3.2 Biological Membranes Flashcards
What are the four main functions of the cell membrane?
1) Physical isolation
2) Regulation of exchange
3) Communication
4) Structural support
What are the two biological meanings of “membrane?
Tissue membranes, thin, translucent layers of cells lining cavities, and cell membranes, phospholipid-protein boundary separating intracellular fluid from the external environment
How does the cell membrane achieve physical isolation?
By separating the intracellular fluid from the extracellular fluid.
How does the cell membrane regulate exchange?
By controlling the entry of ions/nutrients, elimination of wastes, and release of products.
How does the cell membrane facilitate communication?
it contains proteins for cell recognition and response to environmental changes.
How does the cell membrane provide structural support?
Membrane proteins maintain cell shape and stabilize tissue structure through cell-cell and cell-matrix junctions.
What are the main components of biological membranes?
Lipids, proteins, and a small amount of carbohydrates.
Describe the structure of the phospholipid bilayer in cell membranes
It has hydrophilic heads on the surface and hydrophobic tails inside.
What is the function of cholesterol in the cell membrane?
Cholesterol inserts between phospholipids, making the membrane impermeable to small water-soluble molecules and maintaining flexibility.
What are the three main types of lipids in membranes?
Phospholipids, sphingolipids, and cholesterol.
What is the structure of a phospholipid?
A glycerol backbone, two hydrophobic fatty acid tails, and a hydrophilic phosphate group.
What characterizes transmembrane proteins?
They span the entire membrane and have nonpolar segments interacting with lipid tails.
What are integral proteins, and what do they include?
Proteins tightly bound to the membrane, including transmembrane proteins and lipid-anchored proteins.
How do sphingolipids differ from phospholipids?
Sphingolipids have longer tails and can be either phospholipids or glycolipids.
What are peripheral proteins, and how are they attached?
Proteins loosely attached to other membrane proteins, separable without disrupting membrane integrity.
What are lipid rafts, and why are they important?
Specialized patches formed by sphingolipids and cholesterol, crucial for membrane structure and function.
What forms the glycocalyx on the cell’s external surface?
Carbohydrates attached to proteins (glycoproteins) and lipids (glycolipids).
What role do glycoproteins play in the immune system?
They are key in immune responses, such as determining ABO blood groups.
Why does the phospholipid bilayer form in membranes?
Due to the amphipathic nature of phospholipids, creating a hydrophobic barrier.
What does a substance pass through when crossing into a cell?
It passes through two phospholipid bilayers.
