biochemistry 9 Flashcards
what are the components of phospholipids
- platform - usually glycerol or sphingosine
- phosphate
- fatty acid - usually 1 or more
- alcohol
what is sphingosine
- 18 carbon amino alcohol
- unsaturated hydrocarbon tail
- example in sphingomyelin
where does the phosphate in phospholipids come from
ATP
what is the two methods of forming fatty acids for phospholipids
1) phosphaidate formed in the ER or the outer mitochondrial membrane
- two fatty acids added to glycerol-3-phosphate catalysed by glycerol phosphate acyltransferase
2) phopshatidate formed from diacylglycerol catalysed by diacylglycerol kinase using ATP
how is the alcohol added to a phospholipid
- phosphoglycerides - derived from phosphatidate
- via ester bond formed between the phosphate and alcohol
- requires nucleotide activation of phoshatidate or alcohol - PI and CL
- in many glycerophospholipids a nucleotide-phosphate alcohol is added directly to diacylglycerol
what does phosphatidic acid phosphatase catalyse
- conversion of phosphatidate to diacylglycerol
- different lipids synthesised depending on activity
what are the 4 stages of phospholipid synthesis
1) gluconeogenesis
2) triacylglycerol breakdown
3) triacylglycerol synthesis
4) phospholipid synthesis
what os diacylglycerol acylated by
diglyceride acyltransferase
- forms triacylglcerol
how is sphingosine produced
- from ceramide formed from parmitoyl CoA and serine
- occurs in ER
where does ceramide processing occur
plasma membrane
via ceramidase and spingosine kinase
what are glycolipids made form
- carbohydrate containing lipids derived from sphingosine
- carbohydrate linked to the primary alcohol of sphingosine
what are glycolipids used for
- cell-cell recognition and adhesion
- electrical potential across the membrane
what are cerebrosides
containing only one sugar
what are globosides
contain a branched sugar chain
what are gangliosides
contain a branched chain
what are the features of plasmalogens
- one fatty alcohol is attached through an ester linkage
what are the examples of plasmalogens
- Phosphatidylcholine Plasmalogen
- Phosphatidylethanolamine Plasmalogen
how is spingomyelin formed
- phosphorycholine bound to the terminal hydroxyl group
how is cerebroside formed
- single glucose or galactose bound to terminal hydroxyl group
how is gangliosides produced
- additional sugars added
what is myelin
- insulating cover around axons
- stacked bilayers with specific phospholipids
what are the causes and symptoms of tay-sachs disease
- beta-N-acetylhexosaminidase (HEXA) deficiency
- lysosomal enzyme, autosomal recessive mutation
- decrease in ganglioside break down to Gm3
- Gm2 accumulates and toxic levels accumulate in neurons, brain and spinal cord
- muscle weakness, exaggerated reaction of loud noises, hearing and vision loss
what are eicosanoid hormones
- short lived hormones that affect nearby cells - paracrine and autocrine
- 20 carbon polyunsaturated fatty acid
- derived from arachidonate (four double bonds)
what do phospholipase A2 do
- release arachidonate from phospholipids
what do diacylglycerol lipase do
- release arachidonate from diacylglycerols
what is the process that causes inflammation
- inflammation in macrophage or endothelial cells
- inflammatory signal from TLR or puringeric receptor
- increase phospholipase A2
- release arachidonate
how are prostanoids produced
produced from arachidonate by cyclooxyrgenase
what do prostanoids do
- mediate inflammation and pain
- induce sleep
- regulate blood coagulation and blood pressure
- relief of asthma and nasal congestion
what is prostaglandin H2 be used for
- induction of labour at term
- prevention of conception
- termination of pregnancy
what are the 3 types of prostanoids
1) Thromboxanes
2) Prostacyclins
3) Prostaglandins
where are thromboxane produced and what do they do
- produced from PGH2 by thromboxane synthase
- TXA2 synthesised in platelets - facilitate platelet aggregation
where is prostacyclin produced and what does it do
- produced from PGH2 by prostacyclin synthase
- PGI2 produced by epithelial cells
- counters the effect of thromboxane - inhibits platelet activation
how is prostaglandins produced and what does it do
- produced from PGH2 by prostaglandins synthase
- decreases hair length
what do nonsteroidal anti-inflammatory drugs do
- inhibits COX-1 and COX-2
what do COX-2 selective inhibitors do
- reduce side effects in stomach
- major side effects eg. heart attacks and strokes
how are leukotrienes produced and what do they cause
- produced from arachidonates by lipoxygenases
- found in immunocompetent cells
- cause allergic reactions, inflammation, muscle contraction and asthma
how are lipoxins produced
Produced from Arachidonate by Lipoxygenases
what is the dual action of lipoxins
Pro-inflammatory
- Attract monocytes to apoptotic cells
Anti-inflammatory
- Role at the end of inflammation
- Decrease neutrophil infiltration
what are the causes, symptoms and treatments of gout
causes - excess uric acid
symptoms - severe pain, swelling, redness and warmth of joints
urate crystals - damage cellular membranes, release lysosomal enzymes in joints
treatment - anti inflammatory agents and dietary changes
what are the causes, symptoms and treatments of IBS
causes - unknown, increases change with long term NSAIDs use
symptoms - abdominal pain, diarrhoea
treatment - corticosteroids
