Lesson 1: Membrane and ER Flashcards
What is the main function of the plasma membrane?
The plasma membrane separates the cell’s interior from the external environment and regulates molecule import, export, movement, and communication.
What is the basic structure of the plasma membrane?
A phospholipid bilayer with embedded proteins, cholesterol, and glycolipids/glycoproteins.
Name the four key properties of the plasma membrane.
- Maintains structural integrity
- Movement and expansion
- Import and export of molecules
- Receives and transmits information
What components make up the plasma membrane?
Phospholipids (30-40%), proteins (40-50%), cholesterol, and glycolipids/glycoproteins.
What is the role of phospholipids in the membrane?
They form the bilayer, with a hydrophilic head and hydrophobic tails, creating a selective barrier.
What are the two types of phospholipids in the membrane?
Phosphoglycerides (based on glycerol)
sphingolipids (based on sphingosine). - interact more with other phospholipids and the outside environment -> more hydrophilic interactions
What is the role of cholesterol in the plasma membrane?
Cholesterol is a steroid molecule
binds between hydrophobic and hydrophilic part of phospholipid
decreases membrane deformability and permeability while preventing fatty acid crystallization.
What is the glycocalyx, and what is its function?
A glycoprotein and glycolipid layer outside the cell that acts as a protective barrier and aids in cell recognition.
How is membrane fluidity regulated?
By factors such as temperature, fatty acid chain length, protein content, cholesterol, and unsaturation of fatty acids.
What is the asymmetry of the plasma membrane?
Different lipids and proteins are distributed unevenly between the inner and outer layers of the bilayer.
What are the two types of membrane proteins?
Integral (transmembrane) proteins and peripheral (extrinsic) proteins.
Name four functions of membrane proteins.
Transport, cell signaling, adhesion, and enzymatic activity.
How do integral proteins differ from peripheral proteins?
Integral proteins span the membrane, while peripheral proteins are attached to the membrane’s surface.
What is the role of glycoproteins in the plasma membrane?
They participate in cell-cell recognition and adhesion.
What are lipid rafts, and why are they important?
Microdomains rich in cholesterol and sphingolipids, organizing receptors for signal transduction.
Groups of multiple receptors
signal transfer to intracellular environment
What are the three main types of transport across the membrane?
Passive transport, active transport, and vesicular transport.
What is simple diffusion, and what molecules use it?
Movement of small, non-polar molecules (e.g., O₂, CO₂) across the membrane without energy. Very small molecules
How does facilitated diffusion differ from simple diffusion?
It uses protein channels or carriers to move molecules like glucose and ions across the membrane. NO NRG
Required in some special epithelium like the kidneys to regulate H2O diffusion
What is active transport, and what does it require?
Movement of molecules against the concentration gradient using ATP
important for depolarization of cell membrane in neurons to generate electric impulses
What is the main function of the RER?
Protein synthesis and folding.
What is the primary function of the SER?
Lipid synthesis
steroid production (gonads and adrenal gland)
detoxification
ion storage
biogenesis of cell membranes
glycogen metabolism (catabolism of hepatic glycogen)
What type of cells have abundant RER?
Cells with high protein production, like plasma cells and pancreatic cells.
What is a unique function of SER in muscle cells?
It functions as the sarcoplasmic reticulum, regulating calcium storage and release.
How does the ER contribute to protein modification?
Proteins undergo glycosylation (50%), disulfide bond formation, and folding in the RER.
