Exam 2 study guide (simplified)

What organelles make up the endomembrane system?

ER, Golgi, endosomes, lysosomes, vesicles, plasma membrane.

Rough ER is specialized for what?

Protein synthesis/processing.

What are the four major processes of Smooth ER?

Drug detoxification, carbohydrate metabolism, calcium storage, steroid biosynthesis.

What organelle modifies and sorts proteins after ER processing?

Golgi apparatus.

What is the cis face of the Golgi oriented toward?

ER.

What is the trans face of the Golgi responsible for?

Final sorting and trafficking.

Lysosomes maintain what type of internal environment?

Acidic.

Lysosomes primarily function in what process?

Macromolecule degradation.

What is anterograde transport?

ER → Golgi → plasma membrane.

What is retrograde transport?

Golgi → ER.

COPII vesicles mediate what transport direction?

ER → Golgi.

COPI vesicles mediate what transport direction?

Golgi → ER.

Clathrin-coated vesicles are most associated with what processes?

Endocytosis and TGN trafficking.

A defective COPII protein would MOST likely cause accumulation of proteins in what organelle?

ER.

Why do cells use distinct vesicle coats?

Maintain compartmentalization and trafficking specificity.

What recognizes ER signal sequences?

SRP (signal recognition particle).

SRP brings ribosomes to what structure?

ER translocon/Sec61.

Secreted proteins are synthesized on what type of ER?

Rough ER.

What happens if SRP cannot bind signal sequences?

Secretory proteins remain in cytosol.

What does a stop-transfer sequence do?

Anchors protein in membrane.

Internal start-transfer sequences are used by what proteins?

Membrane proteins lacking N-terminal signal sequence.

What is the function of KDEL tags?

Retrieval of ER proteins from Golgi.

Mannose-6-phosphate targets proteins to what organelle?

Lysosome.

KDEL and M6P are similar because they both what?

Bind receptors for trafficking/sorting.

Constitutive secretion occurs how?

Continuous/unregulated.

Regulated secretion requires what?

External signal.

Neurotransmitter release is what type of secretion?

Regulated secretion.

Receptor-mediated endocytosis uses what coat protein?

Clathrin.

What proteins help form clathrin-coated pits?

Clathrin, adaptor proteins, dynamin.

Dynamin functions in what step?

Vesicle pinching/scission.

Phagocytosis internalizes what?

Solid particles.

Pinocytosis internalizes what?

Liquids.

v-SNAREs are located where?

Vesicle membrane.

t-SNAREs are located where?

Target membrane.

Rab GTPases function in what process?

Vesicle targeting/tethering.

NSF and SNAPs function in what?

SNARE complex disassembly.

A protein lacks an ER signal sequence. Where will it remain?

Cytosol.

A protein is constitutively secreted. What vesicles must it pass through?

Anterograde vesicles.

If retrograde transport failed, what proteins would be affected?

KDEL-tagged ER proteins.

Neurons do what?

Transmit electrical signals.

Glial cells function mainly in what?

Support/protection.

Which cells form CNS myelin?

Oligodendrocytes.

Which cells form PNS myelin?

Schwann cells.

Resting membrane potential is normally positive or negative?

Negative.

K⁺ concentration is highest where?

Inside cell.

Na⁺ concentration is highest where?

Outside cell.

The Na⁺/K⁺ pump moves how many Na⁺ out and K⁺ in?

3 Na⁺ out, 2 K⁺ in.

Depolarization is mainly caused by movement of what ion?

Na⁺ influx.

Repolarization is mainly caused by movement of what ion?

K⁺ efflux.

Hyperpolarization occurs because what permeability remains high?

K⁺ permeability.

Voltage-gated Na⁺ channels are responsible for what phase?

Depolarization.

Voltage-gated K⁺ channels are responsible for what phase?

Repolarization.

During absolute refractory period, Na⁺ channels are what?

Inactivated.

Why can APs only move one direction?

Refractory periods.

Saltatory conduction occurs in what type of axons?

Myelinated axons.

APs "jump" between what structures?

Nodes of Ranvier.

Neurotransmitters are released from what structure?

Synaptic bouton.

Neurotransmitter release is triggered by influx of what ion?

Ca²⁺.

Synaptotagmin binds what ion?

Ca²⁺.

GABA is excitatory or inhibitory?

Inhibitory.

Glutamate is excitatory or inhibitory?

Excitatory.

Increased Cl⁻ permeability causes what effect?

Hyperpolarization/decreased excitability.

Blocking voltage-gated Na⁺ channels would impair what?

Action potential propagation.

Preventing Na⁺ channel inactivation would cause what?

Prolonged depolarization.

What distance does endocrine signaling act over?

Long range.

What distance does paracrine signaling act over?

Short range.

What cell does autocrine signaling affect?

Same cell producing signal.

How many transmembrane helices do GPCRs contain?

Seven.

What are G proteins active when bound to?

GTP.

What are G proteins inactive when bound to?

GDP.

What enzyme does Gs activate?

Adenylyl cyclase.

What second messenger does adenylyl cyclase produce?

cAMP.

What kinase does cAMP activate?

PKA.

What lipid does PLC cleave?

PIP2.

What two second messengers does PLC generate?

IP3 and DAG.

What ion does IP3 stimulate release of from the ER?

Ca²⁺.

What kinase do DAG and Ca²⁺ activate?

PKC.

What amino acid do RTKs phosphorylate?

Tyrosine.

How do RTKs activate?

Dimerization/autophosphorylation.

What is Ras active when bound to?

GTP.

What kinase cascade does Ras activate?

MAPK cascade.

What would a mutation preventing GTP hydrolysis by Gα cause?

Constitutive signaling.

What second messenger decreases when blocking adenylyl cyclase?

cAMP.

What second messengers decrease when blocking PLC?

IP3 and DAG.

What are the three major cytoskeletal systems?

Microtubules, microfilaments, intermediate filaments.

What proteins are MT subunits composed of?

α/β-tubulin heterodimers.

What nucleotide is required for MT assembly?

GTP.

Which MT end grows faster?

Plus end.

What is treadmilling?

Addition at plus end/removal at minus end.

What is dynamic instability?

Alternating growth/shrinkage.

What is the MT shrinkage phase called?

Catastrophe.

What is the return to growth phase called?

Rescue.

What functions in MT nucleation?

γ-tubulin.

What type of structure are centrosomes?

MTOCs.

What does colchicine do?

Prevents MT assembly.

What does taxol do?

Stabilizes MTs.

What MT end do kinesins move toward?

Plus end.

What MT end do dyneins move toward?

Minus end.

What direction does kinesin mediate axonal transport?

Anterograde.

What direction does dynein mediate axonal transport?

Retrograde.