Topic 9 - Lipids Flashcards
(27 cards)
How does the polarity of a substance affect its solubility in water?
https://answers.yahoo.com/question/index?qid=20080225123318AAbREZ1
List the biological functions of lipids
- Storage of energy
- Insulation from environment
- water repellant
- Buoyancy control and acoustics in marine mammals
- Membrane structure
- Cofactors for enzymes
- Signalling molecules
- Pigments Antioxidants
Describe the importance of lipids
- Structural and function elements of membranes
- Precursors of bioactive compunds (e.g. hormones)
- Regulate enzymatic actions
- Contribute to membrane potential
- Are involved in cell signalling
- some disorders are due to abnormal lipid metabolism
- therapeutic function (steroids, prostaglandins)
What are lipids?
Organic molecules that are characterised by low solubility in water e.g. hydrophobic
Describe Fatty Acids (saturated & unsaturated)
- carboxylic acids w/ hydrocarbon chains containing b/w 4-36 carbons
- Saturated: no double bonds b/w C’s in the chain. Pack in orderly way
- Monounsaturated: one double bond b/w C’s in the alkyl chain. Pack less orderly due to d/bond kink
- Polyunsaturated: more than one double bond in the alkyl chain
Fatty acid melting point increases with…. and decreases with…. and …..?
Solubility increases with….?
MP & solubility increase w/ chain length
MP decreases w/ unsaturation (number of d/bonds increases)
Fatty acid nomenclature. Describe how to name FA’s
- Remember cis (same side) and trans (different side) -geometric isomers of each other
- Numbering begins at carboxyl C
- A FA 18 C atoms in length w/ no double bonds is 18:0
- A FA 18 C atoms in length w/ 1 double bond at C9 is 18:1(∆9)
Describe naturally occuring FA’s and trans FA
- even no# of C’s
- 1st double bond occurs b/w C9 & C10
- additional d/bonds occur b/w C12-C13 & C15-C16
- D/bonds are in the Cis config (kink)
- Trans FA’s rarely occur in biological systems. Trans d/bond allows a FA to adopt an extended conformation
- Cis 16:1 (∆9)
Describe triacylglycerols
- Nonpolar
- majority of FA’s are found as Triacylglycerols
- solid = fat
- liquid = oil
- primary storage form of lipids
- less dense than water and less soluble in water than FA
Describe waxes
- Esters of long-chain saturated and unsaturated FA w/ long-chain alcohols
- Insoluble, high MP
Describe polar lipids
- Amphipathic (hydrophobic & philic groups)
- Major component of biological membranes
- Properties of head group determine surface properties of membrane
- Form micelles, biylayers and liposomes
Membrane lipid structure and function
(see diagram in answer)
Membrane lipid structure and function
Describe Glycerophospholipids
- Primary constituents of cell membranes
- Head group is charged at physiological pH
- 2 FA form ester linkages w/ 1st & 2nd hydroxyl groups of L-glycerol-3-phosphate
- Unsat. FA are commonly found attached to C2
Membrane lipid structure and function
Describe Phosphatidylcholine
- Major component of eukaryotic cell membranes
Membrane lipid structure and function
Describe Sphingolipids
- Backbone is NOT glycerol, is a long chain amino alcohol sphingosine
- FA is joined to sphingosine via an amide linkage rather than ester linkage
Membrane lipid structure and function
Describe Shingomyelin
- Abundant in myelin sheath of animal nerve cells
- Ceramide (sphingosine + amide-linked FA) + phosphocholine attached to alcohol
- Structurally similar to phosphatidylcholine
How are blood groups determined?
by the type of sugars located on the head groups in glcyosphingolipids
- glycerophospholipid
- phosphosphingolipid
- carbohydrate residues
- glycosphingolipid
Describe sterols and the role
- -steroid nucleus: 4 fused rings
- hydroxyl polar H group in A ring
- various nonpolar side chains
- Cholesterol and related sterols are preseny in membranes of most eularyotic cells
List some signalling lipids
- Lipid soluble vitamins: A, D, E, K
- Ether lipids =>platelet activating factor
- Steroid hormones =>synthesised from cholesterol
- Essential FA =>Alpha-linoleic acid, linoleic acid
