Lipids and membranes

What is the function for cell membranes?

Semi-premeable

separates from external environment

allows nutrient absorption and waste excretion

consist of lipids, carbohydrates and proteins

Why are lipids amphipathic?

Contain hydrophilic/hydrophobic domains

What are the major phospholipids?

Phosphotidylcholine and sphingomyelin (outer)

Phosphotidylserine and phosphotidylethanolamine (inner)

What is the function of cholesterol in the membrane?

Provides structure and rigidity

At cold temps cholesterol prevents phospholipids packing

What are lipid rafts?

Membrane microdomains which allow cell signalling/endocytosis

Name three membrane proteins?

Transmembrane proteins

Monotopic integral membrane proteins

Peripheral membrane proteins

What is the glycocalyx?

In endothelial cells helps prevent thrombus formation

Regulates vascular permeability

Mechanosensors/receptors

In bacteria acts as adhesion, prevents recognition by immune

What is the process of Cathrin mediated endocytosis?

Macromolecules bind to receptors

Receptors cluster and recruit Cathrin to form a clathrin coated pit

Actin network forms around the pit helping it move inwards

The neck is cleaved by dynamin to form clathrin coated vesicles

Fuse with endosomes for cargo sorting

What is the process of caveloae mediated endocytosis?

Flask shaped invaginations with caveloae proteins

Budding is regulated by kinases and phosphatases

needs dynamin

What are the types of extracellular vesicles?

Exosomes

Microvesicles

Apoptotic bodies

How can neurotoxins inhibit exocytosis?

Docking of synaptic vesicles requires the SNARE complex

Neurotoxins cleave the SNARE complex preventing exocytosis

muscle relaxation eg: botulinum

How do phospholipase work?

PLA hydrolyse phospholipids causes inflammation

found in snake venom

How may pathogens utilise the cell membrane to invade cells?

Enter a cell via receptor mediated fusion or endocytosis