Exam II Flashcards
What are some characteristics of fatty acids?
- modify proteins via covalent bonding allowing them to target membranes
- can be stored as fuels in the form of triacylglycerols
- derivatives serve as hormones, signal molecules, and intracellular messengers
What are the two rules discussed in class about the nomenclature of fatty acids?
- derived from the parent hydrocarbon
- no double bond, -anoic
- one double bond, -enoic
- two double bonds, -dienoic
- three double bonds, -trienoic - 18:0 represents a fatty acid with 18 Cs and no double bonds
18: 2 represent a fatty acid with 18 Cs and two double bonds
How are carbon bonds numbered? Double bonds?
carbons:
- starting at carboxyl terminus
- carbon 2 (alpha) and 3(beta)
- methyl carbon at distal end is referred to as omega
Double bonds:
- position of double bond is denoted by (delta) followed by superscript
- counting from the distal end requires the omega to be number one and will be denoted as (omega)-3
What are some properties of fatty acids?
-contain an even number of carbons, between 14-24
+16 and 18 are most common fatty acids
-most unsaturated fatty acids contain cis double bonds
-fatty acids are ionized at physiological pH so it should be referred to as it’s carboxylate form ex. palmitate -> palmitic acid
-unsaturated fatty acids have a lower melting than saturated fatty acids of the same length
-the melting points of saturated fatty acids increase with chain length
What are the essential fatty acids and non-essential? Name the number of Cs, double bonds, and common name.
Nonessential:
- palmitate, 16C, and 0 bonds
- stearate, 18Cs, 0 bonds
omega-6 essential:
- linoleate, 18Cs, 2 bonds
- arachidonate, 20Cs, 4 bonds
omega-3 essential:
-linolenate, 18Cs, 3 bonds
How is an archaea able to withstand such high temperatures?
- the membrane lipid contains an ether linkage which is more resistant to hydrolysis
- the branched and saturated hydrocarbons are more resistant to oxidation
What are the three major membrane lipids?
- phospholipids
- glycolipids
- cholesterol
What are the 4 components of a phospholipid?
- fatty acid- hydrophobic barrier
- backbone to which fatty acids are attached: glycerol (3C alcohol; phosphoglycerides) or spingosine (complex alcohol; sphingomyelin)
- phosphate
- alcohol attached to the phosphate
What is the key intermediate in the biosynthesis of phosphoglycerides?
phosphatidate -> small amount present in membranes
What are the phosphoglycerides derived from phosphatidate and what are their purpose?
- phosphatidylserine: memory and cognition
- phosphotidylcholine: major constituent of cell membrane and pulmonary surfactant
- phosphatidylethanolamine: 25% of phospholipids, found in nervous tissue such as white matter of the brain
- phosphatidylinositol: important signaling and other functional activities in eukaryotic cells
- diphosphatidylglycerol: important component of inner mitochondrial membrane
What is a sphingosine?
an amino alcohol that contains a long, unsaturated hydrocarbon chain
What is sphingomyelin?
- the phospholipid with the sphingosine as the backbone
- amino group of the spingosine backbone linked to a fatty acid via an amide bond
- found in animal cell membranes, especially in the membranous myelin sheath that surrounds some nerve cell axons
What are glycolipids?
- sugar-containing lipids
- derived from sphnigosine
- differ from spingomyelin is the identity of the unit that is linked to the primary hydroxyl group of the sphingosine backbone
- oriented with the sugar residues always on the extracellular side of the membrane
What is the simplest glycolipid and what are some of it’s characteristics?
- cerebroside!
- contains a single sugar residue (glucose or galactose)
- cerebroside is the common name for the group of glycosphingolipids called monoglylceramides which is an important component in animal muscle and nerve cell membranes
What are some characteristics of cholesterol?
-a steroid (most common), present in eukaryotes but not most prokaryotes
-built from 4 fused hydrocarbon rings
-classified as a sterol
-major component of eukaryotic plasma membrane
+absent from the intracellular membranes
+absent in prokaryotes
+oriented parallel to the fatty acid chains of the phospholipids, and the hydroxyl group interacts with the phospholipid head
-metabolic precursor of steroid hormones
