Chapter 5 Notes PDF

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Timothy Steward Chapter 5 Notes...

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Chapter 5- The Structure and Function of Large Biological Molecules:

 5.1 Macromolecules are polymers, built from monomers:  Polymer: a long molecule consisting of many similar or identical monomers linked together by covalent bonds  Carbohydrates  Proteins  Nucleic acids  Monomer: subunit the serves as the building block of a polymer  Macromolecule: large complex molecules  Carbohydrates  Lipids  Protein  Nucleic acid  The Synthesis and Breakdown of Polymers: o Enzyme: macromolecule that serves as a catalyst o Dehydration synthesis: chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule o Hydrolysis: chemical reaction that breaks bonds between two molecules by the addition of water

 The Diversity of Polymers: o A cell has thousands of different macromolecules o Macromolecules vary among cells of an organisms

o A huge variety of polymers can be built from a small set of monomers  5.2 Carbohydrates serve as fuel and building material:  Carbohydrates: a sugar (monosaccharide) or one of its dimers ( disaccharide) or polymer ( polysaccharides) o The simplest carbohydrates are monosaccharides, or simple sugars o Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar buikding blocks  Sugars:  Monosaccharides: have molecular formulas that are usually multiples of CH2O o Serve as a major fuel for cells, and as raw material for building molecules o Drawn as linear skeletons, in aqueous solutions many sugars form rings o Glucose ( C6H12O6) is the most common monosaccharide o Classified by:  The location of the carbonyl group (aldose or ketose)  The number of skeletons in the carbon skeleton  Disaccharide: formed when a dehydration reaction joins two monosaccharides  Glycosidic linkage: covalent bond formed between two monosaccharides by dehydration synthesis

 Polysaccharides:  Polysaccharides: the polymers of sugars, have storage and structural roles o The architecture and function of a polysaccharide are determined by its sugar monomers and the positions of its glycosidic linkages  Storage Polysaccharides:  Starch: storage polysaccharide in plants, consisting of entirely glucose monomers joined by glycosidic linkages  Plants store surplus starch as granules within chloroplasts and other plastids  Amylose is the simplest form of starch  Glycogen: extensively branched glucose storage polysaccharide found in the liver and muscle of animals (animal equivalent of starch) o Hydrolysis of glycogen in these cells releases glucose when the demand for sugar increases  Structural Polysaccharides:  Cellulose: structural polysaccharide of plant cells walls, consisting of glucose monomers joined by b-glycosidic linkages  Chitin: structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods o Insects o Spiders o Crustaceans o Provides structural support for walls of fungi  Starch (alpha configuration) is largely helical

 Cellulose molecules (beta configuration) are straight and unbranched  Glucose Alpha and Beta:

 Enzymes:  Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in cellulose  Cellulose in human food passes through the digestive tract as “insoluble fiber”  Some microbes use enzymes to digest cellulose  Many herbivores, from cows to termite, have symbiotic relationships with these microbes

 5.3 Lipids are a Diverse Group of hydrophobic molecules:  Lipids: any group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water

o The one class of large biological molecules that doesn’t include polymers o Consist mostly of hydrocarbon regions o Fats, phospholipids, and steroids are the most biologically important lipids  Fats:  Fat: consisted from two types of smaller molecules: glycerol and fatty acids o Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon o Separate from water because water molecules hydrogen-bond to each other and exclude the fats o The fatty acids in a fat can be all the same or of two or three different kinds o Fats made from saturated fatty acids are called saturated fats and are solid at room temperature o Most animal fats are saturated o Fats made from unsaturated fatty acids are called unsaturated fats or oils and are liquid at temperature o Plant fats and fish fats are usually unsaturated o Major function of fats is energy storage o Humans and other mammals store their long-term food reserves in adipose cells o Adipose tissue also cushions vital organs and insulated the body  Fatty acid: consists of a carboxyl group attached to a long carbon skeleton o Vary in length (number of carbons) and in the number and locations of double bonds

 Triacylglycerol: lipid consisting of three fatty acids linked to one glycerol molecule  Saturated fatty acid: maximum number of hydrogen atoms possible and no double bonds  Unsaturated fatty acid: fatty acid that has one or more double bonds between carbons in the hydrocarbon tail; such bonding reduces the number of hydrogen atoms attached to the carbon skeleton  Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen  Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds 

 Trans fats: unsaturated fat, formed artificially during hydrogenation of oils, containing one or more trans double bonds  Phospholipids:  Phospholipid: lipid made up of glycerol joined to two fatty acids and a phosphate group  Tails are hydrophobic and heads are hydrophilic  When added to water, they self-assemble into doublelayered sheets called bilayers  At the surface of a cell, phospholipids are also arranged in a bilayer; with the hydrophobic tails pointing toward the interior  The phospholipid bilayer forms a boundary between the cell and its external environment

 Steroids:  Steroid: lipids characterized by a carbon skeleton consisting of four fused rings o Estradiol and testosterone are both steroids with a common carbon skeleton- in one form of four fused rings  These sex hormones differ only in the chemical groups attached to the rings of the carbon skeleton  Cholesterol: type of steroid o Component in animal cell membrane and precursor from which other steroids are synthesized o High levels of cholesterol in the blood may contribute to cardiovascular disease

 5.4 proteins include a diversity of structures, resulting in a wide range of functions:  Catalyst: chemical agent that selectively increases the rate of a reaction without being consumed by the reaction o Enzymes are proteins that act as catalysts to speed up chemical reactions o Enzymes can repeatedly perform functions, functioning as workhorses that carry out the processes of life  Polypeptide: polymer of many amino acids linked together by peptide bonds  Protein: o Biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific 3D structure o Account for more than 50% of the dry mass of most cells o Some proteins speed up chemical reactions o Constructed from the same set of 20 amino acids o Functions include: Defense Storage Transport Cellular communication Movement Structural support

 Amino Acid Monomers: o Amino acid: organic molecule possessing both a carboxyl and an amino group o Serve as monomers of polypeptides o Differ in their properties due to differing side chains, called R-groups

 Polypeptides (Amino Acid Polymers): o Peptide bond: the covalent bond between the carboxyl group on one amino acid and the amino group on another o Formed by dehydration synthesis o Amino acids are linked by peptide bonds o Polymer of amino acids

 Protein Structure and Function: o Denaturation: loss of a protein’s native structure(biologically inactive protein as result)

o In addition to primary structure, physical and chemical conditions can affect structure o Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel o X-ray Crystallography: technique used to study 3-D structure of molecules o Another method is nuclear magnetic resonance (NMR) spectroscopy, which does not require protein crystallization o Bioinformatics is another approach to prediction of protein structure from amino acid sequences  Four Levels of Protein Structure:  The sequence of amino acids determines a protein’s 3-D structure  A protein’s structure determines how it works

 The function of a protein usually depends on its ability to recognize and bind to some other molecule  A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape o Primary: the unique sequence of a protein o Secondary: found in most proteins; consists of coils and folds in the polypeptide chain o Tertiary: determined by interactions among various side chains (R groups) o Quaternary: results when a protein consists of multiple polypeptide chains  Sickle-Cell Disease: o Sickle-cell disease: an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin  The abnormal hemoglobin molecules cause the red blood cells to aggregate into chains and to deform into a sickle shape o Slight change in primary structure can affect a protein’s structure and ability to function  5.5 Nucleic Acids store, transmit, and help exercise hereditary function:  The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene  Genes consist of DNA, a nucleic acid made of monomers called nucleotides  The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene

 Genes consist of DNA, a nucleic acid made of monomers called nucleotides  The Roles of Nucleic Acids:  There are two types of nucleic acids: o Deoxyribonucleic Acid(DNA): o Ribonucleic Acid:  DNA provides directions for its own replication  DNA directs synthesis of messenger RNA 9mRNA) and, through mRNA, controls protein synthesis  Gene Expression:  Each gene along a DNA molecule directs synthesis of a messenger RNA(mRNA)  mRNA molecule interacts with the cell’s proteinsynthesizing machinery to direct production of a polypeptide  The flow of genetic information can be summarized as: o DNA to RNA to protein  The Components of Nucleic Acids:  Nucleic acids are polymers called polynucleotides  Nucleoside= nitrogenous base+ sugar  Nucleotide= nucleoside + phosphate group(s), and a pentose sugar  Two families of Nitrogenous Bases: o Pyrimidine: o Cytosine o Thymine o Uracil o Purines: o Adenine o Guanine

 In DNA the sugar is a (deoxyribose), in RNA the sugar is ribose  Deoxyribose:  Ribose:  Nucleotide Polymers:   The Structures of DNA and RNA molecules:  One DNA molecule includes many genes  DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix:  The backbones run in opposite 5’ to 3’ directions from each other, an arrangement referred to as antiparallel:...