:
A. Serine-threonine kinase
B. SH domain-containing protein
C. GTPase-activating protein
D. Ligand-gated ion channel

In RTK signaling, Grb2 docks to the activated receptor using which domain interaction?
A. SH3 binds phosphotyrosine
B. PH binds phosphotyrosine
C. NLS binds phosphotyrosine
D. SH2 binds phosphotyrosine

After Grb2 binds the RTK, SOS is recruited by binding which Grb2 domain?
A. SH2 domain
B. PH domain
C. SH3 domain
D. Ras domain

Once Ras is GTP-bound, it most directly promotes binding of which target enzyme?
A. Raf
B. STAT
C. PLCβ
D. PTEN

In the RTK cascade, Raf is best classified as:
A. Tyrosine phosphatase
B. MAPKKK
C. Lipid kinase
D. GTPase

Raf’s intrinsic enzymatic activity is best described as:
A. Tyrosine kinase
B. Lipid phosphatase
C. GTP-binding switch
D. Serine protein kinase

A lipid signaling module (PIP2/PIP3) can be generated downstream of which receptor families?
A. Only heptahelical receptors
B. Tyrosine and heptahelical
C. Only tyrosine kinases
D. Only nuclear receptors

PIP2 cleavage into IP3 and DAG is catalyzed by which enzyme class?
A. Phospholipase C
B. PI 3-kinase
C. PTEN
D. Raf

In growth-factor RTK signaling, which PLC isozyme is activated to cleave PIP2?
A. PLCα
B. PLCδ
C. PLCβ
D. PLCγ

In heptahelical GPCR signaling, which PLC isozyme is activated by Gq/11?
A. PLCγ
B. PLCβ
C. PLCε
D. PLCζ

PIP3 forms membrane docking sites for proteins containing which motif?
A. SH3 domain
B. SH2 domain
C. PH domain
D. NLS sequence

A tumor suppressor is lost, causing persistent PIP3 signaling because PIP3 is not converted back to PIP2. What accumulates?
A. PIP3
B. DAG
C. IP3
D. PIP2

Where is phosphatidylinositol predominantly located in the plasma membrane?
A. Outer leaflet
B. Inner leaflet
C. Both leaflets equally
D. Extracellular matrix

Phosphatidylinositol becomes PIP2 by phosphorylation at which inositol carbons?
A. 2′ and 3′
B. 1′ and 6′
C. 3′ and 5′
D. 4′ and 5′

Which enzyme adds a phosphate at the 3′ carbon to convert PIP2 to PIP3?
A. PI 3-kinase
B. PTEN
C. PLCγ
D. Raf

PI 3-kinase activation in RTK signaling depends on binding a specific phosphotyrosine site using which feature?
A. PH domain docking
B. SH3-mediated recruitment
C. SH2 domain binding
D. NLS-mediated transport

In the RTK cascade, activated Raf most directly triggers which downstream program?
A. STAT nuclear translocation
B. MAP kinase pathway
C. SMAD deactivation
D. CFTR opening

In RTK → Ras signaling, which adaptor binds the receptor and recruits SOS?
A. STAT
B. PTEN
C. Raf
D. Grb2

TGF-β signaling brings together type 1 and type 2 receptors to activate what enzymatic activity?
A. Tyrosine kinase activity
B. GTPase activity
C. Serine-threonine kinase activity
D. Chloride channel activity

Which phosphoinositide is cleaved to generate DAG and IP3?
A. PIP2
B. PIP3
C. Phosphatidylcholine
D. Sphingomyelin

The insulin receptor belongs to which receptor family?

A. Serine-threonine kinase receptors
B. JAK-STAT associated receptors
C. Tyrosine kinase receptors
D. Ligand-gated ion channels

The insulin receptor is synthesized as a preformed complex. Which subunit arrangement is correct?
A. α2β2 preformed heterotetramer
B. αβ single-pass monomer
C. β2 homodimer only
D. α2 homodimer only

A mutation prevents insulin receptor autophosphorylation despite normal insulin binding. Which receptor component normally autophosphorylates?
A. Extracellular α domains
B. Disulfide linker region
C. Cytosolic βγ complex
D. Cytosolic β subunits

Immediately after insulin receptor autophosphorylation, which substrate is recruited and phosphorylated?
A. PDK1
B. IRS
C. Akt
D. PLCβ

A patient’s insulin resistance is traced to impaired PI3K signaling. Which insulin receptor branch is most tied to glucose metabolism?
A. PI3K → Akt pathway
B. Grb2 → Ras pathway
C. PLCγ → IP3 pathway
D. STAT → nucleus pathway

In the insulin Akt pathway, which lipid conversion is catalyzed downstream of IRS?
A. IP3 to DAG
B. cAMP to 5′-AMP
C. PIP2 to PIP3
D. PIP3 to PIP2

PIP3 generation recruits two proteins to the plasma membrane before Akt activation. Which pair is correct?
A. Grb2 and SOS
B. PDK1 and Akt
C. Raf and MEK
D. STAT and JAK

At the membrane, which event directly activates Akt (PKB) in insulin signaling?
A. Adenylyl cyclase activation
B. Ras GTP loading
C. PLCγ activation
D. PDK1 phosphorylates Akt

A growth phenotype is driven by insulin receptor signaling through Ras and MAP kinase. Which docking protein most directly links IRS to Ras activation?
A. PDK1
B. Grb2
C. PTEN
D. PDE

Another name for heptahelical receptors is:
A. G-protein coupled receptors
B. Intracellular steroid receptors
C. Tyrosine kinase receptors
D. Ligand-gated ion channels

The “seven-transmembrane” name for GPCRs refers to seven membrane-spanning:
A. β-sheets
B. disulfide bridges
C. α-helices
D. glycosylation sites

GPCR signaling commonly uses which second messengers?
A. cGMP or PIP3
B. ATP or NADH
C. DAG or 5′-AMP
D. cAMP or IP3

When a G-protein α subunit is GDP-bound, it typically:
A. remains associated with βγ
B. dissociates from βγ
C. phosphorylates adenylyl cyclase
D. directly opens CFTR

When a G-protein α subunit becomes GTP-bound, it typically:
A. binds IRS
B. binds PDK1
C. dissociates from βγ
D. hydrolyzes cAMP

Which Gα subtype stimulates adenylyl cyclase?
A. Gαq/11
B. Gα12/13
C. Gαs
D. GαT

Which Gα subtype inhibits adenylyl cyclase?
A. Gαi
B. Gαs
C. GαT
D. Gαq/11

Which Gα subtype activates phospholipase Cβ?
A. Gαs
B. Gαq/11
C. Gαi
D. GαT

Which Gα subtype activates cGMP phosphodiesterase?
A. Gαs
B. Gαi
C. Gαq/11
D. GαT

Platelet shape change is driven by Rho-mediated cytoskeletal remodeling downstream of a GPCR. Which Gα subtype best fits?
A. Gαq/11
B. GαT
C. Gα12/13
D. Gαs

cAMP phosphodiesterases hydrolyze cAMP to:
A. 5′-AMP
B. GMP
C. ATP
D. ADP

Insulin lowers cellular cAMP levels primarily by:
A. activating adenylyl cyclase
B. inhibiting phosphodiesterase
C. activating phosphodiesterase
D. activating PLCβ

cAMP serves as an allosteric activator of:
A. Akt
B. Raf
C. PTEN
D. Protein kinase A

CFTR opening is promoted when it is phosphorylated by:
A. PKA
B. PKB
C. PLCβ
D. PDK1

After IRS phosphorylation, which protein binds a specific phosphotyrosine site to initiate the Akt pathway?
A. Grb2
B. PLCγ
C. Adenylyl cyclase
D. PI 3-kinase

In insulin signaling, Akt is also known as:
A. MAPKKK
B. PKA
C. PKB
D. PDE

A hepatocyte is exposed to glucagon, raising cAMP and activating PKA. Which nuclear protein is phosphorylated by PKA catalytic subunits?
A. STAT
B. SMAD
C. CREB
D. NF-κB

CREB primarily functions as a:
A. Gene transcription factor
B. Membrane ion channel
C. Cytosolic scaffold protein
D. GTPase-activating protein

A bronchial smooth muscle GPCR activates phospholipase Cβ. Which Gα subunit must bind PLCβ?
A. Gαs
B. Gαi
C. GαT
D. Gαq

PLCβ hydrolyzes which membrane lipid to generate DAG and IP3?
A. PIP3
B. PIP2
C. Phosphatidylcholine
D. Sphingomyelin

In this pathway, IP3 most directly stimulates release of:
A. Ca2+
B. cAMP
C. GTP
D. Na+

In the same cascade, DAG most directly activates:
A. PKA only
B. Adenylyl cyclase
C. Ca binding and PKC
D. Guanylyl cyclase

A developmental biologist studies a contact-dependent pathway classically used as the example of juxtacrine signaling. Which pathway is it?
A. JAK-STAT
B. Notch signaling
C. Hedgehog signaling
D. Wnt/β-catenin

Which ligands bind the Notch receptor?
A. EGF and PDGF
B. TGF-β and Activin
C. IL-2 and IFN-γ
D. Delta and Jagged

In Notch signaling, ligand binding triggers an extracellular cleavage removing most of Notch’s ectodomain. Which protease family mediates this step?
A. ADAM proteases
B. Caspases
C. Cathepsins
D. Matrix metalloproteinases

After ADAM cleavage, which enzyme cleaves the remaining Notch segment to release NICD?
A. Proteasome
B. Calpain
C. γ-secretase
D. Phospholipase C

NICD (or notch intracellular domain) ultimately activates which transcription factor to initiate new transcription?
A. CREB
B. CSL
C. STAT
D. AP-1

Notch-driven CSL activation is most associated with:
A. Glycolysis regulation and embryonic development
B. Phototransduction and embryonic development
C. Steroidogenesis and embryonic development
D. Neurogenesis and embryonic development

Serpentine (GPCR) receptors can be desensitized by which set?
A. Phosphorylation, internalization, degradation
B. Dimerization, autophosphorylation, ubiquitination
C. Ligand cleavage, receptor splicing, export
D. Methylation, acetylation, SUMOylation

G-proteins terminate their own signals primarily by:
A. Cleaving PIP2
B. Opening CFTR
C. Hydrolyzing GTP
D. Importing Ca2+

GAPS most directly act by:
A. Blocking receptor phosphorylation
B. Accelerating GTP hydrolysis
C. Synthesizing new G-proteins
D. Exchanging GDP for GTP

A patient with heavy alcohol use develops hepatic steatosis. A toxic acetaldehyde effect is inhibition of:
A. Actin polymerization
B. DNA replication
C. Ribosomal translocation
D. Tubulin polymerization

This acetaldehyde effect decreases hepatic production of:
A. VLDLs
B. Chylomicrons
C. HDL
D. Albumin

The hepatic consequence most directly described is:
A. Cholestatic jaundice
B. Portal hypertension
C. Fatty liver disease
D. Hepatocellular carcinoma

In neutrophils, urate promotes pain in gout by driving conversion of arachidonic acid into:
A. Prostaglandin E2
B. Leukotriene B4
C. Thromboxane A2
D. Prostacyclin

Cholera toxin A causes secretory diarrhea by ADP-ribosylating which G-protein subunit?
A. Gαs
B. Gαi
C. Gαq
D. Gα12/13

In intestinal epithelia, phosphorylation of CFTR:
A. Closes the channel
B. Opens the channel
C. Degrades the channel
D. Internalizes the channel

CFTR is a member of which transport superfamily?
A. SLC
B. P-type ATPase
C. ABC
D. GLUT

Which statement best matches guanylyl cyclase signaling?
A. Cytoplasmic, no G-protein needed
B. Membrane, requires G-protein activation
C. Nuclear, requires STAT dimerization
D. Lysosomal, requires acidic pH

Elevated cGMP most directly activates:
A. Protein kinase A
B. Protein kinase C
C. Protein kinase B
D. Protein kinase G

A patient with exertional angina is treated with a drug that decomposes to NO and activates guanylyl cyclase. Which drug fits?
A. Nesiritide
B. Glycerol trinitrate
C. Sildenafil
D. Epinephrine

A decompensated heart failure patient receives a β-natriuretic peptide ligand that activates a guanylyl cyclase receptor. Which drug fits?
A. Glycerol trinitrate
B. Verapamil
C. Nesiritide
D. Dobutamine

A patient with erectile dysfunction is prescribed a drug that increases cGMP by blocking its breakdown. Which mechanism fits?
A. Stimulates adenylyl cyclase
B. Activates phospholipase Cβ
C. Activates guanylyl cyclase
D. Inhibits cGMP phosphodiesterase