Lecture 4 molecules of life


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Lecture 4 molecules of life

  1. 1. You are What You Eat: Macromolecules of Life & Their Relationship to Diet and Nutrition Text Reading: Chapter 2 (p35-40), Chapter 3 (p53-62, 70-75) <ul><li>Learning Objectives </li></ul><ul><li>Name the four major classes of biological macromolecules. Describe the composition and function of each. Provide examples of each. </li></ul><ul><li>Distinguish between steroids and anabolic steroids, and explain how the use of anabolic steroids can be dangerous to a person’s health. </li></ul><ul><li>Apply this information to interpreting a food label and categorize the food as either healthful or junk food. </li></ul>
  2. 2. Organic Molecules <ul><ul><li>A cell is mostly water. </li></ul></ul><ul><ul><li>Rest of the cell consists mostly of carbon-based molecules. </li></ul></ul><ul><ul><li>Organic chemistry is the study of carbon compounds. </li></ul></ul>
  3. 3. Carbon <ul><ul><li>Carbon (atomic number = 6) is a versatile atom. </li></ul></ul><ul><ul><ul><li>Four electrons in valence shell. </li></ul></ul></ul><ul><ul><ul><li>Can share its electrons with other atoms to form up to four covalent bonds. </li></ul></ul></ul><ul><ul><li>Carbon can use its bonds to </li></ul></ul><ul><ul><ul><li>Attach to other carbons. </li></ul></ul></ul><ul><ul><ul><li>Form an endless diversity of carbon skeletons. </li></ul></ul></ul>
  4. 4. Diversity of Carbon Skeletons
  5. 5. <ul><ul><li>Simplest organic compounds are hydrocarbons . </li></ul></ul><ul><ul><ul><li>Organic molecules containing only carbon and hydrogen atoms. </li></ul></ul></ul><ul><ul><ul><li>Simplest hydrocarbon = methane. </li></ul></ul></ul>Hydrocarbons
  6. 6. Hydrocarbons (cont’d) <ul><ul><li>Larger hydrocarbons are the main molecules in the gasoline. </li></ul></ul><ul><ul><li>The hydrocarbons of fat molecules provide energy for our bodies. </li></ul></ul>
  7. 7. <ul><ul><li>Composition of a molecule determines its </li></ul></ul><ul><ul><ul><li>shape </li></ul></ul></ul><ul><ul><ul><li>function </li></ul></ul></ul><ul><ul><li>Molecules recognize one another based on their shapes. </li></ul></ul>The Composition and Shape of a Molecule is Important for its Function <ul><ul><li>Properties of an organic molecule depend on </li></ul></ul><ul><ul><ul><li>its carbon skeleton </li></ul></ul></ul><ul><ul><ul><li>the atoms attached to the skeleton </li></ul></ul></ul>
  8. 8. Giant Molecules from Smaller Building Blocks <ul><ul><li>On a molecular scale, many of life’s molecules are gigantic. </li></ul></ul><ul><ul><ul><li>Biologists call them macromolecules . </li></ul></ul></ul><ul><ul><ul><li>Examples: DNA, carbohydrates, proteins, lipids </li></ul></ul></ul><ul><ul><li>Most macromolecules are polymers. </li></ul></ul><ul><ul><ul><li>Polymers made by stringing together many smaller molecules ( monomers/subunits) . </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Similar to train cars being linked together to form a train. </li></ul></ul></ul></ul></ul>
  9. 9. Biological Macromolecules <ul><ul><li>There are four categories of macromolecules in cells: </li></ul></ul><ul><ul><ul><li>Carbohydrates </li></ul></ul></ul><ul><ul><ul><li>Lipids </li></ul></ul></ul><ul><ul><ul><li>Proteins </li></ul></ul></ul><ul><ul><ul><li>Nucleic acids </li></ul></ul></ul>
  10. 10. Carbohydrates <ul><ul><li>Major source of energy for cells </li></ul></ul><ul><ul><li>Carbohydrates include </li></ul></ul><ul><ul><ul><li>Simple sugar molecules (fructose, glucose, sucrose) – enter system quickly </li></ul></ul></ul><ul><ul><ul><li>Complex carbohydrates contain branched chains of simple sugars (starch, glycogen) – digested slowly </li></ul></ul></ul>
  11. 11. Carbohydrates (cont’d) <ul><ul><li>3 classes of carbohydrates: </li></ul></ul><ul><ul><ul><li>Monosaccharides </li></ul></ul></ul><ul><ul><ul><li>Disaccharides </li></ul></ul></ul><ul><ul><ul><li>Polysaccharides </li></ul></ul></ul>Figure 2.12
  12. 12. Monosaccharides <ul><ul><li>Monosaccharides are simple sugars. </li></ul></ul><ul><ul><li>Examples: glucose, fructose </li></ul></ul><ul><ul><ul><li>Glucose found in sports drinks </li></ul></ul></ul><ul><ul><ul><li>Fructose found in fruit, corn syrup </li></ul></ul></ul><ul><ul><ul><li>Honey contains both glucose and fructose </li></ul></ul></ul><ul><ul><li>Monosaccharides are the main fuel </li></ul></ul><ul><ul><li>that cells use for cellular work. </li></ul></ul>
  13. 13. Disaccharides <ul><ul><li>A disaccharide is a double sugar. </li></ul></ul><ul><ul><ul><li>Constructed from two monosaccharides. </li></ul></ul></ul><ul><ul><li>Examples: maltose, lactose, sucrose </li></ul></ul><ul><ul><ul><ul><li>Maltose is used to make beer, malted milk shakes, & malted milk ball candies. </li></ul></ul></ul></ul>
  14. 14. <ul><ul><li>Lactose is another type of disaccharide. </li></ul></ul><ul><ul><ul><li>Found in milk products. </li></ul></ul></ul><ul><ul><ul><li>lactose intolerance: inability to digest lactose </li></ul></ul></ul><ul><ul><ul><li>These people don’t make enough lactase, the enzyme the breaks down lactose. </li></ul></ul></ul>Disaccharides (cont’d)
  15. 15. <ul><ul><li>Most common disaccharide is sucrose (table sugar) </li></ul></ul><ul><ul><ul><li>Consists of a glucose linked to a fructose. </li></ul></ul></ul><ul><ul><ul><li>Extracted from sugar cane and roots of sugar beets. </li></ul></ul></ul>Disaccharides (cont’d) <ul><ul><li>USA is one of the world’s leading markets for sweeteners. </li></ul></ul><ul><ul><ul><li>Average American consumes ~64 kg (>140 lbs!!!) of sugar/year </li></ul></ul></ul>
  16. 16. Polysaccharides <ul><ul><li>Complex carbohydrates are called polysaccharides. </li></ul></ul><ul><ul><ul><li>Long chains of sugar units. </li></ul></ul></ul><ul><ul><ul><li>Polymers of monosaccharides. </li></ul></ul></ul><ul><ul><li>Examples: starch, glycogen, cellulose </li></ul></ul><ul><ul><li>Fiber is an indigestible complex carbohydrate </li></ul></ul>
  17. 17. Proteins <ul><ul><li>Proteins perform most of the tasks the body needs to function. </li></ul></ul>Structure Storage Contractile Proteins Transport Defense (Antibodies) Enzymes Hormones Signaling Proteins
  18. 18. The Monomers: Amino Acids <ul><ul><li>Proteins are polymers of amino acids. </li></ul></ul><ul><ul><li>All proteins are constructed from a common set of 20 kinds of amino acids. </li></ul></ul><ul><ul><li>Each amino acid consists of </li></ul></ul><ul><ul><ul><li>A central carbon atom bonded to four covalent partners. </li></ul></ul></ul><ul><ul><ul><li>Side group is variable among all 20. </li></ul></ul></ul><ul><ul><ul><li>The side group gives each amino acid its properties. </li></ul></ul></ul>
  19. 19. Proteins as Polymers <ul><ul><li>Cells link amino acids together to form proteins. </li></ul></ul><ul><ul><ul><li>The resulting bond between them is called a peptide bond . </li></ul></ul></ul><ul><ul><ul><li>String of amino acids sometimes called polypeptide . </li></ul></ul></ul>Figure 2.13
  20. 20. Protein Diversity <ul><ul><li>Your body has tens of thousands of different kinds of proteins. </li></ul></ul><ul><ul><li>Different combinations of amino acids give proteins different properties. </li></ul></ul><ul><ul><li>Most proteins are at least 100 amino acids in length. </li></ul></ul><ul><ul><li>Many different sequences possible with 20 amino acids. </li></ul></ul><ul><ul><li>Analogy: 26 letters can make many different words </li></ul></ul>
  21. 21. <ul><ul><li>Primary structure </li></ul></ul><ul><ul><ul><li>Sequence of amino acids in a protein </li></ul></ul></ul>Protein Structure <ul><ul><li>A slight change in the primary structure of a protein affects its ability to function. </li></ul></ul><ul><ul><ul><li>The substitution of one amino acid in hemoglobin causes sickle-cell disease. </li></ul></ul></ul>
  22. 22. Protein Shape <ul><ul><li>Proteins have four levels of structure. </li></ul></ul>Sequence of amino acids Local folding patterns Examples: alpha helix, beta pleated sheet Overall three-dimensional shape Overall shape when two or more polypeptides bind each other
  23. 23. What Determines Protein Structure? <ul><ul><li>A protein’s amino acid sequence dictates its structure. </li></ul></ul><ul><ul><li>A protein’s shape is also sensitive to the surrounding environment. </li></ul></ul><ul><ul><ul><li>Unfavorable temperature and pH changes can cause a protein to unravel and lose its shape. </li></ul></ul></ul><ul><ul><ul><li>This is called denaturation . </li></ul></ul></ul>
  24. 24. Proteins as Nutrients <ul><ul><li>Our bodies can make several amino acids. </li></ul></ul><ul><ul><li>Essential amino acids : amino acids our bodies cannot make, must obtain from food. </li></ul></ul><ul><ul><li>Complete proteins : contain all essential amino acids. </li></ul></ul><ul><ul><li>Animal proteins (meat) more likely to be complete than plant proteins. Plant proteins can be combined to make complete. </li></ul></ul>Figure 3.2 Lysine Valine (a) Lentils are high in lysine and low in valine. (b) Rice is low in lysine and high in valine. Lysine Valine The side groups of lysine and valine are different.
  25. 25. Lipids <ul><ul><li>Lipids are hydrophobic (water-fearing). </li></ul></ul><ul><ul><ul><li>They do not mix with water. </li></ul></ul></ul><ul><ul><ul><ul><li>Oil and vinegar salad dressing separates into layers. </li></ul></ul></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><li>fats, oils, steroids, wax, cholesterol, phospholipids </li></ul></ul>Figure 2.14
  26. 26. Fats <ul><ul><li>Dietary fat consists largely of the molecule triglyceride. </li></ul></ul><ul><ul><ul><li>Triglyceride is a combination of glycerol and three fatty acids. </li></ul></ul></ul>
  27. 27. <ul><ul><li>Fats perform essential functions in the human body: </li></ul></ul><ul><ul><ul><li>Energy storage </li></ul></ul></ul><ul><ul><ul><li>Cushioning </li></ul></ul></ul><ul><ul><ul><li>Insulation </li></ul></ul></ul>Fats (cont’d)
  28. 28. <ul><ul><li>Unsaturated fatty acids </li></ul></ul><ul><ul><ul><li>Have less than the maximum number of hydrogens bonded to the carbons (ie they have double bonds). Greatest called polyunsaturated . </li></ul></ul></ul><ul><ul><li>Saturated fatty acids </li></ul></ul><ul><ul><ul><li>Have the maximum number of hydrogens bonded to the carbons. </li></ul></ul></ul><ul><ul><li>If all three fatty acids in a fat are saturated, it is a saturated fat . </li></ul></ul><ul><ul><li>If any are unsaturated, it is an unsaturated fat. </li></ul></ul>Saturated vs Unsaturated Fats Figure 3.4 Saturated fat Unsaturated fat
  29. 29. <ul><ul><li>Most animal fats have a high proportion of saturated fatty acids, which can be unhealthy. </li></ul></ul><ul><ul><ul><li>Examples: butter, lard </li></ul></ul></ul><ul><ul><ul><li>Usually solid at room temperature </li></ul></ul></ul><ul><ul><ul><li>Contribute to atherosclerosis and cardiovascular disease </li></ul></ul></ul><ul><ul><li>Most plant and fish oils tend to be low in saturated fatty acids. </li></ul></ul><ul><ul><ul><li>Example: corn oil, canola oil, cod liver oil </li></ul></ul></ul><ul><ul><ul><li>Usually liquid at room temperature </li></ul></ul></ul>Saturated vs Unsaturated Fats (cont’d)
  30. 30. Hydrogenation and Trans Fats <ul><li>Hydrogenation : Conversion of unsaturated fats to saturated fats by adding hydrogen. </li></ul><ul><ul><li>Production of margarine and peanut butter </li></ul></ul><ul><li>Fats created by hydrogenation are unhealthy because trans fats are produced. </li></ul><ul><ul><li>Trans fats: type of unsaturated fat (shortening, margarine) </li></ul></ul><ul><ul><li>Found in many fast food products, although now banned </li></ul></ul><ul><ul><li>No nutritional value </li></ul></ul><ul><ul><li>Increase risk of cardiovascular disease </li></ul></ul><ul><ul><li>Even more unhealthy than saturated fats. </li></ul></ul>
  31. 31. Steroids <ul><ul><li>Another type of lipid. </li></ul></ul><ul><ul><li>Different from fats in structure and function. </li></ul></ul><ul><ul><ul><li>Carbon skeleton is bent to form four fused rings. </li></ul></ul></ul><ul><ul><li>Cholesterol is the “base steroid” </li></ul></ul><ul><ul><li>from which your body produces </li></ul></ul><ul><ul><li>other steroids. </li></ul></ul><ul><ul><ul><li>Example: sex hormones </li></ul></ul></ul><ul><ul><ul><li>(testosterone, estrogen) </li></ul></ul></ul>
  32. 32. <ul><ul><li>Synthetic anabolic steroids are controversial. </li></ul></ul><ul><ul><ul><li>They are variants of testosterone. </li></ul></ul></ul>Anabolic Steroids <ul><ul><li>Some athletes use anabolic steroids to build up their muscles quickly. </li></ul></ul><ul><ul><ul><li>However, these substances can pose serious health risks. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Mood swings </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Depression </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Liver damage </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>High cholesterol </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Shrunken testicles, reduced sex drive, infertility </li></ul></ul></ul></ul></ul>
  33. 33. Nucleic Acids <ul><ul><li>Information storage molecules. </li></ul></ul><ul><ul><ul><li>Provide the directions for building proteins. </li></ul></ul></ul><ul><ul><li>Two types of nucleic acids: </li></ul></ul><ul><ul><ul><li>DNA, deoxyribonucleic acid </li></ul></ul></ul><ul><ul><ul><li>RNA, ribonucleic acid </li></ul></ul></ul><ul><ul><li>The genetic instructions in DNA </li></ul></ul><ul><ul><ul><li>Must be translated from “nucleic acid language” to “protein language.” </li></ul></ul></ul>
  34. 34. Flow of Genetic Information in Cells
  35. 35. Nucleotides: Building Blocks of Nucleic Acids <ul><ul><li>Nucleic acids are polymers of nucleotides : sugar + a phosphate + a nitrogenous base </li></ul></ul><ul><ul><li>DNA nucleotides have one of 4 bases: </li></ul></ul><ul><ul><ul><li>Adenine (A) </li></ul></ul></ul><ul><ul><ul><li>Guanine (G) </li></ul></ul></ul><ul><ul><ul><li>Thymine (T) </li></ul></ul></ul><ul><ul><ul><li>Cytosine (C) </li></ul></ul></ul>Sugar in DNA = deoxyribose Sugar in RNA = ribose <ul><ul><li>RNA contains uracil (U) instead of thymine </li></ul></ul>
  36. 36. <ul><ul><li>Nucleotide monomers are linked into long strands. </li></ul></ul>DNA as Polymers <ul><ul><li>Two strands join together to form DNA double helix. </li></ul></ul><ul><ul><li>Looks like twisted ladder </li></ul></ul>Figure 2.15a
  37. 37. <ul><ul><li>Bonding between bases on opposite strands follow strict rules: </li></ul></ul>DNA Base-Pairing Rules <ul><ul><li>A with T </li></ul></ul><ul><ul><li>G with C </li></ul></ul>Figure 2.15a,b
  38. 38. <ul><ul><li>RNA, ribonucleic acid, is different from DNA. </li></ul></ul><ul><ul><ul><li>Its sugar has an extra OH group. </li></ul></ul></ul><ul><ul><ul><li>It has the base uracil (U) instead of thymine (T). </li></ul></ul></ul><ul><ul><ul><li>It is usually single-stranded. </li></ul></ul></ul>RNA
  39. 39. Review: Complete the Table Biological Molecule (Polymer) Subunits (Building Blocks) Functions Examples Carbohydrates Proteins Nucleic acids Lipids (Fats)
  40. 40. You Are What You Eat Protein Steak Structural proteins, enzymes and energy Amino acids (a) Structural Proteins (b) Carbohydrate breakdown ATP Fat Butter Glycerol and fatty acids Carbohydrates Apple Structural components Energy production Build membranes Stored energy (c) Fat breakdown Fat droplet ATP ATP Figure 3.14
  41. 41. Reading Food Labels Unsaturated fats? Complex carbs? 1 g fat = 9 calories 1 g carb = 4 calories 1 g protein = 4 calories Check out the website links posted on MyGateway!
  42. 42. READ <ul><li>Read end of Chapter 3 (p70-75): </li></ul><ul><ul><li>Body fat </li></ul></ul><ul><ul><li>BMI </li></ul></ul><ul><ul><li>Obesity </li></ul></ul><ul><ul><li>Health effects: diabetes, hypertension, heart attack, stroke, high cholesterol </li></ul></ul><ul><ul><li>Eating disorders </li></ul></ul>