22 Questions
What is the role of the ER in regulating cellular activities?
Regulating cytosolic concentrations of calcium
How do membranous organelles exchange membrane molecules?
Through both lateral diffusion and transport vesicles
What is the primary function of the retrograde pathway?
Recycling membrane molecules dispersed by transport processes
Which of the following is NOT a part of the endomembrane system?
Cytosol
What is the primary function of the anterograde pathway?
Delivering newly synthesized molecules to their destination
Which of the following is a function of the ER?
All of the above
What is the function of aquaporins in the plasma membrane?
To conduct water
What type of proteins are often involved in cell wall interactions and synthesis?
Integral proteins
What is the main function of the endoplasmic reticulum (ER) in plants?
To synthesize, process, and sort proteins
What is the name of the strands that form between the protoplast and cell wall during cold acclimation?
Hechtian strands
What type of proteins are involved in transmembrane activities and are often glycosylated?
Integral proteins
What is the function of the nuclear envelope in relation to the ER?
To connect to the ER
What is the result of increasing the number of Hechtian strands during cold acclimation?
Protection of protoplasts from freeze-induced dehydration
What is the function of the ER in lipid synthesis?
To synthesize lipids
What are the two basic types of membrane proteins according to the original fluid‐mosaic membrane model?
Peripheral and Integral
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
What type of connections do adjacent plant cells have?
Plasmodesmata
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
What is the function of plasmodesmata?
To provide direct channels of communication between adjacent cells
What type of membrane proteins are attached to the bilayer by lipid tails?
Fatty acid-linked, prenyl group-linked, and phosphatidylinositol-anchored
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
What type of connections do adjacent animal cells have?
Gap junctions
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.
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.
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