Cell Biology: Endoplasmic Reticulum and Endomembrane System

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Questions and Answers

What is the role of the ER in regulating cellular activities?

Regulating cytosolic concentrations of calcium (correct)

Regulating cytosolic concentrations of sodium

Regulating cytosolic concentrations of magnesium

Regulating cytosolic concentrations of potassium

How do membranous organelles exchange membrane molecules?

Through both lateral diffusion and transport vesicles (correct)

Neither through lateral diffusion nor transport vesicles

Only through transport vesicles

Only through lateral diffusion

What is the primary function of the retrograde pathway?

Delivering newly synthesized molecules to their destination

Synthesizing new molecules

Recycling membrane molecules dispersed by transport processes (correct)

Breaking down old molecules

Which of the following is NOT a part of the endomembrane system?

Cytosol Signup and view all the answers

What is the primary function of the anterograde pathway?

Delivering newly synthesized molecules to their destination Signup and view all the answers

Which of the following is a function of the ER?

All of the above Signup and view all the answers

What is the function of aquaporins in the plasma membrane?

To conduct water Signup and view all the answers

What type of proteins are often involved in cell wall interactions and synthesis?

Integral proteins Signup and view all the answers

What is the main function of the endoplasmic reticulum (ER) in plants?

To synthesize, process, and sort proteins Signup and view all the answers

What is the name of the strands that form between the protoplast and cell wall during cold acclimation?

Hechtian strands Signup and view all the answers

What type of proteins are involved in transmembrane activities and are often glycosylated?

Integral proteins Signup and view all the answers

What is the function of the nuclear envelope in relation to the ER?

To connect to the ER Signup and view all the answers

What is the result of increasing the number of Hechtian strands during cold acclimation?

Protection of protoplasts from freeze-induced dehydration Signup and view all the answers

What is the function of the ER in lipid synthesis?

To synthesize lipids Signup and view all the answers

What are the two basic types of membrane proteins according to the original fluid‐mosaic membrane model?

Peripheral and Integral Signup and view all the answers

What is the function of the plasma membrane in terms of molecule transport?

It controls the transport of molecules into and out of the cell Signup and view all the answers

What type of connections do adjacent plant cells have?

Plasmodesmata Signup and view all the answers

What is the difference in pressure between plant and animal cells?

Plant cells are under turgor pressure, animal cells are iso-osmotic with their environments Signup and view all the answers

What is the function of plasmodesmata?

To provide direct channels of communication between adjacent cells Signup and view all the answers

What type of membrane proteins are attached to the bilayer by lipid tails?

Fatty acid-linked, prenyl group-linked, and phosphatidylinositol-anchored Signup and view all the answers

What is the function of the plasma membrane in terms of cell wall molecules?

It participates in the synthesis and assembly of cell wall molecules Signup and view all the answers

What type of connections do adjacent animal cells have?

Gap junctions Signup and view all the answers

Study Notes

Cellular Compartments

The endoplasmic reticulum (ER) plays a critical role in regulating cytosolic calcium concentrations, which influence many cellular activities.
The ER gives rise to the endomembrane system, which includes membranous organelles that exchange molecules through lateral diffusion or transport vesicles.

Endomembrane System

The endomembrane system consists of membranous organelles that exchange membrane molecules through lateral diffusion or transport vesicles.
The principal membrane systems connected in this manner include the nuclear envelope, ER, Golgi, trans-Golgi network, multivesicular body, plasma membrane, vacuole, and transport/secretory vesicles.

Membrane Traffic

All membranes of the endomembrane system are connected by anterograde (forward) and retrograde (backward) traffic.
The anterograde pathway delivers newly synthesized molecules to their destination, while the retrograde pathway recycles membrane molecules to their site of origin.

Plasma Membrane

The plasma membrane forms the outermost boundary of the living cell and functions as an active interface between the cell and its environment.
Plasma membrane proteins serve a variety of functions, including transporters, signal receptors, and proteins involved in cell wall interactions and synthesis.
Most plasma membrane proteins involved in these transmembrane activities are of the integral type, often forming larger complexes with peripheral proteins.

Hechtian Strands

Hechtian strands are specialized structures that increase in number during cold acclimation, suggesting that they help protect protoplasts from freeze-induced dehydration.

Endoplasmic Reticulum (ER)

The ER is the most extensive, versatile, and adaptable organelle in eukaryotic cells, consisting of a 3D network of continuous tubules and flattened sacs.
In plants, the principal functions of ER include synthesizing, processing, and sorting proteins targeted to membranes, vacuoles, or the secretory pathway.

Membrane Proteins

Membrane proteins associate with lipid bilayers in many different ways, including peripheral and integral proteins, as well as fatty acid-linked, prenyl group-linked, and phosphatidylinositol-anchored proteins.

Plasmodesmata

Plasmodesmata are membrane tubes that cross cell walls and provide direct channels of communication between adjacent cells, forming a physically continuous plasma membrane.
In contrast, animal cells have separate plasma membranes and communicate through protein channels known as gap junctions.

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Description

Learn about the role of Endoplasmic Reticulum (ER) in regulating cytosolic calcium concentrations and its relationship with the endomembrane system, including membranous organelles and transport vesicles.