Biological Molecules Flashcards
What is an aldose?
Sugars with an aldehyde group
What is a ketose?
Sugars with a ketone group
What is a pyranose?
sugars in a 6 membered ring structure = hexagon shaped. For example, glucopyranose = glucose in a 6 membered ring.
What is furanose?
sugars in a 5 membered ring structure = pentagon shaped. For example, fructofuranose = fructose in a 5 membered ring.
In order to be classified as a carbohydrate, a molecule must have what:
- at least a 3 carbon backbone.
- an aldehyde or ketone group.
- at least 2 hydroxyl groups.
What are the structures for the smallest carbohydrates?
The three common monosaccharides are:
What is the difference between deoxyribose and ribose?
What determines an absolute configuration of a sugar?
The chiral carbon furthest from the carbonyl group determines the absolute configuration L or D of the sugar.
What are epimers?
different configuration in just one chiral carbon.
What are anomers?
different configuration in the chiral, anomeric carbon when the molecule is in the cyclic form.
To assign the cyclic form of a carbohydrate as the α- or β- form:
- In the α- form, the exocyclic O group at the anomeric center is on the opposite face to the -CH2OH group, and
- In the β- form, the exocyclic O group at the anomeric center is on the same face as the -CH2OH group.
Hydrolysis of a glycoside linkage
glycoside + H2O + catalyst → hydrolysis.
Catalysts include: Amylase for starch and glycosylase for nucleotide.
Hemiacetal formation from monosaccharide
-OH attacks carbonyl group = produces ring form.
Acetal formation from monosaccharide
another -OH attack on the same carbonyl group = produces polysaccharides if the -OH is from another monosaccharide.
Mutatorotation
equilibrium between the α and β anomers.
Strong oxidation of monosaccharides.
- Strong oxidation turns aldehyde and terminal hydroxyls to carboxylic acids, and other hydroxyls to ketones.
- The strongest kind of oxidation turns everything to CO2, and this occurs in cellular respiration.
Mild oxidation of monosaccharides
- Mild oxidation is more selective.
- Tollens agent (the test for aldoses, silver reagent) selectively oxidizes the aldehyde to carboxylic acid.
- Nitric acid oxidizes both the aldehyde and the terminal hydroxyl to carboxylic acids, but leaves the other hydroxyls alone.
Reduction of monosaccharides
Reduction turns monosaccharides into polyalcohols.
For proteins, are L and D analogous to R and S?
No. L is not always S, and D is not always R.
When can you interconvert between L/D and R/S?
- If the priority of NH2 > COOH > R, then L=S and D=R. For example, L-Alanine = S-Alanine.
- If the priority of NH2 > R > COOH, then L=R, and D=S. For example, L-Cysteine = R-Cysteine.
When do amino acids exist in a cationic form, anionic form, and a zwitterion?
- At low pH, amino acids exist in the cationic form.
- At high pH, amino acids exist in the anionic form.
- At pH = pI, amino acids exist in the zwitterion form, which is overall neutral.
Acidic amino acids: how to tell if so?
If the R group contains carboxylic acid, then it’s an acidic amino acid. There are two acidic amino acids: aspartic acid and glutamic acid.
Basic amino acids: how to tell if so?
If the R group contains an amine group, then it’s a basic amino acid. There are three basic amino acids: lysine, arginine, and histidine.
When is an amino acid hydrophilic?
Hydrophilic: If the R group contains acids, bases, amines or alcohols.
How is a peptide bond formed?
The peptide bond is formed by the amine group attacking the carbonyl carbon.
Hydrolysis of a peptide bond
The peptide bond is very difficult to hydrolyze. It requires a strong base, or a biological enzyme.
What are three steroids?
Cholesterol, Testosterone, Estrogen
Where are steroids made from?
Steroids are made from the cyclization of squalene, which is a terpene.
What are terpenes and how are they synthesized?
Terpenes are made from the polymerization of isoprene.
Terpenes contain double bonds, which gives the molecule the ability to undergo cyclization.
What is a squalene?
Squalene, the precursor of steroids, is a terpene that consists of 6 isoprene subunits. A complex self-cyclization reaction converts squalene to make steroids.
How are triacyl glycerols made?
Glycerol + 3 Fatty acids → Triacyl Glycerol.
The reverse of triacyl glycerol synthesis is saponification.
Witting Reaction
