Chapter 5: The Structure And Function Of Large Biological Molecules

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BIOLOGY I. Chapter 5 – Biological Molecules BIOLOGY I Chapter 5: The Structure and Function of Large Biological Molecules Evelyn I. Milian Instructor 2012

BIOLOGY I. Chapter 5 – Biological Molecules Inorganic Versus Organic Molecules Inorganic Molecules Organic Molecules Molecules without carbon. Molecules that contain carbon and hydrogen. Usually ionic bonding; usually contain positive and negative ions. Always covalent bonding. Usually small and simple; contain a small number of atoms. Often quite large and structurally complex; with many atoms. Often associated with non-living matter. Often associated with living organisms. Examples: carbon dioxide (CO2), water, and many acids, bases, and salts. Even though it contains carbon, CO2 is usually considered inorganic because it is very simple and lacks hydrogen. CO2 is the source of carbon for all the organic molecules found in organisms. Examples: carbohydrates, lipids, proteins, and nucleic acids. * Carbohydrates, proteins, and nucleic acids are also called macromolecules (huge molecules). Ionic bond Force of attraction that holds ions having opposite charges together. Covalent bond Sharing of two or more electrons rather than gaining or losing electrons. Evelyn I. Milian - Instructor 2

BIOLOGY I. Chapter 5 – Biological Molecules The Structure and Function of Large Biological Molecules The four major classes of organic molecules, or macromolecules (large molecules) are: Carbohydrates Lipids Proteins Nucleic acids Polymer A long molecule consisting of many similar or identical subunits (monomers) linked together. Monomer The repeating subunit (molecule) that serves as the building block of a polymer. Lipids such as oils are digested to glycerol and fatty acids; proteins such as those in meat are digested to amino acids; and carbohydrates such as those in bread and pasta are digested to sugars. Cells use subunit molecules to build their own macromolecules and as a source of energy. Evelyn I. Milian - Instructor 3

BIOLOGY I. Chapter 5 – Biological Molecules The Synthesis and Breakdown of Polymers Monomers form larger molecules (polymers) by a dehydration reaction (condensation), in which two molecules become covalently bonded to each other through the loss of a water molecule. Polymers can disassemble (break down) to monomers by hydrolysis (the reverse of the dehydration reaction), in which molecules are split (lysed) by the addition of a water molecule. Evelyn I. Milian - Instructor 4

BIOLOGY I. Chapter 5 – Biological Molecules Class Collaborative Activity The class will be split into small groups of 4-6 students. Each small group should work together to discuss one of the four groups of biological molecules, as assigned by your instructor: Carbohydrates, lipids, proteins, or nucleic acids. Using your book, previous knowledge and any other resources available, write a paragraph including the following information about the molecules assigned to your group; then you will share your findings with the rest of the students. a) Structural properties: elements or subunits forming the molecules b) Functions or roles and other physiological properties: Describe the functions or roles of these molecules in the body of organisms, and other important characteristics. For example: What do these molecules do for our cells and tissues? Are these molecules hydrophilic or hydrophobic? Etc c) Specific examples of this group of molecules—Write two or three examples by their scientificv names; NOT the foods that contain them. Evelyn I. Milian - Instructor 5

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 6

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions CARBOHYDRATES Organic compounds composed of carbon, hydrogen, and oxygen in the approximate ratio of 1:2:1, (CH2O)n. Perform several major functions in living things, including energy storage and structural function (building material). * Carbohydrates are the main source of energy (fuel) for most living things. Carbohydrates include: Simple sugars such as glucose, fructose, lactose, sucrose Complex carbohydrates such as starch, glycogen, and cellulose. Evelyn I. Milian - Instructor 7

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 8

BIOLOGY I. Chapter 5 – Biological Molecules Carbohydrates Figure 5.3 – The structure and classification of some monosaccharides. Sugars may be aldoses (aldehyde sugars) or ketoses (ketone sugars), depending on the location of the carbonyl group (orange). Sugars are also classified according to the length of their carbon skeletons. A third point of variation is the spatial arrangement around asymmetric carbons (carbon atoms attached to 4 different atoms or groups of atoms). (Compare, for example, the purple portions of glucose and galactose). Straight-chain representation of some monosaccharides (Mono one; saccharide sugar). Evelyn I. Milian - Instructor 9

BIOLOGY I. Chapter 5 – Biological Molecules Carbohydrates: Disaccharides Evelyn I. Milian - Instructor 10

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BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 12

BIOLOGY I. Chapter 5 – Biological Molecules CARBOHYDRATES: Chitin, a structural polysaccharide. Chitin forms the exoskeleton of arthropods. Chitin is also found in many fungi, which use this polysaccharide rather than cellulose as the building material for their cell walls. Chitin is similar to cellulose, except that the glucose monomer of chitin has a nitrogen-containing appendage. Evelyn I. Milian - Instructor 13

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions: LIPIDS Organic compounds composed of carbon, hydrogen, and oxygen that are usually insoluble in water (they are hydrophobic, mixing poorly, if at all, with water). Lipids consist mostly of hydrocarbon regions; they are generally not big enough to be considered macromolecules or true polymers. Functions include: long-term energy storage, waterproof coverings on plant or animal bodies, insulation, components of cell membranes, hormones. Lipids include: fats and oils (triglycerides or triacylglycerols), phospholipids, steroids, and waxes. Evelyn I. Milian - Instructor 14

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 15

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 16

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 17

BIOLOGY I. Chapter 5 – Biological Molecules LIPIDS: Fats and Oils (a) In a dehydration reaction, glycerol and 3 fatty acids are joined to form a fat (triglyceride) molecule. In hydrolysis, the bonds are broken due to the addition of water. (b) A fatty acid is unsaturated if there are double bonds between some of the carbons in the chain. If there are no double bonds, the fatty acid is saturated (with more hydrogen). (c) Space-filling models. 18

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 19

BIOLOGY I. Chapter 5 – Biological Molecules Like cholesterol (a), testosterone (b) and estrogen (c) have different effects on the body due to different functional groups attached to the same carbon skeleton. All steroids have four adjacent rings, but vary by their attached groups. An important component of the plasma membrane, a high level of cholesterol in the blood may contribute to atherosclerosis (a cardiovascular disease). Evelyn I. Milian - Instructor 20

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions PROTEINS Large organic molecules composed of amino acids joined by peptide bonds. They contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Structure of amino acids: an acidic carboxyl group (--COOH), a basic amino group (--NH2), a hydrogen (H) atom, and a variable or side group (--R). The primary difference between the 20 amino acids commonly found in proteins is in their R group. Peptide: Chain of two or more amino acids bonded together by a peptide bond between the carboxyl group of one amino acid and the amino group of another. Polypeptide: Linear chain of many amino acids joined together. Proteins have many different functions. *** Study the functions! Evelyn I. Milian - Instructor 21

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules: PROTEINS Proteins are composed of amino acids joined by peptide bonds. Notice the variable side group or chain (R) attached to the alpha carbon. Evelyn I. Milian - Instructor 22

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules and Their Functions: PROTEINS Evelyn I. Milian - Instructor 23

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules and Their Functions: PROTEINS Evelyn I. Milian - Instructor 24

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules: PROTEINS – Example: Enzymes The enzyme sucrase accelerates hydrolysis of sucrose into glucose and fructose. Acting as a catalyst, the sucrase protein is not consumed during the cycle, but is available for further catalysis. 25 Evelyn I. Milian - Instructor

BIOLOGY I. Chapter 5 – Biological Molecules The 20 Amino Acids of Proteins The amino acids are grouped here according to the properties of their side chains (R groups) and shown in their prevailing ionic forms at pH 7.2, the pH within a cell. The threeletter and oneletter abbreviations for the amino acids are in parenthesis. Evelyn I. Milian - Instructor 26

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules: PROTEINS Two amino acids are joined by the removal of a water molecule (dehydration synthesis) and the formation of a peptide bond between the carboxyl group (–COOH) of one and the amino group (–NH2) of the other. The result is a dipeptide with an amino group at one end (Nterminus) and a carboxyl group at the other end (C-terminus). When many amino acids are joined, a polypeptide is formed. Evelyn I. Milian - Instructor 27

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BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules: PROTEINS Fibrous proteins are structural proteins. (a), (b) Keratin, a protein found in hair, horns and hoofs. (c) Silk, the protein that forms spider webs. The proteins in hair can be altered by water, heat, and chemical substances to achieve a different appearance. The actress Drew Barrymore has straight hair; in order to give her curly hair, water and a hot curler were used. Evelyn I. Milian - Instructor 29

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules: Why is Protein Structure So Important? Changes in protein structure, protein denaturation and misfolding The structure and function of a protein are sensitive to physical and chemical conditions. pH, salt concentration, temperature, etc. Denaturation is a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. Sometimes protein denaturation or misfolding may lead to disease. Examples: Alzheimer disease, mad cow disease (transmissible spongiform encephalopathy). 30

BIOLOGY I. Chapter 5 – Biological Molecules Figure 5.21 – A single amino acid substitution in a protein causes sickle-cell disease. Evelyn I. Milian - Instructor 31

BIOLOGY I. Chapter 5 – Biological Molecules Sickle cell anemia’s molecular basis and its main symptoms Evelyn I. Milian - Instructor 32

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions NUCLEIC ACIDS Large organic molecules composed of subunits called nucleotides. They contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleotides contain these components: a five-carbon sugar (a pentose), a phosphate group, and a nitrogenous base – the four possible bases are: adenine, cytosine, guanine, and thymine (in DNA) or uracil (in RNA). Nucleotides are linked together by bonds between the phosphate of one nucleotide and the sugar of the next nucleotide. Nucleic acids store and transmit hereditary (genetic) information and are involved in protein synthesis. Evelyn I. Milian - Instructor 33

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 34

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions NUCLEIC ACIDS Deoxyribonucleic Acid (DNA) Forms the inherited genetic material inside a cell; stores information for synthesis of proteins. Its pentose sugar is deoxyribose. The four nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G). DNA has two strands of nucleotides wrapped around each other forming a double helix. A gene is a segment of DNA (a sequence of nucleotides in DNA) encoding a functional product (a protein). Evelyn I. Milian - Instructor 35

BIOLOGY I. Chapter 5 – Biological Molecules NUCLEIC ACIDS: DNA Nucleotides (top) are composed of a deoxyribose (in DNA) sugar molecule linked to a phosphate group and to a nitrogenous base. The two nucleotides shown here are linked by hydrogen bonds between their complementary bases. The ladderlike form of DNA’s double helix (bottom) is made up of many nucleotides, with the repeating sugarphosphate combination forming the backbone and the complementary bases the rungs. Evelyn I. Milian - Instructor 36

BIOLOGY I. Chapter 5 – Biological Molecules NUCLEIC ACIDS: DNA DNA is a double helix in which the two polynucleotide strands twist about each other. a. Hydrogen bonds (dotted lines) occur between the complementarily paired bases: C is always paired with G, and A is always paired with T. b. Space-filling model of DNA. Evelyn I. Milian - Instructor 37

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions NUCLEIC ACIDS Ribonucleic Acid (RNA) Relays instructions from the genes to guide each cell’s synthesis of proteins from amino acids. Its pentose sugar is ribose. Contains the nitrogenous base uracil (U) instead of thymine (T). In humans it is single-stranded. Evelyn I. Milian - Instructor 38

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological Molecules NUCLEIC ACIDS: RNA RNA is a single-stranded polymer of nucleotides. When the nucleotides join, the phosphate group of one is bonded to the sugar (ribose) of the next. The bases project out to the side of the resulting sugar-phosphate backbone. Evelyn I. Milian - Instructor 39

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions NUCLEIC ACIDS Evelyn I. Milian - Instructor 40

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions NUCLEIC ACIDS – The Flow of Genetic Information In transcription, DNA is used as a template to produce RNA. Then, RNA is ‘translated’ into a protein. Certain viruses, such as HIV (Human Immunodeficiency Virus, the one that causes AIDS, or Acquired Immunodeficiency Syndrome), can direct synthesis of DNA from their RNA (reverse transcription). Evelyn I. Milian - Instructor 41

BIOLOGY I. Chapter 5 – Biological Molecules Figure 5.26. DNA RNA protein: a diagrammatic overview of information flow in a cell. In a eukaryotic cell, DNA in the nucleus programs protein production in the cytoplasm by dictating the synthesis of messenger RNA (mRNA) through transcription, which travels to the cytoplasm and binds to ribosomes (the site of protein synthesis). As a ribosome (greatly enlarged in this drawing) moves along the mRNA, the genetic message is translated into a polypeptide of specific amino acid sequence. The polypeptide can become a functional protein. Evelyn I. Milian - Instructor 42

BIOLOGY I. Chapter 5 – Biological Molecules Main Biological (Organic) Molecules and Their Functions Introduction to ATP (Adenosine Triphosphate): A Nucleotide ATP is a nucleotide composed of adenosine (adenine and ribose) and three phosphate groups. It is the main energycarrying molecule of all cells; indispensable to the life of the cell. ATP is involved in energydemanding reactions, such as synthesis of proteins and carbohydrates. When ATP breaks down to ADP and inorganic phosphate, a large amount of chemical energy is release for use in other chemical reactions. High-energy phosphate bonds are indicated by wavy lines. Evelyn I. Milian - Instructor 43

BIOLOGY I. Chapter 5 – Biological Molecules Evelyn I. Milian - Instructor 44

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BIOLOGY I. Chapter 5 – Biological Molecules References Audesirk, Teresa; Audesirk, Gerald & Byers, Bruce E. (2005). Biology: Life on Earth. Seventh Edition. Pearson Education, Inc.-Prentice Hall. NJ, USA. Campbell, Neil A.; Reece, Jane B., et al. (2011). Campbell Biology. Ninth Edition. Pearson Education, Inc.-Pearson Benjamin Cummings. CA, USA. Enger, Eldon D.; Ross, Frederick C.; Bailey, David B. (2007). Concepts in Biology. Twelfth Edition. The McGraw-Hill Companies, Inc. NY, USA. Mader, Sylvia S. (2010). Biology. Tenth Edition. The McGraw-Hill Companies, Inc. NY, USA. Presson, Joelle & Jenner, Jan. (2008). Biology, Dimensions of Life. The McGrawHill Companies, Inc. NY, USA. Solomon, Eldra; Berg, Linda; Martin, Diana W. (2008). Biology. Eighth Edition. Cengage Learning. OH, USA. Starr, Cecie. (2008). Biology: Concepts and Applications Volume I. Houston Community College. Thompson Brooks/Cole. OH, USA. Tortora, Gerard J.; Derrickson, Bryan. (2006). Principles of Anatomy and Physiology. Eleventh Edition. John Wiley & Sons, Inc. NJ, USA. www.wiley.com/college/apcentral. Tortora, Gerard J.; Funke, Berdell R.; Case, Christine L. (2010). Microbiology An Introduction. Tenth Edition. Pearson Education, Inc.-Pearson Benjamin Cummings; CA, USA. www.microbiologyplace.com. Evelyn I. Milian - Instructor 46

BIOLOGY I. Chapter 5 - Biological Molecules Class Collaborative Activity The class will be split into small groups of 4-6 students. Each small group should work together to discuss one of the four groups of biological molecules, as assigned by your instructor: Carbohydrates, lipids, proteins, or nucleic acids.

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