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SGU: Membrane Lipid
Biochemistry: Lipids and Membrane Stucture and Transport
| Question | Answer |
|---|---|
| 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
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