BIOL 3510 1st Edition Lecture 2 Outline of Last Lecture I. Introduction to cellsII. MicroscopyIII. Prokaryotes and EukaryotesIV. Model OrganismsOutline of Current Lecture I. Introduction to proteinsII. Types of Non-Covalent Bonds/ForcesIII. Protein structuresIV. Measuring ProteinCurrent LectureProteins are composed of chains of amino acids linked together by peptide bonds. Amino acids can be grouped by their side chains. Peptide bonds are covalent bonds (90 kcal/mol in water or vacuum) where electrons are shared; shared unequally in a polar covalent bond. Polar covalent bonds create dipoles within a molecule due to unequal electron distribution. Peptide bonds form via condensation reactions.The conformation of a protein is specified by its amino acid sequence. 3D shape is inherent. 4 levels of protein structural organization: primary, secondary, tertiary, quaternary.4 Types of Non-Covalent Bonds/Forces in Cells1. Electrostatic attractions (3kcal/mol) forces that attract oppositely charged atoms2. Hydrogen bonds (1kcal/mol) a weak bond between an electronegative atom and a hydrogen bound to another electronegative atom3. Van der Waals interactions (0.1 kcal/mol) fluctuations in the electron cloud surrounding an atom creates a transient dipole. This dipole induces an opposing dipole in a nearby atom generating an attraction4. Hydrophobic forces (not really a bond) exclusion of non-polar surfaces from the hydrogen-bonded water networkThese non-covalent bonds/forces stabilize the 3D conformations of proteinsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Chaperones are proteins that improve the efficiency of protein folding in cellsHydrogen bonds between polypeptide backbone groups create secondary structures.Alpha-helix- Polypeptide twists to form a cylinder- Stabilized by H-bonds between a C=O (n) and a N-H (n+3)- Often found in proteins that span membranes- 2 or 3 of them wrapped around each other form a stable coiled-coilBeta-sheet- Stabilized by h-bonds between the C=O and N-H groups on adjacent lengths of a polypeptide chain- Alternate R groups extend in opposite directions- Can be parallel or anti-parallel- Often form the core of stable proteinsIntrinsically disordered sequences correspond to unstructured regions of some proteins. The final 3D conformation of single polypeptide is the tertiary structure, held together mostly by non-covalent bonds. Quaternary structure is the binding of two or more polypeptides to form a single complex, held together mostly by non-covalent bonds/forces.Protein domains are regions of a polypeptide chain that fold independently into a stable structure. They can be combined to create proteins with new functions.Disulfide bonds are covalent bonds between cysteines that act as “atomic staples” to stabilize extracellular proteins. Proteins have a variety of shapes. Members of protein families have similar 3D structures and often similar amino acid sequences.X-ray crystallography is used to determine the 3D structures of proteins.Nuclear magnetic resonance (NMR) spectroscopy is used to determine the 3D structure of
View Full Document
Unlocking...