Lipids Flashcards
What are the two main types of lipids?
- Storage (neutral)
- Membrane (polar)
What are fatty acids?
Long hydrocarbon chains with a carboxyl group on top (COO-) that are released from fat hydrolysis
What are monocarboxylic acids?
Fatty acids with linear unbranched hydrocarbon chains (typically even number of C atoms)
What are unsaturated fatty acids?
Fatty acids with one or more double CC bonds =(usually 18 and 20) in its hydrocarbon chain.
What is the difference in dehydrogenated and hydrogenated unsaturated fatty acids?
Dehydrogenated: double bonds are in cis formation
Hydrogenated: double bonds are in trans formation
what are the difference between acetic, capirc, lauric, palmitic and stearic fatty acids?
- Acetic: C2
- Capric: C10
- Lauric: C12
- Palmitic: C16
- Stearic: C18
What is the difference between palmitoleic, oleic, linoleic, linolenic, gamma linolenic and alpha linolenic fatty acids?
- Palmitoleic: C16:1(9)
- Oleic: C18:1(9)
- Linoleic: C18:2(9, 12)
- G-linoleic: C18:3(6, 9, 12)
- A-linoleic: C18:3(9, 12, 15)
What are kinds of omega-6-fatty acids?
Linoleic: C18:2n-6
G-Linoleic: C18:3n-6
What is the C:Xn-Y nomenclature in fatty acids?
C represents the number of carbons in the chain
X represents how many double bonds are in the chain
n-Y represents how many carbons away from the METHYL end of the chain the first double bond is located
what is the pKa of fatty acids?
4.5-5
How does the structure of fatty acids influence melting point and solubility?
Melting point: increases with chain length, decreases with double bond count
Solubility: Water soluble up to chains of 6 carbons, and from onwards, only soluble in polar solvents
What are X-glycerides? (X = mono, di, tri…)
Esters of OH-CH2-CHOH-CH2-OH (glycerol) with fatty acids attached at the OH groups.
Why are tracylglycerols used for energy storage?
The carbons in fats are more reduced (more bonds to hydrogen) than carbohydrates and has 2x as much energy per unit mass.
What is saponification?
triacylglycerol + KOH = 3K+ -fatty acid + Glycerol
Separation of fatty acid and glycerol allows fatty acid to form micelles around oil and dirt which is soluble in water due to glycerol.
What are glycerophospholipids?
Derivatives of phosphatidic acid made of glycerol attatched to 2 fatty acid chains and one phosphate group. This phosphate group may have a head group substituent on one of the phosphate oxygens.
What are the most common head groups attached to the phosphate in a phospholipid?
ethanolamine: CH2-CH2-NH3+ [zwitterion]
choline: CH2-CH2-N+(CH3)3 [zwitterion]
Serine: CH2-CH(COO-)-NH3+ [net charge -1]
What do phospholipase A1, A2, C and D target in a phospholipid?
A1: outer fatty acid
A2: middle fatty acid in
C: phosphate
D: Headgroup of phosphate
What is released with phosphoplipase C and phospholipase A?
C: IP3 and DAG - second messengers
A: arachidonic acid - precursor to prostaglandin, thrombocan and leukotrienes (eicosanoids)
What are sphingolipids?
Derivatives of sphingosine (CH2OH - CHNH2-CH(OH)(CH)2(CH2)12(CH3) that play important roles in membranes.
What is a ceramide?
A fatty acid attached to the middle nitrogen in a sphingosine, which creates the structural parent of all sphingolipids: sphingomyelin, glycosphingolipids, gangliosides.
What are sphingomyelins?
Ceramides where the head group on the C1 is a phosphocholine.
What are glycosphingolipids?
Non charged sphingolipids with one sugar unit (cerebroside) or more than one sugar units (globoside) on the head of ceramids. Face outer leafelt and are important in cell recognition events.
What are gangliosides?
Negatively charged complex sphingolipids with oligosaccharides as polar head groups. Their head groups contain one or more residues of N-acetylmuramic acid and sialic acid at termini.
What are non-saponifiable lipids?
Steroids and terpenes, synthesized from isopentenyl pyrophosphate.
What is a monoterpene, sequiterpene, diterpene, triterpene, and tetraterpene?
Mono: 2 isoprene (C10)
Sequi: 3 isoprene (C15)
Di: 4 isoprene (C20)
Tri: 6 isoprene (C30)
tetra: 8 isoprene (C40)
What is beta carotene?
Tetraterpene pigment that may be cleaved by a dioxygenase to produce 2 all trans retinols (Vitamin A) needed for vision.
What are the steps of production of Retinal?
- Beta carotene is cleaved by dioxygenase at the middle double bond (5th) to produce all trans retinal and all trans retinol
- All trans retinol is isomerized by retinol isomerase to form 11-cis retinol
- 11-cis retinol’s end CH2OH is oxidized by retinol reductase to form an aldehyde (CHO)
How does light absorption occur?
- Light absorbed by opsin causes photoisomerization of 11-cis retinal to 11-cis all trans retinal
- conformational change allows interaction with G protein transducin to mediate Ca2+ entry into the cell and neuronal signalling.
- All trans retinal is reduced back to all trans retinol for another round of light activation
What is the cycle of retinol from betacarotene?
- All trans retinol is isomerized to 11-cis retinol
- 11-cis retinol is reduced to 11-cis retinal
- 11-cis retinal is converted by visual light to all trans retinal
- all trans retinal is reduced back to all trans retinol to start again.
What is cholecalciferol and how is it formed?
Hormone that regulates Ca2+ levels in kidneys, intestines and bone. Formed in skin by UV induced photochemical reaction of 7-dehydrocholesterol.
What is vitamin E and how is it formed?
Tocopherols act as biological antioxidants, and deficiency leads to sterility and muscle weakness.
What is vitamin K?
Blood clotting cofactor whose deficiency results in a failure to synthesize prothrombin.
What is coenzyme Q?
electron carriers in electron transport chain in the mitochondria (ubiquinone) or in the chloroplast (plastoquinone)
What are steroids?
Planar rigid 4-fused ring with 3 hexanes and one pentane. Includes cholesterol and cholesterol derived molecules.
What is cholesterol?
Most abundant steroid in humans with a polar head group and an 8 carbon alipathic chain at C17.
How are cholesterols and dietary lipids transported?
Cholesterol is stored and transported as cholesteryl esters (joined w/ fatty acids) to make it more hydrophobic for storage and transport in lipoprotein complexes.
What does the structure of a lipoprotein tell you?
Density of coat is greater than density of the core (high density). Larger core means lower density.
What are large and small lipoproteins?
Large: chylomicrons, very-low density lipoproteins, low density lipoproteins
Small: High density lipoproteins
What are steroids not meant involved in membrane structure?
Hormones testosterone, progesterone, cortisol and aldosterone.
