1 Molecules of Life Chapter 3 Part 1
2 Organic Molecules All molecules of life are built with carbon atomsWe can use different models to highlight different aspects of the same molecule
3 3.1 Carbon – The Stuff of LifeOrganic molecules are complex molecules of life, built on a framework of carbon atoms Carbohydrates Lipids Proteins Nucleic acids
4 Carbon – The Stuff of LifeCarbon atoms can be assembled and remodeled into many organic compounds Can bond with 1-4 four atoms Can form polar or nonpolar bonds Can form chains or rings
5 Representing Structures of Organic MoleculesStructural model of an organic molecule Each line is a covalent bond; two lines are double bonds; three lines are triple bonds
6 Representing Structures of Organic MoleculesCarbon ring structures are represented as polygons; carbon atoms are implied
7 Representing Structures of Organic MoleculesBall-and-stick models show positions of atoms in three dimensions; elements are coded by color
8 Representing Structures of Organic MoleculesSpace-filling models show how atoms sharing electrons overlap
9 3.2 From Structure to FunctionThe function of organic molecules in biological systems begins with their structure The building blocks of organic compounds bond together in different arrangements to form different kinds of complex molecules
10 Functional Groups HydrocarbonAn organic molecule that consists only of hydrogen and carbon atoms Most biological molecules have at least one functional group
11 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
12 one of the estrogens testosterone Figure 3.5Estrogen 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
13 What Cells Do to Organic CompoundsMetabolism 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)
14 What Cells Do to Organic CompoundsCondensation (dehydration synthesis) 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
15 What Cells Do to Organic CompoundsMonomers Molecules used as subunits to build larger molecules (polymers) Polymers Larger molecules that are chains of monomers May be split and used for energy
16 What Cells Do to Organic Compounds
17 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
18 3.1-3.2 Key Concepts: Structure Dictates FunctionWe define cells partly by their capacity to build complex carbohydrates, lipids, proteins, and nucleic acids All of these organic compounds have functional groups attached to a backbone of carbon atoms
19 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
20 Carbohydrates CarbohydratesOrganic molecules that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio Three types of carbohydrates in living systems Monosaccharides Oligosaccharides Polysaccharides
21 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
22 Short-Chain CarbohydratesOligosaccharides Short chains of monosaccharides Example: sucrose, a disaccharide
23 Complex CarbohydratesPolysaccharides 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
24 Cellulose, Starch, and Glycogen
25 Chitin Chitin A nitrogen-containing polysaccharide that strengthens the exoskeleton of animals like crabs, and cell walls of fungi
26 3.3 Key Concepts: CarbohydratesCarbohydrates 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
27 3.4 Greasy, Oily – Must Be LipidsLipids 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
28 Fatty Acids Many lipids incorporate fatty acidsSimple 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
29 Fatty Acids Saturated, monounsaturated, polyunsaturated
30 Fats Fats TriglyceridesLipids with 1, 2, or 3 fatty acid “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)
31 Triglycerides
32 Saturated and Unsaturated FatsSaturated 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
33 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
34 Phospholipids PhospholipidsMolecules 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
35 c Cell membrane sectionFigure 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
36 Waxes Waxes Complex mixtures with long fatty-acid tails bonded to long-chain alcohols or carbon rings Protective, water-repellant covering
37 Cholesterol and Other SteroidsLipids 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)
38 Cholesterol
39 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