W3 Membrane Structure and Function Flashcards
Describe the primary function of the CFTR protein in epithelial cells:
The CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) protein functions as a chloride channel in epithelial cells. It allows chloride ions to move across the cell membrane, which is crucial for maintaining the balance of salt and water on epithelial surfaces, such as those in the lungs and sweat glands
What structural features are present in the CFTR protein?
The CFTR protein is characterized by:
Secondary Structures: It has 12 alpha helices that span the membrane
Functional Role: These helices form a channel through which chloride ions can pass.
Explain the impact of the defective CFTR protein on chloride ion transport and its consequences for patients with cystic fibrosis
In cystic fibrosis, the defective CFTR protein impairs chloride ion transport, leading to reduced secretion of chloride and sodium. This disruption causes thick, sticky mucus to accumulate in organs such as the lungs and pancreas, leading to respiratory infections, inflammation, and digestive issues
What are the main mutations associated with cystic fibrosis, and how do they affect the CFTR protein’s function?
There are over 2000 mutations in the CFTR gene, with the most common being the delta-F508 mutation. This mutation results in the deletion of a phenylalanine residue at position 508, causing improper folding of the CFTR protein. The misfolded protein is not properly transported to the cell surface, leading to defective chloride ion channel activity
What is the significance of the delta-F508 mutation in CF patients?
The delta-F508 mutation is the most prevalent mutation in cystic fibrosis, present in approximately 70% of CF patients. It leads to a defective CFTR protein that fails to reach the cell membrane, resulting in a significant reduction in chloride transport and the characteristic symptoms of cystic fibrosis
How do the treatments Trikafta / Kaftrio work to manage cystic fibrosis?
Trikafta (also known as Kaftrio) contains two correctors (elexacaftor and tezacaftor) and one potentiator (ivacaftor).
Correctors: These compounds help the CFTR protein fold properly and reach the cell surface.
Potentiators: They bind to the CFTR protein and increase the channel’s ability to open and allow chloride ions to pass through, improving chloride transport.
What is the difference between saturated and unsaturated fatty acids in terms of membrane fluidity?
Saturated fatty acids have no double bonds and are straight, leading to tighter packing and reduced membrane fluidity. Unsaturated fatty acids have one or more double bonds, creating kinks that prevent tight packing, thereby increasing membrane fluidity
What are the 3 key components of the plasma membrane, and what roles do they play?
The plasma membrane is composed of:
- Phospholipids: Form the lipid bilayer, providing a semi-permeable barrier.
- Proteins: Embedded in or associated with the membrane, facilitating various functions such as transport, signaling, and structural support.
- Carbohydrates: Attached to proteins (glycoproteins) and lipids (glycolipids), involved in cell recognition and protection
Explain the fluid mosaic model of membrane structure:
The fluid mosaic model describes the plasma membrane as a dynamic and flexible structure with a fluid lipid bilayer in which proteins are embedded and can move laterally. This model emphasizes the diversity of membrane proteins and the fluid nature of the lipid bilayer, allowing proteins and lipids to diffuse freely within the membrane
How does cholesterol affect membrane fluidity?
Cholesterol stabilizes the membrane by filling the gaps between phospholipids. At high temperatures, it reduces fluidity by making the membrane less permeable. At low temperatures, it prevents the membrane from becoming too solid by disrupting the packing of phospholipids.
Differentiate between peripheral and integral membrane proteins
Peripheral Proteins: These are attached to the membrane surface and interact with membrane lipids or other proteins. They do not penetrate the lipid bilayer
Integral Proteins: These span the entire lipid bilayer (transmembrane) and have hydrophobic regions that interact with the interior of the membrane, as well as hydrophilic regions that interact with the aqueous environments inside and outside the cell
Describe the function and significance of membrane carbohydrates, including glycolipids and glycoproteins
Membrane carbohydrates, found as glycolipids and glycoproteins, are involved in cell recognition, adhesion, and protection. They form the glycocalyx, which helps protect the cell surface and participate in cell-cell interactions.
What is passive transport, and how does it differ from active transport?
Passive transport is the movement of ions or molecules across a membrane down their concentration gradient without the need for energy. Active transport requires energy (usually from ATP) to move ions or molecules against their concentration gradient
Explain the roles of channel proteins and carrier proteins in membrane transport:
Channel Proteins: Form pores in the membrane that allow specific ions or molecules to pass through by diffusion. They are typically selective for particular substances
Carrier Proteins: Bind to specific molecules and undergo conformational changes to transport the molecules across the membrane. They can be involved in both facilitated diffusion and active transport
Define and distinguish between uniporters, symporters, and antiporters:
- Uniporters: Transport a single type of molecule in one direction (e.g., glucose transporter).
- Symporters: Transport two or more types of molecules simultaneously in the same direction (e.g., sodium-glucose symporter).
- Antiporters: Transport two or more types of molecules simultaneously in opposite directions (e.g., sodium-potassium pump)
