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Transcript
Chapter 3 The Molecules of Life PowerPoint® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Lectures by Chris C. Romero, updated by Edward J. Zalisko © 2010 Pearson Education, Inc. Biology and Society: Got Lactose? • Lactose is the main sugar found in milk. • Some adults exhibit lactose intolerance, the inability to properly digest lactose. • Lactose-intolerant individuals are unable to digest lactose properly. • Lactose is broken down by bacteria in the large intestine producing gas and discomfort. There is no treatment for the underlying cause of lactose intolerance. • Affected people must – Avoid lactose-containing foods or – Take the enzyme lactase when eating dairy products © 2010 Pearson Education, Inc. Evolution Connection: Evolution and Lactose Intolerance in Humans • Most people are lactose-intolerant as adults: – African Americans and Native Americans — 80% – Asian Americans — 90% – But only 10% of Americans of northern European descent are lactose-intolerant © 2010 Pearson Education, Inc. • Lactose tolerance appears to have evolved in northern European cultures that relied upon dairy products. • Ethnic groups in East Africa that rely upon dairy products are also lactose tolerant. © 2010 Pearson Education, Inc. • Polymers are made by stringing together many smaller molecules called monomers. • A dehydration reaction – Links two monomers together – Removes a molecule of water • Organisms also have to break down macromolecules. • Hydrolysis – Breaks bonds between monomers – Adds a molecule of water – Reverses the dehydration reaction © 2010 Pearson Education, Inc. LARGE BIOLOGICAL MOLECULES • There are four categories of large molecules in cells: – Carbohydrates – Lipids – Proteins – Nucleic acids © 2010 Pearson Education, Inc. Carbohydrates • Carbohydrates are sugars or sugar polymers. They include – Small sugar molecules in soft drinks – Long starch molecules in pasta and potatoes © 2010 Pearson Education, Inc. Monosaccharides & Disaccharides • Monosaccharides are simple sugars that cannot be broken down by hydrolysis into smaller sugars. • Common examples are – Glucose in sports drinks – Fructose found in fruit • A disaccharide is – A double sugar – Constructed from two monosaccharides – Formed by a dehydration reaction © 2010 Pearson Education, Inc. • Disaccharides include – Lactose in milk (see next slide) – Maltose in beer, malted milk shakes, and malted milk ball candy – Sucrose in table sugar • Sucrose is – The main carbohydrate in plant sap – Rarely used as a sweetener in processed foods • High-fructose corn syrup is made by a commercial process that converts natural glucose in corn syrup to much sweeter fructose. © 2010 Pearson Education, Inc. Galactose Glucose Lactose Figure 3.7 processed to extract Starch broken down into Glucose converted to sweeter Fructose added to foods as high-fructose corn syrup Ingredients: carbonated water, high-fructose corn syrup, caramel color, phosphoric acid, natural flavors Figure 3.8 Polysaccharides • Polysaccharides are – Complex carbohydrates – Made of long chains of sugar units and polymers of monosaccharides – Examples include: starch, glycogen and cellulose © 2010 Pearson Education, Inc. Glucose monomer Starch granules a Starch Glycogen granules b Glycogen Cellulose fibril Cellulose molecules c Cellulose Figure 3.9 • Starch is – A familiar example of a polysaccharide – Used by plant cells to store energy • Potatoes and grains are major sources of starch in the human diet. • Glycogen is – Used by animals cells to store energy – Converted to glucose when it is needed • Cellulose – Is the most abundant organic compound on Earth – Forms cable-like fibers in the tough walls that enclose plants – Cannot be broken apart by most animals © 2010 Pearson Education, Inc. Lipids • Lipids are – Neither macromolecules nor polymers – Hydrophobic, unable to mix with water © 2010 Pearson Education, Inc. Oil (hydrophobic) Vinegar (hydrophilic) Figure 3.10 Fats • A typical fat, or triglyceride, consists of a glycerol molecule joined with three fatty acid molecules via a dehydration reaction. © 2010 Pearson Education, Inc. Fatty acid Glycerol (a) A dehydration reaction linking a fatty acid to glycerol (b) A fat molecule with a glycerol “head” and three energy-rich hydrocarbon fatty acid “tails” Figure 3.11 • Fats perform essential functions in the human body including – Energy storage – Cushioning – Insulation © 2010 Pearson Education, Inc. • Most animal fats – Have a high proportion of saturated fatty acids – Can easily stack, tending to be solid at room temperature – Contribute to atherosclerosis, a condition in which lipidcontaining plaques build up within the walls of blood vessels © 2010 Pearson Education, Inc. • Most plant oils tend to be low in saturated fatty acids and liquid at room temperature. • Hydrogenation – Adds hydrogen – Converts unsaturated fats to saturated fats – Makes liquid fats solid at room temperature – Creates trans fat, a type of unsaturated fat that is even less healthy than saturated fats © 2010 Pearson Education, Inc. TYPES OF FATS Saturated Fats Unsaturated Fats Margarine INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED COTTONSEED OIL, PARTIALLY HYDROGENATED COTTONSEED OIL AND SOYBEAN OILS, MONO AND DIGLYCERIDES, TBHO AND CITRIC ACID Plant oils Trans fats ANTIOXIDANTS Omega-3 fats Figure 3.12 Steroids • Steroids are very different from fats in structure and function. – The carbon skeleton is bent to form four fused rings. • Cholesterol is – A key component of cell membranes – The “base steroid” from which your body produces other steroids, such as estrogen and testosterone © 2010 Pearson Education, Inc. Cholesterol Testosterone A type of estrogen Figure 3.13 • Synthetic anabolic steroids – Resemble testosterone – Mimic some of its effects – Can cause serious physical and mental problems – Are abused by athletes to enhance performance © 2010 Pearson Education, Inc. Proteins • Proteins – Are polymers constructed from amino acid monomers – Perform most of the tasks the body needs to function – Form enzymes, chemicals that change the rate of a chemical reaction without being changed in the process © 2010 Pearson Education, Inc. MAJOR TYPES OF PROTEINS Structural Proteins Storage Proteins Contractile Proteins Transport Proteins Enzymes Figure 3.15 Proteins as Polymers • Cells link amino acids together by dehydration reactions, forming peptide bonds and creating long chains of amino acids called polypeptides. • The specific sequence of amino acids in a protein is its primary structure. © 2010 Pearson Education, Inc. Amino acids b Secondary structure c Tertiary structure d Quaternary structure a Primary structure Pleated sheet Protein with four polypeptides Polypeptide Alpha helix Figure 3.20-4 What Determines Protein Shape? • A protein’s shape is sensitive to the surrounding environment. • Unfavorable temperature and pH changes can cause denaturation of a protein, in which it unravels and loses its shape. • High fevers (above 104º F) in humans can cause some proteins to denature. © 2010 Pearson Education, Inc. • Misfolded proteins are associated with – Alzheimer’s disease – Mad cow disease – Parkinson’s disease © 2010 Pearson Education, Inc. Nucleic Acids • Nucleic acids – Are macromolecules that provide the directions for building proteins – Include DNA and RNA – Are the genetic material that organisms inherit from their parents © 2010 Pearson Education, Inc. • DNA resides in cells in long fibers called chromosomes. • A gene is a specific stretch of DNA that programs the amino acid sequence of a polypeptide. • The chemical code of DNA must be translated from “nucleic acid language” to “protein language.” © 2010 Pearson Education, Inc. Gene DNA Nucleic acids RNA Amino acid Protein Figure 3.22 • Nucleic acids are polymers of nucleotides. • Each nucleotide has three parts: – A five-carbon sugar – A phosphate group – A nitrogenous base © 2010 Pearson Education, Inc. • Each DNA nucleotide has one of the following bases: – Adenine (A) – Guanine (G) – Thymine (T) – Cytosine (C) © 2010 Pearson Education, Inc. Base pair Hydrogen bond b Double helix two polynucleotide strands Figure 3.25b • Two strands of DNA join together to form a double helix. • Bases along one DNA strand hydrogen-bond to bases along the other strand. • The functional groups hanging off the base determine which bases pair up: – A only pairs with T. – G can only pair with C. © 2010 Pearson Education, Inc. • RNA, ribonucleic acid, is different from DNA. – RNA is usually single-stranded but DNA usually exists as a double helix. – RNA uses the sugar ribose and the base uracil (U) instead of thymine (T). © 2010 Pearson Education, Inc. Large biological molecules Carbohydrates Functions Components Examples Monosaccharides: glucose, fructose Disaccharides: lactose, sucrose Polysaccharides: starch, cellulose Dietary energy; storage; plant structure Monosaccharide Lipids Long-term energy storage fats; hormones steroids Fatty acid Glycerol Components of a triglyceride Amino group Proteins Enzymes, structure, storage, contraction, transport, and others Fats triglycerides; Steroids testosterone, estrogen Carboxyl group Side group Lactase an enzyme, hemoglobin a transport protein Amino acid Phosphate Base Nucleic acids Information storage DNA, RNA Sugar Nucleotide Figure UN3-2