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SGU: Membrane Lipid

Biochemistry: Lipids and Membrane Stucture and Transport

QuestionAnswer
What are the different functions of Lipids? Storage of fat (TAGs), energy metabolism, thermal insulator, plasma membrane, vitamins A,D,K,E, steroid hormones
Describe the structure and properties of fatty acids. Long hydrocarbon tail with charged carboxyl, amphipathic, MP increases with chain length and decreases with degree of unsaturation, free fatty acids are esterified
Describe fatty acids in humans in humans 16-20 carbons & double bonds cis @ 3-interval carbons. Can only be desaturated between carbons 9/10 or between 9/10 and carboxyl end
Synthesis of fatty acids usually leads to: palmitate
What are the essential fatty acids? linoleic acid and alpha linolenic acid
Can humans change a fatty acid of a high family to a lower? no but a smaller member of the same family can be used to form a larger fatty acid
What is linoleic acid essential for and what happens during its deficiency? Synthesis of arachidonic acid. Deficiency leads to mead acid (marker for EFA deficiency)
What is the intravenous method to administer EFA? total parenteral nutrition
What is the clinical relevance of TAGs? Main form of storage of fatty acids. Can be stored in adipocytes which only increase/decrease in size in non-obese ppl
Which phospholipids contain a different backbone other than glycerol? spingomyelin-contains a sphingosine backbone
Describe glycolipids Spingolipids with sugars attached to ceramide
Describe the synthesis of ceramide palmitoyl-CoA and serine (plus vitB) produces ceramide
What is ceramide a component of? spingomyelin, cerebrosides, globosides and gangliosides
What is the function of ceramide in skin? regulates the water permeability of skin
What is the importance of sphingomyelin? found in outer leaflet of PMs and important for myelin of nerve fibers & grey matter.
What is the biological importance of glycosphingolipids and sphingomyelin? defective degradation leads to lysosomal storage disease
Describe the synthesis of cerebrosides and globosides. Ceramide+sugar=cerebroside +sugars=globoside
Describe the synthesis of gangliosides N-acetyl-neuraminic acid+globoside
What is the biological importance of cerebrosides, globosides and gangliosides? cerebro and globo found in brain and peripheral nervous tissue and myelin, gangliosides in ganglion cells of CNS
Describe the structure of glycerophospholipids. phosphatidic acid. 1 fatty acid is saturated, 2 fatty acid unsaturated
Biological importance of phospatidylcholine major component of membrane lipids. Analogue of plasmalogen in heart.
Biological importance of phospatidylethanolamine major component of membrane lipids. Analogue of plasmalogen in nerve tissue.
Which glcerophospholipid is not a major membrane lipid? phosphatidylserine
Biological importance of phospatidylinositol Used to form PIP2 which is cleave by phospholipase C to DAG and IP3 in Ca2+ second messenger system.
Where is cardolipin found? inner mito membrane
Biological importance of cardiolipin Deficiency leads to Barth's syndrome a rare but severe cardiomyopathy.
Biological importance of phospatidylcholine Major membrane component. Released in bile. Used for sphingomyelin synthesis. Provides dipalmitoyl-PC for lung surfactant.
How is phoshpotidylcholine made? from choline or phosphotidylethanolamine methylation
How can you predict lung maturity in infants? the lecithin (phosphotidylcholine)/sphingomyelin ratio must be 2 or above
What are all the functions of cholesterol in the body? unpolar-storage/transport in lipoproteins, regulation of PM fluidity, steroid hormone synthesis, vitD synthesis, liver bile acid synthesis
What steroid hormones are formed by cholesterol? adrenal cortex:cortisol, aldosterone, androgens. ovaries:estradiol. testes:testosterone
What is the precursor of cholesterol used for vit D deficiency? 7-dehydrocholesterol
What are the functions of biological membranes? separate cell from external environment, allow specific reactions to be localized
What is the glycocalyx composed of and what is its function? glycolipids and glycoproteins. acts as a shield and involved in cell-cell recognition
Describe the functions of cholesterol inside the lipid bilayer. increases fluidity inside bilayer while sterol rings decrease fluidity close to polar heads. Can increase/decrease fluidity with temp change.
How do fatty acids affect membrane fluidity? unsaturated and shorter fatty acids make membrane more fluid
Examples of unsaturated fatty acids in membranes? oleic acid, linoleic acid and arachiodonic acid
What types of molecules can penetrate the lipid bilayer? gases, hydrophobic molecules and small polar molecules.
What cannot pass the membrane? charged and large polar molecules
What kind of transport is required for glucose inside of a cell? passive facilitated diffusion.
What does a high Kt signify? low affinity of transporter to substrate.
Describe the transporter of glucose 12 TM domains. , (low Kt for both). , liver, kidney and beta-cells of pancreas
Where is GLUT-1 found? GLUT-1 (low Kt) in RBC and brain
Where is GLUT-2 found? GLUT-2 (high Kt) intestinal mucosal cell (enterohepatic circulation), liver, kidney and beta-cells of pancreas
Where is GLUT-3 found? GLUT-3 (low Kt) in neurons
Where is GLUT-4 found? insulin-dependent-fat cells and muscle (low Kt)
Where is GLUT-5 found? (high Kt) intestinal mucosal cell (intestinal lumen) and testes. (mainly frutose transport, glucose at high concentration)
What is the biological relevance of GLUT-4? patients with diabetes can't use GLUT-4 efficiently. It is stored inside the cell.
Describe the SGLT transporter. secondary active symporter. pumps glucose into intestinal mucosal cells with 2 Na ions
Describe the CFTR channel ABC-transporter. Phosphorylation gated (PKA). Two ATPs cleaved and channel opens for chloride ions and Na exits via paracellular tight junctions. Water follows
What happens to males with CF? congenital bilateral absence of vas deferens
Describe the mutation leading to CF codon deletion of phenylalanine causing CFTR to not be transported to the membrane
What affect does cholera have on CFTR? leads to an unregulated CFTR
Created by: mnoronha on 2011-02-08



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