BioChemL3

Lecture 3

Importance of proteins and amino acids?

Amino Acids

• 20 types (essential and non essential)

• Makeup proteins and the building blocks

Proteins

• Growth and repair for muscles, bones, organs, and skin

• Enzymes and hormones (Catalyze chem functions in body)

• Immune defense via antibodies

• Structural and transport

Structural levels of protein

Primary - AA linked chain

Secondary - Structural patterns (Alpha, beta, helix)

Tertiary - 3D folding of polypeptide

Quaternary - 2+ polypeptide subunits (functional in cells)

Significance of R groups?

R group determines chem properties —> protein structure and function

R groups influence binding pockets of enzymes where drugs bind

Different R groups affect how amino acids are metabolized

α-Amino Acid groups

Amino group (-NH2) ; Carboxyl group (-COOH) ; R group; Hydrogen atom ; α-Carbon separates amino and carboxyl groups; Chiral (except GLYSINE)

Glysine (Gly) ; G

Alanine (Ala) ; A

Valine (Val) ; V

Leucine (Leu); L

Isoleucine (Ile) ; I

Phenylalanine (Phe); F

Proline (Pro) ; P

Serine (Ser) ; S

Threonine (Thr) ; T

Tyrosine (Tyr) ; Y

Cysteine (Cys); C

Methionine (Met); M

Lysine (Lys); K

Arginine (Arg); R

Histidine (His); H

Tryptophan (Trp) ; W

Aspartic Acid (Asp) ; D

Glutamic Acid (Glu); E

Asparagine (Asn); N

Glutamine (Gln) ; Q

Nonpolar R groups (define + examples)

• Mediate hydrophobic effects

• Often buried inside proteins

• 3D structure of proteins

Glycine, alanine, valine, leucine, isoleucine, methionine, proline

Polar R groups (Define + examples)

• Can form HYDROGEN bonds

• Contribute to 3D structure

Serine, threonine, tyrosine, cysteine, asparagine, glutamine

Aromatic R groups (define + examples)

• Stable ring structure

• Can absorb UV light

Phenylalanine, tryptophan, tyrosine

Positive charged R groups

• Often DNA/RNA binding

Lysine, arginine, histidine

Negative charged R groups

• Very acidic

Aspartate, glutamate

Uncommon Amino Acids

• 4-hydroxyproline: Modified AFTER protein synthesis

• Pyrrolysine: Modified DURING protein synthesis

• Carboxyglutamate: Found in blood clotting protein

• Desmosine: Crucial for function of elastin (elasticity of tissues)