Exam 3 Flashcards
(208 cards)
Dihydroxyacetone
- is a ketose
- has the same atomic composition as glyceraldehyde and they are tautomers which can interconvert
Isoprenoids
- Biomolecules found in membranes that consist of terpenes (found in essential oils) and steroids
GM2, or Tay-Sachs ganglioside
- disease results from incomplete enzyme processing of the glycan portion of glycosphingolipids
- neural diseases
- Tay-Sachs lysomes cannot digest ganglioside GM2 due to mutation in HEXA gene
- HEXA responsible for breakdown of fatty acid substance GM2
- Accumulation of GM2 causes the lysosomes in the neuronal cells and the neuronal cells themselves to bulge and die causing the disease
- constituents of the ABO blood group antigens
Examples of Fatty Acids
- When the hydrophilic head is in ionic form, then the acid is just referred to as stearate or oleate
1. Stearic acid - saturated(all carbons have H’s, no double bonds) fatty acid
2. Oleic acid - unsaturated(double bonds) fatty acid
- one CIS double bond
How are fatty acids synthesized?
- by the sequential addition of 2-carbon precursors.
- fatty acids are synthesized stepwise from acetyl (2 C) building blocks
- this is why most fatty acids have an even number of carbon atoms
Glyscosides
- monosaccharide derivative
- elimination of water between the anomeric hydroxyl of a cyclic monosaccharide and the hydroxyl group of another compound yields O-glycoside
- O signifies the hydroxyl attachment
- newly formed bond is a glycosidic bond (ether like)
Tetroses
- monosaccharides where n=4
- The keto form of a tetrose is erythrulose, which only has one asymmetric carbon
Cyclization
- creates a new asymmetric center
- The new center is called an anomeric center and is designated as α (Oh group down) or β (Oh group is up/on the same side of CH2OH group)
- Anomers interconvert by mutarotation (center figure)
- These rings are shown in Haworth projection
- C1 is the anomeric carbon in ring structures
Ceramides
- sphingolipid derivatives
- consist of sphingosine and a fatty acid
- if a fatty acid is linked via an amide bond to the NH2 group that is on the C-2, it is called a ceramide
Compounds with >1 asymmetric carbon (chiral carbons)
- may be enantiomers (mirror images) or diastereomers
Anomers
- stereoisomers that differ in conformation at the anomeric carbon
- The carbon in a cyclic sugar that is the carbonyl carbon in the open-chain (acyclic) form
- start counting here
Cholesterol
- Bulky, rigid structure disrupts regular fatty acid chain packing in membranes
- weakly amphipathic because of –OH (hydroxyl group)
- Fatty acid esters of cholesterol are extremely apolar
- precursor to all steroids
- major sterol in animal tissues
- really no such thing as “good” or “bad”
What do the numeric abbreviations for fatty acids tell you about their composition? 18:3cΔ9,12,15
- 18 = Number of carbons
- 3 = number of unsaturated double bonds
- c = cis orientation
- Δ#= carbons at which double bonds occur
Alditol
- monosaccharide derivative
- reduction of the sugar carbonyl yields alditol
- The reduction of glucose yields D-glucitol, also called sorbitol
Example of a Triaglycerol
- Tristearin
- the triglyceride form of stearic acid
Oligosaccharide
- Compound formed by linking several monosaccharides together (example, disaccharide, with 2)
Galactosylceramide
- is found on brain cell membranes
Furanose
- A five-member closed chain form of a monosaccharide
- one of the ribose carbons cannot fit in the ring
- heterocyclic compound is furan
Reducing and nonreducing sugars
- Free anomeric carbon = reducing end (OH group on anomeric carbon)
- Sucrose has no free anomeric carbons(no OH group on anomeric carbon), thus no reducing ends. It is a nonreducing sugar.
- lactose is a reducing sugar
Niemann-Pick disease
- Sphingomyelin accumulation
- an individuals deficient in acid sphingomyelinase
- Niemann-Pick is similar in pathology to Gaucher’s.
Lactones and Acids
- monosaccharide derivative
- oxidation of monosaccharides forms these, proceeds in several diff ways depending on oxidizing agent
ex: D-gluconic acid. - Oxidation at C1 forms an aldonic acid
- The aldonic acid is in equilibrium with the lactone (cyclic ester) form
ex: β-D-glucuronic acid - Oxidation at C6 forms a uronic acid
Enantiomers
- optical isomers that are non-superimposable mirror images of eachother
Glyceraldehyde
- is an aldose
- has the same atomic composition as dihydroxyacetone and they are tautomers which can interconvert
- contains a chiral carbon thus it has two stereoisomers otherwise known as enantiomers. (R=D, L=S)
Diastereomers
- are optical isomers that are not mirror images
- with 2 enantiomers each