Lecture 2

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Nucleic Acids and Amino Acids

Nucleic Acids:

-Are DNA and RNA

-Nucleotides are building blocks, or monomers to nucleic acids

-They:

Provide acidic character

Under intracellular conditions, the phosphate group is negatively charged

-Composition:

Pentose sugar

Phosphate group

Ribose or deoxyribose

N-Base

-Bond linking the base and sugar is glycosidic

-Bond linking the sugar and phosphate is phosphodiester

-Ribose has a hydroxyl group on the 2' carbon while deoxyribose has a H on 2' C

-Pentose linked to a nitrogen and carbon ring is referred to as a base

-Bases are either purines or pyrimides:

Purines (Adenine and Guanine) have 2 fused rings

Pyrimidines (Cytosine, Uracil and Thymine) have only 1 ring

-Nucleoside: sugar and base without the phosphate group

-Nucleotides are nucleosides

Amino Acids:

-Building blocks of polypeptides

-Protein functions:

Catalysis: catalyze intra/extracellular reactions

Structure: rigidity

Transport: flow of material across a membrane

Regulatory: act as sensors or switches to control protein activity and gene fcn

Signalling: external signals to cell interior

Motor: motion

-Shape of the protein is very important to function

-20 types of amino acids whose properties are determined by the R groups

-They vary in size, shape, charge, hydrophobicity and reactivity

-Amino acids have 2 possible isomers: D or L (enantiomers)

-Majority of them are L

-The alpha carbon in an amino acid has:

amino group

carboxyl group

H atom

side chain or R group

-Hydrophilic amino acids are polar and water soluble, some have charged R groups and some don't

-Hydrophobic are insoluble in water and non polar

-Amino acid components are important bc they determine how a protein will fold

-Special amino acids:

CYSTEINE: forms disulfide (S-S) bonds with other cyteines, intra/extracellular crosslinking, stabilize folded structure

GLYCINE: compacts the amino acids, important for sharp turns and has symm Hs

PROLINE: rigid ring structure