CHMA11H3 Lecture Notes - Lecture 38: Protein Structure, Peptide, Cell Nucleus
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4 Apr 2019
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CHMA11 Lecture 35: Protein structure and Intro to Nucleic Acids
- There are 4 levels of protein structure
o Primary Structure: sequence of amino acids in a protein
▪ A simple list of all the amino acids in the protein linked by peptide bonds
▪ Identifies the N and C terminals of proteins
o Secondary Structure: regular periodic patterns in the amino acid chain
▪ Stabilized by hydrogen bonds between close by amino acids on
neighboring amino acid chains
▪ Two key distinct structures
• Alpha Helix: twisted polypeptide chain
o Hydrogen bonds from lower levels twist upward to form a
twist helix shape
• Beta Sheet: polypeptide chain that makes a U turn
o Involves hydrogen bonds between 2 parallel amino acid
chains
• Overall hydrogen bonds play a major role in stabilizing the
secondary structure elements
o Tertiary Structure: interactions within proteins that give it its shape
▪ Refers to the overall structure of the entire polypeptide chain
▪ Determined by interactions between the R groups of the amino acids and
their surroundings
• Causes the proteins to fold in certain unique ways
▪ Key structures
• Disulfide Link: link between two sulfur molecules
• Salt Bridge: form bridge between acidic and basic site groups in
amino acids
▪ Proteins with one single polypeptide chain will end at the tertiary
structure
o Quaternary Structure: structural relationship between two or more polypeptide
chains within a protein
▪ Essentially just a combination of two or more polypeptide chains within a
proteins
- Nucleic Acids: contains the genetic information needed to make proteins
o Third form of macromolecule
o Central Dogma: outlines the flow of genetic information
▪ Claims that genetic information flows from DNA into RNA via
transcription and then RNA to protein via translation
▪ DNA sequences therefore are codes for the amino acid sequences of
proteins