Molecules of Life Chapter 3 Part 1

Impacts, Issues: Fear of Frying Trans fats in hydrogenated vegetable oil raise levels of cholesterol in our blood more than any other fat, and directly alter blood vessel function

Organic Molecules All molecules of life are built with carbon atoms We can use different models to highlight different aspects of the same molecule

3.1 Carbon – The Stuff of Life Organic molecules are complex molecules of life, built on a framework of carbon atoms Carbohydrates Lipids Proteins Nucleic acids

Carbon – The Stuff of Life Carbon atoms can be assembled and remodeled into many organic compounds Can bond with one, two, three, or four atoms Can form polar or nonpolar bonds Can form chains or rings

Carbon Rings

Representing Structures of Organic Molecules Structural model of an organic molecule Each line is a covalent bond; two lines are double bonds; three lines are triple bonds

Representing Structures of Organic Molecules Carbon ring structures are represented as polygons; carbon atoms are implied

Representing Structures of Organic Molecules Ball-and-stick models show positions of atoms in three dimensions; elements are coded by color

Representing Structures of Organic Molecules Space-filling models show how atoms sharing electrons overlap

Three Models of a Hemoglobin Molecule

Figure 3.3 Visualizing the structure of hemoglobin, the oxygen-transporting molecule in red blood cells (top left). Models that show individual atoms usually depict them color-coded by element. Other models may be shown in various colors, depending on which features are highlighted. Fig. 3-3 (top), p. 37

Figure 3.3 Visualizing the structure of hemoglobin, the oxygen-transporting molecule in red blood cells (top left). Models that show individual atoms usually depict them color-coded by element. Other models may be shown in various colors, depending on which features are highlighted. red blood cell Fig. 3-3 (top), p. 37

A A space-filling model of hemoglobin shows the Figure 3.3 Visualizing the structure of hemoglobin, the oxygen-transporting molecule in red blood cells (top left). Models that show individual atoms usually depict them color-coded by element. Other models may be shown in various colors, depending on which features are highlighted. A A space-filling model of hemoglobin shows the complexity of the molecule. Fig. 3-3a, p. 37

Figure 3.3 Visualizing the structure of hemoglobin, the oxygen-transporting molecule in red blood cells (top left). Models that show individual atoms usually depict them color-coded by element. Other models may be shown in various colors, depending on which features are highlighted. B A surface model of the same molecule reveals crevices and folds that are important for its function. Heme groups, in red, are cradled in pockets of the molecule. Fig. 3-3b, p. 37

Figure 3.3 Visualizing the structure of hemoglobin, the oxygen-transporting molecule in red blood cells (top left). Models that show individual atoms usually depict them color-coded by element. Other models may be shown in various colors, depending on which features are highlighted. C A ribbon model of hemoglobin shows all four heme groups, also in red, held in place by the molecule’s coils. Fig. 3-3c, p. 37

3.2 From Structure to Function The function of organic molecules in biological systems begins with their structure The building blocks of carbohydrates, lipids, proteins, and nucleic acids bond together in different arrangements to form different kinds of complex molecules

Functional Groups Hydrocarbon An organic molecule that consists only of hydrogen and carbon atoms Most biological molecules have at least one functional group A cluster of atoms that imparts specific chemical properties to a molecule (polarity, acidity)

Common Functional Groups in Biological Molecules

Figure 3.4 Common functional groups in biological molecules, with examples of where they occur. Because such groups impart specific chemical characteristics to organic compounds, they are an important part of why the molecules of life function as they do. Stepped Art Fig. 3-4, p. 38

Animation: Functional group

Effects of Functional Groups: Sex Hormones

Figure 3.5 Estrogen and testosterone, sex hormones that cause differences in traits between males and females of many species such as wood ducks (Aix sponsa). Figure It Out: Which functional groups differ between these hormones? Answer: The hydroxyl and carbonyl groups differ in position, and testosterone has an extra methyl group. Fig. 3-5a, p. 38

one of the estrogens testosterone Figure 3.5 Estrogen and testosterone, sex hormones that cause differences in traits between males and females of many species such as wood ducks (Aix sponsa). Figure It Out: Which functional groups differ between these hormones? Answer: The hydroxyl and carbonyl groups differ in position, and testosterone has an extra methyl group. one of the estrogens testosterone Fig. 3-5a, p. 38

Figure 3.5 Estrogen and testosterone, sex hormones that cause differences in traits between males and females of many species such as wood ducks (Aix sponsa). Figure It Out: Which functional groups differ between these hormones? Answer: The hydroxyl and carbonyl groups differ in position, and testosterone has an extra methyl group. Fig. 3-5b, p. 38

female wood duck male wood duck Figure 3.5 Estrogen and testosterone, sex hormones that cause differences in traits between males and females of many species such as wood ducks (Aix sponsa). Figure It Out: Which functional groups differ between these hormones? Answer: The hydroxyl and carbonyl groups differ in position, and testosterone has an extra methyl group. Fig. 3-5b, p. 38

What Cells Do to Organic Compounds Metabolism Activities by which cells acquire and use energy to construct, rearrange, and split organic molecules Allows cells to live, grow, and reproduce Requires enzymes (proteins that increase the speed of reactions)

What Cells Do to Organic Compounds Condensation Covalent bonding of two molecules to form a larger molecule Water forms as a product Hydrolysis The reverse of condensation Cleavage reactions split larger molecules into smaller ones Water is split

What Cells Do to Organic Compounds Monomers Molecules used as subunits to build larger molecules (polymers) Polymers Larger molecules that are chains of monomers May be split and used for energy

What Cells Do to Organic Compounds

Condensation and Hydrolysis

Figure 3.6 Two examples of what happens to the organic molecules in cells. (a) In condensation, two molecules are covalently bonded into a larger one. (b) In hydrolysis, a water-requiring cleavage reaction splits a larger molecule into two smaller molecules. A) Condensation. An —OH group from one molecule combines with an H atom from another. Water forms as the two molecules bond covalently. B) Hydrolysis. A molecule splits, then an —OH group and an H atom from a water molecule become attached to sites exposed by the reaction. Stepped Art Fig. 3-6, p. 39

Animation: Condensation and hydrolysis

3.1-3.2 Key Concepts: Structure Dictates Function We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids All of these organic compounds have functional groups attached to a backbone of carbon atoms

3.3 Carbohydrates Carbohydrates are the most plentiful biological molecules in the biosphere Cells use some carbohydrates as structural materials; others for stored or instant energy

Carbohydrates Carbohydrates Organic molecules that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio Three types of carbohydrates in living systems Monosaccharides Oligosaccharides Polysaccharides

Simple Sugars Monosaccharides (one sugar unit) are the simplest carbohydrates Used as an energy source or structural material Backbones of 5 or 6 carbons Example: glucose

Short-Chain Carbohydrates Oligosaccharides Short chains of monosaccharides Example: sucrose, a disaccharide

glucose + fructose sucrose + water Figure 3.7 The synthesis of a sucrose molecule is an example of a condensation reaction. You are already familiar with sucrose—it is common table sugar. Fig. 3-7b, p. 40

glucose + fructose sucrose + water Figure 3.7 The synthesis of a sucrose molecule is an example of a condensation reaction. You are already familiar with sucrose—it is common table sugar. Stepped Art Fig. 3-7b, p. 40

Complex Carbohydrates Polysaccharides Straight or branched chains of many sugar monomers The most common polysaccharides are cellulose, starch, and glycogen All consist of glucose monomers Each has a different pattern of covalent bonding, and different chemical properties

Cellulose, Starch, and Glycogen

Figure 3.8 Structure of (a) cellulose, (b) starch, and (c) glycogen, and their typical locations in a few organisms. All three carbohydrates consist only of glucose units, but the different bonding patterns that link the subunits result in substances with very different properties. Fig. 3-8a, p. 41

Figure 3.8 Structure of (a) cellulose, (b) starch, and (c) glycogen, and their typical locations in a few organisms. All three carbohydrates consist only of glucose units, but the different bonding patterns that link the subunits result in substances with very different properties. Fig. 3-8b, p. 41

Figure 3.8 Structure of (a) cellulose, (b) starch, and (c) glycogen, and their typical locations in a few organisms. All three carbohydrates consist only of glucose units, but the different bonding patterns that link the subunits result in substances with very different properties. Fig. 3-8c, p. 41

Chitin Chitin A nitrogen-containing polysaccharide that strengthens hard parts of animals such as crabs, and cell walls of fungi

3.3 Key Concepts: Carbohydrates Carbohydrates are the most abundant biological molecules They function as energy reservoirs and structural materials Different types of complex carbohydrates are built from the same subunits of simple sugars, bonded in different patterns

3.4 Greasy, Oily – Must Be Lipids Lipids function as the body’s major energy reservoir, and as the structural foundation of cell membranes Lipids Fatty, oily, or waxy organic compounds that are insoluble in water

Fatty Acids Many lipids incorporate fatty acids Simple organic compounds with a carboxyl group joined to a backbone of 4 to 36 carbon atoms Essential fatty acids are not made by the body and must come from food Omega-3 and omega-6 fatty acids

Fatty Acids Saturated, monounsaturated, polyunsaturated

stearic acid oleic acid linolenic acid Figure 3.10 Examples of fatty acids. (a) The backbone of stearic acid is fully saturated with hydrogen atoms. (b) Oleic acid, with a double bond in its backbone, is unsaturated. (c) Linolenic acid, also unsaturated, has three double bonds. The first double bond occurs at the third carbon from the end of the tail, so oleic acid is called an omega-3 fatty acid. Omega-3 and omega-6 fatty acids are “essential fatty acids.” Your body does not make them, so they must come from food. stearic acid oleic acid linolenic acid Fig. 3-10, p. 42

Fats Fats Triglycerides Lipids with one, two, or three fatty acids “tails” attached to glycerol Triglycerides Neutral fats with three fatty acids attached to glycerol The most abundant energy source in vertebrates Concentrated in adipose tissues (for insulation and cushioning)

Triglycerides

triglyceride, a neutral fat glycerol + 3H2O Figure 3.11 Triglyceride formation by the condensation of three fatty acids with one glycerol molecule. The photograph shows triglyceride-insulated emperor penguins during an Antarctic blizzard. triglyceride, a neutral fat three fatty acid tails Fig. 3-11a, p. 42

Figure 3.11 Triglyceride formation by the condensation of three fatty acids with one glycerol molecule. The photograph shows triglyceride-insulated emperor penguins during an Antarctic blizzard. Fig. 3-11b, p. 42

Animation: Triglyceride formation

Saturated and Unsaturated Fats Saturated fats (animal fats) Fatty acids with only single covalent bonds Pack tightly; solid at room temperature Unsaturated fats (vegetable oils) Fatty acids with one or more double bonds Kinked; liquid at room temperature

Trans Fats Trans fats Partially hydrogenated vegetable oils formed by a chemical hydrogenation process Double bond straightens the molecule Pack tightly; solid at room temperature

Cis and Trans Fatty Acids

cis double bond a oleic acid Figure 3.12 The only difference between (a) oleic acid (a cis fatty acid) and (b) elaidic acid (a trans fatty acid) is the arrangement of hydrogens around one double bond. Trans fatty acids form during chemical hydrogenation processes. a oleic acid Fig. 3-12a, p. 43

trans double bond b elaidic acid Figure 3.12 The only difference between (a) oleic acid (a cis fatty acid) and (b) elaidic acid (a trans fatty acid) is the arrangement of hydrogens around one double bond. Trans fatty acids form during chemical hydrogenation processes. b elaidic acid Fig. 3-12b, p. 43

Phospholipids Phospholipids Molecules with a polar head containing a phosphate and two nonpolar fatty acid tails Heads are hydrophilic, tails are hydrophobic The most abundant lipid in cell membranes

Phospholipids

Figure 3.13 Phospholipid, (a) structure and (b) icon. Phospholipids are the main structural component of all cell membranes (c). Fig. 3-13a, p. 43

hydrophilic head two hydrophobic tails Figure 3.13 Phospholipid, (a) structure and (b) icon. Phospholipids are the main structural component of all cell membranes (c). Fig. 3-13b, p. 43

c Cell membrane section Figure 3.13 Phospholipid, (a) structure and (b) icon. Phospholipids are the main structural component of all cell membranes (c). c Cell membrane section Fig. 3-13c, p. 43

Waxes Waxes Complex mixtures with long fatty-acid tails bonded to long-chain alcohols or carbon rings Protective, water-repellant covering

Cholesterol and Other Steroids Lipids with a rigid backbone of four carbon rings and no fatty-acid tails Cholesterol Component of eukaryotic cell membranes Remodeled into bile salts, vitamin D, and steroid hormones (estrogens and testosterone)

Cholesterol

3.4 Key Concepts: Lipids Lipids function as energy reservoirs and waterproofing or lubricating substances Some are remodeled into other substances Lipids are the main structural components of cell membranes

Animation: Sucrose synthesis

Animation: Cholesterol

Animation: Fatty acids

Animation: Molecular models of the protein hemoglobin

Animation: Phospholipid structure

Animation: Secondary and tertiary structure

Animation: Structure of an amino acid

Animation: Structure of ATP

Animation: Structure of starch and cellulose

Animation: Sucrose synthesis