The Lipid Bilayer Flashcards
Learning Objectives - Understand the composition and the structural organization of the lipid bilayer - Describe the structure and function of membrane proteins - Discuss the synthesis and intracellular movement of phospholipids, sphingolipids, and cholesterol - Discuss the engineering membrane proteins for biomedical applications
What are cell membranes composed of and what can they referred to as?
- Lipids, proteins, and carbs
- Both a structural barrier and a functional interface
What does the fluid mosaic model say about membranes?
Dynamic, fluid structures with proteins embedded in a phospholipid bilayer
How is membrane fluidity maintained?
Unsaturated phospholipids and cholesterol allow movement of proteins and lipids within the membrane plane
Describe the structure of the lipid bilayer
Two horizontal layers of molecules with phospholipid heads facing outwards and tails directed inwards
How do integral membrane proteins appear in the membrane?
- Large globular structures embedded within the bilayer
- Some span from inner membrane to outer surface of membrane
How do peripheral proteins appear in the membrane?
- Smaller oval or irregularly shaped structures attached to the membrane surface
How do lipid rafts appear in the membrane?
- Clustered areas within the bilayer
- Often thicker and enriched in cholesterol and sphingolipids
What function do integral proteins serve in the membrane?
- Transporters (ion channels, carriers)
- Receptors
- Enzymes
- Cell to cell adhesion structures
What role do peripheral proteins serve in the membrane?
- Provide structural support
- Involved in cell signaling by interaction with receptors and enzymes
- Loosely attached to membrane
Describe the ability of motion of certain proteins?
- Some move freely
- Others restricted by cytoskeletal interactions or are part of lipid rafts
What role do lipid rafts serve?
- Signaling platforms
- Clustering proteins involved in cell communication and immune responses
- Help in endocytosis (bring material into the cell)
- Sort proteins for transport
What do proteins tethered to cytoskeletal elements do?
Prevent random movement and allow for localized signaling
What do glycoproteins do?
- Cell recognition and signaling
- Help immune cells distinguish self from non-self
What do glycolipids do?
Contribute to cell adhesion and interactions between neighboring cells
What are carbohydrate structures unique to each cell type that act as an ID tag?
Glycoproteins and glycolipids
How do viruses use lipid rafts?
- Use them to attach to the host cell, enter cytoplasm, and initiate infection
- Think of fast passes
Describe phospholipids
- Most abundant membrane lipids
- Consist of a hydrophilic head and hydrophobic tails
Describe sphingolipids.
- Found in neuronal membranes and lipids rafts
- Play roles in signaling and cell recognition
Where are phospholipids synthesized?
Smooth ER
Where are sphingolipids synthesized?
Golgi apparatus
How and where is cholesterol made?
acetyl-CoA in ER and cytoplasm
Name one disease with some sort of defective lipid mechanism
Tay-Sachs disease (defective sphingolipid metabolism)
Name 3 mechanisms of lipid distribution in cells.
- Vesicular transport
- Direct contact
- Lipid transfer proteins
Describe the vesicular transport of lipids.
Lipids move between organelles by way of the secretory pathway
