Where is ATP made in cells?
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ATP is made in our cells by capturing some of the energy released from energy molecules when they are broken down in energy pathways. Most of the ATP made in our body is made in mitochondria (singular: mitochondrion). For this reason mitochondria are often referred to as the “powerhouses” of our cells. A relatively small portion of the ATP generated in our cells each day will be made in the intracellular fluid outside the mitochondria. As you might expect, cells with higher energy demands will have more mitochondria. This is certainly true for heart and skeletal muscle cells and cells within our liver. |
What does the term metabolism mean?
Each and every second of every day our cells are engaged in the operations that help keep them alive and well. At the same time the efforts of each cell also contribute to the proper functioning of our body as a whole. To do so each cell must perform an incredible number of chemical reactions every second. The term metabolism refers to those chemical reactions collectively.
The term metabolism is somewhat general. For instance, total body metabolism refers to all the energy released from all the chemical reactions and associated processes in our body. Said differently, total body metabolism is the total of all reactions taking place in each cell added together. However, if we wanted to describe just those chemical reactions within a specific tissue, such as muscle or bone, we would say “muscle metabolism” or “bone metabolism.” We can be even more focused and use the term metabolism to describe only those reactions associated with a single nutrient or nutrient class. For example, if we were discussing the chemical reactions that involve only proteins or carbohydrates, we would be discussing protein or carbohydrate metabolism, respectively.
In general, chemical reactions and/or pathways will release energy. Ultimately, this extra energy will be converted to heat. Since body temperature remains fairly constant, the heat produced in metabolism must be removed from our body. Therefore, our total body metabolism can be estimated by measuring how much heat is lost from our body. Researchers can do this in specialized laboratory facilities.
What is the skeleton?
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The exquisite appearance of the human body is founded upon our skeleton. Our skeleton is a combination of 206 separate bones and supporting ligaments and cartilage. The bones of our skeleton are attached to muscles, which allow us to move about. Bones also provide protection. For instance, the skull and the vertebrae enclose the brain and spinal cord, respectively, thereby protecting the invaluable central nervous system (CNS). Twelve pairs of ribs extend from our vertebrae and protect the organs of our chest. Bone also serves as a storage site for several minerals, such as calcium and phosphorus, and is the site of formation for many of our blood cells. By about six weeks of pregnancy the skeleton is rapidly developing and is visible in a sonogram. Bones continue to grow until early adulthood, complementing the growth of other body tissue. Up until this point, bones grow in both length and diameter. Around this time the longer bones of our body, such as the femur, humerus, tibia, and fibula, begin to lose the ability to grow lengthwise and our adult height is realized. Some of the bones of the lower jaw and nose continue to grow throughout our lives, although the rate of growth slows dramatically. |
As you may expect, the longest, heaviest, and strongest bone in our body is the femur or thigh bone. These bones extend nearly two feet in some of us, and provide much of the support we need against the force of gravity. Meanwhile, the three small bones in the inner ear are the smallest bones in our body. In addition, the tiny pisiform bone of the wrist is also very small, having the approximate size of a pea.
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