Lipids and Cell Membranes Flashcards
What is a lipid?
A chemical that is describe as having a low solubility in water.
What do lipids do?
They provide a source of energy, form cell membranes are participate in cell signalling
Describe some of the features of fatty acids
These are a good store of energy. Naturally occurring fatty acids have even numbers of carbons. They are rarely found freely in the body and are more frequently found as part of the lipid molecule or attached to a carrier protein
Describe how short, medium and long fatty chains are taken in?
short and medium are absorbed into the blood stream but long fatty acids are unable to be absorbed so are synthesised by cells.
What radio of carbon to double bonds makes a fat polyunsaturated?
20:4
How are omega fatty acids names?
Omega then number. This number is the first carbon to carbon double bond from the methyl end.
Give some examples of sterols
Bile acids, steroids, vitamins and cell membranes
Name some inherited disorders in lipid pathways and what this causes
Gaucher's (most common) Niemann Pick Tay-Sachs Fabry Disease It causes defects in enzymes that metabolise lipids leading to lipid accumulation. Effects neurological system, liver, spleen and bone marrow
Name the three types of membrane lipids and give an example
Phospholipids (Glycerophospholipids and Spingolipids)
Glycolipids (spingolipids)
Sterols (cholesterol)
What are the ranger of different phospholipids and what are they defined by?
Defined by their different polar head group. The rage of phospholipids are;
Choline, Ethanoalmine, serine and inositol
Define amphipathic
A molecule having both hydrophobic and hydrophilic parts.
What are the energetically favourable and unfavourable bilayer formations
Planar phospholipid bilayer is unfavourable as the edges are exposed to water. The more favourable formation is spherical as this is a sealed compartment and no lipids are exposed to water
What is membrane fluidity and why is it important?
This means that lipids and proteins can undergo rotational and later movement. It allows for the diffusion of membrane proteins and lipids from the site they are produced
How can you measure membrane fluidity?
Measure the fluorescence recovery time after bleaching. It measures how quickly the fluorescent lipids travel to the bleached area.
What increases the viscosity of membranes?
Cholesterol
How are phospholipids generated?
Synthesised by enzymes at the ER in the cytosol. They use fatty acids available in the cytosol. Phospholipids are released in the cytoplasm and travel to the outer leaflet of the membrane. Flippases transfer them to the inner leaflet. Flippases are specific to certain phospholipids.
Describe how membrane is synthesised.
New memebrane synthesis occurs at the ER. The membrane is then transported to other parts of the cell. This occurs via a process of vesicle budding and fusions (vesicle trafficking)
What is exocytosis?
Delivery of lipids and membrane proteins to the plasma membrane. Also involved in the release of other molecules.
What is endocytosis?
Movement of material into a cell via vesicles.
What are lipid rafts?
They are organising centres used in vesicle trafficking and cell signalling.
Name some types of membrane proteins
Transmembrane - the hydrophobic amino acid side chain stabilises its presence in hydrophobic regions
Membrane associated - contain domains that selectively bind to phospholipids
Lipid anchored - work through GPI anchors
Protein attached - important in signal transduction
