DLA1 Flashcards
Membrane Components
Lipids
Proteins
3 major classes of lipids
- Phospholipids
* Cholesterol • Glycolipids
2 major classes of proteins of membrane
Integral membrane
Peripheral membrane
Location of cholesterol in membrane and its effect on membrane fluidity
• Intercalates between phospholipids
• Affects membrane fluidity in temperature dependent manner
Reduce membrane fluidity.
What is glycolipid and where is it found?
- Sugar-containing lipid molecules
* Found exclusively in outer monolayer
6 General Categories of Integral Membrane Proteins
- Pumps/Carriers/Transporters
- Channels
- Receptors
- Linkers
- Enzymes
- Structural proteins
What does pumps, carriers, transporters transport?
Transport specific ions across the membrane
• Sodium
• Potassium
Transport metabolic precursors
• Amino acids • Sugars
What are channels for?
Transport of ions, small molecules and water
• Passive diffusion
Aquaporins
• Water
Gap junctions
• Passage of ions, small molecules between adjacent cells
What is glycocalyx?
Cell coat where sugar residues are attached to cell surface (glycolipid, glycoprotein, proteoglycan)
- carbohydrate rich zone on the cell surface
Function of glycocalyx
• Protection
• Cell recognition
• Cell to Cell Interaction
-Lectins: Carbohydrate binding proteins
4 features of Membrane Structure
- Lipid Bilayer
2 . Asymmetry
3.Lipid rafts
4.Fluid mosaic model
Where is phosphatidyl located in membrane and what happens to it during cell death?
Phosphatidylserine localizes to the inner leaflet
• Enzymatically transferred to the outer leaflet during programmed cell death
• Triggers phagocytic removal of dying cells
What is lipid rafts?
• Specialized cholesterol enriched microdomains
2functions of lipid rafts
- Signal transduction
* Endocytosis
Example of Regulated exocytosis
Secretory cells
- ligand bind to receptor (stimulus)
- then there is Ca2+ influx which allow Fusion of secretory vesicles with plasma membrane
Pathway of receptor-mediated endocytosis
Clathrin-dependent pathway
- Cargo protein binds to cargo receptor.
- Then Clathrin molecules interact with cargo receptors via Adaptin forming clathrin coated pit.
- Vesicle formation
- Dynamin mediates the vesicle pinching-off from the plasma membrane
- Clathrin and adaptins are recycled
Examples of Receptor recycled, ligand degraded (Receptor-Mediated Endocytosis)
- Low-density lipoprotein (LDL) receptor
- Insulin-glucose transporter receptor
- Other peptide hormones & their receptors
Examples of Receptor and, ligand recycled (Receptor-Mediated Endocytosis)
- Iron, transferrin & transferrin receptor
* Major histocompatibility complex I & II
Examples of Receptor and, ligand degraded (Receptor-Mediated Endocytosis)
• Epidermal growth factor (EGF) & receptor
Examples of Receptor and, ligand transcytosis (Receptor-Mediated Endocytosis)
- Secretion of immunoglobulins (secretory IgA) into saliva
* Secretion of maternal IgG into milk
Pathway of vesicle targeting using Rab-GTPase
1.Rab-GRPase interact with vesicle.
2. RabGTPase interact with tethering proteins, immobilizing the vesicle near target membrane.
3. Rab-GTPase and receptor immobilize
the vesicle near target membrane, forming docking complex.
4. v-snare which is vesicle specific interact with t-snare which is target specific, forming cis-snare complex, opening up the vesicle.
Difference between early and late endosome
Early endosome
• Functions to sort and recycle proteins
Late endosome
• Receives proteins for degradation
• Receives newly synthesized lysosomal enzymes from the Golgi
• Matures into a lysosome
3 types of endocytosis
- Receptor-mediated
• Cargo-specific
• Clathrin-dependent - Pinocytosis
• Non-specific
• Clathrin-independent - Phagocytosis
• Clathrin-independent
• Actin-dependen
“Cell Drinking”
Pinocytosis
