BNUR 2003 Biomedical Chemistry & Lab Diagnostics PDF

2023-10-16 Learning Objectives 1. List the four categories of macromolecule found in the body. BNUR 2003 2. Understand the chemical composition of amino acids and how they are linked together to form proteins. Biomedical Chemistry and Lab Diagnostics 3. Understand the four hierarchical levels o...

2023-10-16 Learning Objectives 1. List the four categories of macromolecule found in the body. BNUR 2003 2. Understand the chemical composition of amino acids and how they are linked together to form proteins. Biomedical Chemistry and Lab Diagnostics 3. Understand the four hierarchical levels of protein structure and the forces that influence them. 2-Important Biochemical Molecules and Macromolecules 2-1 Proteins 2-2 Carbohydrates + Lipids 2-3 Nucleic acids and mutations 4. Describe what protein denaturation is and how it occurs. 5. Understand the principles of protein electrophoresis and how it is used in healthcare. Describe what an enzyme is. 6. Understand the chemical composition of various carbohydrates and how they are related. 7. Understand the chemical composition of various lipids and how their properties are related to fatty acid composition. 1 2 Biochemical Molecules and Macromolecules Proteins Amino Acids Peptide Bonds Structure • • • • All biochemical molecules are derived from simple precursors from our environment (CO2, H2O, etc.) These are converted into larger molecular weight organic subunits (monomers) Monomers are linked together to form four major types of macromolecules (proteins, carbohydrates, lipids, nucleic acids) Classes Carbohydrates Denaturation Electrophoresis Macromolecules Enzymes Lipids Macromolecules are essential to life and abundant in cells. Monosaccharides Disaccharides Polysaccharides Triglycerides Nucleic Acids 3 Phospholipids Other lipids 4 1 2023-10-16 Proteins and Amino Acids Proteins are the most abundant organic molecules in cells. They all contain ________, ________, ________, ________, and usually ________. 5 6 Proteins and Amino Acids Proteins and Amino Acids The subunits of proteins are amino acids. There are 20 different amino acids that make up proteins. All amino acids consist of a carbon atom attached to: • An ________ group • A ________ group • A ________ atom • A ________(denoted R) 7 The characteristic properties of individual amino acids (in other words, the side chains) contribute to the structure and function of proteins. Here is an example amino acid, Tyrosine: 8 2 2023-10-16 Proteins and Amino Acids Q:What characteristics can different side chains give amino acids? Net Charge: Some amino acids have a net negative charge (acidic), others have a net positive charge (basic), and others are neutral. Polarity: Some amino acids are nonpolar (hydrophobic) and others are polar (hydrophilic). Sulfur: Two amino acids have sulfur in their structure. 9 10 Proteins and Amino Acids • • Aspartate and glutamate are negatively charged Arginine, histadine, and lysine are positively charged Proteins and Amino Acids Proteins are formed by linking together amino acids. Although there are only 20 amino acids, there is no limit on protein length, so possibilities are endless. How are amino acids linked to form proteins? To link two amino acids, a is formed and one molecule of water is generated. This reaction is an example of dehydration synthesis. 11 12 3 2023-10-16 Proteins and Amino Acids Polypeptides always consist of an N-terminus and a C-terminus. Polypeptides are identified by naming amino acids from the N-terminal. In this case the polypeptide is ala-ser-gly. 13 Levels of Protein Structure Levels of Protein Structure Protein structure can be broken down to four hierarchical levels: primary, secondary, tertiary, and quaternary structure. Primary structure refers to the amino acid _______.The primary structure is 2-dimensional, but determines the 3dimensional shape of the protein. 14 Levels of Protein Structure Secondary structure refers to localized folding of the polypeptide backbone due to hydrogen bonds between the carboxyl group of one peptide bond and the amino group of another peptide bond. Two types of secondary structure: (1) ___________ (2) ________________ α-helix • Hydrogen bonds form between amino acids that are 4 amino acids away on the same polypeptide chain. 15 16 • Side chains point out of the helix. • Form a “toilet paper roll” type structure. 4 2023-10-16 Levels of Protein Structure ß-pleated sheet • Several polypeptides are arranged such that they lie parallel to each other in the shape of a sheet. • Hydrogen bonds form between carboxyl and amino groups on different polypeptides. Levels of Protein Structure Tertiary structure refers to the overall 3-dimensional folding of the polypeptide chain. Different from secondary structure in several ways • Not repetitive • Involves the _______ ________ of amino acids Tertiary structure is stabilized mostly by three noncovalent forces: (1) Hydrophobic interactions (2) Ionic bonds (3) Hydrogen bonds 17 Levels of Protein Structure 18 Levels of Protein Structure Quaternary structure refers to the interaction of two or more polypeptides to form a larger protein that operates as a single functional unit (an oligomer). • Subunits may not be active. • Multiple subunits may allow increased activity. 19 20 5 2023-10-16 Levels of Protein Structure Levels of Protein Structure Hemoglobin is an oligomer consisting of four polypeptide chains. 21 Levels of Protein Structure We will study two major classes of proteins – globular and fibrous. Globular proteins are often water _______ with ionic groups on the outside of the molecule and hydrophobic pockets tucked on the inside of the molecule. • Transportation molecules • Enzymes • Antibodies 23 22 Levels of Protein Structure Hydrophilic exterior (R groups of charged and hydrophilic amino acids point outwards) Fibrous proteins are water _______ and usually function in a structural capacity. Common fibrous proteins in humans include collagen and keratin. Hydrophobic pocket (R groups of hydrophobic amino acids point inwards, away from water.) 24 6 2023-10-16 Denaturation of Proteins The normal three-dimensional structure of a protein is called the native state. Loss of the native state usually renders proteins non-functional. This loss is called denaturation. Note that no break in the primary structure of a protein is involved in denaturation. Why is denaturation good? Denaturation of Proteins The structure of proteins can be disrupted by four types of force: 1. Agents that disrupt hydrogen bonds • • • _________ Shear forces Chemicals (e.g., urea, guanidinium chloride) 2. Agents that disrupt hydrophobic interactions • _________ _________ (acetone, alcohol) 3. Agents that disrupt electrostatic interactions Why is denaturation bad? • changes in _________ 4. Agents that disrupt disulfide bridges • _________ 25 Protein Electrophoresis Proteins may be either positively or negatively charged depending on the number of positively or negatively charged amino acids. We can take advantage of this property to identify proteins using protein electrophoresis. Electrophoresis uses an electric field to separate proteins. 26 Protein Electrophoresis One early use of protein electrophoresis was the rapid identification of individuals with sickle cell anemia. Sickle cell anemia involves a mutation at the 6th amino acid in one of the protein subunits of __________. HbA Negatively charged 27 HbS Neutral 28 7 2023-10-16 Protein Electrophoresis Enzymes Enzymes are important macromolecules needed to sustain life. They are almost always ________ proteins. The change of just one amino acid affects the migration of the protein in the electric field! • HbA Negatively charged -neg cathode HbS We will talk much more about them in later units, but for now note that enzymes are proteins and the structure of individual enzymes is critically important to their function. Neutral +pos anode HbA HbS HbS/HbA 29 30 8