* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Proteins
Ancestral sequence reconstruction wikipedia , lookup
Endomembrane system wikipedia , lookup
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Gene expression wikipedia , lookup
Magnesium transporter wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
Genetic code wikipedia , lookup
Bottromycin wikipedia , lookup
Expanded genetic code wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Metalloprotein wikipedia , lookup
Protein (nutrient) wikipedia , lookup
Homology modeling wikipedia , lookup
Interactome wikipedia , lookup
Protein domain wikipedia , lookup
Circular dichroism wikipedia , lookup
Protein folding wikipedia , lookup
Protein moonlighting wikipedia , lookup
Western blot wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
List of types of proteins wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Protein mass spectrometry wikipedia , lookup
Protein adsorption wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Biochemistry wikipedia , lookup
Dr. Tarek El Sewedy Department of Medical Laboratory Technology Faculty of Allied Medical Sciences Structure And Function of proteins INTENDED LEARNING OUTCOMES By the end of this lecture, students will learn: 1. Protein structure , function , reactions. Lecture Content • Levels of Protein structure: Primary, Secondary, Tertiary and Quaternary. • Protein structure • Classification of proteins. • Hydrolysis of proteins. • Denaturation of proteins. Proteins Proteins are Macromolecules consisting of long sequences of amino acids in peptide linkage. Protein accounts for almost 20% of total body weight. The human body is made up of approximately 100 trillion cells - each one has a specific function. Each cell has thousands of different proteins, which together make the cell do its job - the proteins are tiny machines within the cell. One gram of protein or carbohydrate contains 4 calories, while one gram of fat has 9 calories. Levels of protein structure There are 4 levels of protein structure: 1. Primary 2. Secondary 3. Tertiary 4. Quaternary 1. Primary structure of proteins Describes the order of the amino acids joined together to make the protein (exact sequence of amino acids before folding). The end of the peptide chain with the -NH2 group is known as the N-terminal, and the end with the COOH group is the C-terminal 2. Secondary Structure It is the simple folding of a protein to create simple structures. The secondary structure of a protein or polypeptide is due to hydrogen bonds forming between amide and carboxyl groups. There are two possible types of secondary structure: 1. Alpha helix, the hydrogen bonding causes the polypeptide to twist into a helix. 2. Beta sheet the hydrogen bonding enables the polypeptide to fold back and forth upon itself like a pleated sheet. Tertiary structure Refers to the three-dimensional structure of the entire polypeptide chain. result from four different bonds: 1. Ionic interactions 2. Hydrogen bonds 3. van der Waals forces 4. Disulphide bond Quaternary Structure It is the interaction between several chains of polypeptide subunits. Not all proteins have quaternary structure, since they might be functional as monomers. The quaternary structure is stabilized by the same range of interactions as the tertiary structure. Hemoglobin is an example of a heterotetramer Proteins could be classified by 1. Shape Globular Fibrous 2.Function 3. structure 1. Catalytic as enzyme Simple 2. Structural as collagen, keratin Conjugated 3. storage as ferritin (store iron). 4. Protective as immunoglobulins 5. Regulatory : hormones as insulin 6. Communication as neurotransmitters 7. Motion as actin/myosin; in muscle 8. Transporter proteins as hemoglobin. 9. Carrier as albumin. Glycoprotein: Immunogloulin. Metalloprotein: Hemoglobin Nucleoprotein: RNA bound protein Phosphoprotein: casein Lipoprotein: Low density lipoprotein (LDL), HDL. Fibrous proteins • Water insoluble and found as structural materials, e.g. collagen, keratin. Globular proteins • Compact, roughly spherical, water soluble and comprise all other types of protein as albumins and globulins. Hydrolysis of proteins Hydrolysis of proteins results in breaking down the peptide bonds to give amino acids thus it disrupts the primary structure of protein . Hydrolysis can be achieved by Enzymes as Proteases. Biological role of hydrolysis: 1. Convert inactive prohormones into active hormones. ex; Proinsulin (inactive) → Insulin (active). 2. Digestion of protein by enzyme as trypsin and pepsin. Inactive form Hydrolysis Active form Protein denaturation It is a process in which proteins can lose their structures and function, without breaking the peptide bonds by denaturing agents such as: 1.Heat, U.V radiation. 2.Heavy metal as mercury. 3.Soaps. 4.Organic acids as acetic acid. 5.Strong acids and bases as sulfuric acid and sodium hydroxide. Note: Denaturation disrupts 2ry,3ry,4ry structure of protein not 1ry structure. • All proteins have unique shapes that define their roles and interaction with other proteins. • Environmental factors and genetic mutations can affect a protein's structure, or three-dimensional shape, causing it to misfold. • Misfolded proteins can no longer perform their functions leading to various diseases. • Misfolded proteins often clump together, forming aggregates. • The aggregates are toxic to some cells such as neurons and lead to diseases such as Alzheimer's Disease. رحمه مسعد عبد اللطيف نورهان أشرف السيد ASSIGNMENTS • Selected students are requested to prepare slides about one of the following topics (To be delivered before next lecture): • Digestion of proteins • Essential amino acids. • Non essential amino acids • Physical properties of amino acids. • Chemical properties of amino acids. • Disease resulting from disturbance in amino acid metabolism. • Ketone bodies and amino acids • Translation of RNA Suggested readings: Principles of Biochemistry, Donald J. Voet, Judith G. Voet, Charlotte W. pratt; Willey, 3rd ed.