Membrane Basics
What is the main function of the cell membrane?
To control what enters and exits the cell (selective permeability).
100: Which parts of a phospholipid are hydrophilic and hydrophobic?
The phosphate head is hydrophilic, and the fatty acid tails are hydrophobic.
100: What are the two main types of membrane proteins?
Integral and peripheral proteins.
100: What is passive transport?
🟰 Movement of substances across the membrane without energy (down a concentration gradient).
100: What is endocytosis?
🟰 The process of taking materials into the cell by engulfing them in a vesicle.
What type of molecule primarily makes up the cell membrane?
Phospholipids
200: What structure is formed by phospholipids in water- when they are submerged/surrounded by water and contain water?
A phospholipid bilayer
200: What is the role of channel proteins?
To allow specific molecules or ions to pass through the membrane
200: Name two types of passive transport.
🟰 Simple diffusion and facilitated diffusion.
200: What is exocytosis?
🟰 The release of substances from a cell via vesicles fusing with the membrane.
What does "fluid mosaic model" mean in terms of the cell membrane?
It describes the membrane as flexible (fluid) with various proteins and molecules embedded in or attached to it (mosaic).
300: Why do the phospholipids form a bilayer in aqueous environments?
Hydrophilic heads face water; hydrophobic tails face inward, away from water.
300: What is the role of glycoproteins in the membrane?
Cell recognition and communication
300: What is osmosis?
🟰 The diffusion of water through a selectively permeable membrane.
300: What is the function of cholesterol in animal cell membranes?
🟰 It stabilizes membrane fluidity at various temperatures.
What is the name of the protein that spans the membrane and helps move substances across?
Integral or transmembrane protein.
400: What would happen if phospholipids did not have both hydrophilic and hydrophobic regions?
They would not form a stable bilayer and the membrane wouldn’t function properly.
400: How do carrier proteins differ from channel proteins?
Carrier proteins change shape to move substances across; channels form pores
400: What is active transport and what does it require?
🟰 Movement against the concentration gradient using ATP and carrier proteins.
400: Compare pinocytosis and phagocytosis.
Pinocytosis takes in liquid; phagocytosis takes in large particles.
Describe two roles of the cell membrane in cell communication.
Contains receptor proteins for signaling molecules and allows cell recognition via glycoproteins.
Explain how the amphipathic nature of phospholipids contributes to membrane fluidity.
The flexible interaction between heads and tails and lack of strong bonds allows movement within the layer.
What is the function of adhesion proteins in the cell membrane?
They help cells stick to each other and to the extracellular matrix, maintaining tissue structure and enabling communication.
500: Explain the role of sodium-potassium pumps in active transport.
🟰 They move 3 Na⁺ out and 2 K⁺ into the cell against their gradients using ATP.
500: Describe the role of vesicles in protein secretion.
Vesicles transport proteins from the rough ER to the Golgi and then to the membrane for exocytosis.