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Energy and Life ENERGY is the ability to do work. When cars run out of gasoline, which gives the car energy to run, the car comes to a stop. When our power goes out to our house, our appliances stop working, because no energy is available to run them. Besides just cars and appliances, living things requires energy to run too. Where to living things get energy from? Living things receive their energy from the food that they eat, but at the root of it all, the main source of energy is from the sun. Many plants and some animals receive their main source of energy directly from the sun. These types of organisms that receive their energy this way are known as AUTOTROPHS. Other organisms such as most animals, cannot receive their energy directly from the sun. Instead, they must obtain their energy from the foods that they consume. These types of organisms are known as HETEROTROPHS. Types of energy Energy can come in many forms…Light, heat, electricity, etc. Cells, however, receive their energy from certain chemical fuels. The main type of chemical fuel that provides energy for all types of cells is ADENOSINE TRIPHOSPHATE. This can be abbreviated as ATP. ATP is composed of a nitrogencontaining compound called ADENINE, a 5-carbon sugar called RIBOSE and three PHOSPHATE GROUPS. Cells can also use a compound called ADENOSINE DIPHOSPHATE (ADP), which is identical to ATP, but with one less phosphate group. How do cells receive energy from ATP and ADP? Energy is released into the cell by breaking the bonds between the phosphate groups in ATP. When bonds break, energy is released and the ATP becomes ADP. Cells can also store energy by “charging” ADP with phosphate groups. Think of ADP and ATP as a rechargeable battery. The body contains only a small amount of ATP at a time. Only enough to run cellular functions that need to be taken care of immediately. Instead, the cells use organic molecules such as glucose to store large amounts of energy that will later be turned into ATP. A single molecule of glucose can release 90 times the energy of a single ATP molecule. Adenosine Triphosphate, or ATP, is what powers the cell by taking energy from breaking of the phosphate bonds, turning ATP to ADP. ATP (3 Phosphates) Break Bonds Between Phosphate Release of Energy ADP (2 Phosphates) Plants, being autotrophs, can’t eat to get the glucose it needs for ATP production, instead, it needs an alternative method. Plants use the energy of sunlight to convert water and carbon dioxide into oxygen and highenergy glucose. Photosynthesis Equation Sunlight + 6CO2 + 6H2O C6H12O6 + 6O2 How did we first find out about PHOTOSYNTHESIS? Jan van Helmont In the 1600’s a Belgian physician known as JAN VAN HELMONT set up an experiment in which he weighed out a tree seedling and a pot full of soil. He watered it on a regular basis for 5 years. Helmont then weighed the tree and found it had grown approximately 75kg, yet the soil’s weight had remained virtually unchanged. From his experiment, he concluded that the mass gain must have been due to water because it was the only thing that he added. Helmont didn’t realize however, that there was carbon dioxide in the air which played a part. Joseph Priestly Roughly 100 years after Helmont, an English minister, JOSEPH PRIESTLY performed yet another experiment on photosynthesis. Priestly took a lit candle and placed it underneath a glass jar. Soon the candle’s flame went out. Priestly concluded that it must have been due to something in the air that got used up. (It was oxygen) Next, he put a plant underneath the jar for a few days, then lit a candle. The candle stayed lit. The plant produced enough oxygen to keep the candle burning. Jan Ingenhousz JAN INGENHOUSZ, a Dutch scientist perfected Priestly’s experiment by showing that it only worked when the plant was exposed to light. This showed that light was necessary for a plant to produce oxygen. All in all, all three scientist’s experiments showed that in the presence of light, plants transform carbon dioxide and water into glucose and oxygen.