Types of Energy Resources in Biology

The Sun

• Plants are primary users of the sun's energy through the process of photosynthesis. Plants have cells called chloroplasts that contain chlorophyll. The chloroplasts collect sunlight and, using the chlorophyll, convert this energy into sugars such as glucose. Carbon dioxide from the air and water from the soil also play a part in this process. The formation of sugars in plants is one of the most important first steps in the food chain.

Sugars

• Carbohydrates are compounds that provide energy to living cells. Glucose is a carbohydrate and an essential source of energy in plant and animal life. It is a simple sugar, or monosaccharide, and is also referred to as dextrose. In humans, the metabolism processes glucose to produce carbon dioxide, water and nitrogen compounds. These provide energy that is then used by cells. Because it is a primary energy source, it requires no digestion, which is a reason for some hospital patients being put on an intravenous glucose drip. Fructose, or fruit sugar, is another important energy source for humans. Aide from fruit, it is also found in honey and is the sweetest of the sugars.

Starches

• Starch is another type of carbohydrate. In starch, glucose units join to form polysaccharides, which are capable of storing energy for later use. For example, starch forms inside grains such as wheat. The grain has an insoluble outer layer protecting the starch until its energy is needed. When it is used, the starch breaks down into small, soluble glucose units. Starch-rich foods, such as potatoes, rice and grains are important sources of energy for humans. The digestive system uses enzymes to break down a slice of bread into glucose, which then circulates around the blood as an energy source.

Adenosine Triphosphate

• Animals eat plants and convert the plant sugars into energy in the mitochondria, which are similar in function to plant chloroplasts. The mitochondria, or energy factories, produce energy-rich adenosine triphosphate (ATP) from the energy stored in food. Humans need ATP for just about every function, and it is present in the cytoplasm and nucleoplasm of every cell. All physiological functions draw directly on stored ATP, which is constantly replenished by our food consumption