Amino Acids:

Structure & Function

-α carbon, amino group, carboxyl group, and side chain

-Protein function/structure

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Nucleotides:

Structure & Function

-nitrogenous base, 5-membered sugar, 1to 3 phosphate groups

-DNA/RNA structure

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Carbohydrates:

Structure & Function

-Carbon, oxygen, and hydrogen (2:1 H to O ratio)

-Energy conversion

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Lipids:

Structure & Function

-Polar carboxyl head (hydrophilic) and non-polar hydrocarbon tail (hydrophobic)

-Membranes and energy storage

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Amino acid stereochemistry:

D/L system 

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-Based on the amino group (L=left, D=right)

-Carbonyl (COOH) on top and side chain (R) on the bottom

Amino acid stereochemistry:

R/S system

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Hand trick: Thumb on 'lowest' priority group (H) and curl your fingers following the priority from 1 to 3;

-Right hand: R

-Left hand: S

Priority is: 1-NH3, 2-COOH, 3-side chain, 4-hydrogen

*EXCEPTION: cysteine's side chain (2) has greater priority than the carboxyl (3)

Most amino acids are naturally L-configuration and thus have a S absolute configuration, except L-cysteine which is R

Stereochemistry:

D/L vs R/S

Amino Acids:

α, β, and γ carbons

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Ranked with respect to the carboxyl group

-directly attached: α

-1 atom away: β

-2 atoms away: γ

-All have an amino (NH₂) group attached