1 2 3 4 Bio 1101 Lecture 3 Chapter 3: Molecules of Life Organic Molecules Many of the compounds we are concerned with in biology are carbon-based compounds The study of carbon-based compounds is called organic chemistry Carbon-based molecules are very reactive, because they can form 4 covalent bonds Organic molecules vary in the number of carbons in their skeletons Hydrocarbons are simple organic molecules that consist of only hydrogen and carbon atoms Methane, CH 4, is the simplest hydrocarbon Our fossil fuels are hydrocarbons (e.g. octane contains 8 carbons) Carbon skeletons vary in their structure, from linear, to branched, to ring-shaped 5 6 7 In addition to the number of carbons in the skeleton of an organic molecules, another important characteristics in the functional group Functional group = groups of atoms attached to the carbon skeleton and directly involved in chemical reactions In methane, the functional groups are simply the hydrogens attached to the carbon Other functional groups include hydroxyl groups (-OH) found in alcohols, or carboxyl groups (-COOH) found in proteins Many biological molecules contain more than one functional group Many biological molecules are very large and are called macromolecules Examples: proteins, DNA, and carbohydrates Polymers = long strands of monomers Polymers form through dehydration reactions Involves removing a molecule of water Functional groups H and OH combine to form the water Polymers can be broken by hydrolysis reactions Cells break bonds between monomers by adding water OH and H are added to the monomer ends 8 9 1
Carbohydrates, lipids, proteins, and nucleic acids are the main groups of macromolecules we will focus on 10 Main Features of Major Classes of Macromolecules Carbohydrates include sugars and starches All are composed of one or more simple sugars (aka monosaccharides) One important carbohydrate we ll talk more about later is glucose (a monosaccharide) Formula for glucose: C 6 H 12 O 6 This is the product of photosynthesis, and the fuel that is consumed in cellular respiration Carbohydrates are hydrophilic (that is, water sticks to their surface) 11 12 Glucose may be found in linear and ring-shapes, but mostly exists as a ring Glucose and fructose are two common monosaccharides, which have the same chemical formula (C 6 H 12 O 6 ), but with different structures; these are called isomers Different isomers can have different properties because the arrangement of the atoms are different Glucose is absorbed by essentially all cells in the human body and used as fuel Fructose can only be processed by the liver and turned into fat 13 14 15 Disaccharides are constructed from two monosaccharides Examples: sucrose is formed when glucose and fructose combine; lactose is formed when glucose and galactose combine Polysaccharides are long chains of sugars Starch is an example of a polysaccharide Glucose is the monomer that makes up starch Glycogen is a polysaccharide stored in animal tissues Mostly stored in liver and muscles Has a branched structure Broken down into glucose when need energy Cellulose is also a polysaccharide made up of glucose monomers Linkages between glucose different from starch; cannot be broken by animal enzymes 16 17 Lipids include fats and steroids 2
Lipids are hydrophobic (that is, they repel water molecules) For example, imagine mixing oil and water Fats are efficient energy stores in animals and plants (a pound of fat stores more energy than a pound of carbohydrate) Steroids are structurally different than fats, and are made of carbon rings instead of linear carbon strands Cholesterol, testosterone, and estrogen are all steroids 18 19 20 21 22 Some fats are unsaturated What do the terms saturated and unsaturated mean? Refers to the number of carbon-hydrogen bonds in a fatty acid If the carbons are saturated with bonds to hydrogen atoms (meaning they couldn t be bonded with any more), then it is a saturated fat. These tend to be linear molecules which are solid at room temperature, as show in previous slide If the carbon-hydrogen tail of the fatty acid has one or more carbon-carbon double bonds, thus reducing the number of bonds with hydrogens, then it is an unsaturated fat These ten to have kinks/bends in them, usually making them liquid at room temperature In terms of nutrition and health, are fats bad for you? It isn t that simple Fats are high in calories they store a lot of energy so consuming a lot of them can increase your body weight On the other hand, some fat is necessary for health, and certain types of fats can be beneficial Especially monounsaturated and polyunsaturated fats Saturated fats and trans-fats are the unhealthy types of fats Health basics of fat video: https://www.youtube.com/watch?v=mvvx2yqrbzq FDA ruled trans-fats unsafe in 2015 and gave food manufacturers 3 years to phase out the ingredient Trans fats now banned in US (see Washington Post article https://www.washingtonpost.com/news/wonk/wp/2018/06/18/artificial-trans-fatswidely-linked-to-heart-disease-are-officially-banned/?utm_term=.3655b50d5c0b) Bonus Activity 1 1. Monomers are joined together to form larger polymers through reactions. Such reactions release a molecules of. 2. All carbohydrates consist of one or more. 3. Table sugar, also known as, is composed of and 3
. 4. Which of the following terms includes all of the others in the list? a) Polysaccharide b) Carbohydrate c) Monosaccharide d) Disaccharide 23 24 25 5-minute break Proteins are elaborate polymers consisting of amino acid monomers There are many different types of proteins, including structural proteins (e.g. those that compose hair), contractile proteins (e.g. those in muscle), antibodies, and enzymes There are 20 different amino acids, which are the monomers from which proteins are made There are 4 levels of protein structure: primary, secondary, tertiary, and quaternary Primary Protein Structure: the sequence of amino acids in the polymer Secondary Protein Structure: local patterns that occur due to hydrogen bonding (two types include the alpha helix and the pleated sheet) Tertiary Protein Structure: the overall three-dimensional shape of the protein, reinforced by chemical bonds Quaternary Protein Structure: Proteins that are composed of two or more polypeptide chains, which bond together 26 27 28 29 Bonds between adjacent amino acids in a protein are called peptide bonds Therefore, proteins are called polypeptides, because many peptide bonds are present A polypeptide is a long strand of amino acids, but a given polypeptide may be cut up and/or combined with other polypeptides, and folded into a specific shape, in order to form various proteins A polypeptide is a single linear chain of amino acids A protein is the finished, functional product, and may be composed of one or more polypeptides 30 4
Sequence of amino acids in the chain determines how the protein will function; any error can damage the protein 31 Nucleic Acids contain information for the synthesis of proteins (the genetic material) DNA = Deoxyribonucleic acid The genetic material in the nucleus of the cell RNA = Ribonucleic acid Nucleic acids are polymers of nucleotides Nucleotides consist of three parts: a sugar, a phosphate group, and a nitrogenous base Four different bases in DNA: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) Four different bases in RNA: Adenine (A), Guanine (G), Cytosine (C), and Uracil (U) 32 33 The sugars and phosphates alternate in the back bone of a DNA strand DNA is double-stranded The bases of each nucleotide pair up in a specific way: A s bond with T s, and C s bond with G s, through weak hydrogen bonds The strands are thus complementary 34 35 36 37 Using the rules of base-pairing, if you know the sequence of bases in one strand of DNA, you can determine the sequence in the complementary strand A chromosomes is composed of a long strand of DNA, which carries genes, and associated proteins involved in organizing the DNA A gene is a specific stretch of DNA that codes for a sequence of amino acids in a polypeptide (protein) RNA is similar in structure to DNA RNA is a polymer of nucleotides (sugar, phosphate and base) Three important differences between DNA and RNA The sugar in RNA is ribose (instead of deoxyribose in DNA) One of the four bases in RNA is different from DNA: RNA has AUCG, whereas DNA has ATCG (uracil found in RNA instead of thymine) RNA is single-stranded, whereas DNA is double-stranded 5
38 39 The sequence of bases is the language of DNA Provides information for making all the proteins in the body Genes are discrete sequences of DNA that code for proteins The code is a function of the sequence of ATCG Any error in the DNA sequence of a gene can affect the structure of a protein Example: Tay Sachs Disease is a point mutation, where a single base is changed in the gene (GAG is mutated into GUG); results in misfolded enzyme protein; enzyme no longer able to break down lipids in the brain Video on Tay Sachs: https://www.youtube.com/watch?v=03ncebjafz8 40 41 BONUS ACTIVITY 2 1. A glucose molecule is to a as a nucleotide is to a. 2. Which of the following substances are hydrophobic? a) Olive oil b) Butter fat c) Honey d) Glucose e) Cholesterol 3. Name three differences between DNA and RNA. 4. What is the sequence of the DNA strand that is complementary to this sequence? A T T G C A G G C a) 42 Random Animal of the Day! Smallest Vertebrate Animal in the World Paedophryne amanuensis Just 7.7mm long! Discovered 2012 in Papua New Guinea 6