BCHM 125 Lecture 7-11 Biochemistry for Nurses PDF
Document Details
NCU
Alexia Ximinies
Tags
Summary
This document is a lecture on biological compounds, covering biomolecules, functional groups, and their roles. It's part of a biochemistry course for nurses, and includes details on carbohydrates, proteins, lipids, and nucleic acids.
Full Transcript
1 Biological Compounds Lecture 7 BCHM 125 BIOCHEMISTRY FOR NURSES LECTURER: ALEXIA XIMINIES, Ph.D....
1 Biological Compounds Lecture 7 BCHM 125 BIOCHEMISTRY FOR NURSES LECTURER: ALEXIA XIMINIES, Ph.D. CONTACT: [email protected] © 2011 Pearson Education, Inc. 2 Lecture Objectives At the end of this lecture, you should be able to: Define what are biomolecules Identify the common functional groups found in biomolecules Outline the categories of biomolecules with specific examples Discuss the biochemical role of biomolecules Forthis lecture, read Lehninger Principles of Biochemistry 4th edition, chapter 3, 7, 8, 10. Organic Molecules 3 Used by eighteenth-century chemists to describe substances obtained from living sources such as plants and animals. Organic substances are considered to include all compounds of carbon except oxides of carbon, carbonates, carbides and cyanides. 4 Organic Molecules Organicsubstances include those derived from living organisms as well as numerous synthetic substances. Organic molecules are complex molecules of life, built on a framework of carbon atoms Biomoleculesoften consist of large carbon chains or rings Organic Molecules 5 Carbon has 4 valence electrons Carbon can form 4 covalent bonds (single, double, triple) Once bound to other elements (or to other carbons), it is very stable Straight, branching, ring Varies in length, number and location of double bonds, and presence of other elements Forms isomers C6H12O6 chemical formula for glucose, fructose, & galactose 6 Carbon Chemistry Therepulsion force between electrons is what gives rise to the shape of molecules. Inthe structure of methane, the hydrogen atoms are located as far apart as possible. Giving angles of 109.5o between them. Thisgives rise to a tetrahedral shape around the central carbon atom. 7 Carbon Chemistry Carbonatoms often form multiple bonds with each other to satisfy the octet rule. Theclass of hydrocarbons that form single bonds are known as alkanes Whilealkenes and alkynes are the names given to the class of hydrocarbons that form double and triple bonds, respectively. 8 Carbon Chemistry Carbon bonds may be arranged as: Straight chains Branched chains Rings Carbon Linkages 9 Carbon binds to more than just hydrogen! To OH groups in sugars To NH2 groups in amino acids To H2PO4 groups of nucleotides of DNA, RNA, and ATP OH, NH2, PO4 are called ‘functional groups’! 10 Functional Groups Hydrocarbon Anorganic molecule that consists only of hydrogen and carbon atoms Most biological molecules have at least one functional group A cluster of atoms that imparts specific chemical properties to a molecule (polarity, acidity) Common 11 Functional Groups Common 12 Functional Groups 13 Macromolecules Thereare 4 categories of macromolecules: Carbohydrates Proteins Lipids Nucleic acids 14 Carbohydrates Carbohydrates are the most plentiful biological molecules in the biosphere Cells use some carbohydrates as structural materials; others for stored or instant energy 15 Carbohydrates Carbohydrates Organic molecules that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio Three types of carbohydrates in living systems Monosaccharides Disaccharides Oligosaccharides Polysaccharides Monosaccharides 16 Monosaccharides (one sugar unit) are the simplest carbohydrates Usedas an energy source or structural material Backbones of 3 to 6 carbons Example: glucose Disaccharides 17 Disaccharides (two sugar unit) Double sugars Two6-C chains or rings bonded together 18 Oligosaccharides Oligosaccharides are short-chain carbohydrates 3 – 10 units in length Shortchains of disaccharide & monosaccharide Polysaccharides 19 Polysaccharides are complex carbohydrates Straight or branched chains of many sugar monomers Starch Cellulose Glycogen Chitin Polysaccharides 20 The most common polysaccharides are cellulose starch glycogen All consist of glucose monomers Each has a different pattern of covalent bonding, and different chemical properties 21 Cellulose, Starch, and Glycogen 22 Chitin Chitin A nitrogen containing polysaccharide that strengthens hard parts of animals such as crabs, and cell walls of fungi Lipids 23 Lipids function as the body’s major energy reservoir, and as the structural foundation of cell membranes Lipids Fatty, oily, or waxy organic compounds that are insoluble in water 24 Fatty Acids Many lipids incorporate fatty acids Simple organic compounds with a carboxyl group joined to a backbone of 4 to 36 carbon atoms Essentialfatty acids are not made by the body and must come from food Omega-3 and omega-6 fatty acids Saturated, monounsaturated, polyunsaturated 25 Fats - Triglycerides Fats Lipids with one, two, or three fatty acids “tails” attached to glycerol Triglycerides Neutral fats with three fatty acids attached to glycerol The most abundant energy source in vertebrates Concentrated in adipose tissues (for insulation and cushioning 26 Saturated and Unsaturated Fats Saturated fats (animal fats) Fatty acids with only single covalent bonds Pack tightly; solid at room temperature Unsaturated fats (vegetable oils) Fatty acids with one or more double bonds Kinked; liquid at room temperature 27 Phospholipids Phospholipids Moleculeswith a polar head containing a phosphate and two nonpolar fatty acid tails Headsare hydrophilic, tails are hydrophobic The most abundant lipid in cell membranes 28 Waxes Waxes Complex mixtures with long fatty acid tails bonded to long chain alcohols or carbon rings Protective, water repellant covering 29 Waxes 30 Cholesterol and Other Steroids Steroids Lipids with a rigid backbone of four carbon rings and no fatty acid tails Cholesterol Component of eukaryotic cell membranes Remodeled into bile salts, vitamin D, and steroid hormones (estrogens and testosterone) Proteins 31 Proteins are the most diverse biological molecule structural nutritious enzyme transport communication defense proteins Cells build thousands of different proteins by stringing together amino acids in different orders 32 Proteins and Amino Acids Protein An organic compound composed of one or more chains of amino acids Amino acid A small organic compound with an amine group (-NH3+), a carboxyl group –COO-, the acid), and one or more variable groups (R group) 33 Proteins and Amino Acids Polypeptides 34 Protein synthesis involves the formation of amino acid chains called polypeptides Polypeptide A chain of amino acids bonded together by peptide bonds in a condensation reaction between the amine group of one amino acid and the carboxyl group of another amino acid 35 Peptide Bond Formation 36 Peptide Bond Formation 37 Levels of Protein Structure Primary structure The unique amino acid sequence of a protein 38 Levels of Protein Structure Secondary structure The polypeptide chain folds and forms hydrogen bonds between amino acids 39 Levels of Protein Structure Tertiary structure A secondary structure is compacted into structurally stable units called domains Forms a functional protein 40 Levels of Protein Structure Quaternary structure Some proteins consist of two or more folded polypeptide chains in close association Example: hemoglobin 41 Sequence Specificity Hemoglobin contains four globin chains, each with an iron containing heme group that binds oxygen and carries it to body cells In sickle cell anemia, a DNA mutation changes a single amino acid in a beta chain, which changes the shape of the hemoglobin molecule, causing it to clump and deform red blood cells Just One Wrong Amino Acid… 42 Globin Chains in Hemoglobin Hemoglobin contains four globin chains Each with an iron containing heme group that binds oxygen and carries it to body cells. 43 Molecular Basis of Sickle Cell Anemia 44 Molecular Basis of Sickle Cell Anemia 45 Molecular Basis of Sickle Cell Anemia 46 Protein Denaturation Proteinsfunction only as long as they maintain their correct three-dimensional shape Heat, changes in pH , salts, and detergents can disrupt the hydrogen bonds that maintain a protein’s shape When a protein loses its shape and no longer functions, it is denatured 47 Nucleic Acids Nucleic acids Polymers of nucleotides in which the sugar of one nucleotide is attached to the phosphate group of the next RNA and DNA are nucleic acids Some nucleotides are subunits of nucleic acids such as DNA and RNA Some nucleotides have roles in metabolism 48 Nucleotides Nucleotide A small organic molecule consisting of a sugar with a five-carbon ring, a nitrogen-containing base, and one or more phosphate groups ATP A nucleotide with three phosphate groups Important in phosphate group (energy) transfer 49 RNA RNA (ribonucleic acid) Containsfour kinds of nucleotide monomers, including ATP Important in protein synthesis 50 DNA DNA (deoxyribonucleic acid) Twochains of nucleotides twisted together into a double helix and held by hydrogen bonds Contains all inherited information necessary to build an organism, coded in the order of nucleotide bases 51 Four Nucleotides of DNA 52 53 54 Next Class 55 Cellular Respiration For next lecture read Lehninger Principles of Biochemistry 4th edition, CHAPTERS 14, 15, 16. Digestion of Macromolecules Lecture 8 BCHM 125 BIOCHEMISTRY FOR NURSES LECTURER: ALEXIA XIMINIES, Ph.D. CONTACT: [email protected] 57 Carbohydrate Digestion and Absorption Disaccharides and starches are digested into monosaccharides. Monosaccharides are easily absorbed. Fiber passes through the GI tract undigested 58 Carbohydrate Digestion 59 Carbohydrate Digestion 60 Carbohydrate Digestion 61 Carbohydrate Digestion 62 Absorption of Carbohydrates Once digested to monosaccharides Absorbed through the intestinal cell mucosa. Transported to the liver via the portal vein. Metabolic needs direct fate of the monosaccharides Galactose and fructose Used by the liver for energy Converted to glucose Glucose Used for energy Converted to glycogen through glycogenesis Converted to glycerol and fatty acids for storage in adipocytes 63 Mechanisms For Absorption Two mechanisms are responsible for the absorption of monosaccharides: active transport (against concentration gradient i.e. from low to high concentration) passive transport (by facilitated diffusion). 64 Mechanisms For Absorption Active transport requires specific sugar structures: Hexose ring OH group at position 2 at the right side. Both of which are present in glucose and galactose. Fructose, which does not contain - OH group to the right at position 2 is absorbed more slowly than glucose and galactose by passive diffusion (slow process). A methyl or a substituted methyl group should be present at carbon 5. 65 Mechanisms of Absorption Active transport In the cell membrane of the intestinal cells, there is a mobile carrier protein called sodium-dependent glucose transporter (SGLT-1) SGLT-1 transports glucose inside the cell using energy. The energy is derived from the sodium-potassium pump. The transporter has 2 separate sites, one for sodium and the other for glucose. It transports them from the intestinal lumen across the cell membrane to the cytoplasm. Then both glucose and sodium are released into the cytoplasm allowing the carrier to transport more glucose and sodium. 66 Mechanisms of Absorption The sodium is transported from low to high concentration (with concentration gradient) At the same time, the carrier to transports glucose against its concentration gradient. The Na+ is expelled outside the cell by sodium pump. Which needs ATP as a source of energy. The reaction is catalyzed by an enzyme called Adenosine triphosphatase (ATPase). Active transport is much faster than passive in tissues containing insulin receptors e.g. muscles transport. Insulin increases the number of glucose transporters on adipose tissue. 67 Mechanisms of Absorption Passive transport (facilitated diffusion) Sugars pass with the concentration gradient (from high to low concentration). It needs no energy. It occurs using a sodium-independent facilitative transporter GLUT-5. Fructose and pentoses are absorbed by this mechanism. Glucose and galactose can also use the same transporter if the concentration gradient is favorable. There is also a sodium-independent transporter GLUT-2. GLUT-2 facilitates the transport of sugars out of the intestinal mucosal cell and into portal circulation. 68 Glucose Transporters 69 Glucose Transporters 70 Lipid Digestion Lipid digestion begins in the mouth Lingual lipase breaks down short chain FAs to disaccharides In adults, it plays a minor role It is secreted continuously from lingual serous glands and accumulates in the stomach between meals, when gastric pH is
