copyright © 2011 pearson education inc.biology: life on earth, 9e biological molecules chapter 3
TRANSCRIPT
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e BIOLOGICAL MOLECULES Chapter 3
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Why Is Carbon So Important in Biological Molecules? Organic/inorganic molecules and functional groups Organic refers to molecules containing a carbon skeleton bonded to hydrogen atoms Inorganic refers to carbon dioxide and all molecules without carbon
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Why Is Carbon So Important in Biological Molecules? The carbon atom is key Is versatile because it has four electrons in the outer shell Is stable by forming up to four bonds single, double, or triple covalent Result organic molecules can assume complex shapes: branched chains, rings, sheets, and helices Functional groups in organic molecules Are less stable than the carbon backbone and are more likely to participate in chemical reactions Determine the characteristics and chemical reactivity of organic molecules
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Table 3-1
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Dehydration Synthesis Small organic molecules (called monomers) are joined to form longer molecules (called polymers) Monomers are joined together through dehydration synthesis, at the site where an H + and an OH - are removed, resulting in the loss of a water molecule (H 2 O) The openings in the outer electron shells of the two subunits are filled when the two subunits share electrons, creating a covalent bond dehydration synthesis
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Hydrolysis Polymers are broken apart through hydrolysis (water cutting) Water is broken into H + and OH - and is used to break the bond between monomers Digestive enzymes use to break down food hydrolysis
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Biological Molecules The important organic molecules found in living things: CarbohydratesLipidsProteinsNucleic Acids Sugar FatEnzymesDeoxyribonucleic Starch Structural ProteinsRibonucleic Acid Cellulose All contain Carbon, Hydrogen, and generally Oxygen.
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Carbohydrates Carbohydrate molecules are composed of C, H, and O in the ratio of 1:2:1 Monosaccharide - consists of just one sugar molecule Disaccharide - Two linked monosaccharides Polysaccharide - polymer of many monosaccharides
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Carbohydrates Hydrophilic due to the polar OH - functional group Only mono- and disaccharides Functions: Energy source Combine with other molecules through dehydration synthesis (plasma membrane, cell wall, exoskeletons)
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Carbohydrates hydrogen bond hydroxyl group water There are several monosaccharides with slightly different structures The basic monosaccharide structure is: A backbone of 37 carbon atoms Most of the carbon atoms have both a hydrogen (-H) and an hydroxyl group (-OH) attached to them Chemical formula (CH 2 O) n
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Monosaccharides When dissolved in the cytoplasmic fluid of a cell, the carbon backbone usually forms a ring Glucose (C 6 H 12 O 6 ) is the most common monosaccharide in living organisms Fructose (fruit sugar found in fruits, corn syrup, and honey) Galactose (milk sugar found in lactose) Ribose and deoxyribose (found in RNA and DNA) galactosefructose ribosedeoxyribose Note missing oxygen atom
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Disaccharides glucosefructose sucrose dehydration synthesis Functions: They are used for short-term energy storage When energy is required, they are broken apart by hydrolysis Examples: Sucrose (table sugar) = glucose + fructose Lactose (milk sugar) = glucose + galactose Maltose (malt sugar) = glucose + glucose
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Polysaccharides Storage polysaccharides include: Starch, an energy-storage molecule in plants, formed in roots and seeds Glycogen, an energy-storage molecule in animals, found in the liver and muscles (b) A starch molecule (a) Potato cells (c) Detail of a starch molecule starch grains
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Polysaccharides Polysaccharides as a structural material Cellulose (a polymer of glucose) It is found in the cell walls of plants Most abundant organic molecule on Earth It is indigestible for most animals due to the orientation of the bonds between glucose molecules
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Polysaccharides Chitin (a polymer of modified glucose units) Nitrogen-containing functional group The outer coverings (exoskeletons) of insects, crabs, and spiders The cell walls of many fungi
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Review 1.What are carbohydrates used for? 2.What are the major classes of carbohydrates? 3.What are the types and functions of polysaccharides?
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Lipids are a diverse group of molecules that contain regions composed almost entirely of hydrogen and carbon All lipids contain large chains of non-polar hydrocarbons hydrophobic
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Lipids are diverse in structure and serve a variety of functions: energy storage waterproof coverings on plant and animal bodies primary component of cellular membranes hormones Lipids are classified into three major groups 1.Oils, fats, and waxes 2.Phospholipids 3.Steroids
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Oils, fats, and waxes Carbon, hydrogen, oxygen Made of one or more fatty acid subunits Fats and oils Are used primarily as energy-storage molecules, containing twice as many calories per gram as carbyhydrates and proteins Are formed by dehydration synthesis Three fatty acids + glycerol triglyceride
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e glycerolfatty acids triglyceride Synthesis of a Triglyceride Fig. 3-12 Dehydration synthesis
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Oils, fats, and waxes Fats are solid at room temperature are saturated (the carbon chain has as many hydrogen atoms as possible, and mostly or all C-C bonds); for example, beef fat Produced in animals
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Oils, fats, and waxes Oils are liquid at room temperature are unsaturated (with fewer hydrogen atoms, and many C=C bonds); for example, corn oil Produced by plants Unsaturated trans fats have been linked to heart disease
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Oils, fats, and waxes Waxes are similar to fats Most animals dont have the enzymes to break them down. Functions: form waterproof coatings such as on: Leaves and stems of land plants Fur in mammals Insect exoskeletons used to build honeycomb structures
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Phospholipids These form plasma membranes around all cells Phospholipids consist of two fatty acids + glycerol + a short polar functional group containing nitrogen Hydrophilic polar functional groups form the head Hydrophobic non-polar fatty acids form the tails polar head glycerol backbone phosphate group variable functional group (hydrophilic) (hydrophobic) fatty acid tails
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Lipids Steroids Composed of four carbon rings fused together with various functional groups protruding from them Examples: Cholesterol (animal cell membranes) Male and female sex hormones
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins Functions Enzymes are proteins that promote chemical reactions Structural proteins (e.g., elastin, keratin) provide support Hormones Antibodies Toxins
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins Polymers of amino acids joined by peptide bonds All amino acids have a similar structure All contain amino and carboxyl groups All have a variable R group Some R groups are hydrophobic Some are hydrophilic Cysteine R groups can form disulfide bridges amino group hydrogen variable group carboxylic acid group
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins The sequence of amino acids in a protein dictates its function Amino acids are joined to form chains by dehydration synthesis An amino group reacts with a carboxyl group, and water is lost amino acid amino group amino group carboxylic acid group amino acidpeptide water peptide bond dehydration synthesis
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins Amino acids are joined to form chains by dehydration synthesis The covalent bond resulting after the water is lost is a peptide bond, and the resulting chain of two amino acids is called a peptide Long chains of amino acids are known as polypeptides
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins Proteins exhibit up to four levels of structure Primary structure is the sequence of amino acids Secondary structure is a helix, or a pleated sheet Repeating structure with hydrogen bonds Tertiary structure refers to complex foldings of the protein chain held together by disulfide bridges, hydrophobic/hydrophilic interactions, and other bonds Quaternary structure occurs where multiple polypeptides are linked together
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e The Four Levels of Protein Structure Fig. 3-21 (a) Primary structure: The sequence of amino acids linked by peptide bonds (c) Tertiary structure: Folding of the helix results from hydrogen bonds with surrounding water molecules and disulfide bridges between cysteine amino acids (d) Quaternary structure: Individual polypeptides are linked to one another by hydrogen bonds or disulfide bridges (b) Secondary structure: Usually maintained by hydrogen bonds, which shape this helix helix hydrogen bond heme group leu val lys gly his ala lys val lys pro
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Proteins The functions of proteins are linked to their three- dimensional structures Precise positioning of amino acid R groups leads to bonds that determine secondary and tertiary structure Disruption of secondary and tertiary bonds leads to denatured proteins and loss of function Extreme heat Extreme changes in pH UV radiation
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e sugar phosphate base Nucleotides and Nucleic Acids Nucleotides act as energy carriers and intracellular messengers Nucleotides are the monomers of nucleic acid chains Three parts: Phosphate group Five-carbon sugar Nitrogen-containing base Deoxyribose Nucleotide
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Nucleotides and Nucleic Acids Nucleotides act as energy carriers Adenosine triphosphate (ATP) is a ribose nucleotide with three phosphate functional groups ADP and cAMP NAD and FAD: electron carriers
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e Nucleic Acids DNA and RNA, the molecules of heredity Polymers of nucleotides DNA (deoxyribonucleic acid) is found in chromosomes and carries genetic information needed for protein construction RNA (ribonucleic acid) makes copies of DNA and is used directly in the synthesis of proteins
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e hydrogen bond Nucleic Acids Each DNA molecule consists of two chains of millions of nucleotides that form a double helix linked by hydrogen bonds
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- Copyright 2011 Pearson Education Inc.Biology: Life on Earth, 9e The Pleated Sheet: An Example of Secondary Structure Fig. 3-21 pleated sheet hydrogen bond