Organic and Carb Chemistry Notes PDF

The Chemistry of Organic Molecules Dr. Joanne Sadier  Learning objectives Explain how the properties of carbon enable it to produce diverse organic molecules Explain the relationship between a functional group and the chemical reactivity...

The Chemistry of Organic Molecules Dr. Joanne Sadier  Learning objectives Explain how the properties of carbon enable it to produce diverse organic molecules Explain the relationship between a functional group and the chemical reactivity of an organic molecule. Compare the role of dehydration synthesis and hydrolytic reactions in organic chemistry. Explain the structure and the function of carbs Distinguish between saturated and unsaturated fatty acids. Contrast the structures of fats, phospholipids, and steroids and compare their functions Describe the functions of proteins in cells. Explain how a polypeptide is constructed from amino acids. Compare the four levels of protein structure. Distinguish between a nucleotide and nucleic acid. Compare the structure and function of DNA and RNA nucleic acids. Explain how ATP is able to store energy.  Chemistry of life Chemists of the nineteenth century thought that the molecules of cells must contain a vital force, so they divided chemistry into: organic chemistry the chemistry of living organisms inorganic chemistry the chemistry of nonliving matter  Organic Molecules Organic molecules contain both carbon and hydrogen atoms. Four classes of organic molecules (biomolecules) exist in living organisms: Functions of the four biomolecules in the cell are Carbohydrates Lipids diverse. Despite their functional differences, the variety of organic molecules is based on the unique chemical properties of Proteins Nucleic acids the carbon atom.  What is there about carbon that makes organic molecules the same but also different? Generally, carbon forms those bonds with other atoms of carbon, plus hydrogen, nitrogen, oxygen, phosphorus, and sulfur—  The Carbon Atom Carbon can form four covalent bonds. Bonds with carbon, nitrogen, hydrogen, oxygen, phosphorus and sulfur. The C-C bond is very stable. Long carbon chains, hydrocarbons, can be formed. Besides single bonds, double bonds, triple bonds, and ring structures are also possible. Branches may also form at any carbon atom, making complex carbon chains.  The Carbon Skeleton and Functional Groups The carbon chain of an organic molecule is called its skeleton or backbone. Likewise, the diversity of organic molecules comes from the attachment of different functional groups to the carbon skeleton Functional groups is a specific combination of bonded atoms that always has the same chemical properties and therefore always reacts in the same way, regardless of the carbon skeleton to which it is attached. Functional groups determine the chemical reactivity and polarity of organic molecules. Typically, the carbon skeleton acts as a framework for the positioning of the functional groups Example: Replacement of an H by -OH in the 2-carbon hydrocarbon ethane turns it into ethanol, and from hydrophobic to hydrophilic. lists some of the more common functional groups The R indicates the “remainder” of the molecule. This is the place on the functional group that attaches to the carbon skeleton. R = remainder of molecule  Isomers Isomers are organic molecules that have identical molecular formulas but different arrangements of atoms.  The Biomolecules of Cells Carbohydrates, lipids, proteins, and nucleic acids are called biomolecules. Usually consist of many repeating units Each repeating unit is called a monomer. A molecule composed of monomers is called a polymer (many parts). Example: amino acids (monomer) are joined together to form a protein (polymer) Lipids are not polymers because they contain two different types of subunits ((glycerol and fatty acids).  The Biomolecules of Cells Category Subunits (monomers) Polymer Carbohydrates* Monosaccharide Polysaccharide Lipids Glycerol and fatty acids N/A Proteins* Amino acids Polypeptide Nucleic acids* Nucleotide DNA, RNA  Synthesis and Degradation A dehydration reaction is a chemical reaction in which subunits are joined together by the formation of a covalent bond and water is produced during the reaction. Because the equivalent of a water molecule(H2O)—that is, an −OH(hydroxyl group) and an −H (hydrogen atom)—is removed as subunits are joined. Used to connect monomers together to make polymers Example: formation of starch (polymer) from glucose subunits (monomer)  Synthesis and Degradation A hydrolysis reaction is a chemical reaction in which a water molecule is added to break a covalent bond. Used to break down polymers into monomers Example: digestion of starch into glucose monomers  Synthesis and Degradation Special molecules called enzymes are required for cells to carry out dehydration synthesis and hydrolysis reactions. An enzyme is a molecule that speeds up a chemical reaction. Enzymes are not consumed in the reaction. Enzymes are not changed by the reaction. Enzymes are catalysts. Carbohydrates Functions: are almost universally used as an immediate energy source in living  Contain carbon, organisms, but in some organisms they hydrogen, and also have a structural function oxygen atoms in a 1:2:1 ratio (CH2O).  Chain length varies from a few sugars to hundreds of sugars. The monomer subunits, called monosaccharides, are assembled into long polymer chains called polysaccharides.  Monosaccharides A monosaccharide is a single sugar molecule. It is also called a simple sugar. It has a backbone of 3 to 7 carbon atoms. Examples: Glucose (blood sugar), fructose (fruit sugar), and galactose (dairy products, avocados, sugar beets) Hexoses – six carbon atoms Ribose and deoxyribose (sugars contained in nucleotides, the monomer of DNA) Pentoses – five carbon atoms  Disaccharides A disaccharide contains two monosaccharides joined together by dehydration synthesis. Examples: Lactose (milk sugar) is composed of galactose and glucose. Sucrose (table sugar) is composed of glucose and fructose. Maltose is composed of two glucose molecules. Lactose intolerant individuals lack the enzyme lactase which breaks down lactose into galactose and glucose.  Polysaccharides: Energy-Storage and Structural Molecules A polysaccharide is a polymer of monosaccharides. Examples: Starch provides energy storage in plants. Glycogen provides energy storage in animals. Cellulose is found in the cell walls of plants. Most abundant organic molecule on earth Animals are unable to digest cellulose. Chitin is found in the cell walls of fungi and in the exoskeleton of some animals. Peptidoglycan is found in the cell walls of bacteria. Monomers contain an amino acid chain. Polysaccharides: Energy-Storage and Structural Molecules (2) (photos): (a): ©Jeremy Burgess/SPL/Science Source; (b): ©Don Fawcett/Science Source  Polysaccharides: Structural Molecules Structural polysaccharides include cellulose in plants, chitin in animals and fungi, and peptidoglycan in bacteria. The cellulose monomer is simply glucose. Wood, a cellulose plant product, is used for construction, and cotton is used for cloth. over 100 billion tons of Figure 3.8 Cellulose fibrils. Cellulose fibers criss-cross in plant cellulose are produced by cell walls for added strength. A cellulose fiber contains several plants each year microfibrils, each a polymer of glucose molecules—notice that the linkage bonds differ from those of starch. Every other glucose is flipped, permitting hydrogen bonding and greater strength between the microfibrils.  Lipids Varied in structure Type Functions Human Uses Fats Long-term energy Butter, lard Large, nonpolar molecules storage and insulation in that are insoluble in water animals Oils Long-term energy Cooking oils Functions: storage in plants and their seeds Long-term energy storage Phospholipids Component of plasma Food additive membrane Structural components Steroids Component of plasma Medicines Heat retention membrane (cholesterol), Sex hormones Cell communication and Waxes Protection, prevention Candles, polishes regulation of water loss (cuticle of Protection plant surfaces), beeswax earwax  Triglycerides: Long-Term Energy Storage Also called fats and oils Functions: long-term energy storage and insulation Consist of one glycerol molecule linked to three fatty acids by dehydration synthesis  Saturated fatty acids Each fatty acid consists of a long hydrocarbon Fatty acids may be either chain with an even number of carbons and a −COOH (carboxyl) unsaturated or saturated. opposite (trans) side of the double bond Saturated – no double bonds between carbons Tend to be solid at room temperature Examples: butter, lard  Unsaturated fatty acids Unsaturated – one or more double bonds between carbons Tend to be liquid at room temperature Example: plant oils Can have chemical groups on the same (cis) or Trans– a triglyceride with at least one bond in a trans configuration  Do you know? Triglycerides containing fatty acids with unsaturated bonds melt at a lower temperature than those containing only saturated fatty acids. The reason is that a double bond creates a kink in the fatty acid chain that prevents close packing between the hydrocarbon chains This difference has applications useful to living organisms. For example, the feet of reindeer and penguins contain unsaturated triglycerides, and this helps protect those exposed parts from freezing.  Phospholipids: Membrane Components The structure is similar to triglycerides. It consists of one glycerol molecule linked to two fatty acids and a modified phosphate group. The fatty acids (tails) are nonpolar and hydrophobic. The modified phosphate group (head) is polar and hydrophilic. Phospholipids Form Membranes Function: forms plasma membranes of cells. In water, phospholipids aggregate to form a lipid bilayer (double layer). Polar phosphate heads are oriented towards the water. Nonpolar fatty acid tails are oriented away from water.  Steroids: Four Fused Carbon Rings They are composed of four fused carbon rings. Various functional groups attached to the carbon skeleton Functions: component of animal cell membrane, regulation Cholesterol is an essential component of an animal cell’s plasma membrane, where it provides physical stability. Cholesterol is the precursor of several other steroids, such as the sex hormones testosterone and estrogen Cholesterol can also contribute to circulatory disorders.  Proteins Proteins are polymers of amino acids linked together by peptide bonds. A peptide bond is a covalent bond between amino acids. As much as 50% of the dry weight of most cells consists of proteins. Several hundred thousand have been identified. There are 20 different common amino acids. Amino acids differ by their R, or variable groups, which range in complexity.  Amino Acids: The building blocks of proteins In the physiological pH range, both carboxylic and amino groups are completely ionized  Zwitterionic form of amino acids Under normal cellular conditions amino acids are zwitterions (dipolar ions) have both a positive and a negative charge : Amino group = -NH3+ Carboxyl group = -COO- They can act as either an acid or a base Prentice Hall c2002 Chapter 3 33  Amino acids are the building blocks of proteins Three major parts: carboxyl group, amino group, and side chain. Central C atom called alpha carbon. Amino acids can differ in their side chains (R). L-form found almost exclusively in proteins The D form of amino acids is only found in a few isolated instances which mainly consist of short peptide chains of bacterial cell walls and certain peptide antibiotics.  Peptide bonds Proteins are sometimes called polypeptides since they contain many peptide bonds R1 O H R2 O + H3N C C OH + H N C C O- H H R1 O R2 O + C N C C O- + H2O H3N C H H H  Amino acids can form peptide bonds Amino acid residue Proteins are peptide units molecules that dipeptides consist of one or more polypeptide tripeptides chains oligopeptides polypeptides Peptides are linear polymers that range from ~8 to 4000 amino acid residues How many different naturally occurring amino acids are there in most species encoded by the genome? Linear arrays of amino acids can make a huge number of molecules Consider a peptide with two amino acids AA1 AA2 20 x 20 = 400 different molecules AA1 AA2 AA3 20 x 20 x 20 = 8000 different molecules For 100 amino acid protein the # of possibilities are: 20100 = 1.27 x10130 Characteristics of R side Chain The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine  Proteins Two or more amino acids joined together are called peptides. Long chains of amino acids joined together are called polypeptides. A protein is a polypeptide that has folded into a particular shape, which is essential for its proper functioning.  Functions of Proteins Metabolism Most enzymes are proteins that act as catalysts to accelerate chemical reactions within cells. Support Some proteins have a structural function, for example, keratin and collagen. Transport Membrane channel and carrier proteins regulate what substances enter and exit cells. Hemoglobin protein transports oxygen to tissues and cells. Defense Antibodies are proteins of our immune system that bind to antigens and prevent them from destroying cells. Regulation Hormones are regulatory proteins that influence the metabolism of cells. Motion Microtubules move cell components to different locations. Actin and myosin contractile proteins allow muscles to contract. Functions of proteins… Enzymes: the most highly specialized proteins are those with catalytic activity – the enzymes. All the chemical reactions of organic biomolecules in cells are catalyzed by enzymes. Transport proteins: These proteins in blood bind and carry specific molecules or ions from one organ to another, e.g. Hemoglobin, lipoprotein Nutrient and storage proteins: The seeds of many plants store nutrient proteins required for the growth of germinating seedling,. The ferritin found in some bacteria and in plant and animal tissues stores iron.  Functions of proteins… Contractile or motile proteins: Some proteins endow cells and organisms with the ability to contract, change shape, or move about. Actin and myosin function in the contractile system of skeletal muscle and in many other cells. Structural proteins: Many proteins serve as supporting filaments. The major component of tendons and cartilage is the fibrous protein of collagen, which has very high tensile strength. Leather is almost pure collagen. Hairs, fingernails and feathers consist of the tough, insoluble protein keratin. The major component of silk fibers and spider webs is fibroin.  Functions of proteins… Defense proteins: Many proteins defend organism against invasion by other species or protect them from injury. The immunoglobulins or antibodies, the specialized proteins made by the lymphocytes of vertebrates can recognize and precipitate or neutralize invading bacteria, viruses or foreign proteins of another species. Fibrinogen and thrombin are blood-clotting factors that prevent loss of blood when the vascular system is injured.  Functions of proteins Regulatory proteins: Some proteins help regulate cellular or physiological activities, e.g. Insulin, a hormone regulates the metabolism of sugars. Other regulatory proteins bind to DNA and regulates the biosynthesis of enzymes and RNA molecules, involved in cell division in both prokaryotes and eucaryotes.  Shapes of Proteins and Levels of Protein Structure Proteins cannot function properly unless they fold into their proper shape. When a protein loses it proper shape, it said to be denatured. Exposure of proteins to certain chemicals, a change in pH, or high temperature can disrupt protein structure. Proteins can have up to four levels of structure: Primary Secondary Tertiary Quaternary  Four Levels of Protein Structure Primary level Primary level is the linear sequence of amino acids. Hundreds of thousands of different polypeptides can be built from just 20 amino acids. Changing the sequence of amino acids can produce different proteins. Secondary level Secondary level is characterized by the presence of alpha helices and beta (pleated) sheets held in place with hydrogen bonds.  Four Levels of Protein Structure Tertiary level Tertiary level is the overall three-dimensional shape of a polypeptide. It is stabilized by the presence of hydrophobic interactions, hydrogen, ionic, and covalent bonding. Quaternary level Quaternary level consists of more than one polypeptide.  The Importance of Protein Folding and Protein-Folding Diseases Chaperone proteins help proteins fold into their normal shapes and may also correct misfolding of new proteins. Defects in chaperone proteins may play a role in several human diseases, such as Alzheimer’s disease and cystic fibrosis.  The Importance of Protein Folding and Protein-Folding Diseases Prions are misfolded proteins that have been implicated in a group of fatal brain diseases known as TSEs. Transmissible spongiform encephalopathies , also known as prion diseases, are a group of rare degenerative brain disorders characterized by tiny holes that give the brain a "spongy" appearance Mad cow disease is one example of a TSE. Prions are believed to cause other proteins to fold the wrong way.  Nucleic Acids Nucleic acids are polymers of nucleotides. Two varieties of nucleic acids: DNA (deoxyribonucleic acid) Genetic material that stores information for its own replication and for the sequence of amino acids in proteins RNA (ribonucleic acid) Performs a wide range of functions within cells which include protein synthesis and regulation of gene expression  Structure of a Nucleotide Each nucleotide is composed of three parts: A phosphate group A pentose sugar A nitrogen-containing (nitrogenous) base There are five types of nucleotides found in nucleic acids. DNA contains adenine, guanine, cytosine, and thymine. RNA contains adenine, guanine, cytosine, and uracil.  Nucleotides a. Nucleotide structure b. Deoxyribose versus ribose Nucleotides are joined together by a series of dehydration synthesis reactions to form a linear molecule called a strand, which is a sequence of nucleotides. Structure of DNA and RNA The backbone of the nucleic acid strand is composed of alternating sugar-phosphate molecules. DNA is composed of two strands held together by hydrogen bonds between the nitrogen-containing bases. The two strands twist around each other, forming a double helix.  Structure of DNA and RNA The nucleotides may be in any order within a strand but between strands: Adenine (purine) makes hydrogen bonds with thymine (pyrimidine). Cytosine (pyrimidine) makes hydrogen bonds with guanine (purine). The bonding between the nitrogen- containing bases in DNA is referred to as complementary base pairing. The number of A + G (purines) always equals the number of T + C (pyrimidines). DNA packaging  Structure of DNA and RNA Table 3.4 DNA Structure Compared to RNA Structure DNA RNA Sugar Deoxyribose Ribose Adenine, guanine, Adenine, guanine, uracil, Bases thymine, cytosine cytosine Strands Double stranded with Single stranded base pairing Helix Yes No  Figure 1-5 Central Dogma © 2017 Pearson Education, Ltd.  ATP (Adenosine Triphosphate) ATP (adenosine triphosphate) is a nucleotide composed of adenine and ribose (adenosine) and three phosphates. ATP is a high-energy molecule due to the presence of the last two unstable phosphate bonds, which are easily broken. Hydrolysis of the terminal phosphate bond yields: The molecule ADP (adenosine diphosphate) An inorganic phosphate, P Energy to do cellular work The hydrolysis of the ATP molecule can be coupled with chemically unfavorable reactions in the cell to allow the reactions to proceed. Example: key steps in the synthesis of carbohydrates and proteins, and muscle contraction and nerve impulse conduction  ATP ATP is therefore called the energy currency of the cell. Slide Title TITLE LOREM IPSUM Sit Dolor Amet  2 Define what carbohydrates are and what are their benefits for human boday Define. Explain The difference between digestible and indigestible carbohydrates List List the hormones that control blood sugar level and how they function Learning Describe Describe the difference between simple and complex carbohydrates, objectives. Discuss how carbohydrates are digested and absorbed by our body, Discuss. Explain Explain the potential health risks associated with diets high in refined sugars List List five foods that are good sources of carbohydrates Identify Identify three alternative sweeteners. Case study In this chapter, we will explore the differences between simple and complex carbohydrates and learn why some carbohydrates really are better than others. We ll also learn how the human body breaks down carbohydrates and uses them to maintain our health and to fuel our activity and exercise  What Are Carbohydrates? ◦ Carbohydrates are one of the three macronutrients. As such, they are an important energy source for the entire body and are the preferred energy source for nerve cells, including those of the brain. ◦ The term carbohydrate literally means hydrated carbon. Water (H2O) is made of hydrogen and oxygen, and, when something is said to be hydrated, it contains water. Thus, the chemical abbreviation for carbohydrate (CHO) indicates the atoms it contains: carbon, hydrogen, and oxygen. ◦ We obtain carbohydrates predominantly from plant foods, such as fruits, vegetables, and grains. Plants make the most abundant form of carbohydrate, called glucose, through a process called photosynthesis.  Carbohydrates ◦ Ideal nutrients ◦ Energy needs ◦ Feed brain and nervous system ◦ Keep digestive system fit ◦ Keep your body lean ◦ Digestible and indigestible carbohydrates ◦ Complex vs. simple carbohydrates (Simple carbohydrates contain either one or two molecules, whereas complex carbohydrates contain hundreds to thousands of molecules).  Photosynthesis ◦ Plants continually store glucose and use it to support their own growth. Then, when we eat plant foods, our body digests, absorbs, and uses the stored glucose. Plants make carbohydrates through the process of photosynthesis. Water, carbon dioxide, and energy from the sun are combined to produce glucose.  Simple Carbohydrates Include Monosaccharides and Disaccharides ◦ Simple carbohydrates are commonly referred to as sugars. Four of these ◦ Monosaccharides sugars are called monosaccharides ◦ Glucose, Fructose, Galactose, and Ribose Are because they consist of a single sugar Monosaccharides molecule (mono means one, and saccharide means sugar ). The other three sugars are disaccharides, which ◦ Disaccharides consist of two molecules of sugar ◦ Lactose, Maltose, and Sucrose joined together (di means two ).  How Monosaccharides Join to Form Disaccharides Very slight differences in the arrangement Interestingly, human breast milk has more lactose than of the atoms in these three monosaccharides cause cow s milk does, making human breast milk taste sweeter major differences in their levels of sweetness. Simple carbs  Polysaccharides Are Complex Carbohydrates ◦ Complex carbohydrates, the second major type of carbohydrate, generally consist of long chains of glucose molecules called polysaccharides (poly means many ). They include starch, glycogen, and most fibers Our cells cannot use the complex starch molecules exactly as they exist in plants. Instead, our body must break them down into the monosaccharide glucose, from which we can then meet our energy needs.  Glycogen Is a Polysaccharide Stored by Animals ◦ Glycogen is the storage form of glucose for animals, including humans ◦ As plants contain no glycogen, it is not a dietary source of carbohydrate. ◦ We store glycogen in our liver and muscles  A Close Look at Carbohydrates – Glycogen ◦ Storage form of glucose ◦ Animal bodies ◦ Chains are longer than starch ◦ More highly branched ◦ Undetectable in meats  Fiber Is a Polysaccharide That Gives Plants Their Structure ◦ Like starch, fiber is composed of long polysaccharide chains; however, our body does not easily break down the bonds that connect fiber molecules. This means that most fibers pass through the digestive system without being digested and absorbed, so they contribute no energy to our diet. Insoluble fibers are generally found in whole grains, such as wheat, rye and brown rice citrus fruits, berries, oat products, and beans Other benefits  Why Do Nutrition Experts Recommend Fiber-Rich Foods? ◦ Health benefits ◦ Reduced risk of heart disease ◦ Reduced risk of hypertension ◦ Reduced risk of diabetes ◦ Reduced risk of bowel disease ◦ Promotion of healthy body weight ◦ Sources of fiber  Why Do We Need Carbohydrates? ◦ Carbohydrates Provide Energy: Carbohydrates, an excellent source of energy for all our cells, provide 4 kilocalories (kcal) of energy per gram Some of our cells can also use fat and even protein for energy if necessary. However, our red blood cells can utilize only glucose, and our brain and other nervous tissues primarily rely on glucose. This is why we get tired, irritable, and shaky when we haven t eaten any carbohydrate for a prolonged period of time  the body relies mostly on both carbohydrates and fat for energy. Fat is the predominant energy source used by our body at rest and during low-intensity activities When we exercise, whether running, briskly walking, bicycling, or performing any other activity that causes us to breathe harder and sweat, we begin to use more glucose than fat  Low Carbohydrate Intake Can Lead to Ketoacidosis ◦ When we do not eat enough carbohydrate, our body seeks an alternative source of fuel for our brain and begins to break down stored fat. ◦ This process, called ketosis which is an important mechanism for providing energy to the brain during situations of fasting, low carbohydrate intake, or vigorous exercise. ◦ However, ketones also suppress appetite and cause dehydration and acetone breath (the breath smells like nail polish remover). ◦ If inadequate carbohydrate intake continues for an extended period of time, the body will produce excessive amounts of ketones. Because many ketones are acids, high ketone levels cause the blood to become very acidic, leading to a condition called ketoacidosis. The high acidity of the blood interferes with basic body functions, causes the loss of lean body mass, and damages many body tissues.  Carbohydrates Spare Protein ◦ If the diet does not provide enough carbohydrate, the body will make its own glucose from protein. This involves breaking down the proteins in blood and tissues into amino acids, then converting them to glucose. This process is called gluconeogenesis ( generating new glucose ). ◦ When our body uses amino acids for energy, they are not available to make new cells, repair tissue damage, support our immune system, or perform any of their other functions. During periods our body will then from other of starvation take amino acids tissues, such as from the blood muscles, heart, first liver, and kidneys.  Carbohydrates and Body Weight fat is more energy dense than FATS? carbohydrate: It contains 9 kcal per gram, whereas carbohydrate contains only 4 CARBS? kcal per gram. Thus, gram for gram, fat is twice as fattening as carbohydrate  How Does Our Body Break Down Carbohydrates? Digestion Breaks Down Most Carbohydrates into Monosaccharides ◦ Carbohydrate digestion begins in the mouth ◦ salivary amylase An enzyme in saliva that breaks starch into smaller particles and eventually into the disaccharide maltose. ◦ The next time you eat a piece of bread, notice that you can actually taste it becoming sweeter; this indicates the breakdown of starch into maltose How Does Our Body Break Down Carbohydrates? sucrase maltase lactase  The Liver Converts Most Non-Glucose Monosaccharides into Glucose ◦ Once the monosaccharides enter the bloodstream, they travel to the liver, where fructose and galactose are converted to glucose. If needed immediately for energy, the glucose is released into the bloodstream On average, the liver can store 70 g (280 kcal) and the muscles can normally store about 120 g (480 kcal) of glycogen ◦ Between meals, our body draws on ◦ The glycogen stored in our muscles liver glycogen reserves to maintain continually provides energy to our blood glucose levels and support the muscle cells, particularly during needs of our cells, including those of intense exercise our brain, spinal cord, and red blood cells Once the storage capacity of the liver and muscles is reached, any excess glucose can be stored as fat in adipose tissue. A Variety of Hormones Regulates Blood Glucose Levels ◦ When blood glucose levels increase after a meal, Glucose molecules are too large to cross cell membranes independently. the pancreas secretes insulin. Insulin opens gates in the cell membrane to allow the passage of glucose into the cell. Insulin also stimulates the liver and muscles to take up glucose and store it as glycogen.  Effect of glucagon Glucagon acts in an opposite way to insulin ◦ When you have not eaten for a period of time, your blood glucose level declines. This decrease in blood glucose stimulates the pancreas to secrete another hormone, glucagon ◦ Glucagon also assists in the breakdown of body proteins to amino acids, so that the liver can stimulate production of glucose from AA  Effect of other hormones ◦ Epinephrine, norepinephrine, cortisol, and growth hormone are additional hormones that work to increase blood glucose. ❑ Epinephrine and norepinephrine are secreted by the adrenal glands and nerve endings when blood glucose levels are low. They act to increase glycogen breakdown in the liver, resulting in a subsequent increase in the release of glucose into the bloodstream.  Effect of other hormones ◦ Cortisol and growth hormone are secreted by the adrenal glands to act on liver, muscle, and adipose tissue.: ❑ Cortisol increases gluconeogenesis and decreases the use of glucose by muscles and other body organs. ❑Growth hormone decreases glucose uptake by our muscles, increases our mobilization and use of the fatty acids stored in our adipose tissue, and increases our liver s output of glucose. The Glycemic Index Shows How Foods Affect Our Blood Glucose Level ◦ The glycemic index is a measure of the potential of foods to raise blood glucose levels. Foods with a high glycemic index cause a sudden surge in blood glucose. This in turn triggers a surge in insulin, which may then be followed by a dramatic drop in blood glucose. ◦ Foods with a low glycemic index cause low to moderate fluctuations in blood glucose. When foods are assigned a glycemic index value, they are often compared to the glycemic effect of pure glucose. Why do we care about the glycemic index and glycemic load? ◦ glycemic load The amount of carbohydrate in a food multiplied by the glycemic index of the carbohydrate. ◦ Foods and meals with a lower glycemic load are better choices for someone with diabetes because they will not trigger dramatic fluctuations in blood glucose. They  Why do we care about the glycemic index and glycemic load? ◦ Foods and meals with a lower glycemic load are better: ◦ They may also reduce the risk for heart disease and colon cancer because they generally contain more fiber, and fiber helps decrease fat levels in the blood ◦ Diets with a low glycemic index and low glycemic load are also associated with a reduced risk for prostate cancer people are encouraged to eat a variety of fiber-rich and less processed carbohydrates, such as beans and lentils, fresh vegetables, and whole-wheat bread, because these forms of carbohydrates have a lower glycemic load and they contain a multitude of important nutrients  How Much Carbohydrate Should We Eat? ◦ The Recommended Dietary Allowance (RDA) for carbohydrate is based on the amount of glucose the brain uses. ◦ The current RDA for adults 19 years of age and older is 130 g of carbohydrate per day. It is important to emphasize that this RDA does not cover the amount of carbohydrate needed to support daily activities; ◦ it covers only the amount of carbohydrate needed Most health agencies agree that most of the to supply adequate glucose to the brain. carbohydrates you eat each day should be high in fiber, whole-grain and unprocessed  Good versus bad choices ◦ Keep in mind that fruits are predominantly composed of simple sugars and contain little or no starch. They are healthful food choices, however, as they are good sources of vitamins, some minerals, and fiber. much of our sugar intake comes from added sugars. Added sugars are defined as sugars and syrups that are added to foods during processing or preparation ◦ 12-oz cola contains 38.5 g of sugar, or almost 10 teaspoons ◦ Americans drink an average of 40 gallons per person each year.. ◦ In addition, a surprising number of processed foods you may not think of as sweet actually contain a significant amount of added sugar, including many brands of peanut butter, flavored rice mixes etc…  Sugars Are Blamed for Many Health Problems ◦ Why do sugars have such a bad reputation? 1. they are known to cause tooth decay 2. they cause hyperactivity in children 3. sugar could increase the levels of unhealthful lipids, or fats, in our blood, increasing our risk for heart disease. 4. High intakes of sugar have also been blamed for causing diabetes and obesity. Is all that true?  1. Sugar Causes Tooth Decay ◦ Yes Sugars do play a role in dental problems because the bacteria that cause tooth decay thrive on sugar. These bacteria produce acids, which eat away at tooth enamel and can eventually cause cavities and gum disease ◦ Eating sticky foods that adhere to teeth such as caramels, crackers, sugary cereals, and licorice increase the risk for tooth decay. ◦ Even breast milk contains sugar, which can slowly drip onto the baby s gums. As a result, infants should not routinely be allowed to fall asleep at the breast.  2. There Is No Link Between Sugar and Hyperactivity in Children ◦ there is little scientific evidence to support this claim. Some children actually become less active shortly after a high-sugar meal ◦ Behavioral and learning problems are complex issues, most likely caused by a multitude of factors. ◦ Because of this complexity, the Institute of Medicine has stated that, overall, there does not appear to be enough evidence to state that eating too much sugar causes hyperactivity or other behavioral problems in children 3. High Sugar Intake Can Lead to Unhealthful Levels of Blood Lipids ◦ Yes Research evidence suggests that consuming a diet high in sugars, particularly fructose, can lead to unhealthful changes in blood lipids ◦ higher intakes of sugars are associated with increases in our blood of both low-density lipoproteins (LDL, commonly referred to as bad cholesterol ) and triglycerides. ◦ At the same time, high sugar intake appears to decrease our high-density lipoproteins (HDL), which are protective and are often referred to as good cholesterol. 4. High Sugar Intake Does Not Cause Diabetes but May Contribute to Obesity ◦ studies examining the relationship between sugar intake and type 2 diabetes report no association between sugar intake and diabetes. ◦ However, people who have diabetes need to moderate their intake of sugar and closely monitor their blood glucose levels ◦ There is somewhat more evidence linking sugar intake with obesity. Another study found that for every extra sugared soft drink a child consumes per day, the risk for obesity increases by 60%.  Do you get enough fiber-rich carbohydrates each day? ◦ If you eat only about 2 servings of fruits or vegetables each day; this is far below the recommended amount. We Need at Least 25 for women and 38 g Grams of Fiber Daily for men ◦ It is also important to drink plenty of fluid as you increase your fiber intake, as fiber binds with water to soften stools. ◦ ATTENTION: Because fiber binds with water, it causes the body to eliminate more water in the feces, so a very-high-fiber diet could result in dehydration  Attention ◦ Fiber also binds many vitamins and minerals, so a high-fiber diet can reduce our absorption of important nutrients, such as iron, zinc, and calcium. In children, some elderly, the chronically ill, and other at-risk populations, extreme fiber intake can even lead to malnutrition they feel full before they have eaten enough to provide adequate energy and nutrients Looking for source of fibers?  Alternative Sweeteners? ◦ Remember that all carbohydrates, including simple and complex, contain 4 kcal of energy ◦ Other nutritive sweeteners are the sugar per gram. Because sweeteners such as sucrose, alcohols, such as mannitol, sorbitol, isomalt, and fructose, honey, and brown sugar contribute xylitol. Calories (or energy), they are called nutritive sweeteners. ◦ Popular in sugar-free gums and mints, sugar alcohols are less sweet than sucrose because sugar alcohols are absorbed slowly and incompletely from the small intestine, they Sugar alcohols are sweeteners that provide less energy than sugar, usually 2 to 3 kcal of energy per gram. have about half the calories of regular sugar. They occur naturally in ◦ However, because they are not completely certain fruits and vegetables, but some absorbed from the small intestine, they can are man-made attract water into the large intestine and cause diarrhea Alternative Sweeteners Are Non-Nutritive ◦ Because these products provide little or no energy, they are called non-nutritive, or alternative, sweeteners. Contrary to popular belief, alternative sweeteners have been determined to be safe for adults, children, and individuals with diabetes to consume. ◦ The major alternative sweeteners currently available on the market are saccharin, acesulfame-K, aspartame, and sucralose. ◦ saccharin is about 300 times sweeter than sucrose ◦ Acesulfame-K a Calorie-free sweetener that is 200 times sweeter than sugar. ◦ Aspartame is 180 times sweeter than sucrose ◦ Sucralose It is 600 times sweeter than sucrose and is stable when heated, so it can be used in cooking