Chapter 11 Nutrition: Food for Thought Do you think about the food that goes into your body and how it affects you? How can you interpret the various nutrition information found in the press? What are trans fats? Good carbs vs. bad ones?
Useful Terms Malnutrition is caused by a diet lacking in the proper mix of nutrients, even though the energy content of the food eaten may be adequate. Undernourishment, is experienced when the daily caloric intake is insufficient to meet the metabolic needs of a person. Although there are cases of malnourished and undernourished people in the U.S., 66% of the adult population is classified as overweight with almost half of that population classified as obese. Obesity and its related adverse health effects are overtaking smoking as the No. 1 cause of death in the United States. 11.1
Remember: Calories are often used to express the energy released when food is metabolized. 1 calorie (cal) is the amount of energy required to raise the temperature of 1.0 g of water by 1 o C. This is a small quantity of energy, so we typically use kilocalories (kcal): 1 kcal = 1,000 cal The dietary Calorie (C) is also 1,000 cal. And 1 cal = 4.184 J 11.1
A Typical Food Label Tells Us: Caloric Content Total Fats Total Carbohydrates and Proteins What do these things mean at the microscopic level? What are saturated/unsaturated fats, fiber, sugars, and cholesterol? 11.1
We are what we eat! Composition of the human body Just 11 elements make up over 99% of your body 11.1
Mass percentages of the major elements of the human body, along with their relative abundances. Oxygen has the highest mass percent. Hydrogen is the most abundant on a per-atom basis. 11.1
Fats and Oils Properties of fats: greasy, slippery, soft, low-melting, water insoluble solids. Butter, cheese, cream, whole milk, and certain meats and fish are loaded with them. All of these products are of animal origins. But margarine and some shortenings are evidence that fats can also be of vegetable origin. Oils, such as those obtained from olives, corn, or nuts, exhibit many of the properties of animal-based fats, but in liquid form. Stearic acid: condensed formula CH 3 (CH 2 ) 16 COOH Stearic acid: ball-and-stick molecular formula 11.2
Fatty acids are characterized by two structural features: 1. A long hydrocarbon chain generally containing an even number of carbon atoms (typically 12 to 24) 2. A carboxylic acid group (-COOH, or CO 2 H) at the end of the chain. O OH Here is a fatty acid with a double bond: a monounsaturated fatty acid 11.2
Fats are triglycerides that are solid at room temperature, whereas oils are triglycerides that are liquid at room temperature. A triglyceride is simply an ester of three fatty acid molecules and one glycerol molecule. O CH 3 (CH) 16 C OH O + CH 3 (CH) 16 C OH triglyceride O glycerol CH 3 (CH) 16 C OH Triglycerides belong to the lipid family, a class of compounds that includes cholesterol and other steroids and some complex compounds such as lipoproteins that contain fatty segments. 11.2
Ester functional group The formation of a triglyceride made from 3 molecules of stearic acid and one glycerol molecule: O CH 3 (CH) 16 C O HO H H OH C C C H H glycerol H OH + C CH 3 (CH) 16 OH O C CH 3 (CH) 16 OH O C CH 3 (CH) 16 OH stearic acid CH 3 (CH) 16 C O H O O C C C H H H CH 3 (CH) 16 + 3 H 2 O H O C O Ester formation was covered in Chapter 10 11.2
Saturated fatty acids contain only C-to-C single bonds between the carbon atoms. A fatty acid is unsaturated if the molecule contains one or more C-to-C double bonds between carbon atoms. CH 3 (CH 2 ) 16 COOH Stearic acid, a saturated fatty acid CH 3 (CH 2 ) 7 CH=CH (CH 2 ) 7 COOH Oleic acid, a monounsaturated fatty acid CH 3 (CH 2 ) 4 CH=CH CH 2 CH=CH (CH 2 ) 7 COOH Linoleic acid, a polyunsaturated fatty acid CH 3 CH 2 CH=CH CH 2 CH=CH CH 2 CH=CH (CH 2 ) 7 COOH Linolenic acid, a polyunsaturated fatty acid 11.2
Saturated and Unsaturated Fats 11.2
Partially Hydrogenated Fats Hydrogenation reduces C=C bonds to C-C bonds; H 2 is added across the double bond. A metal catalyst is required. CH 3 (CH 2 ) 4 CH=CH CH 2 CH=CH (CH 2 ) 7 COOH + H 2 CH 3 (CH 2 ) 4 CH 2 CH 2 CH 2 CH=CH (CH 2 ) 7 COOH The number of double bonds in the fatty acid decreases, and it is transformed from an oil into a semisolid fat. The hydrogenation can be controlled to yield products with desired melting point, softness, and spreadability. 11.2
Cholesterol Cholesterol is a lipid, and falls into the class of compounds called steroids. (more on steroids in Ch. 10) Cholesterol a b Healthy artery (a) vs. one clogged with plaque (b). High levels of cholesterol in the blood appear to be linked to a greater risk of heart attack or stroke. 11.2
High cholesterol Risk Uncertainty? 11.2
What s a Carbohydrate? Carbohydrates are compounds containing carbon, hydrogen, and oxygen. The best known dietary carbohydrates are sugars (like glucose) and starch. A single sugar, or monosaccharide alcohol groups Starch A disaccharide 11.3
Carbohydrates have a 2:1 ratio of H to O atoms (like water) Single sugars have the formula C 6 H 12 O 6 ringed structures containing either 4 or 5 carbon atoms and one oxygen atom. The single sugars are also called monosaccharides. and b refer to the 3-D position of the OH group (or CH 2 OH group) at the indicated carbons. is pointing down, b is up: the fructose is shown in an atypical, upside down position. 11.3
When many sugars are linked together you have polysaccharides, which are natural polymers: Because the single sugars can be either or b, two different linkages arise. When glucose polymerizes, an linkage makes starch and a b linkage makes cellulose. 11.3
Polysaccharides Starch is the primary carbohydrate component of several foods such as potatoes. Cellulose is the primary fibrous component in the cell walls of plants. Glycogen is the polysaccharide form of carbohydrate that is stored in our bodies; this is our storehouse of energy. We humans are able to digest starch, but we lack the enzymes required to digest cellulose. 11.3
Proteins Proteins are an essential part of every living cell. They are also major components in hair, skin, and muscle; and they transport oxygen, nutrients, and minerals through the bloodstream. Many of the hormones that act as chemical messengers are proteins, as are all the enzymes that catalyze the chemistry of life. Proteins are polyamides or polypeptides, polymers made up of amino acid monomers. The great majority of proteins are made from various combinations of the 20 different naturally occurring amino acids. Examples of different amino acids 11.4
Proteins are made of amino acids. The general formula for an amino acid includes four groups attached to a carbon atom: (1) a carboxylic acid group, -COOH; (2) an amine group, -NH 2 ; (3) a hydrogen atom, -H; and (4) a side chain designated as R: They differ from one another by the different R groups 11.4
Two amino acids can link together via a peptide bond: The two molecules join, expelling a molecule of water. Peptide bond The process may repeat itself over and over, creating a peptide chain. Once incorporated into the peptide chain, the amino acids are known as amino acid residues. 11.4
Vitamins are defined by their properties: They are essential in the diet, although required in very small amounts They all are organic molecules with a wide range of physiological functions They generally are not used as a source of energy, although some of them help break down macronutrients 11.5
Minerals (either ions or inorganic compounds) are essential for good health. The important, essential minerals are shown on this periodic table. In the body, metallic elements typically exist as cations (pos. charge), and the nonmetals usually occur as anions (neg. charge). 11.5
Energy from the Metabolism of Food C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (chlorophyll acts as a catalyst) The breaking of chemical bonds in glucose and oxygen molecules requires the absorption of energy. But a greater amount of energy is released as carbon dioxide and water are formed. There is a net release of energy; it is an exothermic reaction. 11.6