How do organisms transform chemical energy in the food they eat into other forms of energy? Part IA: It s All About Energy Have you ever wondered why we eat, why we get hungry, or why you may crash right before lunch or the end of the day? It all has to do with a transfer of energy. The energy stored in the food we eat is transferred to our bodies. This energy transfer provides the energy for everything we do! The food that we eat starts to breakdown as soon as we begin to chew. Enzymes in saliva start to break food molecules down into simpler parts. In the stomach, acids break the food down even further. By the time the food enters our small intestine, the food molecules are broken down into very small parts that the body can more easily absorb. The basic process of the transfer of energy from food to our body is known as digestion. 1
How do organisms transform chemical energy in the food they eat into other forms of energy? Part IB: Where Does the Energy Come From? All of the food that we eat is made of a combination of biomolecules. Three of the main biomolecules that are found in the foods we eat are lipids, proteins, and carbohydrates. These biomolecules are polymers that are made of smaller building blocks called monomers. Lipids These biomolecules are great for long-term energy storage. Lipids are otherwise known as fats, oils, and waxes. The monomers of lipids are fatty acids. Proteins These biomolecules are essential to biological organisms. Amino acids are the monomers of proteins. We must eat proteins as our bodies can not make amino acids. When we digest, our bodies break the proteins down into amino acids that our bodies can then use for everything, including energy. Carbohydrates These biomolecules are great for storing short-term energy. Large carbohydrates are called polysaccharides and come in the form of such things as starch. Smaller carbohydrates are called sugars. The monomer of carbohydrates is the simplest sugar glucose. Go to page 1 of your Student Journal. Fill out the What I Have Eaten Today? chart. Separate the foods that you have eaten into carbohydrates, lipids, and proteins. Then answer the questions on that page. 2
What energy transformations take place before, during, and after digestion? Part II: Breaking the Bonds So where does the energy come from? The atoms that make up molecules are held together by chemical bonds. Look at the molecule for glucose shown below. Glucose is the monomer (or most basic unit) of carbohydrates. The gray, white, and red circles represent three types of atoms Carbon, Hydrogen and Oxygen. The yellow lines between the circles represent the chemical bonds that hold the atoms together. Glucose Molecule The chemical formula for glucose is C 6 H 12 O 6. There are: 6 gray carbon (C) atoms 12 white hydrogen (H) atoms 6 red oxygen (O) atoms. When you eat carbohydrates (for example), the chemical bonds between the atoms are broken as the food gets digested. Each time a chemical bond is broken, energy is released. Our bodies can then use this released energy to do work such as building tissues, repairing cells, or any other body function that requires energy. During digestion, the chemical energy contained in the chemical bonds of the food molecule is converted to mechanical energy that is used for work in the body. As you can imagine, if a molecule has many chemical bonds, then there is a lot of energy that can potentially be released. Look at the examples on page 2 of your Student Journal, and then answer the questions on page 3 of your Student Journal. 3
How do muscles of an organism rely on chemical energy to produce motion? Part III: Fueling the Machine Lets go back to the glucose molecule. This molecule is one of the major sources of energy for all of our body functions. In our bodies, the molecule glucose is broken down, piece by piece, in a process called cellular respiration. The chemical energy found in food molecules is used to create ATP, which then provides the mechanical energy for all of our body functions. What does your body need energy for? Each time you breathe, blink, swallow, or turn your head, you are using muscles. Each time you use your muscles, you need (or use) energy. The cells in your body are constantly working. They require a never-ending supply of energy. Cellular respiration is happening every second of every day! The process of digestion uses a lot of energy as well. Muscles contract, cells are put to work, and the food molecules must be transported throughout the body. All this work creates heat or thermal energy. As heat is released, energy is released, which means that our bodies need to work hard to maintain a constant temperature - which equals more work and more energy demands! The energy your body needs is provided from the ATP made from the breakdown of food molecules. The more work your body does, the more energy it needs. After a while, you use all of your available energy (like a car running out of gas) and you need to refuel. If we do not eat enough, then our energy stores run out and we feel tired. If we eat too much, then the surplus is stored for future use in our fat cells. 4
How do muscles of an organism rely on chemical energy to produce motion? Part III: Fueling the Machine The energy released from the food that you eat can be measured! You may be familiar with this unit. It is called a Calorie or cal. for short. As the food that we eat is broken down in our digestive system, energy is released. This energy is what fuels our bodies throughout the day and even the night. The energy released during cellular respiration (review page 4 of your Student Guide) is called food energy. When the digesting food reacts with the oxygen found in our cells (breaking bonds), food energy is released and made available to do work. Different foods provide different types of food energy. Look at the following calories for the 3 main types of biomolecules that can be found in foods: Proteins 1 gram = 4 calories Carbohydrates 1 gram = 4 calories Lipids 1 gram = 9 calories The United States Department of Agriculture recommends that close to 50% of your calories should come from carbohydrates, 30% from fats, 20% from proteins. How are you doing in your diet? Could there be a reason why you feel sluggish at certain times of the day? Go to page 4 of your Student Journal and read the instructions. Fill in the Food Calorie Chart on page 4 of your Student Journal as you complete the instructions. Once you have completed your task, answer the Reflections and Conclusions questions on page 5 of your Student Journal. 5
How do muscles of an organism rely on chemical energy to produce motion? Part III: Fueling the Machine Get into your groups and gather your What Have I Eaten Today? charts. Next, log on to: www.myfoodapedia.gov Follow steps 1 through 8 (below) for each group member. 1. On the home page, you will see a box that says Enter Food Name. 2. The first person in the group adds one food item that they have eaten today for either breakfast or lunch. 3. Once you enter the food and press Enter, the website will take you to another page. 4. Make the food entry more specific. For example, if you put Eggs in the box on the Home Page, then choose what type of eggs on this page. If the group member at scrambled eggs cooked with butter, then you would choose Scrambled egg (cooked with fat). 5. A new window will open. On the upper right, you will see a box that says Choose an Amount. Make sure that you choose the correct portion of what was eaten for the meal. If the group member ate 2 scrambled eggs, then choose 2. 6. If ketchup was added, then make sure to check the Add-ons box. 7. The results for 2 large scrambled eggs cooked with fat and topped with ketchup would look like this. Total Calories 202 calories Extras* 86 calories *(solid fats, added sugars, and alcohol) 8. Add the total calories and put this information in the chart on page 5 of the Student Journal. When you have competed the calculations for the first food item, press New Search. Then repeat for all of the other food items in your meal. 6