Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The Molecules of Life Within cells, small organic molecules are joined together to form larger molecules Macromolecules are large molecules composed of thousands of covalently connected atoms. The four classes of macromolecules that are important to life are: – Carbohydrates – Lipids – Proteins – Nucleic acids

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar or identical building blocks called monomers A polypeptide ( a polymer ) Glycogen ( a polymer ) is made of glucose monomers (monomers)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Most macromolecules are polymers, built from monomers Three of the four classes of life’s organic molecules are polymers: – Carbohydrates – Proteins – Nucleic acids

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Synthesis of Polymers by DEHYDRATION REACTIONS Monomers form larger molecules called polymers by condensation reactions called dehydration reactions. A dehydration reaction occurs when two monomers bond together through the loss of a water molecule v=UyDnnD3fMaU

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dehydration removes a water molecule, forming a new bond Short polymerUnlinked monomer Longer polymer Dehydration reaction in the synthesis of a polymer HO H2OH2O H H H (a)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Breakdown of Polymers by HYDOLYSIS REACTIONS Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction. In hydrolysis, bonds are broken by the addition of water molecules.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fig. 5-2b Hydrolysis adds a water molecule, breaking a bond Hydrolysis of a polymer HO H2OH2O H H H (b)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carbohydrates serve as fuel and building material Carbohydrates include single (simple) sugars and their polymers Carbohydrates may be classified as: – Monosaccharides (the simplest) – Disaccharides – Oligosaccharide (3-9) – Polysaccharides

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides Monosaccharides have molecular formulas that are usually multiples of CH 2 O (CH 2 O) n where n ranges from 3-7 Glucose (C 6 H 12 O 6 ) is the most common monosaccharide.

LE 5-3 Triose sugars (C 3 H 6 O 3 ) Glyceraldehyde Aldoses Ketoses Pentose sugars (C 5 H 10 O 5 ) Ribose Hexose sugars (C 6 H 12 O 6 ) Glucose Galactose Dihydroxyacetone Ribulose Fructose

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides Functions of monosaccharides: – major fuel (source of energy) for cells and – raw material for building other molecules such as fatty acids and amino acids.

Glucose Maltose Fructose Sucrose Glucose Dehydration reaction in the synthesis of maltose Dehydration reaction in the synthesis of sucrose 1–4 glycosidic linkage 1–2 glycosidic linkage A disaccharide is formed when a dehydration reaction joins two monosaccharides The covalent bond joining two monosaccharides is called a glycosidic linkage Disaccharides

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polysaccharides Polymers of monosaccharides Based on their function, there are two types of polysaccharides: – Storage polysaccharides. – Structural polysaccharides.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 2.3 Carbohydrates Consist of Sugar Molecules

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 2.3 Carbohydrates Consist of Sugar Molecules

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellulose (A Structural Polysaccharides) Cellulose is a major component of the tough wall of plant cells Cellulose is a polymer of  -glucose. PlayList&p=D962AE54DF078C61&index=11&playnext=2& playnext_from=PL

LE 5-8 Cellulose molecules Cellulose microfibrils in a plant cell wall Cell walls Microfibril Plant cells 0.5 µm  Glucose monomer

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats Fats are constructed from one glycerol and three fatty acid molecules Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon A fatty acid consists of a carboxyl group attached to a long hydrocarbon skeleton

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fatty acids vary in length (number of carbons) and in the number and locations of double bonds Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds Unsaturated fatty acids have one or more double bonds Fatty Acids Alpha linolenic acid (ALA) An Omega-3 f.a. and the parent of other omega-3 f.a s

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats Three fatty acids are joined to a glycerol molecule by three dehydration reactions creating a fat, triglyceride, OR triacylglycerol molecule. The bond between each fatty acid and glycerol is called an ester linkage.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats (Saturated fats) Fats made from saturated fatty acids are called saturated fats Most animal fats are saturated Saturated fats are solid at room temperature A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats (Unsaturated fats) Fats made from unsaturated fatty acids are called unsaturated fats Plant fats and fish fats are usually unsaturated Plant fats and fish fats are liquid at room temperature and are called oils

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats because they are hydrophobic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Major Functions of Fats 1- Good source of energy. One gram of fat stores more than twice as much energy as one gram of a polysaccharide, such as starch. 2- Adipose tissue (the tissue that stores fats in the body) also functions to: – cushion vital organs such as the kidneys. – insulate the body (a layer of fat beneath the skin). The subcutaneous layer is especially thick in whales, seals, and most other marine mammals.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipids In a phospholipid, two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head Hydrophobic tails hydrophilic head

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipids in water (a micelle formation)

WATER Hydrophilic head Hydrophobic tails WATER Phospholipids in water (a bilayer formation) The structure of phospholipids in water results also in a bilayer arrangement found in cell membranes Phospholipids are the major component of all cell membranes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Steroids Steroids are lipids characterized by a carbon skeleton consisting of four fused rings Different steroids are created by varying functional groups attached to the rings. Estradiol Testosterone Female lion Male lion

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cholerterol (A Steroid) Cholesterol, an important steroid, is a component in animal cell membranes Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease