Biomolecules - Lecture notes MCAT Week PDF

Preview

Summary

MCAT Organic Chemistry...

Description

Ch 7 | Biologically Important Molecules Friday, May 21, 2021

10:27 AM

Amino Acids - Amino acids can be in L or D configuration ○ We can determine this by drawing a Fischer projection: § Most oxidized carbon is at the top, final carbon at the bottom, substituents on each carbon occupy the horizontal positions on the chain □ We assume horizontal lines project towards us, vertical lines project into the plane away from us ○ L-configuration Amino Acids- have the amino group drawn on the left side in Fischer projection § All animal amino acids are L ○ D-configuration amino acids- have the amino group drawn on the right side in Fischer projection § Occur in bacterial cell wall amino acids § All naturally occurring carbohydrates have the D configuration - our digestive enzymes are specific for D sugar ○ L and D amino acids and carbohydrates are enantiomeric stereoisomers - Peptide bonds: the bond between the carbonyl and N is not rotatable because of resonance- the LP on nitrogen is delocalized and gives it double bond character

Glyceraldehyde L&D - To determine the L or D configuration of carbohydrates, look at the last chiral carbon in the Fischer projection ○ If the OH is on the left, it's L § Built up from L glyceraldehyde ○ If the OH is on the right, it's D § Built up from D glyceraldehyde - All animal amino acids are derived from L-glyceraldehyde and have the L configuration - All animal carbohydrates are derived from D-glyceraldehyde and have the D configuration

Configuration Classifications - (+) and (-) are used to describe optical activity ○ Means the same thing as d and l ○ Clockwise + or counterclockwise - R and S describe the absolute configuration of stereochemistry on chiral carbons - D and L describe the basic precursor of a molecule from glyceraldehyde ○ All D sugars have R configuration of the penultimate carbon ○ All L sugars have S configuration of the penultimate carbon ○ All L amino acids are S ○ All D amino acids are R § Exception: Cysteine

Extra Knowledge About Amino Acids for MCAT Nine Essential Amino Acids: - Lysine - Histidine - Threonine - Valine - Leucine - Isoleucine - Phenylalanine - Tryptophane - Methionine ► Hydroxyl containing amino acids (S, T, Y) are often phosphorylated by kinase in regulation

Lipids - Nomenclature of unsaturated fatty acids ○ For a fatty acid with a cis double bond between carbons 3 and 4 § (Z)-𝝙 3...