Unit 2: Topic 4 - Plasma Membranes Flashcards
In the cell membrane, there are hydrophobic and hydrophilic regions; what component of the membrane is responsible for these regions?
Phospholipids are responsible for the hydrophobic and hydrophilic regions of the membrane.
What is the orientation of phospholipids in the cell membrane, and how does this contribute to the separation of the extracellular and intracellular regions?
The hydrophilic (polar) phosphate heads are oriented toward the aqueous extracellular/intracellular environments, while the hydrophobic (nonpolar) fatty acid tails face each other within the interior of the phospholipid bilayer. A feature of the phospholipid bilayer is its selective permeability, establishing two separate (intracellular and extracellular) environments. This is due to the orientation of the phospholipids. Certain molecules cannot cross phospholipid bilayers, such as most polar molecules, ions, and large molecules (without assistance). While polar molecules can interact with the polar phospholipid heads of the cell membrane, these molecules cannot cross or diffuse through the cell membrane because the nonpolar hydrophobic phospholipid tails repel them. Contrarily, most nonpolar molecules can cross the cell membrane with assistance or due to their small size.
What are phospholipids made up of?
An individual phospholipid consists of two hydrophobic fatty acid tails and a single hydrophilic head composed of phosphate and glycerol.
What is the purpose of hydrophilic and hydrophobic side groups in embedded proteins?
Many functions of embedded proteins rely on hydrophobic and hydrophilic side groups. One such embedded protein, the channel protein, can transport polar molecules across the cell membrane. When transporting polar molecules, the inner passageway is lined with hydrophilic side groups, which is the source of this hydrophilic environment. Embedded proteins, including the channel protein, have hydrophobic side groups where they interact with hydrophobic tails and hydrophilic side groups where they interact with the intracellular and extracellular regions. Hydrophobic side groups interacting with hydrophobic tails within the cell membrane cause the protein to be anchored in the cell membrane by London dispersion forces.
What components make up a fluid mosaic model of a cell membrane, and what are their functions?
A fluid mosaic model of a cell membrane includes phospholipids embedded with steroids, glycolipids, and glycoproteins. The phospholipid bilayer makes up most of the fluid mosaic model/cell membrane. Steroids, which are lipids, create a more rigid and impermeable membrane (however, the membrane is still fluid) and function by creating nonpolar interactions with the tails of phospholipids when embedded in the plasma membrane. Cholesterol is an example of one such steroid in eukaryotes. Membrane carbohydrates are linked to proteins called glycoproteins and to lipids called glycolipids. Both aid in cell recognition. Within the membrane, proteins flow around the cell’s surface. The flow of such molecules explains the reasoning behind the name “Fluid Mosaic Model.”
