Amino Acids - Summary Zwitterions Acid / Base Chemistry (Buffers) Optical Isomerism – chiral centre, CORN Peptide – Secondary Amides Naming dipeptides – NH 2 on left Hydrolysis of peptides Condensation to form polypeptides and proteins
Protein Structure 4 levels of structure:- oPrimary Structure – Sequence of Amino Acids ; oSecondary Structure – Spatial arrangement of sections of primary Structure (e.g. helices); oTertiary Structure – Overall 3D Shape of protein ; oQuaternary Structure – Protein “Monomers” coordinated into tetramers (haemoglobin), or hexamers (insulin).
Building Proteins Cells build proteins directly from L-Amino Acids. To synthesise a protein, a Chemist would need:- 1)Instructions / knowledge of the primary structure; 2)Supplies of pure amino acids; 3)A method of forming peptide links. Cells adopt a similar approach – Protein Synthesis.
Protein synthesis – The role of RNA 1)Messenger RNA - Temporary set of instructions for one protein molecule; 2) Transfer RNA – collects amino acids; 3) Ribosomal RNA – present in ribosomes, which catalyse the formation of peptide links between amino acids.
Transcription – in the nucleus 1) DNA double helix unwinds; 2) hydrogen bonds break; 3) free nucleotides hydrogen bond to the complementary exposed bases; 4) Enzyme (RNA polymerase) links the hydrogen bonded nucleotides to form a strand of mRNA; 5) mRNA is released and the DNA double helix is reformed.
How Cells Make Proteins DNAmRNA Protein Chain TranscriptionTranslation a.a. activation
Translation - in the cytoplasm 1)mRNA attaches to ribosome; 2)Hydrogen bonding between complementary bases binds the correct tRNA anticodon to the 1 st codon (set of 3 bases on mRNA); 3)A 2 nd tRNA – amino acid complex binds to the adjacent mRNA codon in the ribosome; 4)Ribosome catalyses the formation of the peptide bond between amino acids; 5)The tRNA is released once the amino acid is delivered; 6)Ribosome moves along the mRNA chain to the end.
How Cells Make Proteins DNAmRNA Protein Chain 3D Protein TranscriptionTranslation a.a. activation Folding