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Chapter 2 pt 3 Atoms, Molecules, and Life Including the lecture Materials of Gregory Ahearn University of North Florida with amendments and additions by John Crocker Copyright © 2009 Pearson Education, Inc.. 2.5 How Are Biological Molecules Joined Together Or Broken Apart? Biomolecules are polymers (chains) of subunits called monomers A huge number of different polymers can be made from a small number of monomers Biomolecules Are Joined Through Dehydration and Broken by Hydrolysis Copyright © 2009 Pearson Education Inc. Organic Molecule Synthesis Monomers are joined together through dehydration synthesis An H and an OH are removed, resulting in the loss of a water molecule (H2O) Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Organic Molecule Synthesis Polymers are broken apart through hydrolysis (“water cutting”) Water is broken into H and OH and used to break the bond between monomers Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Organic Molecule Synthesis All biological molecules fall into one of four categories Carbohydrates Lipids Proteins Nucleic Acids Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. 2.6 What Are Carbohydrates? Composition: C, H, and O in the ratio of 1:2:1 Construction: Simple or single sugars are monosaccharides Two linked monosaccharides are disaccharides Long chains of monosaccharides are polysaccharides Copyright © 2009 Pearson Education Inc. Monosaccharides Basic monosaccharide structure Backbone of 3-7 carbon atoms Many –OH and –H functional groups Usually found in a ring form in cells Simple sugars provide important energy sources for organisms. Most small carbs are water-soluble due to the polar OH functional groups Copyright © 2009 Pearson Education Inc. A simple sugar CH2OH H O H 6 H H 5 C H 4 C O O H 3 C 2 C O H H O H H (a) Glucose, linear form H 1 C C O O H H H H HO OH H H OH OH (b) Glucose, ring form Fig. 2-13 Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Monosaccharides Example monosaccharides continued Fructose (found in corn syrup and fruits) Galactose (found in lactose) Ribose and deoxyribose (found in RNA and DNA) Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Most small carbs are water-soluble due to the polar OH functional groups Copyright © 2009 Pearson Education Inc. Disaccharides Disaccharides are two-part sugars Sucrose (table sugar) = glucose + fructose Lactose (milk sugar) = glucose + galactose Maltose (malt sugar)= glucose + glucose Copyright © 2009 Pearson Education Inc. Manufacture of a disaccharide glucose fructose CH2OH O H H HOCH2 CH2OH O O H H + HO OH H H OH OH sucrose HO H OH HO H dehydration CH2OH synthesis H H HO HOCH2 H OH H H OH O H OH O H HO CH2OH H O H H Fig. 2-14 Copyright © 2009 Pearson Education Inc. Polysaccharides Monosaccharides are linked together to form chains (polysaccharides) Polysaccharides are used for energy storage and structural components Copyright © 2009 Pearson Education Inc. Polysaccharides Storage polysaccharides Starch (polymer of glucose) Formed in roots and seeds as a form of glucose storage Glycogen (polymer of glucose) Found in liver and muscles Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Polysaccharides Structural polysaccharides Cellulose (polymer of glucose) Found in the cell walls of plants Indigestible for most animals due to orientation of bonds between glucoses Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Polysaccharides Structural polysaccharides continued Chitin (polymer of modified glucose units) Found in the outer coverings of insects, crabs, and spiders Found in the cell walls of many fungi Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. 2.7 What Are Lipids? Molecular characteristics of lipids Lipids are molecules with long regions composed almost entirely of carbon and hydrogen. The nonpolar regions of carbon and hydrogen bonds make lipids hydrophobic and insoluble in water. Copyright © 2009 Pearson Education Inc. What Are Lipids? Lipids are diverse in structure and serve in a variety of functions Energy storage Waterproofing Membranes in cells Hormones Copyright © 2009 Pearson Education Inc. Lipid classification Group 1: Oils, fats, and waxes Group 2: Phospholipids Group 3: Steroids Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes Formed by dehydration synthesis 3 fatty acids + glycerol triglyceride Contain only carbon, hydrogen, and oxygen Contain one or more fatty acid subunits in long chains of C and H with a carboxyl group (–COOH) Ring structure is rare Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Fats and oils form by dehydration synthesis from three fatty acid subunits and one molecule of glycerol. etc. CH2 CH2 CH2 H H C OH O CH HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH H C OH O HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc. + H C OH H glycerol O HO C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc. fatty acids Fig. 2-16 Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Fats and oils formed by dehydration synthesis are called triglycerides. Triglycerides are used for long-term energy storage in both plants and animals. etc. CH2 CH2 CH2 H O CH H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH + O H O O H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc. + H O H C O C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc. H + H triglyceride H H O H 3 water molecules Fig. 2-16 Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Characteristics of fats Solidity is due to the prevalence of single or double carbon bonds Fats are solid at room temperature. Fats have all carbons joined by single covalent bonds. The remaining bond positions on the carbons are occupied by hydrogen atoms. Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Fatty acids of fats are said to be saturated and are straight molecules that can be stacked. (a) Beef fat (saturated) Fig. 2-18a Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Characteristics of oils Oils are liquid at room temperature. Some of the carbons in fatty acids have double covalent bonds. There are fewer attached hydrogen atoms, and the fatty acid is said to be unsaturated. Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Unsaturated fatty acids have bends and kinks in fatty acid chains and can’t be stacked. (b) Peanut oil (unsaturated) Fig. 2-18b Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Characteristics of waxes Waxes are solid at room temperature. Waxes are highly saturated. Waxes are not a food source. Waxes are composed of long hydrocarbon chains and are strongly hydrophobic Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Waxes form waterproof coatings Leaves and stems of plants Fur in mammals Insect exoskeletons Used to build honeycomb structures Copyright © 2009 Pearson Education Inc. Group 1: Oils, fats, and waxes (continued) Bees use waxes to store food and honey. Fig. 2-17b Copyright © 2009 Pearson Education Inc. Group 2: Phospholipids Phospholipids: form dual layered plasma membranes around all cells Construction like oils except one fatty acid is replaced by a phosphate group attached to glycerol. 2 fatty acids + glycerol + a short polar functional group water-soluble heads and water-insoluble tails. Copyright © 2009 Pearson Education Inc. Group 2: Phospholipids (continued) The phosphate end of the molecule is water soluble; the fatty acid end of the molecule is water insoluble. CH3 O– H3C - N+- CH2 - CH2 -O-P- O -CH2 O CH3 O HC-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH O CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 H2C-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH3 polar head glycerol (hydrophilic) fatty acid tails (hydrophobic) Fig. 2-19 Copyright © 2009 Pearson Education Inc. Group 3: Steroids Steroids contain four fused carbon rings. Various functional groups protrude from the basic steroid “skeleton”. Examples of steroids Cholesterol Found in membranes of animal cells Male and female sex hormones Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. 2.8 What Are Proteins? Functions of proteins Proteins act as enzymes to catalyze (speed) many biochemical reactions. They provide structure (ex/ elastin) They can act as energy stores. They are involved in carrying oxygen around the body (hemoglobin). They are involved in muscle movement. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Some proteins are structural and provide support in hair, horns, spider webs, etc. Fig. 2-21 Copyright © 2009 Pearson Education Inc. Proteins are formed from chains of amino acids. All amino acids have the same basic structure: A central carbon An attached amino group An attached carboxyl group An attached variable group (R group) variable Some are hydrophobic group Some are hydrophilic amino group Copyright © 2009 Pearson Education Inc. carboxylic acid group hydrogen Copyright © 2009 Pearson Education Inc. Amino acid monomers join to form chains by dehydration synthesis. Proteins are formed by dehydration reactions between individual amino acids. The –NH2 group of one amino acid is joined to the –COOH group of another, with the release of H2O and the formation of a new peptide (two or more amino acids). The resultant covalent bond is a peptide bond Copyright © 2009 Pearson Education Inc. Long chains of amino acids are known as polypeptides or just proteins Copyright © 2009 Pearson Education Inc. The sequence of amino acids in a protein dictates its three dimensional structure This structure gives proteins their functions. Long chains of amino acids fold into threedimensional shapes in cells, which allows the protein to perform its specific functions. When a protein is denatured, its shape has been disrupted and it may not be able to perform its function. Copyright © 2009 Pearson Education Inc. Four Levels of Structure Proteins exhibit up to four levels of structure Primary structure is the sequence of amino acids linked together in a protein Secondary structures are helices and pleated sheets Tertiary structure refers to complex foldings of the protein chain held together by disulfide bridges, hydrophobic/hydrophilic interactions, and other bonds Quaternary structure is found where multiple protein chains are linked together Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Three Dimensional Structures The type, position, and number of amino acids determine the structure and function of a protein Precise positioning of amino acid R groups leads to bonds that determine secondary and tertiary structure Disruption of these bonds leads to denatured proteins and loss of function Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Structure of nucleic acids Nucleic acids are long chains of similar, but not identical, subunits called nucleotides. Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Structure of nucleic acids (continued) All nucleotides have three parts. A five-carbon sugar (ribose or deoxyribose) A phosphate group A nitrogen-containing molecule called a base Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Deoxyribose nucleotide base NH2 phosphate N C C N OH HO P HC O CH2 O H N C N CH O sugar H H OH H H Fig. 2-25 Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Types of nucleotides Those that contain the sugar ribose. Those that contain the sugar deoxyribose. Nucleotides string together in long chains as nucleic acids with the phosphate group of one nucleotide bonded to the sugar group of another. Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Nucleotide chain base sugar phosphate Fig. 2-26 Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? DNA and RNA, the molecules of heredity, are nucleic acids. There are two types of nucleic acids. Deoxyribonucleic acid (DNA): contains the genetic code of cell Ribonucleic acid (RNA): is used in the synthesis of proteins Copyright © 2009 Pearson Education Inc. 2.9 What Are Nucleic Acids? Other nucleotides perform other functions. Adenosine monophosphate: acts as a messenger in the cell, carrying information to other molecules Adenosine triphosphate: carries energy from place to place in the cell Copyright © 2009 Pearson Education Inc. Section 3.6 Outline What Are Nucleic Acids? Structure of Nucleic Acids DNA and RNA, the Molecules of Heredity, Are Nucleic Acids Other Nucleotides Act as Intracellular Messengers, Energy Carriers, or Coenzymes Copyright © 2009 Pearson Education Inc. What Are Nucleic Acids? Nucleotides are the monomers of nucleic acid chains Copyright © 2009 Pearson Education Inc. What Are Nucleic Acids? All nucleotides are made of three parts Phosphate group Five-carbon sugar Nitrogen-containing base Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Molecules of Heredity Two types of nucleotides Ribonucleotides (A, G, C, and U) found in RNA Deoxyribonucleotides (A, G, C, and T) found in DNA Copyright © 2009 Pearson Education Inc. Molecules of Heredity Two types of polymers of nucleic acids DNA (deoxyribonucleic acid) found in chromosomes Carries genetic information needed for protein construction RNA (ribonucleic acid) Copies of DNA used directly in protein construction Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Molecules of Heredity Each DNA molecule consists of two chains of nucleotides that form a double helix Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc. Other Nucleotides Nucleotides as intracellular messengers Cyclic nucleotides (e.g. cyclic AMP) carry chemical signals between molecule Copyright © 2009 Pearson Education Inc. Other Nucleotides Nucleotides as energy carriers Adenosine triphosphate (ATP) carries energy stored in bonds between phosphate groups NAD+ and FAD carry electrons Copyright © 2009 Pearson Education Inc. Other Nucleotides Nucleotides as enzyme assistants Coenzymes help enzymes promote and guide chemical reactions Copyright © 2009 Pearson Education Inc. Copyright © 2009 Pearson Education Inc.