The Digestive System Part I The Chemistry of Life

Questions for Consideration 1.List the 5 nutrients required to maintain good health; 2.List two ways the body uses: a)Lipids b)Proteins c)Carbohydrates d)Vitamins e)Minerals 3.List some foods that are mainly carbohydrates. 4.List some foods that are mainly fats. 5.Are fats good or bad for you? Justify your answer.

Chemistry of Life Carbohydrates Are the primary energy source for all cells. Proteins Structural and functional components of the cell (e.g. Building blocks of muscles). Composed of amino acids. Fats (Lipids) Energy storage compound. Structural component of cell membranes. Vitamins and Minerals Help in chemical reactions Found in complex chemicals (such as hormones and enzymes). Chemicals of Life

The Chemistry of Life In order to fully understand the digestive system you must have a good understanding of both biology (anatomy) and chemistry. Biochemistry

Chemistry of Life Food can be classified into 3 nutrient types: 1.Carbohydrates 2.Proteins 3.Fats (also called lipids)

Chemistry of Life Carbohydrates The body’s most important source of energy; The largest component of our regular diet ; Sources of carbohydrates include: potatoes, rice, corn, bread, pasta and Many fruits (high sugar content)

Chemistry of Life Carbohydrates Carbohydrates are made of either single sugar molecules or chains of sugar molecules. Saccharide = Greek word meaning “sugar” Monosaccarides = a carbohydrate made of only 1 sugar molecule Disaccharides = carbohydrates made of 2 sugar molecules

Chemistry of Life Carbohydrates Monosaccarides = a carbohydrate made of only 1 sugar molecule (e.g. Glucose and fructose) Sugars are made of carbon, oxygen and hydrogen Glucose The simplest sugar C 6 H 12 O 6 Most sugars end in “ose”

Chemistry of Life Carbohydrates Fructose = a sugar found in fruit Lactose = a sugar found in milk Maltose = a sugar found in beer Sucrose = table sugar (made of glucose + fructose)

Chemistry of Life Complex Carbohydrates Carbohydrates made up of many sugar molecules linked in long chains. Starch = glucose molecules Excess sugars are usually stored as starches by plants. When a plant needs energy it breaks down a starch molecule into individual glucose molecules. Wheat products (such as bread and pasta are rich sources of starches.

Chemistry of Life Complex Carbohydrates Cellulose A polysaccaride that makes up the cell walls of plants. Often called fiber or roughage in our diet Indigestible Holds water in our large intestine and helps to eliminate wastes

Chemistry of Life Checking Your Understanding 1)What is the difference between a monosaccaride, a disaccaride and a polysaccharide? 2)What is the difference between gluose, sucrose and starch? 3)What is the difference between starch and cellulose? 4)What is the primary purpose of carbohydrates in our diet?

Chemistry of Life Lipids Lipids can be divided into 3 groups: 1.Fats, oils and waxes; 2.Phospholipids; 3.Steroids Lipids are also storage compounds for energy (like carbohydrates) One gram of lipid contains 2x as much energy as 1 g of carbohydrate

Chemistry of Life Lipids What lipids do in the body: absorption of vitamins, insulate the body, a major component of cell membranes, protect and cushion the organs of the body, are building blocks for hormones.

Chemistry of Life Unsaturated vs. Saturated Fats Saturated fats = contain no double bonds and the maximum number of hydrogen atoms Saturated fats are often solid (like butters and lard) Animal fats are usually saturated Unsaturated fats = contain one or more double bonds and therefore are missing hydrogen atoms. Unsaturated fats are often very soft or liquids (oils) Many plant fats are unsaturated.

Chemistry of Life

Hydrogenation of Fats Unsaturated fats (like plant fats) can be made more solid by adding hydrogen atoms. Margarine is an example of a hydrogenated fat.

Chemistry of Life Checking Your Understanding #2 1)What are fats? 2)Name the three groups of lipids. 3)What is the difference between saturated and unsaturated fats? 4)What is hydrogenation? What is the result of hydrogenation?

Chemistry of Life Proteins Proteins are used to build cellular structures; Proteins are used in chemical activities; Enzymes are proteins that control the rates of many reactions (including digestion and cellular respiration). Proteins are NOT usually used for energy.

Chemistry of Life Proteins Proteins are made of carbon, oxygen, hydrogen and NITROGEN (and sometimes sulfur). Proteins are made of 20 different amino acid building blocks. Small proteins may contain 8 amino acids, others contain more than 4000 amino acids. Polypeptide = a chain of several amino acids forming a protein.

The 20 Amino Acids

Polypeptide Formation

Chemistry of Life Proteins in our diet Our bodies can make most amino acids but there are 8 that our bodies can’t make – we must eat these. We call these 8 amino acids “Essential Amino Acids”

Chemistry of Life

Sources of Proteins in our diet Meats & Fish Beans Nuts & Seeds Dairy products Tofu Some Veggies

Chemistry of Life Checking Your Understanding #3 1)What are proteins used for? 2)What are amino acids? 3)List some foods that are good sources of proteins?

Mini Quiz Match the following structures with the correct nutrient: 1ASimple Carbohydrate 2BLipid 3CProtein 4DComplex Carbohydrate