Biological-Engineering for Beginners Biochemistry II: Proteins Leigh Casadaban and Alina Gatowski July 26, 2009

Biological-Engineering Biological-Engineering for Beginnersfor Beginners

Biochemistry II: ProteinsBiochemistry II: Proteins

Leigh Casadaban and Alina GatowskiLeigh Casadaban and Alina Gatowski

July 26, 2009July 26, 2009

What are Proteins?What are Proteins?

What are proteins made of?What are proteins made of? Does every cell have the same Does every cell have the same

proteins? proteins?

QuickTime™ and a decompressor

are needed to see this picture.



Structure of ProteinsStructure of Proteins

Primary Structure: Amino Acid Sequence

Secondary Structure: Alpha Helix Beta Sheet

Tertiary Structure: Hydrophobic core Disulfide bonds Salt bridges

Quaternary Structure Protein subunits form into

complex



Structure of Amino AcidsStructure of Amino Acids

Primary Structure is Primary Structure is made of Amino Acidsmade of Amino Acids

Polypeptide Chain:Polypeptide Chain:Peptide bond is an Peptide bond is an « amide bond »« amide bond »







Anatomy of an Amino AcidAnatomy of an Amino Acid



Peptide Bond FormationPeptide Bond Formation



FUN FACTFUN FACT

Essential Amino Acids need to come from the food we eat.

phenylalanine, valine, phenylalanine, valine, threonine, tryptophan, threonine, tryptophan, isoleucine, methionine, isoleucine, methionine,

leucine, and lysineleucine, and lysine

Amino AcidsAmino Acids





The genetic codeThe genetic code

Use the genetic code to Use the genetic code to turn mRNA nucleotides turn mRNA nucleotides to amino acidsto amino acids

Three nucleotides make Three nucleotides make up a codonup a codon

4x4x4 = 64, so why only 4x4x4 = 64, so why only 20 amino acids?20 amino acids?



Degeneracy of the Genetic CodeDegeneracy of the Genetic Code

The genetic code has The genetic code has redundancy but no redundancy but no ambiguity ambiguity

GAA and GAG both GAA and GAG both specify glutamic acid specify glutamic acid (redundancy), neither (redundancy), neither of them specifies any of them specifies any other amino acid (no other amino acid (no ambiguity)ambiguity)





CENTRAL DOGMACENTRAL DOGMA



Transcription

Translation

20 Amino Acids 20 Amino Acids

Amino acids form Amino acids form polypeptide chainspolypeptide chains

http://www.nclark.net/AminoAcids.ram



Point MutationsPoint Mutations



Secondary StructureSecondary Structure



Ramachandran plotRamachandran plot

Dihedral angles Dihedral angles and and for amino acid residues in for amino acid residues in protein structureprotein structure

Shows steric hindrance Shows steric hindrance and conformationand conformation

Glycine can adopt angles Glycine can adopt angles in all four quadrantsin all four quadrants





Alanine (R) and Glycine (L)Alanine (R) and Glycine (L)

Tertiary StructureTertiary Structure



1. Disulfide bonds 2. Hydrophobic

interactions 3. Hydrogen bonds4. Ionic interactions

Quaternary StructureQuaternary Structure



Quaternary structure refers to the association of multiple subunits.

The subunits may be identical or different

When they are different, each subunit tends to have a different function

Primary Structure can Primary Structure can predict fold?predict fold? QuickTime™ and a

decompressorare needed to see this picture.



R group functionR group function

TyrosineTyrosine PhenylalaninePhenylalanine TryptophanTryptophan







Fun FactsFun Facts

Aspartame is used in low-calorie artificial Aspartame is used in low-calorie artificial sweeteners: Equal, NutraSweet, and Canderelsweeteners: Equal, NutraSweet, and Canderel

It is 200 times sweeter than sugar, without the It is 200 times sweeter than sugar, without the high energy value of sugarhigh energy value of sugar

Aspartame is the methyl ester of a Aspartame is the methyl ester of a phenylalanine/aspartic acid dipeptidephenylalanine/aspartic acid dipeptide



Documents

Biological-Engineering for Beginners Biochemistry II: Proteins Leigh Casadaban and Alina Gatowski July 26, 2009