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Boston College
CHEM 1105
Riley Mcminn

CHEMISTRY FINAL Articles: FDA PACKAGE USE OF BPA -fda says there is insufficient scientific evidence to ban bisphenor A in food packaging -prohibit the use of endocrine disruptor in food contact materials -shows that the exposure to dietary BPA is much lower -emphasizes that dozens of animal studies have shown BPA’s harmful health effects at low doses and epidemiology studies suggest that human exposure to the compound can cause cardiovascular problems as well as obesity and metabolic changes that could lead to diabetes Coconut Oil -avoid it because it is a saturated fat -saturated fatty acides tend to raise levels of LDL cholesterol in the blood -best diet for the heart is an appropriate balance of saturated, and polyunsaturated and monosaturated -when coconut oil is hydrogenated, it becomes a trans fat -coconut oil stimulates underactive thyroid Electricity and Carbon Dioxide Used to Generate Alternative Fuel -method for converting carbon dioxide into liquid fuel isobutanol using electricity -chemical batteries, hydraulic pumping, and water splitting suffer from low energy density storage or incompatibility with current transportation infrastructure -storing electrical energy as chemical energy in higher alcohols, which can be used as liquid transportation fuels -store electricity with lithium ion batteries, but now, they use liquid fuel -use it as transportation fuel without needed to change current infrastructure Prion -infectious agent composed of protein in a misfolded form -does not need to contain nucleic acis (DNA, RNA) -prion is derived from protein and infection -responsible for the transmissible spongiform encephalopathies in a variety of mammals, including bovine spongiform (mad cow disease) -prion diseases affect the structure of the brain or other neural tissue and all are currently untreatable and universally fatal Confusion Reigns over EPA green chemistry stance -EPA has sent the country’s green chemists on a rollercoaster ride as it struggles to make up its mind whether it wants to fund -many green chemists protested saying thar the grants represented one of the few isntances of major US government support for green chemistry since the discipline’s birth two decades ago -someone stole money from the agency Enzyme Biotechnology in Everyday Life -with time research and improved protein engineering methods, many enzymes have been genetically modified to be more effective at the desired temperatures, pH, or under other manufacturing conditions -stickies removal, detergent, textiles, foods and beverages Nobel Prize -Sidney Altman and Thomas Cech for RNA, rinonucleic acid in living cells is not only a molecule of heredity but also can function as a biocatalyst -biocatalysts are called enzymes -in saliva there is an enzyme that converts start to glucose -RNA is a molecule of heredity that can serve as a biocatalyst innocent Project -national litigation and public policy organization dedicated to exonerating wrongfully convicted people through DNA testing and reforming the criminal justice system to prevent future injustice Soy Materials Make a Green Mark -companies looking to get greener and use renewable materials toreplace petrochemical products are turning to soybeans Lorenzo’s Oil -film about two parents in a relentless search for the cure for their son -he has Adrenoleukodystrophy (ALD) -adding an oil containing two specific long chain fatty acids isolated from rape seed oil and olive oil to their son’s diet Vitamin E in Diet Protects Many Cancers -two forms of vitamin E, gamma and delt-tocopherols -prevent coilon, lung, breast and prostate cancers Linus Pauling -field of quantum chemistry and molecular biology -proposed the DNA was a triple helix Component of Pizza Seasoning Herb Oregano Kills Prostate Cancer Cells -oregano is healthy but a new ingredient to this spice could be used to treat prostate cancer, the second leading cause of cancer death in men -the compound induces apotisis -it possesses anti-bacterial as well as anti inflammatory properties, but its effect on cancer cells really elevate the spice to the level of a super spice like turmeric Aspartame Controversy -artificial sweetener aspartame has been the subject of several controversies since its initial approval by the FDA -alleged to cause sclerosis, lupus, methanol toxicity blindness, spasms etc. Plant Perfumes Woo Beneficial Bugs to their Roots -maize crops emit chemical signals which attract growth promoting microbes to live amongst their roots -first chemical sign that has been shown to attract beneficial bacteria to the maize root environment Insecticides -insecticide is a form of pesticide that is used against insects in agriculture -become a problem for birds and wildlife Organic Farming is Rarely Enough -organic farming is sometimes touted as a way to feed the world’s burgeoning population without destroying the environment -farming without the use of chemical fertilizers and pesticides could supply needs in some circumstances Natuonal Organic Program -NOP is the federal regulatory framework governing organic food Aspirin Evident to Explain Additional Health Benefits -salicylate, the active ingredient in aspirin, increases the activity of the protein AMPK, a key player in regulating cell growth and metabolism -considered a cellular fuel gauge is switched on by exercise and commonly used anti-diabetic medication metformin Basic or Applied Research -x-rays provide a good example of seemingly impractical basic research projects with far reaching unforeseen applications Biochemistry is the chemistry of living things and life processes. This is where chemistry and biology overlap. This is also said to be at the “interface” between chemistry and biology. • Thousands of chemical processes are regulated and orchestrated in a truly amazing fashion • Biopolymers play a big roleThe Cell The basic structural unit of all living organisms is the cell. All cells are enclosed in a cell membrane which regulates the passage of nutrients and wastes. In addition to a cell membrane, plant cells are surrounded by a cell wall composed of cellulose. The Cell Nucleus: the largest structure within the cell. The nucleus contains the genetic material that controls heredity. DNA is found here. DNA is a biopolymer. Ribosomes: the structure where protein synthesis occurs. Proteins are biopolymers. Mitochondria: the cell structure where energy production occurs. Chloroplasts: found only in plant cells. In the chloroplasts, photosynthesis occurs. Plant cell Animal Cell Energy in Biological Systems • Green plants contain chloroplasts which are capable of taking the radiant energy of the sun and storing it as chemical energy (potential energy) in glucose molecules. 6 CO2 + 6 H2O → C6H12O6 (glucose) + 6 O2 • Plant cells can also convert carbohydrate molecules to fat molecules and some are even capable of converting them to proteins. • Animals cannot produce their own energy. They must obtain such energy by eating plants or animals that eat plants. Energy in Biological Systems Metabolism is defined as the series of chemical reactions that keep a cell alive. Metabolic reactions are divided into two categories: Catabolism: the process of breaking down molecules to produce energy. Anabolism: the process of syn thesizing molecules. For example, we will discuss protein biosynthesis.Carbohydrates Carbohydrates are polyhydroxy aldehydes or ketones or compounds that can be hydrolyzed to form such compounds. Glucose may be written as C6(H2O)6, a “hydrate of carbon” Monosaccharides: carbohydrates that cannot be hydrolyzed into simpler compounds. Monosaccharides: carbohydrates that cannot be hydrolyzed (cleaved by a reaction with water) into simpler compounds. These are three isomers with the formula C6H12O6 Especially look at the similarity between glucose and galactose – these are called “stereoisomers” Monosaccharides {The word saccharide comes from the Greek word sákkharon, meaning “sugar”} • Glucose = dextrose • Fructose (fruit sugar)* • Galactose (a component of lactose, which is the sugar in milk) • Aldoses: glucose and galactose • Ketose: fructose *Have you ever heard of high-fructose corn syrup? See video Carbohydrates Most monosaccharides actually exist in cyclic form. ▯ • In the structures above, look at positioning of atoms highlighted in green and look two slides back Monosaccharides Actual 3-D Structure • This is called the “chair” conformation See Carbohydrates Disaccharides consist of molecules that can be hydrolyzed into two monosaccharide units. table sugar • Mono- and disaccharides commonly called ‘sugars’ p?ID=58&othername=Complex %20Carboh ydrates# Key Hydrolysis* Reactions: Sucrose + H2O → Glucose + Fructose Lactose + H2O→ Glucose + Galactose *Splitting a molecule into smaller fragments by a reaction of water (this is the opposite of condensation reaction, which we have studied previously) Carbohydrates Polysaccharides are composed of large molecules that can be hydrolyzed into many monosaccharide units. Examples include starch, cellulose, and glycogen. • Note monomer/polymer analogy from Chapter 10! Carbohydrates ← Starch • Both are polymers of glucose Yet, one is edible for us and one is not !! Cellulose → • Starch and cellulose have different structural and biochemical properties ! Announcements • Exam #2 Range 38/75 (50.7%) to 74/75 (98.7%) with one outlier. The curve is +4%. Sometimes I apply a curve to the overall course grade. Example: Say you received a 63 out of 75. This is 63/75 x 100 = 84.0%. Grade with curve: 84% + 4% = 88%. Grade: B+ • Homework Assignment - Chapter 16 (Biochemistry): Read and study first time through, doing Self-Assessment Questions. Target date: April 13th • Next Extra Credit deadline is April 12th • There will be four more class periods on Biochemistry (Chapter 16) • Last time we left off with the structures of starch and cellulose Cellulose makes up the structural units of plants. Cellulose chains are composed of parallel bundles called fibrils. Carbohydrates Plant starch is composed of two polymers, amylose and amylopectin. In amylose, the glucose molecules are connected in long parallel chains. In amylopectin, the chains are branched. Carbohydrates Glycogen is known as animal starch. It is similar to amylopectin in that the glucose polymers are branched. see granular particles → Fats and Other Lipids Lipids are biological molecules that are insoluble in water but are soluble in nonpolar organic solvents such as benzene – they are mainly hydrocarbons. This class of molecules includes fats, steroids (such as cholesterol), sex hormones, and certain vitamins. Fats are esters of long-chain fatty acids and glycerol. Fats are often called triglycerides or triacylglycerols (commonly tested for in blood samples; see above). Fatty Acids – one component of natural fats • Soaps are salts of fatty acids! Fats and Other Lipids Palmitic Acid Triglycerides are triesters of glycerol and fatty acids: • Recall from Chapter 9 that glycerol is used as a softener in skin lotions and as a moisturizer in cakes and can be converted to the explosive called nitroglycerin. condensation reaction Fats and Other Lipids Saturated fatty acids have no carbon-to-carbon double bonds. (See two slides back – palmitic acid) Monounsaturated fatty acids have one carbon-to- carbon double bond. Polyunsaturated fatty acids have two or more carbon- to-carbon double bonds. Hydrogenation reactions convert unsaturated alkanes to saturated alkanes (refer back to Chapter 9 material) Fats and Other Lipids Solid fats have a high proportion of saturated fatty acids. Why? Liquid oils have only unsaturated fatty acids. Iodine number is a measure of the degree of unsaturation of a fat or oil. The iodine number is the number of grams of I2 that are consumed by 100 g of a fat or oil. • Higher iodine numbers corresponds to more unsaturation • The addition reaction between alkenes and iodine is like that between alkenes and hydrogen gas (H2). This process is called iodination: Fats and Other Lipids Iodine Number • Saturated fats are generally said to be bad for your health. In the table above then, coconut oil would be expected to be the worst. However, it’s not clear that coconut oil is really bad for you. Proteins are a vital component of all living things • Proteins are almost everywhere in your body • They are found in all living things • Note backbone and pendant group (side- chain) as with polymers in Chpt. 10) • Note that backbone is held together by a series of amide bonds • Enzymes (biological catalysts) are proteins • Proteins (in the form of keratin) also play a structural role: silk, hair, nails, claw, horns • See video on chemical behavior of cotton (carbohydrate) vs. hair (protein). Certain dye molecules will react only with amine groups. Proteins Proteins are (co)polymers of amino acids. Amino acids contain both an amine and carboxylate group attached to the same carbon called the alpha carbon. Recall Chapter 9!! This is called an alpha (α) amino acid because the acid and amine group are attached to the same carbon. The central C atom is called the alpha carbon Proteins In water, amino acids tend to exist as a dipolar ion or inner ion called a zwitterion. (“zwitter” is German for “hybrid)” • Note three-letter and one-letter codes for each amino acid Proteins • Plants are amazing “factories” that can synthesize proteins from carbon dioxide (CO2), water (H2O), and minerals like nitrates (NO3-) or sulfates (SO42-). • Animals must consume proteins as part of their diet. • Humans can synthesize some amino acids, but must obtain essential amino acids in a normal diet. (see previous two slides) The Peptide Bond • Amino acids are linked to each other to form proteins by an amide (Chapter 9) linkage between the amine of one amino acid to the carboxylate of another amino acid. This amide linkage is known as the peptide bond. See cute video on peptide bond formation on your own The Peptide Bond Dipeptide is formed when two amino acids are joined. Tripeptides contain three amino acid units. (tetra, penta, hexa, hepta, etc.) Polypeptides contain 10 or more amino acid units. Proteins may contain 10,000 or more amino acid units. Molecular masses can be as high as one million and more! The Peptide Bond The sequence of the amino acids in a protein is critical. The sequence is always denoted from the free amino group (N-terminal) to the free carboxyl group (C- terminal) from left to right. a.k.a. “amino terminus” a.k.a.“carboxy terminus” Announcements • The next extra credit is due on April 12th. I will open the hand-in window a few days ahead of time and will notify you by e-mail. Your paper must be uploaded to Blackboard Vista. • First articles will be posted soon ▯ Carbohydrates ▯ Fats and other lipids Proteins, con’d DNA and RNA Structure of Proteins Primary Structure: The primary structure of a protein is simply the sequence of amino acids from N-terminal to C-terminal. Example: The primary structure of angiotensin II (a peptide hormone) is: Asp-Arg-Val-Tyr-Ile-His-Pro-Phe • NOTE: If you reverse the order – the result is an entirely different molecule! Structure of Proteins Secondary Structure: This is how the polypeptide chain folds and coils due to hydrogen bonding of the backbone amide groups. Examples include the alpha helix and beta pleated sheet. Alpha Helix • Wool is an alpha helix protein • A telephone cord illustrates features of secondary (helical) and tertiary (fold of cord) structures (more later) Large Protein with Many Alpha Helical Regions: ↓ loop region has no distinct structure This is a backbone ribbon type depiction Structure of Proteins Beta Pleated Sheet • Silk is a beta sheet protein Beta Pleated Sheet Larger Protein with both Alpha and Beta Regions A Beta Barrel Protein Proteins with alpha helical and beta sheet regions Screensaver%20Lifesaver%20Proteins# Screensaver %20Lifesaver%20Proteins Collagen (triple helix) is found in connective tissues such as tendons and ligaments Video protein folding Tertiary Structure is the three-dimensional shape of a protein due to the spatial relationships of groups that are far apart on the protein chain. Recall the telephone cord on a previous slide. One example is the protein chain in “globular” proteins. This is the protein called myoglobin, which binds and transports O2 in the body. (cofactor) The heme group contains an iron atom in the middle – we call this a metalloprotein. There are many proteins that require metals in order to function properly or at all. Quaternary Structure: this involves the interaction of more than one peptide chain (subunit). This is hemoglobin, which is essentially four associated myoglobin subunits. This binds and transports O2 in your blood. • Misfolded proteins and “prion” diseases – see text page /hemoglobin/ Sickle cell anemia is due to one error in the hemoglobin amino acid sequence! Structure of Proteins Four Ways to Link Protein Chains • Hydrogen Bond: The secondary structures occur when hydrogen bonds are formed between amide nitrogen (N- H) and carboxyl oxygen (C=O). (see next slide) Tertiary structures also involve hydrogen bonding between side chains of the amino acids. • Ionic Bonds: Are sometimes called salt bridges. These occur between oppositely charged side chains. • Disulfide Linkages: When two cysteine side chains are oxidized, (-S-S-) disulfide linkage can form. (like rubber polymer vulcanization!! Chapter 10) • Dispersion Forces: These are attractive forces between two nonpolar side chains. Structure of Proteins Beta Pleated SheetStructure of Proteins • Permanent curling of hair depends on breaking and remaking disulfide bonds! After the S-S bonds in the hair protein are chemically broken, the hair may be coiled. Then S-S bonds are reformed by another chemical reaction and the hair holds the curl due to new cross linkages. Enzymes Enzymes are biological catalysts. Most are proteins. Many are highly specific, only catalyzing a single reaction or related group of reactions. The substrate is the reactant organic molecule whose reaction the enzyme catalyzes. Enzymes The activity of many enzymes can be explained by the induced fit model. According to the induced fit model, the substrate molecule bonds to the enzyme at the active site, forming an enzyme-substrate complex. This complex can then catalyze the reaction of the substrates and form products. Enzyme + Substrate(s) → Enzyme-substrate(s) complex ↔ Enzyme + Product(s) • The enzyme, like all catalysts, is unchanged after the reaction is complete. What is a catalytic cycle? (for example, see next slide) • See video of enzymes in action Depiction of an Enzyme Catalytic Cycle Different Ideas About How Enzymes Work ←This hypothesis is generally favored Depictions of Enzyme Active Sites surface charge depiction Number in the N ▯ C peptide sequence ▯ Enzymes Inhibition The action of enzymes can be inhibited (slowed down or stopped). One mechanism of enzyme inhibition has a molecule bonding to the enzyme protein at another site other than the active site. This changes the shape of the protein and prevents the substrate from bonding at the active site. This mechanism is used to control the action of certain enzymes. This is called noncompetitive inhibition. Enzyme Inhibition Substrate no longer fits ▯ ▯ it is bound poorly ▯ Add inhibitor This is called noncompetitive inhibition Competitive Enzyme Inhibition • The unnatural substrate (in red) binds tightly but does not react and does not permit the natural substrate to enter the active site. • See video with two substrate inhibitor molecules in a different enzyme; note that zinc is required. Manganese (Mn) is required in the example above. See summary video. Announcements • Quiz on Tuesday, 4/17 Coverage in Chapter 16 to be announced • Extra Credit #2 “window” is now open. The window closes on April 12th at 9 PM. Please upload your paper using the course Blackboard Vista web page. • Aiming to finish Chapter 16 on Thursday this week, 4/12 • View videos on inhibition not viewed during last lecture Enzymes Cofactors: Some enzymes require another molecule to be present for proper functioning of the enzyme. Cofactors can be inorganic ions (Zn2+, Mg2+, ... see two slides back) or organic molecules. Heme has both iron bound to an organic molecule (see previous slides on hemoglobin and myoglobin). Coenzyme: A cofactor that is a non-protein organic molecule. Some are vitamins or vitamin derivatives. Apoenzyme: Pure protein part of an enzyme (with cofactor(s) and coenzymes removed). Enzymes in Medicine • Diabetes test strips use two enzymes to measure blood sugar. One enzyme catalyzes the oxidation of glucose, producing hydrogen peroxide (H2O2) as a by- product. The other enzyme catalyzes the breakdown of hydrogen peroxide and oxidizes a dye to produce a color change (‘colorimetric’ test). Another method involves electrical current generation. • Enzymes can be monitored to diagnose liver damage or heart damage. • Enzymes can also be used to break up clots after a heart attack or to increase clotting to treat hemophilia. (see related video next slide) • Some diseases can be treated with active site inhibitors. Example: See next slide Enzymes in Medicine – HIV Protease Inhibitor • See videos (a,d) • A protease is an enzyme that cleaves proteins by hydrolysis of amide bonds Enzymes in Industry Enzymes in intact organisms (for example yeast) are used to make bread, beer, wine, yogurt and cheese Isolated enzymes have many industrial applications including: • baby foods – proteases predigest complex proteins • convert corn starch to corn syrup (glucose) • convert glucose to fructose (sweeter) – isomerization reaction by an isomerase enzyme - Recall high fructose corn syrup discussion • make beer and fruit juices clear • fade blue jeans – cellulases (enzymes) break down cotton fibers Enzymes in Everyday Life Enzymes are used in stain removers (proteases attack protein-based stains such as blood) and meat tenderizers. Those among us who are lactose-intolerant can also take enzymes to reduce the discomfort caused by ingesting dairy foods. Worldwide production of enzymes is BIG business - worth more than $2 billion per year! Label for ActiveZyme • a product said to aid in food digestion Animal Cell Nucleic Acids Nucleic acids serve as the information and control centers of the cell. They are in two major forms: d__eoxyribo_n_ucleic _a_cid (DNA) and ribonucleic acid (RNA). Both consist of long chains of ‘monomers’ called nucleotides. Each nucleotide is composed of a sugar unit, phosphate unit, and a heterocyclic amine base. Nucleic Acids Nucleic Acids Nucleotides are composed of a sugar, phosphate, and an amine base. DNA Double Helix - Watson & Crick* • Rosalind Franklin (1920-1958) measured key x-ray data • All genetic Information held in base pair sequence • Protein synthesis is encoded/guided by DNA *With Wilkins, they received the 1962 Nobel Prize in Medicine The double helix of DNA is held together by base pairing. Complimentary bases are thymine and adenine, and cytosine and guanine. These complimentary bases are held together by hydrogen bonding. Other combinations of bases do not occur as pairs! See video See also: RNA Structure • RNA is single stranded • Recall that RNA has the base U not T • RNA can fold more like a protein and can actually catalyze reactions Nucleic Acids DNA: Self-Replication Chromosomes: threadlike bodies of DNA that are tightly coiled into X-shaped bodies.* Human body cells contain 46 chromosomes. 23 come from the egg of the mother, 23 from the sperm of the father. See upcoming video Gene: section of a DNA molecule that controls the synthesis of protein. DNA is the “blueprint” for protein synthesis. Replication: copying of DNA during cell division. *About two meters of DNA is packaged in each cell nucleus! Announcements • There will be a quiz on Tuesday, April 17th. It will cover text pages 453 - 470, inclusive. You need not memorize amino acid names nor their structures. (you will however have to do this selectively for exam #3 – more information to come shortly) • Extra Credit #2 is due tonight, April 12th at 9 PM. Please upload your paper using the course Blackboard Vista web page. • I plan to finish Chapter 16 today. Next up is Chapter 17 (Food) • The final exam will only be given at the scheduled time. I will however have some office hours between the last class and the exam. DNA: Self-Replication • A protein called helicase (not shown here, shown in video) pulls the strands apart • During cell division See videos, above is only a snapshot in time ← enzyme Examples of DNA-Binding Proteins RNA: Protein Synthesis and the Genetic Code During protein synthesis, the genetic information of DNA is transferred (transcribed) to RNA by a process known as transcription. During transcription, messenger RNA (mRNA) is synthesized. RNA: Protein Synthesis and the Genetic Code The genetic code is carried on a sequence of three bases known as a codon. The codon codes for a specific protein by base-pairing the anticodon with a specific transfer RNA (tRNA) through a process known as translation. Transcription ← enzyme See video The genetic code is carried in a three-base sequence known as a codon. start→ ↑Amino acid alanine RNA: Protein Synthesis and the Genetic Code Translation: • Protein synthesis on a ribosome • A ribosome is a protein- RNA complex UUU encodes for Phe • After being synthesized the protein folds into the right structure. See folding and unfolding (denaturation) videos. ← Complimentary to GUA • Transfer RNA on m-RNA!!! GUA is the codon (tRNA) for valine (val) See translation video tRNA Structure The Human Genome Genetic Testing One DNA sequencing technique is known as polymerase chain reaction (PCR).* The 1993 Nobel Prize in Chemistry was awarded, in part, for the invention of PCR. In the PCR technique, the DNA is cleaved by enzymes; bacterial enzymes called DNA polymerases are used to multiply the amount of DNA fragments so very small quantities suffice. The fragments are separated from longest to shortest and a “print” is obtained. This technique is useful for finding the source of genetic diseases and for criminal investigations. DNA fingerprinting (see image next page) can also determine the parentage of children in, for example, paternity law suits. • DNA segments of different lengths will move different distances on an electrophoresis gel. The patterns will be different for each individual. The Human Genome Recombinant DNA is DNA that is produced artificially and contains DNA from two different sources (different species). In one technique, restriction enzymes are used to cleave the DNA. The DNA fragments can then be inserted into bacterial plasmids and the plasmid inserted into a host organism. There it replicates, producing exact copies of itself. Producing many copies of the same recombinant molecule is called cloning. • For example, one can clone a human gene into a bacterium such as E. coli (see next slide) Recombinant DNA • Human insulin (a polypeptide protein) is produced in bacteria to treat diabetes patients • Some day it may be possible to insert genes for insulin production directly into human beings • Many other proteins used in therapy made by recombinant DNA technology – see text for list. Included are human growth hormone and leptin (for obesity treatment) 16_28-01.JPG Genetic engineering has been used to incorporate beta-carotene into rice. Beta- carotene, the color of carrots) is a precursor to vitamin A. Vitamin A deficiency is an enormous problem in some parts of the world. The Human Genome Gene therapy involves introducing a functioning gene into a person’s cells to correct the action of a defective gene. Viruses are used to carry the DNA into cells. Gene therapy is still experimental. Only modest successes have been achieved to date. • Problems to solve: directing therapeutic gene to the right location, targeting it to the desired cells • About one in ten people has or will develop a genetic disorder! The Human Genome Controversy and Promise in Genetic Engineering Cloning of animals and plants holds much promise for food production (Chapter 17 – next topic) and treatment of disease. There is also much controversy and concern. Cows can be made to produce useful human proteins. In plants – genetic engineering can make plants herbicide resistant or able to withstand low temperatures or to produce pesticides that they are not normally able to. The Food We Eat • ‘Molecular gastronomy’ – the molecular science of good eating • Foods are made up of chemicals (that is, chemical compounds). They include carbohydrates, fats and proteins, along with water, vitamins, minerals, and fiber. Our bodies are about 2/3 water. • About one billion people are hungry worldwide. • An estimated 9 million people die of hunger per year worldwide. • Even in the US, millions of children are hungry. • Poor diet and obesity contribute to health problems, including heart disease and cancer and to soaring health insurance costs. • In this Chapter, we will first consider carbohydrates, fats, and proteins. We should think of these all as chemicals. Later, we will examine topics such as vitamins and food additives.Carbohydrates in the Diet The monosaccharide glucose (energy supply/‘fuel’, ‘blood sugar’, starch and cellulose monomer) and fructose (fruit), and the disaccharide sucrose (‘table sugar’) are the most common dietary sugars. (Chapter 16) Carbohydrates in the Diet Digestion and Metabolism of Carbohydrates Glucose and fructose are absorbed directly into the bloodstream. Sucrose is hydrolyzed into glucose and fructose. Sucrose + H2O → Glucose + Fructose Carbohydrates in the Diet Lactose, found in milk, is hydrolyzed to glucose and galactose. Lactose + H2O → Glucose + Galactose Some people lack the enzyme necessary to hydrolyze lactose. This is known as lactose intolerance. Symptoms include cramps, diarrhea and nausea. Galactose is converted to glucose (the two are isomers) during metabolism. Some babies lack the enzyme (galactosemia) necessary for this conversion and require a synthetic formula for proper nutrition. Carbohydrates in the Diet Complex Carbohydrates: Starch and cellulose Starch is a polymer of glucose connected by alpha linkages; most animals and humans possess the enzymes necessary to hydrolyze starch to glucose that can then serve as a source of energy. (this is like ‘time release’ glucose/energy for athletes) Carbohydrates such as starch produce 4 kcal of energy per gram. Ideally, carbohydrates should be obtained from whole grains, fruits, vegetables, and beans as opposed to simple sugars and refined starches. Cellulose is a polymer of glucose connected by beta linkages; most animals and humans lack the enzymes necessary to hydrolyze cellulose, and it serves as a source of roughage or dietary fiber (see later). As you know, the Boston Marathon was yesterday. Glucose as fuel Starch hydrolysis catalyzed by carbohydrase enzymes (such as amylase): (C6H10O5)n + n H2O → n C6H12O6 C6H12O6 + O2 → 6CO2 + 6H2O + Energy (exothermic reaction) • The latter reaction is the reverse of photosynthesis • Your metabolism requires 50 chemical steps to achieve this overall reaction!! Carbohydrates in the Diet Glycogen is the means by which animals store glucose. (Recall Chapter 16) - It is a highly branched polymer of alpha glucose. It is sometimes known as animal starch. Excess glycogen is converted to and stored as fat. Some bacteria found in the gut of termites and digestive tract of grazing animals can hydrolyze cellulose to glucose thus these animals can use cellulose as a source of food. Fats and Cholesterol Fats are esters of fatty acids and glycerol. Some fat is metabolized or “burned” for energy and produces 9 kcal per gram. Some is used for cell membranes. Fats and Cholesterol Digestion and Metabolism of Fats • Fats are digested in the small intestine. Enzymes called lipases hydrolyze triacylglycerols into mono and diacyl glycerols, fatty acids, and glycerol. • Fats are stored in the body in adipose tissue in locations called fat deposits. Fat deposits are located around major organs beneath the skin. Fat moderates environmental temperature changes and can act as a cushion to prevent injury. Fats and Cholesterol Dietary saturated fats and cholesterol have been implicated in arteriosclerosis and cardiovascular disease. Deposits form on the inner walls of arteries called plaque. Normal Artery Hardened Artery • We need a certain amount of cholesterol for cell membranes and for the production of hormones. It gets produced mainly by the liver. Plaques that clog arteries are rich in cholesterol. Cholesterol is a fat-like steroid molecule that is common to animal tissue. Cholesterol is carried in the blood by lipoproteins. Lipoproteins are classified according to their density. Very low density lipoproteins (VLDLs) transport triglycerides. Low-density lipoproteins (LDLs) carry cholesterol from the liver to the blood and are responsible for the formation of plaques. LDLs are the so-called “bad” cholesterol. High-density lipoproteins (HDLs) carry the cholesterol to the liver and are the so-called “good” cholesterol. Insoluble in H2O ecules.asp?ID=92# Fats and Cholesterol • How does the body “solve the problem” of transporting water- insoluble lipid molecules in the blood, which is mostly water?? See video on lipid transport Fats and Cholesterol Diets high in saturated fats and trans fats have been linked to high LDL levels in blood. It is recommended that one limit the amount of saturated fat and “trans” fat in the diet. In addition to saturated fats, trans fats are formed when unsaturated fats are partially hydrogenated in order to make margarines or other solid fats. What is this reaction? (see Chapter 9) Saturated (a) vs. “trans” (b) vs. “cis” unsaturated (c) fats •The US FDA required, as of January 1, 2006, that amounts of trans fat be listed on food labels. • Saturated and trans fats are more likely to be solids whereas cis fats are more typically liquids. • Olive and canola oils are good sources of dietary lipids (see Chapter 16). They have unsaturated fatty acids and can lower the level of “bad cholesterol” - LDL • Fish oils EPA and DHA may have the same effect. CH3(CH2CH=CH)5(CH2)3COOH EPA CH3(CH2CH=CH)6(CH2)2COOH DHA These are “omega-3” fatty acids name=omega-3%20essential%20fatty%20acid Consider “Lorenzo’s Oil” (another example of chemistry in the movies, 1992) ← Note that krill oil is now getting much attention. Krill are small shrimp- like marine crustaceans. Proteins Proteins are digested into individual amino acids. These amino acids are used to synthesize proteins for growth and repair of tissue. proteins + nH2O → individual amino acids (catalyzed by proteases) •This is an hydrolysis reaction The human body cannot synthesize all 9 of the amino acids necessary for protein synthesis. These 9 amino acids are called essential amino acids (Chapter 16) and include: isoleucine, lysine, a
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