Lecture Review: Cell Biology - Endomembrane System and Signal Transduction

These flashcards cover key concepts and mechanisms related to the endomembrane system, signal transduction, and cellular signaling, useful for exam preparation in cell biology.

What are the components of the endomembrane system?

Smooth ER, Rough ER, Golgi apparatus, peroxisomes, endosomes, lysosomes, and occasionally the nuclear envelope.

What is the main role of the Golgi apparatus?

Modification, sorting, and packaging of proteins and lipids for secretion or delivery.

Why are mitochondria and chloroplasts not considered part of the endomembrane system?

They originated from symbiotic bacteria and are isolated.

What is the function of the nuclear localization signal (NLS)?

It is recognized by import receptors (importins) to facilitate transport of proteins into the nucleus.

What is the purpose of GTP in nuclear transport?

GTP hydrolysis provides the energy for the nuclear transport process.

What happens to the NLS during importin binding?

Importin can bind to nuclear cargo only when it is not bound by Ran.

What are the key differences between Ran GEF and Ran GAP?

Ran GEF exchanges GDP for GTP, increasing Ran's affinity for importin; Ran GAP accelerates GTP hydrolysis to GDP, decreasing affinity for importin.

During translation in the ER, what happens to the ER signal sequence?

It is cleaved off, making mature soluble proteins in the ER lumen shorter than those synthesized in the cytosol.

What are the three main mechanisms by which proteins are transported into organelles?

Through nuclear pores, protein translocators, and transport vesicles.

What is the initial site of glycosylation in the secretory pathway?

The Endoplasmic Reticulum (ER).

What type of feedback occurs when a downstream protein activates an upstream protein?

Positive feedback.

What types of cells respond to the same signal differently due to different receptors?

Cells can respond differently depending on the expression of distinct genes and proteins.

What is the effect of estrogen binding to intracellular estrogen receptors?

It affects gene expression, leading to a slower response due to transcription and translation processes.

What are the three classes of cell-surface receptors?

Ion channel-coupled receptors, G-protein coupled receptors, and enzyme-coupled receptors.

How many transmembrane domains do GPCRs have?

GPCRs have 7 transmembrane domains.