Chapter 10 Flashcards
(33 cards)
What are the 8 major categories of lipids?
Fatty acids Glycerolipids Glycerophospholipids Sphingolipids Sterol lipids Prenol lipids Saccharolipids Polyketides
Describe Fatty Acids
- Carboxylic acids with hydrocarbon chains containing from 4 to 36 carbons
- Almost all natural fatty acids have an even number of carbons
- Most natural fatty acids are unbranched
- Saturated: no double bonds between carbons in the chain
- Monounsaturated: one double bond between carbons in the alkyl chain
- Polyunsaturated: more than one double bond in the alkyl chain
Describe Fatty acid nomenclature-
- named from the carboxylic end
- ex: 18:1 (delta 9) cis-9- octadecenoic acid
- there are 18 carbons and 1 double bond occurring at carbon 9
What are saturated fatty acids?
- have no double bonds
- melting point increases as carbon chain length increases
- solubility decreases as carbon chain length increases
- more soluble in benzene than in water
- at room temperature they are solids
What are unsaturated fatty acids?
- have one or more double bonds
- melting point decreases as the chain increases
- liquid at room temperature
- the double bonds in natural unsaturated fatty acids are commonly in cis configuration which introduces a kink in the chain
Properties of saturated vs. unsaturated fatty acids in aggregates
Saturated fatty acids pack tightly
Unsaturated cis fatty acid pack less regular due to the kink
If incorporated into a membrane: rigidity can be regulated by manipulating saturated/unsaturated fatty acid ratios
Trans Fatty Acids
- Naturally occurring fatty acids are found in the cis configuration
- Trans fatty acids are produced in the rumen of dairy animals (small amounts of trans fatty acids can be found in the meat and milk of animals.
- a trans double bond allows a given fatty acid to adopt an extended conformation; pack more regularly; show higher melting points than cis forms
- Most trans fats are produced by the industrial process of hydrogenation of unsaturated fatty acids to make liquid oils solid at room temperature (i.e.margarine)
- Trans fatty acids activate the inflammatory response and increase the LDL (bad cholesterol) levels while decreasing the HDL (good cholesterol) levels in the body
Describe Triacylglycerols (fats and oils)
- storage lipid
- are fatty acid esters of glycerol (non-polar, hydrophobic)
- Majority of fatty acids in biological systems
- Solid ones are called fats
- Liquid ones are called oils
- Triacylglycerols are the primary storage form of lipids (body fat)
- High levels in the blood have been linked with atherosclerosis, heart disease and stroke
How do Fats provide efficient fuel storage?
- Fatty acid carry more energy per carbon because they are more reduced (yield more than twice as much energy than the same gram amount of carbohydrates)
- Fatty acids carry less water along because they are nonpolar
- Glucose and glycogen are for short-term energy needs, quick delivery
Fats are for long term (months) energy needs, good storage, slow delivery
what two types of lipids comprise a typical wax?
Biological waxes are esters of long chain (C14 to C36) saturated and unsaturated fatty acids with long-chain (C16 to C30) alcohols.
What are the membrane lipids?
phospholipids
glycolipids
archeal tetraether lipids
sterols
What are the two types of phospholipids?
glycerophospholipids and sphingolipids
What are the types of glycerophospholipids?
- phosphatidylcholine
- plasmogen (ether lipid)
- pllatelet-activating facter (ether lipid)
General Structure of Glycerophospholipids
- Unsaturated fatty acids are commonly found to be connected to C2 of glycerol
- The highly polar phosphate group may be further esterified by an alcohol; such substituent groups are called the head groups
Glycerophospholipid example: Phosphatidylcholine
Major component of most eukaryotic cell membranes
Many prokaryotes, including E. coli cannot synthesize this lipid
Glycerophospholipid example: Plasmalogen (ether lipid)
- Common in vertebrate heart tissue (~ one-half of phospholipids are plasmalogens)
- Also found in some protozoa and anaerobic bacteria
- Function is not well understood
- Resistant to cleavage by common lipases(that cleave ester linkages)
- Increase membrane rigidity?
- Sources of signaling lipids?
- May be antioxidants?
Glycerophospholipid example:Platelet-activating factor (ether lipid)
- Aliphatic ether analog of phosphatidylcholine
- Acetic acid has esterified position C2
- First signaling lipid to be identified
- Released from leukocytes (basophils)
- Stimulates aggregation of blood platelets
- Plays role in mediation of inflammation and the allergic response
What are the types of sphingolipids?
ceramides
sphingomyelin
glycosphingolipid
gangliosides
Ceramides
are the parents of all sphingolipids. This is a sphingosine attached through an amide linkage to the –NH2 of C-2
Sphingomyelin
Have phosphatidylcholine or phosphatidylethanolamine as its head group (found in the plasma membrane; found in cells of the myelin sheath)
Glycosphingolipids
occur in the outer face of the plasma membrane
Cerebrosides-single sugar (i.e. galactose or glucose)-found in nervous tissue
Globosides- two or more sugars (usually glucose, galactose or N-acetylgalactosamine)
Gangliosides
polar head groups with one or more N-acetylneuraminic acid (NANA)
Phospholipases and other enzymes that degrade modified lipids
- Phospholipids and Sphingolipids are degraded in lysosomes
- Genetic defects in lysosomal enzymes leads to a build-up of gangliosides (i.e. Tay-Sachs disease, Gaucher disease, etc.)
Properties of Sterols and cholesterol
Sterol: -Steroid nucleus: four fused rings -Hydroxyl group (polar head) in the A-ring -Various non-polar side chains The steroid nucleus is almost planar
