© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko 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 Chapter 3 The Molecules of Life

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. © 2010 Pearson Education, Inc.

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. ORGANIC COMPOUNDS A cell is mostly water. The rest of the cell consists mainly of carbon-based molecules. Carbon forms large, complex, and diverse molecules necessary for life’s functions. Organic compounds are carbon-based molecules.

© 2010 Pearson Education, Inc. Carbon Chemistry Carbon is a versatile atom. –It has four electrons in an outer shell that holds eight. –Carbon can share its electrons with other atoms to form up to four covalent bonds.

© 2010 Pearson Education, Inc. Carbon can use its bonds to –Attach to other carbons –Form an endless diversity of carbon skeletons Animation: Carbon Skeletons

© 2010 Pearson Education, Inc. The simplest organic compounds are hydrocarbons, which are organic molecules containing only carbon and hydrogen atoms. The simplest hydrocarbon is methane, consisting of a single carbon atom bonded to four hydrogen atoms.

Structural formula Figure 3.2a

© 2010 Pearson Education, Inc. Larger hydrocarbons form fuels for engines. Hydrocarbons of fat molecules fuel our bodies.

© 2010 Pearson Education, Inc. Each type of organic molecule has a unique three-dimensional shape. The shapes of organic molecules relate to their functions.

© 2010 Pearson Education, Inc. The unique properties of an organic compound depend on –Its carbon skeleton –The atoms attached to the skeleton The groups of atoms that usually participate in chemical reactions are called functional groups. Two common examples are –Hydroxyl groups (-OH) –Carboxyl groups (C=O)

© 2010 Pearson Education, Inc. Giant Molecules from Smaller Building Blocks On a molecular scale, many of life’s molecules are gigantic, earning the name macromolecules. Three categories of macromolecules are –Carbohydrates –Proteins –Nucleic acids

© 2010 Pearson Education, Inc. Most macromolecules are polymers. Polymers are made by stringing together many smaller molecules called monomers. A dehydration reaction –Links two monomers together –Removes a molecule of water Animation: Polymers

© 2010 Pearson Education, Inc. 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 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 Glucose and fructose are isomers, molecules that have the same molecular formula but different structures. Animation: L-Dopa Animation: Isomers

© 2010 Pearson Education, Inc. Monosaccharides are the main fuels for cellular work. In aqueous solutions, many monosaccharides form rings.

© 2010 Pearson Education, Inc. Disaccharides A disaccharide is –A double sugar –Constructed from two monosaccharides –Formed by a dehydration reaction Animation: Disaccharides

© 2010 Pearson Education, Inc. Disaccharides include –Lactose in milk –Maltose in beer, malted milk shakes, and malted milk ball candy –Sucrose in table sugar

© 2010 Pearson Education, Inc. 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.

processed to extract broken down into converted to sweeter added to foods as high-fructose corn syrup Starch Glucose Fructose Ingredients: carbonated water, high-fructose corn syrup, caramel color, phosphoric acid, natural flavors Figure 3.8

© 2010 Pearson Education, Inc. The United States is one of the world’s leading markets for sweeteners. –The average American consumes about 45 kg of sugar (about 100 lbs.) per year.

© 2010 Pearson Education, Inc. Polysaccharides Polysaccharides are –Complex carbohydrates –Made of long chains of sugar units and polymers of monosaccharides Animation: Polysaccharides

© 2010 Pearson Education, Inc. 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.

© 2010 Pearson Education, Inc. Glycogen is –Used by animals cells to store energy –Converted to glucose when it is needed

© 2010 Pearson Education, Inc. Cellulose –Is the most abundant organic compound on Earth –Forms cable-like fibrils in the tough walls that enclose plants –Cannot be broken apart by most animals

© 2010 Pearson Education, Inc. Monosaccharides and disaccharides dissolve readily in water. Cellulose does not dissolve readily in water. Almost all carbohydrates are hydrophilic, or “water-loving,” adhering water to their surface.

© 2010 Pearson Education, Inc. Lipids Lipids are –Neither macromolecules nor polymers –Hydrophobic, unable to mix with water

Oil (hydrophobic) Vinegar (hydrophilic) Figure 3.10

© 2010 Pearson Education, Inc. Fats A typical fat, or triglyceride, consists of a glycerol molecule joined with three fatty acid molecules via a dehydration reaction. Animation: Fats

© 2010 Pearson Education, Inc. Fats perform essential functions in the human body including –Energy storage –Cushioning –Insulation

© 2010 Pearson Education, Inc. If the carbon skeleton of a fatty acid has –Fewer than the maximum number of hydrogens, it is unsaturated –The maximum number of hydrogens, then it is saturated A saturated fat has no double bonds, and all three of its fatty acids are saturated.

© 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 lipid- containing 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.

© 2010 Pearson Education, Inc. 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

Saturated Fats TYPES OF FATS Unsaturated Fats Margarine Plant oils Trans fats Omega-3 fats INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED COTTONSEED OIL, PARTIALLY HYDROGENATED COTTONSEED OIL AND SOYBEAN OILS, MONO AND DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS Figure 3.12

Saturated Fats Figure 3.12a

Figure 3.12b Unsaturated Fats Margarine Plant oils Trans fats Omega-3 fats INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED COTTONSEED OIL, PARTIALLY HYDROGENATED COTTONSEED OIL AND SOYBEAN OILS, MONO AND DIGLYCERIDES, TBHO AND CITRIC ACID  ANTIOXIDANTS 

© 2010 Pearson Education, Inc. Steroids Steroids are very different from fats in structure and function. –The carbon skeleton is bent to form four fused rings. –Steroids vary in the functional groups attached to this core set of rings.

© 2010 Pearson Education, Inc. 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. 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 –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

MAJOR TYPES OF PROTEINS Structural ProteinsStorage Proteins Contractile ProteinsTransport ProteinsEnzymes Figure 3.15

Structural Proteins  provide support  Figure 3.15a

Storage Proteins  provide amino acids for growth  Figure 3.15b

Contractile Proteins  help movement  Figure 3.15c

Transport Proteins  help transport substances  Figure 3.15d

Enzymes  help chemical reactions  Figure 3.15e

© 2010 Pearson Education, Inc. The Monomers of Proteins: Amino Acids All proteins are constructed from a common set of 20 kinds of amino acids. Each amino acid consists of a central carbon atom bonded to four covalent partners in which three of those attachment groups are common to all amino acids.

© 2010 Pearson Education, Inc. Proteins as Polymers Cells link amino acids together by dehydration reactions, forming peptide bonds and creating long chains of amino acids called polypeptides.

© 2010 Pearson Education, Inc. Your body has tens of thousands of different kinds of protein. Proteins differ in their arrangement of amino acids. The specific sequence of amino acids in a protein is its primary structure.

© 2010 Pearson Education, Inc. A slight change in the primary structure of a protein affects its ability to function. The substitution of one amino acid for another in hemoglobin causes sickle-cell disease.

Normal red blood cell  a  Normal hemoglobin Normal hemoglobin SEM Figure 3.19a

© 2010 Pearson Education, Inc. Protein Shape A functional protein consists of one or more polypeptide chains, precisely folded and coiled into a molecule of unique shape.

© 2010 Pearson Education, Inc. Proteins consisting of –One polypeptide have three levels of structure –More than one polypeptide chain have a fourth, quaternary structure

© 2010 Pearson Education, Inc. Animation: Protein Structure Introduction Blast Animation: Protein Secondary Structure Blast Animation: Protein Primary Structure Animation: Primary Protein Structure Blast Animation: Alpha Helix Animation: Quaternary Protein Structure Animation: Tertiary Protein Structure Blast Animation: Protein Tertiary and Quaternary Structure Animation: Secondary Protein Structure

© 2010 Pearson Education, Inc. A protein’s three-dimensional shape –Recognizes and binds to another molecule –Enables the protein to carry out its specific function in a cell

© 2010 Pearson Education, Inc. 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. 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)

Adenine  A  Guanine  G  Thymine  T  Cytosine  C  Adenine  A  Guanine  G  Thymine  T  Cytosine  C  Space-filling model of DNA Figure 3.24

Adenine  A  Guanine  G  Thymine  T  Cytosine  C  Figure 3.24a

Adenine  A  Guanine  G  Thymine  T  Cytosine  C  Space-filling model of DNA Figure 3.24b

© 2010 Pearson Education, Inc. Dehydration reactions –Link nucleotide monomers into long chains called polynucleotides –Form covalent bonds between the sugar of one nucleotide and the phosphate of the next –Form a sugar-phosphate backbone Nitrogenous bases hang off the sugar-phosphate backbone.

Sugar-phosphate backbone Nucleotide Base pair Hydrogen bond Bases  a  DNA strand  polynucleotide   b  Double helix  two polynucleotide strands  Figure 3.25

Sugar-phosphate backbone Nucleotide Bases  a  DNA strand  polynucleotide  Figure 3.25a

Base pair Hydrogen bond  b  Double helix  two polynucleotide strands  Figure 3.25b

© 2010 Pearson Education, Inc. 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).

The Process of Science: Does Lactose Intolerance Have a Genetic Basis? Observation: Most lactose-intolerant people have a normal version of the lactase gene. Question: Is there a genetic basis for lactose intolerance? Hypothesis: Lactose-intolerant people have a mutation but not within the lactase gene. © 2010 Pearson Education, Inc.

Prediction: A mutation would be found nearby the lactase gene. Experiment: Genes of 196 lactose-intolerant people were examined. Results: A 100% correlation between lactose intolerance and one mutation was found.

DNA Human cell  DNA in 46 chromosomes  Chromosome 2  one DNA molecule  Section of chromosome 2 Lactase gene 14,000 nucleotides C at this site causes lactose intolerance T at this site causes lactose tolerance Figure 3.27

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 but due to different mutations.

Large biological molecules FunctionsComponentsExamples Carbohydrates Lipids Proteins Nucleic acids Dietary energy; storage; plant structure Long-term energy storage  fats  ; hormones  steroids  Enzymes, structure, storage, contraction, transport, and others Information storage Monosaccharides: glucose, fructose Disaccharides: lactose, sucrose Polysaccharides: starch, cellulose Fats  triglycerides  ; Steroids  testosterone, estrogen  Lactase  an enzyme , hemoglobin  a transport protein  DNA, RNA Monosaccharide Components of a triglyceride Amino acid Nucleotide Fatty acid Glycerol Amino group Carboxyl group Side group Phosphate Base Sugar Figure UN3-2

FunctionsComponentsExamples Dietary energy; storage; plant structure Monosaccharides: glucose, fructose Disaccharides: lactose, sucrose Polysaccharides: starch, cellulose Monosaccharide Carbohydrates Figure UN3-2a

FunctionsComponentsExamples Lipids Long-term energy storage  fats  ; hormones  steroids  Fats  triglycerides  ; Steroids  testosterone, estrogen  Components of a triglyceride Fatty acid Glycerol Figure UN3-2b

FunctionsComponentsExamples Proteins Enzymes, structure, storage, contraction, transport, and others Lactase  an enzyme , hemoglobin  a transport protein  Amino acid Amino group Carboxyl group Side group Figure UN3-2c

FunctionsComponentsExamples Nucleic acids Information storage DNA, RNA Nucleotide Phosphate Base Sugar Figure UN3-2d