Biol1110 2022 Proteins Lecture Notes PDF

Biol1110 Genes to Organisms Proteins Lecture 8 – Proteins  Lecture outline The role of proteins in cells Amino acids – the building blocks of proteins How the chemical nature of different amino acids are determined The four levels of protein structure and how...

Biol1110 Genes to Organisms Proteins Lecture 8 – Proteins  Lecture outline The role of proteins in cells Amino acids – the building blocks of proteins How the chemical nature of different amino acids are determined The four levels of protein structure and how structure is related to function in proteins Protein folding Lecture 8 – Proteins Flow of information Lecture 8 – Proteins  RNA Messenger RNA (mRNA) – The molecule into which DNA is transcribed; takes the genetic information to the ribosome Transfer RNA (tRNA) – Carries individual amino acids to the ribosome Ribosomal RNA (rRNA) – Constituent of the ribosome, along with proteins There are other types of RNA Lecture 8 – Proteins  Translation occurs at ribosomes Complex mixture of RNA and proteins Reads mRNA and recruits tRNA to add amino acids to growing polypeptide chain Lecture 8 – Proteins  Proteins Proteins account for more than 50 % of the dry mass of most cells Protein functions include: – Enzymes – Defensive – Storage – Transport – Hormonal – Receptor – Movement – Structural Lecture 8 – Proteins  Enzymes Analogous to lock & key mechanism Lecture 8 – Proteins  Defensive Recognise and target foreign bodies like pathogens and target them for destruction Lecture 8 – Proteins  Storage Source of nutrition Lecture 8 – Proteins  Transport Carrying molecules Lecture 8 – Proteins  Hormonal Allows different components (organs or tissues) of an organism to communicate Lecture 8 – Proteins  Receptor Signals a response to a stimuli Lecture 8 – Proteins  Movement Flagella, cilia & muscle Lecture 8 – Proteins  Structural Support Lecture 8 – Proteins  Proteins consist of polypeptides Polypeptides are polymers built from the 20 amino acids A protein consists of one or more polypeptides Polypeptides usually range from 10 to >1000 amino acids in length Lecture 8 – Proteins  Amino acids Amino acids are organic molecules with carboxyl and amino groups Amino acids differ in their properties due to differing side chains, called R groups Lecture 8 – Proteins  Amino acids There are 20 amino acids Every amino acid has the same basic structure The unique properties of individual amino acids are associated with their R-groups (aka side chains) Lecture 8 – Proteins  Polypeptides A polypeptide is a polymer of amino acids Amino acids (monomer) are linked by peptide bonds Polypeptides range in length from a few to more than a thousand amino acids Each polypeptide has a unique linear sequence of amino acids Lecture 8 – Proteins  Peptide bonds Carboxyl (COOH) and amino (NH2) groups form peptide bonds to join amino acids together end to end Lecture 8 – Proteins  Protein structure & function A functional protein consists of one or more polypeptides twisted, folded, and coiled into a three-dimensional shape The sequence of amino acids determines the structure of a protein The structure of a protein determines its function – only some amino acids are exposed on the surface of the protein – The physical and chemical properties of these amino acids also affect Lecture 8 – Proteinsfunction Protein structure & function Lecture 8 – Proteins Protein structure & function Lecture 8 – Proteins  Protein structure Primary structure of a protein is its unique sequence of amino acids Secondary structure consists of coils and folds in the polypeptide chain Tertiary structure is their 3-D shape and is determined by interactions among various side chains (R groups) Quaternary structure results when a protein consists of multiple polypeptide chains Lecture 8 – Proteins  Primary structure Primary structure of a protein is its unique sequence of amino acids – determined by DNA Lecture 8 – Proteins  Secondary structure Secondary structure consists of coils and folds from hydrogen bonds between amino acids in the polypeptide secondary structures a helix (coil) and b pleated sheet (fold) Lecture 8 – Proteins  Tertiary structure Tertiary structure is determined by interactions between R groups These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions Strong covalent bonds called disulfide bridges may reinforce the protein’s structure Lecture 8 – Proteins  Chemical bonds Hydrogen bonds – Hydrogen atom and an electronegative atom (e.g. O & N) van der Waals interactions – Uneven distribution of electrons resulting in dynamic positive and negative charge which allows weak bonding between molecules Ionic bonds – between a cation (positive) and an anion (negative) Disulphide bonds – Covalent bond between two sulphur atoms (Cys) Lecture 8 – Proteins Chemical bonds & protein folding Lecture 8 – Proteins  Quaternary structure Quaternary structure results when two or more polypeptide chains form one macromolecule Lecture 8 – Proteins  Protein structure https://commons.wikimedia.org/wiki/File%3A225_Peptide_Bond-01.jpg Lecture 8 – Proteins  Protein structure Physical and chemical conditions can also affect protein structure pH, salt concentration, temperature, or other environmental factors can cause a protein to unfold This loss of the native protein structure is called denaturation A denatured protein is biologically inactive http://bodybuilding- mauritius.blogspot.com/20 13/06/whats-deal-with- raw-eggs-by-vic- goyaram.html Lecture 8 – Proteins  Mutations & protein folding Lecture 8 – Proteins  Protein folding is important Diseases – Alzheimer's disease – Cardiac arrhythmias, Isolated – Diabetes mellitus type 2 atrial amyloidosis – Parkinson's disease – Rheumatoid arthritis – Transmissible spongiform – Familial amyloid polyneuropathy encephalopathy – Hereditary non-neuropathic – Huntington's Disease systemic amyloidosis – Medullary carcinoma of the – Dialysis related amyloidosis thyroid – Lattice corneal dystrophy – Atherosclerosis – Cerebral amyloid angiopathy – Aortic medial amyloid – Cerebral amyloid angiopathy – Prolactinomas (Icelandic type) – Finnish amyloidosis – Systemic AL amyloidosis – Sporadic Inclusion Body Myositis Lecture 8 – Proteins  Lecture summary Proteins perform many functions in organisms Proteins are made up of polypeptides; amino acids (monomer) make up the polypeptide chain Amino acids have an amino and carboxyl side There are 20 amino acids (hydrophobic, hydrophilic, charged) Sequence of amino acids determines the shape and function of a protein Lecture 8 – Proteins  Lecture summary There are four stages of protein structure; primary, secondary, tertiary and quaternary Disulfide, ionic, hydrophobic, van der Waals, and hydrogen bonds are important contributors to protein folding and occur between the R groups of amino acids Proteins can denature, leading to biologically inactive proteins Mutations and incorrect protein folding determines many diseases Lecture 8 – Proteins