A Molecular Approach, 4e - Notes for Chapter (22).doc

Chapter 22. Biochemistry Chapter 22. Biochemistry Chapter 22. Biochemistry Student Objectives 22.1 Diabetes and the Synthesis of Human Insulin Know that diabetes is a disease due to the absence or insufficiency of insulin, a protein synthesized in the pancreas that helps regulate cellular and blood glucose levels. Know that genetic engineering has allowed modified bacteria to produce human insulin, allowing it to be harvested for human use. Know that biochemistry is the chemistry of living organisms, often involving macromolecules such as lipids, carbohydrates, proteins, and nucleic acids. 22.2 Lipids Give a general description of lipids with respect to structure and function. Know that fatty acids can be saturated (all C–C bonds) or unsaturated (at least one C=C bond). Know and understand how the tri-alcohol glycerol combines with fatty acids to form triglycerides. Know and understand that fats are solids and oils are liquids at room temperature, a consequence of the structures of the fatty acids in triglycerides. Know that natural geometric isomers of unsaturated fatty acids are typically cis, that trans forms are introduced when hydrogenation is used to control potential rancidity, and that trans fatty acids are not considered healthful by nutrition experts. Give a general description of phospholipids with respect to structure and function. Draw and recognize representations of phospholipids and their role in lipid bilayers. Recognize the structure of cholesterol and know that it serves as a structural component of cell membranes and as a precursor to other steroids in the body. 22.3 Carbohydrates Know that carbohydrates are polyhydroxy aldehydes and ketones that are nutritional sugars and starches and that serve as energy sources for the body. Recognize the general structures of monosaccharides like glucose and fructose. Know and understand how monosaccharides like glucose and fructose form rings that can combine to make more complex structures such as disaccharides (e.g. sucrose) or polysaccharides (e.g. cellulose, starch, glycogen). 22.4 Proteins and Amino Acids Know and understand that proteins are macromolecules that serve as structural components, enzymes, and hormones and have additional roles in transport, storage, protection, and mobility. Know that there are 20 common amino acids and that ten essential ones must be consumed since the body cannot produce them from other molecules. Know the general structure of amino acids, and write reactions for the formation of peptide bonds. 22.5 Protein Structure Know that proteins are characterized as fibrous or globular. Know that protein structure consists of four levels: primary, secondary, tertiary, and quaternary. Know that the primary structure of a protein gives the sequence of amino acids. Recognize the two common components of secondary structure, -helices and -pleated sheets, and know that hydrogen bonding enables the formation of both. Understand the different intermolecular interactions that maintain tertiary structure. Know that multimeric proteins exhibit quaternary structure. 22.6 Nucleic Acids: Blueprints for Proteins Understand the basic structure of nucleic acids: sugars, bases, and phosphate links. Know and understand how the nucleotides are covalently combined to make a single strand and how two complementary strands form a double helix through hydrogen bonding. Define and understand codon, gene, and chromosome. 22.7 DNA Replication, the Double Helix, and Protein Synthesis Know and understand the process of DNA replication. Know how proteins are synthesized from an RNA copy of DNA and understand how the codons direct the ribosome to attach particular amino acids to each other to make the specific protein sequence. Section Summaries Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples Teaching Tips Suggestions and Examples Misconceptions and Pitfalls Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 22.1 Diabetes and the Synthesis of Human Insulin Diabetes insulin biotechnology: genetic engineering Biochemistry Intro figure: illustration of spiral timeline, structures of biomolecules 22.2 Lipids Fatty acid structure even number of carbons, C4 to C20 chains saturated unsaturated cis trans Glycerides triglycerides phospholipids phosphatidylcholine lipid bilayers Cholesterol membrane structure biosynthetic precursor to testosterone, estradiol unnumbered figures: Lewis structures, space-filling models of myristic acid, oleic acid Table 22.1 Fatty Acids Figure 22.1 The Effect of Unsaturation Figure 22.2 The Formation of Tristearin unnumbered figure: photo of lard package unnumbered figure: Lewis structure, space-filling model of tristearin, triolein Figure 22.3 Phosphatidylcholine Figure 22.4 Schematic for Phospholipid or Glycolipid Figure 22.5 Lipid Bilayer unnumbered figure: Lewis structure of cholesterol, testosterone, -estradiol 22.3 Carbohydrates General structure: (CH2O)n Monosaccharides carbonyl: aldehyde or ketone OH groups cyclic form Disaccharides glycosidic linkage sucrose (from glucose and fructose) Polysaccharides cellulose starch glycogen unnumbered figure: Lewis structure, space-filling model of glucose, fructose Example 22.1 Carbohydrates and Optical Isomerism Figure 22.6 Intramolecular Reaction of Glucose to Form a Ring unnumbered figure: Lewis structures of ring forms of glucose, fructose, galactose Figure 22.7 Formation of a Glycosidic Linkage unnumbered figures: Lewis structures of cellulose, starch Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 22.1 Diabetes and the Synthesis of Human Insulin There are several examples of essential proteins that are missing and can be replaced. Diabetes affects about 11% of the population. Other examples include human growth hormone and thyroid hormone. Biotechnology or genetic engineering is commonly used to make important proteins and biomedical molecules. Not all missing or damaged proteins can be replaced. Insulin is an example of one that can be. 22.2 Lipids Fatty acids and glycerol are the building blocks of triglycerides, the components of nutritional fats and oils. The space-filling models give a good sense of the shapes. Melting points give a sense of how well the molecules can pack together. Trans fats and the trans fatty acids from which they are made appear often in the nutrition literature and in the media. Trans fats do occur in nature but in small quantities. The interactions of phospholipids with water make the membranes containing phospholipids even more stable. The structural properties of fats and oils come primarily from the chain length and degree of unsaturation of the fatty acids. 22.3 Carbohydrates When compared with the lipids, carbohydrate structures are more complex, including issues such as the nature of the monosaccharide, ring structures, and the glycosidic linkage between any two monosaccharides in more complex molecules. The microscopic and macroscopic properties of the more complex sugars arise from the nature of the monosaccharides and the glycosidic linkages between them. Monosaccharides occur primarily in the cyclic form in water. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 22.4 Proteins and Amino Acids Classes enzymes hormones structure, transport, storage, contraction, protection Amino acids general structure 20 common amino acids 10 essential amino acids cannot be biosynthesized Table 22.2 Protein Functions unnumbered figure: Lewis structures of amino acids Table 22.3 Common Amino Acids Example 22.2 Peptide Bonds 22.5 Protein Structure Structural categories fibrous (linear) example: collagen globular example: hemoglobin Levels primary: amino acid sequence secondary: -helices, -pleated sheets tertiary: intramolecular interactions quaternary: subunits Figure 22.8 Fibrous and Globular Proteins Figure 22.9 Levels of Protein Structure unnumbered figure: photo of normal and sickled red blood cells Figure 22.10 Primary Structure of Egg-White Lysozyme Figure 22.11 The -Helix Structure Figure 22.12 The -Pleated Sheet Structure Figure 22.13 Interactions within Proteins 22.6 Nucleic Acids: Blueprints for Proteins Basic nucleotide structure phosphate sugar: ribose or deoxyribose base: purine or pyrimidine Genetic code nucleotide codon gene chromosome Figure 22.14 DNA Structure unnumbered figure: Lewis structures of DNA and RNA bases Figure 22.15 Base Pairing in DNA Figure 22.16 Short Strand of DNA Figure 22.17 Genetic Structure Figure 22.18 Chromosomes Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 22.4 Proteins and Amino Acids The combination of amino acids to form polypeptides is an example of a condensation reaction. The acid portion of one amino acid combines with the amine portion of another, yielding a peptide bond and a water molecule. The 20 common amino acids can be placed in a few categories according to their R group: alkyl groups, alcohols and thiols, carboxylic acids, amines and amides, and aromatic rings. Conceptual Connection 22.1 Peptides The essential amino acids are ones that cannot be biosynthesized by humans and therefore must be consumed (eaten). 22.5 Protein Structure Protein structural categories arise from different functions. The fibrous examples like collagen serve as structural elements in muscles for example. Globular proteins are often more water soluble and serve as enzymes or to support other functions besides structure. The levels of protein structure arise from the size, complex structure, and functions of many proteins. The intramolecular interactions often arise from the side chains of the amino acids. Sickle-cell anemia is due to a protein defect in which a single amino acid is replaced with one that is less functionalized. The ability of the red blood cell to carry oxygen is reduced. Protein structure involves intramolecular interaction between amino acid components that extends far beyond the mere order of the amino acids in a protein. 22.6 Nucleic Acids: Blueprints for Proteins The structures of RNA and DNA are relatively simple considering their importance. For example, only four bases are used to code for a host of proteins. The simple structure, though, enables duplication and repair. Conceptual Connection 22.2 The Genetic Code Base-pairing in DNA occurs through specific hydrogen bonding interactions. Base-pair mismatches do not have those proper hydrogen bonding interactions. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 22.7 DNA Replication, the Double Helix, and Protein Synthesis Replication DNA double helix structure complementary single strands base-pair match Protein synthesis RNA copies of DNA codons ribosomes Figure 22.19 Watson and Crick Figure 22.20 DNA Double Helix Figure 22.21 DNA Replication Figure 22.22 Protein Synthesis Chemistry and Medicine: The Human Genome Project Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 22.7 DNA Replication, the Double Helix, and Protein Synthesis The Human Genome Project has provided the identity and order of bases for all genetic material in humans. Now, the effort is to identify on which chromosome each gene resides and the mechanisms by which the massive amount of information is organized. Protein synthesis makes use of three-amino-acid codons. As each codon is read by the ribosome, an amino acid is added to the polypeptide. Additional Problem for Carbohydrates and Optical Isomerism (Example 22.1) Examine the structure of deoxyribose, part of the backbone in DNA. Does deoxyribose exhibit optical isomerism? If so, which carbon atoms are chiral? Chiral Centers Examine each carbon to see which have four different atoms or groups attached. Carbons 3 and 4 are chiral centers. Carbon 1 is the carbonyl C=O; carbon 2 and carbon 5 have two H attached apiece. Optical Isomerism With two chiral centers, deoxyribose exhibits optical isomerism. Additional Problem for Peptide Bonds (Example 22.2) Show the tripeptide that results from linking the amino acids glycine, valine, and serine in that order. Label the N-terminus and C-terminus ends of the tripeptide. Peptide Bonds A peptide or amide bond forms when the hydroxyl –OH from the carboxylic acid of one amino acid is removed, together with the hydrogen from the amino group of the adjacent amino acid. Water is removed each time a peptide bond is formed. They appear in the boxes. Tripeptide The resulting tripeptide is: H2N – glycine – valine – serine – CO2H 300 Copyright © 2017 by Education, Inc. 301 Copyright © 2017 by Education, Inc.