Human Biology 11 Introduction: “You Are What You Eat” VideoYou Are What You Eat

 Living things are made of non-living chemicals  All of these chemical are made of carbon, oxygen, hydrogen and sometimes nitrogen.  These non-living chemicals are found in the food we eat and are called nutrients.  Food can be classified into three major groups of nutrients: 1. Carbohydrates 2. Fats (or lipids) 3. Proteins  Also, we need vitamins and minerals, but in much smaller amounts. Chemistry of Life

 Carbohydrates are the body’s most important source of energy.  Carbs make up the largest part of our diets  Carbs be used as a source of energy very quickly  We obtain most carbs from plants (eg. tapitats) or food that comes from plants (eg. flour)  Carbs are made of sugar molecules.

 Simple sugar is made of single molecules and includes glucose (which is found in all cells in your body), fructose (found in fruits) and galactose (found in milk). Another word for simple sugars is monosaccharide (mono=one)  Combining simple sugars together makes disaccharides (di=two). Examples include lactose (in milk), sucrose (table sugar) and maltose (malt sugar used to make beer)  Complex carbohydrates are made of many sugar molecules in long chains. Examples include starch (which is sugar that is stored by plants, as in tapitats and wheat products), cellulose (in the cell walls of plants; this is fibre for humans), and glycogen (which is a type of sugar stored in our liver and muscles).

 Like carbs, lipids supply energy to the cells. But, unlike carbs, lipids are hard to break down. That’s why your stomach feels full longer after eating a fatty meal rather than simple carbs like the rice in Chinese food.  Lipids are important energy storage, helps the body to absorb vitamins, keeps us warm, protects the organs, makes up the cell membrane and is an important ingredient in hormones and other chemicals made by cells.  Lipids include saturated fats (bad fats), unsaturated fats (“better” fats), cholesterol (good & bad) and phospholipids (in cell membranes & steroids).

 Proteins are made by cells to build structures and are used in chemical activities. All cells are made of protein. So, protein is the basic building material in our bodies.  Proteins are made from a combination of 20 different chemicals called amino acids. Our bodies can make many of these, but 8 are considered to be essential amino acids and must be obtained in our food. The lack of any one of these essential acids will lead to specific protein deficiencies and disease.  One example is phenylalanine found in breast milk and many types of food.