Energy

Energy is defined as strength or power, efficiently exerted. It fuels your body's biological processes and physical activities. It also sustains the work of biosynthesis of cellular and extracellular components, the transport of ions and organic chemicals against concentration gradients, the conduction of electrical impulses in the nervous system, the movement of cells, and the coordination of your whole body. 

Energy is essentially needed to operate the biochemical machinery of the entire body. The functions of energy are classified into three types:

• Transport Work - Energy is used to transport substances across cell membranes.
• Mechanical Work - Energy is used to facilitate mechanical activities in the body such as muscle contraction, blood circulation, and gross body movement. 
• Chemical Work - Energy is used to synthesize the multi-thousands types of macromolecules that the cells need for existence.

ATP (Adenosine Triphosphate), The Primary Energy Currency
ATP serves as the primary energy currency of the cell. ATP is the most widely distributed high-energy compound within your body. It is used to build complex molecules, contract muscles, and generate electricity in your nerves. All fuel sources of nature such as air and food produce ATP, which in turn empowers every activity of your cells. The energy level it carries is just the right amount for most biological reactions. 

Production of Energy
The continual and uninterrupted production of energy is an important function of the cells. In order to produce an adequate supply of energy, the cells of the body require biofuels (sugars, fats, proteins) and certain essential nutrients like vitamins, minerals, trace elements, and amino acids that act as biocatalysts on these fuels to accelerate the enzyme reactions involved in energy production. These essential nutrients, enzymes, and other biomolecules of cells have unique chemical structures and unique electromagnetic frequency patterns that produce energy.

Even when your body is completely at rest, all your cells are continuously metabolizing or releasing energy by the action of enzymes on chemical substrates. They use that energy for the synthesis or breakdown of vital substances, for maintaining the integrity of the cell by regulating influx and efflux across the membrane, and for carrying out their own specialized functions such as to facilitate heart beat and muscles used for breathing.

Basal life processes includes:

• Cell metabolism
• Synthesis and metabolism of enzymes and hormones
• Growth and synthesis of new tissues
• Transport of substances throughout the body
• Maintenance of body temperature
• Muscular activity
• Ongoing functioning of muscles including the heart and brain function

Sunlight is the ultimate source of energy for life. Photosynthetic cells use light energy to produce chemical energy and reduce compounds for the convertion of carbon dioxide into organic chemicals such as glucose. The energy from the oxidation of carbohydrates, fats, and proteins sustains the biochemical reactions required for life.

Energy is primarily supplied from two sources:

• Carbohydrates - in the form of glycogen stored in the muscles
• Fat - stored around the body

• Anabolism - uses energy to create cells. It is the phase of metabolism in which simple substances are synthesized into the complex materials of living tissue. Anabolism is necessary for body-building, growth, and repair. It produces peptides, proteins, polysaccharides, lipids, and nucleic acids. These molecules comprise all the materials of living cells, such as membranes and chromosomes, as well as specialized products of specific types of cells, such as enzymes, antibodies, hormones, and neurotransmitters. Cells use anabolic reactions to synthesize enzymes, hormones, sugars, and other molecules needed to sustain themselves, grow, and reproduce.
• Catabolism - breaks down cells to create energy. It is the set of metabolic pathways that breaks down molecules into smaller units and releases energy. Energy released from organic nutrients during catabolism is stored within the molecule adenosine triphosphate (ATP), in the form of the high-energy chemical bonds between the second and third molecules of phosphate. The cell uses ATP for synthesizing cell components from simple precursors, for the mechanical work of contraction and motion, and for transport of substances across its membrane. ATP's energy is released when this bond is broken, turning ATP into adenosine diphosphate (ADP). The cell uses the energy derived from catabolism to fuel anabolic reactions that synthesize cell components.

Most common Causes of Low Energy Levels:

• Aging - Aging has been associated with the loss of muscle mass, often referred to as Sarcopenia. This decrease in muscle tissue begins around the age of 30, yet is dramatically observed around the age of 50. This is due to the decrease in the production of anabolic hormones such as testosterone, growth hormone and insulin-like growth factor-1, which impairs the capacity of skeletal muscles to incorporate amino acids and synthesize proteins. In addition, an increase in the release of catabolic agents, specifically interleukin-6, intensifies the rate of muscle wasting among the elderly. Muscles become less dense, which makes the arms and legs look thinner, and muscle tissues become less flexible, which results in diminished muscle function. Even mild loss of muscle strength places increased stress on certain joints like the knees, thus raises your risks of arthritis or accidental falling. The types of muscle fibers are affected by aging as well. The number of muscle fibers that contract faster (fast twitch muscles) decrease much more than the number of muscle fibers that contract slower (slow twitch muscles). Thus, muscles are not able to contract as quickly in old age which affects even simple day-to-day activities. Aging brings a number of physical changes. In women, the onset of menopause creates changes that may cause fatigue. As estrogen levels decline, many women have hot flashes, which can interrupt sleep and even lead to chronic insomnia.
  
  
• Dehydration - Your body is 75% water. Water is found in your body's intracellular space (within the cells of your body), intravascular space (blood vessels), and interstitial space (spaces between cells).  Our bodies lose water in three ways: urinating and bowel movement, perspiring, and breathing. Dehydration takes place when the amount of water leaving the body is greater than the amount being taken in. It can be caused by diarrhea, vomiting, sweating, diabetes, and burns. There is electrolyte abnormality in dehydration when important chemicals like sodium and potassium are lost from the body. Abnormal electrolyte levels manifest muscle weakness due to low potassium, heart rhythm disturbances due to either low or high potassium, and seizures due to low sodium.


• Alcohol Abuse - Unlike other food substance, alcohol does not undergo the normal digestive process. It is not converted and transported to cells and tissues; rather it is hauled directly to the bloodstream. About 20 percent of the alcohol is absorbed directly into the blood through the stomach walls and 80 percent is absorbed into the bloodstream through the small intestine. Alcohol reduces blood flow to the muscles, making you feel weak and less-energized.


• Depression - Depression is an emotional disorder that manifests many physical symptoms. Due to the symptoms of depression such as fatigue, dizziness, and trouble sleeping, weakening of the body follows. About 65% of patients report their depression is accompanied by pains and lack of energy.


• Hormonal Imbalance - The thyroid is the gland responsible for production of hormones. It controls your metabolism (the speed at which your body converts fuel into energy). A low thyroid level (hypothyroidism) can cause fatigue, muscle weakness, lethargy, weight gain, depression, memory problems, constipation, dry skin, intolerance to cold, coarse and thinning hair, brittle nails, or a yellowish tint to the skin. A high thyroid level (hyperthyroidism) can also cause fatigue, weight loss, increased heart rate, intolerance to heat, sweating, irritability, anxiety, muscle weakness, and thyroid enlargement.


• Underlying Diseases - Illnesses that become more common with age can deplete your energy. Atherosclerosis or narrowing of the arteries may lead to muscle spasm and cramps because adequate blood supply and nutrients are not able to be delivered to the appropriate muscle. Cancer, systemic lupus, rheumatoid arthritis,  AIDS, anemia, scleroderma are some illnesses that also manifest symptoms of body weakening and lack of energy.