Week 11 / Cell Structure Lecture Flashcards
What are the major structural components of the plasma membrane (cell membrane)? [4]
Phospholipid bilayer
Cholesterol
Proteins (integral and peripheral)
Attached carbohydrates (glycolipids and glycoproteins)
What are the main functions of the plasma membrane? [4]
Acts as a barrier between the inside and outside of the cell
Controls the entry of materials (transport)
Receives chemical and mechanical signals
Transmits signals between intracellular and extracellular spaces
What are phospholipids described as?
What do they form ?
How is the polar region oriented ?
Phospholipids are amphipathic.
- They form a bilayer with nonpolar fatty acid chains in the middle.
- The polar regions are oriented toward the surfaces of the membrane, attracted to the polar water molecules in the extracellular fluid and cytosol.
What are the characteristics of the phospholipid structure in the plasma membrane?
- Fatty acid tails are hydrophobic.
- The phosphate group head is hydrophilic.
Where can cholesterol be found?[1]
What does cholesterol form and how ?
What is the role of the thing formed ?
- The extracellular plasma membrane contains cholesterol, while intracellular membranes have very little.
- Cholesterol associates with specific phospholipids and proteins to form clusters.
- These clusters help pinch off portions of the membrane to form vesicles that transport contents to intracellular organelles.
What is cholesterol described as ?
Which group is polar ?
What does the polar group do ?
Which group is non-polar ?
What does the non-polar group do ?
- Cholesterol molecules are weakly amphipathic.
- The —OH group is the only polar region, forming hydrogen bonds with the polar heads of phospholipids and glycolipids.
- The stiff steroid rings and hydrocarbon tail are nonpolar
-fitting among the fatty acid tails of phospholipids and glycolipids.
How does cholesterol affect membrane fluidity in different temperatures?
- At warm temperatures, cholesterol restrains phospholipid movement, reducing fluidity.
- At cold temperatures, cholesterol maintains fluidity by preventing tight packing of phospholipids.
What is the structure of glycolipids ?
Where are they found?
What do they contribute to?
- The carbohydrate groups form a polar “head,” while the fatty acid “tails” are nonpolar.
- Glycolipids are found only in the membrane layer facing the extracellular fluid,
-contributing to the asymmetry of the bilayer.
What are the integral membrane proteins associated with ?
What happens if they are extracted?
What can they described as ?
What do Integral proteins span the entire membrane called , What do they cross?
What are the functions of integral membrane proteins (what do they form , transmit)? [1]
- Integral proteins are closely associated with membrane lipids
-cannot be extracted without disrupting the lipid bilayer.
-They are amphipathic.
- Most integral proteins span the entire membrane and are called transmembrane proteins.
Many transmembrane proteins cross the lipid bilayer multiple times. - Some form channels for ions or water, while others transmit chemical signals or anchor extracellular and intracellular protein filaments to the plasma membrane.
What are peripheral membrane proteins described as ?
Do they associate with non-polar regions ?
Where are they located , Where do they bind to ?
- Peripheral membrane proteins are not amphipathic
-do not associate with the nonpolar regions of the membrane lipids.
- They are located at the membrane surface, where they bind to the polar regions of integral membrane proteins.
what are the roles of glycocalyx in the plasma membrane? [1]
What do the carbohydrate parts of the glycolipids and glycoprotein form?[1]
What are many membrane proteins ,
What are attached to “ proteins “ ,and where are attached things facing
?[1]
- The glycocalyx acts like a molecular “signature,” enabling cells to recognize one another.
- The carbohydrate portions of glycolipids and glycoproteins form a sugary coat called the glycocalyx.
- Many membrane proteins are glycoproteins, which have carbohydrate groups attached to their ends that protrude into the extracellular fluid.
“What are the 2 main classifications and types of plasma membrane proteins, and what are their key functions?”
-The two main classifications of membrane proteins by position and by function
The types of proteins under each classification (e.g., integral, peripheral, anchoring, recognition, enzymes, receptor, carrier, and channel proteins)
The specific functions of each protein type (e.g., structural components, attaching membranes, identifying cells, catalyzing reactions, binding ligands, moving solutes, etc.)
What are cells joined by?
What are the types of cell junctions ?
What are integrins ,
what are their roles the role of integrins in the plasma membrane?
- Cells are physically joined by junctions:
desmosomes, tight junctions, and gap junctions.
- Integrins are transmembrane proteins that bind to specific proteins in the extracellular matrix and link them to membrane proteins on adjacent cells.
What are desmosomes characterised by?
Where are desmosomes located ?
What purpose do desmosomes serve as ?
What are the function of desmosomes ?
What do cadherins do ?
- Desmosomes are characterized by dense plaques of protein
- on the cytoplasmic surface of the plasma membrane
-serving as anchoring points for cadherins.
-Desmosomes hold adjacent cells firmly together, particularly in areas subjected to considerable stretching, such as the skin.
- Cadherins extend from the cell into the extracellular space, linking and binding with cadherins from adjacent cells.
How do tight junctions in cell membranes form?
Whats the difference between desmosomes and tight junctions
(shape)?
- Tight junctions form when the extracellular surfaces of two adjacent plasma membranes join together, leaving no extracellular space between them.
- Unlike desmosomes, which are limited to a disk-shaped area, tight junctions occur in a band around the entire circumference of the cell.
