Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 5 The Structure and Function of Macromolecules PowerPoint lectures are originally from Campbell / Reece Media Manager and Instructor Resources for BIOLOGY, 7th & 8th Edition by N. A. Campbell & J. B. Reece Copyright 2005 & 2008 Pearson Education, Inc. Publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The Molecules of Life • All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids • Macromolecules are large molecules composed of thousands of covalently connected atoms • Molecular structure and function are inseparable © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ©Copyright 2011 Pearson Education, Inc. The Molecules of Life • 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 • 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 Macromecules are made of monomers • Carbohydrates, Proteins, and Nucleic Acids are all polymers made from building blocks. Building blocks can be called monomers monomer Macromolecule Type Carbohydrate Protein Nucleic Acid (DNA and RNA) Name of Monomer monosaccharide Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amino acid nucleotides 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings HO 1 2 3 H Short polymer HO Unlinked monomer Dehydration removes a water molecule, forming a new bond HO 1 2 H 3 H2O 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer 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 HO 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond HO 1 2 3 (b) Hydrolysis of a polymer Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings H H H2O HO H Concept 5.2: Carbohydrates serve as fuel and building material • Carbohydrates include single (simple) sugars and their polymers • Carbohydrates may be classified as: – Monosaccharides (the simplest) – Disaccharides – Polysaccharides Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides • Monosaccharides have molecular formulas that are usually multiples of CH2O (CH2O)n where n ranges from 1-7 • Glucose (C6H12O6) is the most common monosaccharide. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides • Monosaccharides have two functional groups: 1- One carbonyl group that is either: – An aldehyde group OR – a ketone group 2- Many hydroxyl groups. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides • Monosaccharides are classified by: – The specific type of the carbonyl group: • Aldoses • ketoses – and the number of carbons in the carbon skeleton: • Trioses (3 Carbons) • Tetroses (4 Carbons) • Pentoses (5 Carbons) • Hexoses (6 Carbons) • Heptoses (7 Carbons) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 5-3 Triose sugars (C3H6O3) Pentose sugars (C5H10O5) Hexose sugars (C5H12O6) Glyceraldehyde Ribose Galactose Glucose Dihydroxyacetone Ribulose Fructose 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. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides • Though often drawn as a linear skeleton, in aqueous solutions they form rings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings alpha and Beta Forms of Glucose • There are two interconvertible forms of glucose that differ in the placement of the hydroxyl group attached to the number 1 carbon in the ring form of glucose. • These forms are α-glucose and β-glucose. α-Glucose Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings β-Glucose Disaccharides • A disaccharide is formed when a dehydration reaction joins two monosaccharides • The covalent bond joining two monosaccharides is called a glycosidic linkage Dehydration reaction in the synthesis of maltose 1–4 glycosidic linkage Glucose Glucose Dehydration reaction in the synthesis of sucrose Maltose 1–2 glycosidic linkage Glucose Fructose Sucrose 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 Storage Polysaccharides • Store glucose and are hydrolyzed as needed to provide sugar for cells. • Examples on storage polysaccharides: – Starch in Plants – Glycogen in animals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5.6b Mitochondria Glycogen granules 0.5 m Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Starch (A Storage Polysaccharides in Plants) • Starch is a carbohydrate polymer consists entirely of α-glucose monomers. • Starch is a storage polysaccharide in plants. • Two types of starch: – Amylose is the unbranched polymer. – Amylopectin is the branched polymer. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 5-6a Chloroplast Starch 1 µm Amylose Amylopectin Starch: a plant polysaccharide Glycogen (A Storage Polysaccharides in Animals) • Glycogen is a storage polysaccharide in animals • Humans and other vertebrates store glycogen mainly in liver and muscle cells Glycogen: an animal polysaccharide Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structural Polysaccharides • The polysaccharide cellulose is a major component of the tough wall of plant cells • Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ • The difference is based on two ring forms for glucose: alpha () and beta () © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ©Copyright 2011 Pearson Education, Inc. Figure 5.8 Cellulose microfibrils in a plant cell wall Cell wall Microfibril 10 m 0.5 m Cellulose molecules Glucose monomer Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellulose Digestion • Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in cellulose • Humans can’t digest cellulose. Cellulose in human food passes through the digestive tract as insoluble fiber • Some microbes use enzymes to digest cellulose • Many herbivores, from cows to termites, have symbiotic relationships with these microbes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chitin (A Structural Polysaccharides) • Chitin is found in the exoskeleton of arthropods • Chitin also provides structural support for the cell walls of many fungi • Chitin can be used as surgical thread Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5.9b Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.3: Lipids are a diverse group of hydrophobic molecules • Lipids are the one class of large biological molecules that do not form polymers • The unifying feature of lipids is having little or no affinity for water (Hydrophobic) • Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ©Copyright 2011 Pearson Education, Inc. Lipids • The most biologically important lipids are: – fats – Phospholipids – steroids 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 Figure 5.10 Fatty acid (in this case, palmitic acid) Glycerol (a) One of three dehydration reactions in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fatty Acids • 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Alpha linolenic acid (ALA) An Omega-3 f.a. and the parent of other omega-3 f.as 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trans Fatty Acids • Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen • Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds • These trans fats may contribute more than saturated fats to cardiovascular disease 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, and a layer of fat beneath the skin insulates the body. 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydrophobic tails Hydrophilic head Figure 5.12 Choline Phosphate Glycerol Fatty acids Hydrophilic head Hydrophobic tails (a) Structural formula (b) Space-filling model Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (c) Phospholipid symbol Phospholipids in water (a micelle formation) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipids in water (a bilayer formation) The structure of phospholipids in water results also in a bilayer arrangement found in cell membranes Hydrophilic head WATER WATER Hydrophobic tails Phospholipids are the major component of all cell membranes 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 Female lion Male lion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Testosterone 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lipid Summary Type of Lipid Structure of Lipid Made out of one glycerol molecule (blue part below) with three fatty acids attached (black parts below). Triglycerides These are entirely hydrophobic. The "tri" prefix of the name comes from having three fatty acids. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Function of Lipid These are the "fats" and also the "oils." They are used for long-term sugar storage or for insulation of a multicellular organism. Lipid summary cont’d Type of Lipid Structure of Lipid Phospholipids have the special property of having both hydrophobic and hydrophilic parts, although they are still mostly hydrophobic. A molecule that is both hydrophilic and hydrophobic is called amphipathic. Phospholipids Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Function of Lipid Phospholipids help to make up the basis of cellular membranes-- you will learn much more about these when we study membranes. Lipid summary cont’d Type of Lipid Steroids (a sterol derivative) Structure of Lipid They are entirely hydrophobic, and have their own special structure that does NOT include fatty acids. These molecules are all ringed structures, with 4 carbon rings. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Function of Lipid This group includes cholesterol, estrogen, testosterone, progesterone, and cortisone. Most steroids are used as hormones. Lipids, Nutrition, and Health Functions of Fats • Used to build cells and parts of the cell (e.g. brain cells, nerve tissues, cell membrane) • Stored in the body in adipose tissue – Adipose tissue are called fat depots • Surround vital organs (e.g. heart, kidney, spleen) to serve as protective cushion • Stored under the skin for insulation • Fat reserves are converted to glycerol and fatty acids ( 9 kcal per gram) – Glycerol is burned for energy or converted to glucose The human adipocyte • Compose adipose tissue • For storage and synthesis of triacylglycerides, insulation, energy storage (higher energy content than glycogen) • White fat cells: lipid droplet with peripheral cytoplasm and nucleus; semiliquid fat with some sterol derivatives • Brown fat cells: lipid droplets scattered, high mitochondria content www.cnrs.fr, www.vulgaris-medical.com Fats Transport • Some important blood lipoproteins – Group of proteins with a triglyceride or cholesterol – Very-low density lipoprotein (VLDL) • Transport new triglycerides from liver to adipose tissue – Low density lipoprotein (LDL) • Transport cholesterol from liver to cells – High density lipoprotein (HDL) • Transport cholesterol from tissues to liver Atherosclerosis: Not just a simple clogging problem! From: http://www.nia.nih.gov/NR/rdonlyres/C3B176CB-3173-4F89-8FDA2774FB751108/4227/pic_atherosclerosis.jpg Cholesterol biosynthesis From: http://banon.cshl.edu/cgi-bin/eventbrowser?DB=gk_current&FOCUS_SPECIES=Homo%20sapiens&ID=191273& Lowering cholesterol synthesis • Use hypolipidemic drugs (eg. Statins) • STATINS are HMG-CoA inhibitors – Eg. Lovastatin Table from: http://en.wikipedia.org/wiki/Statin Crisco and Olestra (by P&G) 1911: Shortening “To eat, or not to eat - fat is the question.” - from the Introduction of Mary Enig, Know your Fats: The Complete Primer for Understanding the Nutrition of Fats, Oils, and Cholesterol, Bethesda Press, USA, 2000. Olestra • 1998, Proctor and Gamble introduced a new fat/oil substitute called Olestra (brand name Olean® • material replaces fats in snack foods such as potato chips • claimed that food using Olestra in place of digestible fats provide less calories since the Olestra is not digested and passes through the body unchanged • Some side effects include abdominal cramping and loose stools Olestra How does Olestra work? http://www.cnn.com/HEALTH/9802/10/fakefat.olestra/olestra.large.jpg Olean® Olean® http://static.howstuffworks.com/gif/question526-fat-chips.jpg http://static.howstuffworks.com/gif/question526-olestra-chips.jpg Carnitine Craze • Responsible for fatty acid transport from cyosol to mitochondria where the FA is metabolised • Naturally synthesized from Lys and Met (L-isomer) in liver and kidneys Image from http://en.wikipedia.org/wiki/Image:AcylCoA_from_cytosol_to_the_mitochondrial_matrix.gif Carnitine Craze • • • • • Highest amount in meat, dairy, nuts Healthy individuals, including strict vegetarians, generally synthesize enough Lcarnitine to prevent deficiency. The roles of L-carnitine supplementation as an adjunct to standard medical therapy in myocardial infarction, heart failure, angina pectoris, Alzheimer's disease, and HIV infection require further research. Although recent studies in rats suggest acetylL-carnitine supplementation may be beneficial in preventing age-related declines in energy metabolism and memory, it is not known whether acetyl-L-carnitine supplementation will help prevent such agerelated declines in humans. There is little evidence that L-carnitine supplementation improves athletic performance in healthy people. Info from: http://en.wikipedia.org/wiki/Carnitine, The Linus Pauling Institute (Oregon State University). http://lpi.oregonstate.edu/infocenter/othernuts/carnitine/