So it's not surprising that many people think of it in its simplest sense: as something that influences how easily our bodies gain or lose weight. That's where calories come in. A calorie is a unit that measures how much energy a particular food provides to the body. A chocolate bar has more calories than an apple, so it provides the body with more energy — and sometimes that can be too much of a good thing.
Just as a car stores gas in the gas tank until it is needed to fuel the engine, the body stores calories — primarily as fat. If you overfill a car's gas tank, it spills over onto the pavement. Likewise, if a person eats too many calories, they "spill over" in the form of excess body fat. The number of calories someone burns in a day is affected by how much that person exercises , the amount of fat and muscle in his or her body, and the person's basal metabolic rate BMR. BMR is a measure of the rate at which a person's body "burns" energy, in the form of calories, while at rest.
The BMR can play a role in a person's tendency to gain weight. For example, someone with a low BMR who therefore burns fewer calories while at rest or sleeping will tend to gain more pounds of body fat over time than a similar-sized person with an average BMR who eats the same amount of food and gets the same amount of exercise.
BMR can be affected by a person's genes and by some health problems. It's also influenced by body composition — people with more muscle and less fat generally have higher BMRs. But people can change their BMR in certain ways.
For example, a person who exercises more not only burns more calories, but becomes more physically fit, which increases his or her BMR. September 04, Receive an email when new articles are posted on.
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Back to Healio. Read more about energy metabolism. A wrecking ball can perform a large amount of damage, even when moving slowly. However, a still wrecking ball cannot perform any work and therefore has no kinetic energy.
A speeding bullet, a walking person, the rapid movement of molecules in the air that produces heat, and electromagnetic radiation, such as sunlight, all have kinetic energy. What if that same motionless wrecking ball is lifted two stories above a car with a crane? If the suspended wrecking ball is not moving, is there energy associated with it? Yes, the wrecking ball has energy because the wrecking ball has the potential to do work.
This form of energy is called potential energy because it is possible for that object to do work in a given state. Objects transfer their energy between potential and kinetic states. Once the ball is released, its kinetic energy increases as the ball picks up speed. At the same time, the ball loses potential energy as it nears the ground.
Other examples of potential energy include the energy of water held behind a dam or a person about to skydive out of an airplane. Potential energy vs. Moving water, such as in a waterfall or a rapidly flowing river, has kinetic energy. Potential energy is not only associated with the location of matter, but also with the structure of matter. A spring on the ground has potential energy if it is compressed, as does a rubber band that is pulled taut. The same principle applies to molecules.
On a chemical level, the bonds that hold the atoms of molecules together have potential energy. This type of potential energy is called chemical energy, and like all potential energy, it can be used to do work.
For example, chemical energy is contained in the gasoline molecules that are used to power cars. When gas ignites in the engine, the bonds within its molecules are broken, and the energy released is used to drive the pistons.
The potential energy stored within chemical bonds can be harnessed to perform work for biological processes. Different metabolic processes break down organic molecules to release the energy for an organism to grow and survive. Chemical energy : The molecules in gasoline octane, the chemical formula shown contain chemical energy.
This energy is transformed into kinetic energy that allows a car to race on a racetrack. An anabolic pathway requires energy and builds molecules while a catabolic pathway produces energy and breaks down molecules. The processes of making and breaking down carbohydrate molecules illustrate two types of metabolic pathways. A metabolic pathway is a step-by-step series of interconnected biochemical reactions that convert a substrate molecule or molecules through a series of metabolic intermediates, eventually yielding a final product or products.
For example, one metabolic pathway for carbohydrates breaks large molecules down into glucose. Another metabolic pathway might build glucose into large carbohydrate molecules for storage. The first of these processes requires energy and is referred to as anabolic. The second process produces energy and is referred to as catabolic. Consequently, metabolism is composed of these two opposite pathways:. Anabolic and catabolic pathways : Anabolic pathways are those that require energy to synthesize larger molecules.
Catabolic pathways are those that generate energy by breaking down larger molecules. Anabolic pathways require an input of energy to synthesize complex molecules from simpler ones.
One example of an anabolic pathway is the synthesis of sugar from CO 2. Other examples include the synthesis of large proteins from amino acid building blocks and the synthesis of new DNA strands from nucleic acid building blocks. Catabolic pathways involve the degradation of complex molecules into simpler ones, releasing the chemical energy stored in the bonds of those molecules.
Some catabolic pathways can capture that energy to produce ATP, the molecule used to power all cellular processes. Other energy-storing molecules, such as lipids, are also broken down through similar catabolic reactions to release energy and make ATP. Chemical reactions in metabolic pathways rarely take place spontaneously. Each reaction step is facilitated, or catalyzed, by a protein called an enzyme.
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