Basics of cellular energy (Pt. 2)
Extraction of energy from food, the mitochondria
Of all the different structures that comprise the cell, we will focus on the mitochondria. The mitochondria is where the cellular energy known as ATP is manufactured out of nutrients (oxygen and food). The mitochondria is contained inside the cytosol, the fluid portion of the cell (4).
The main substances from which cells extract energy are oxygen and the food we ingest: carbohydrates, fats, and proteins. Carbohydrates are converted into glucose by the digestive tract and liver before they reach the cell, proteins are converted into amino acids and fats into fatty acids. Then they all enter the cell. Inside the cell the food reacts chemically with the oxygen under the influence of various enzymes. Almost all of these oxidative reactions occur in the mitochondria, and the energy that is released is used to form the very high energy compound known as ATP (Adenosine triphosphate). ATP then is used throughout the cell to energize almost all the intracellular metabolic reactions.
What is ATP?
ATP is a small simple compound that supplies all the energy used by every cell in the body, including the heart. It is for this reason that it is known as the‘powerhouse of the cell’. As long as the cell is given two basic ingredients: food and oxygen, the cycle of energy utilization and supply goes on unimpeded millions of times per second in every cell in the body. This continual cycle of energy supply and demands keeps the cell fully charged with energy and maintains a constant level of ATP no matter how hard the heart is working.
When one of these ingredients is missing, sickness follows. A good example of this is lack of oxygen; oxygen starvation always results in a heart attack. Blocked arteries can deprive the heart cells of oxygenated blood flow, causing the tissues to consume their energy supplies faster than they can be restored (1).
The human heart has approximately 700 milligrams of ATP and this is enough to pulsate at a rate of one beat per second for 60 seconds. This may sound like a lot but it is a considerable slow rate for a healthy person. For this, 6,000 grams of ATP will need to be generated per day.
Magnesium is always found attached to ATP in cells. It has important functions like helping ATP move around within the cell, and attracting various structures in the cell that require energy to function.
ATP is composed of adenine, ribose and three phosphate radicals connected by high energy phosphate bonds. Each of these bonds are known as ‘high energy bonds’ because they contain about 12,000 calories of energy per mole of ATP. When ATP releases its energy, a radical is split away and ADP is formed (adenosine diphosphate), which recombines over and over to form new ATP. Because ATP can be spent and remade again and again, it is called the ‘energy currency of the cell’.
Uses of ATP
ATP is then used to:
- Supply energy for the transport of sodium, calcium, magnesium, phosphate, and chloride ions through the cell membrane, among other substances. This transport of ions is so important for the cell that some use as much as 80% of the ATP made by the cells for this purpose alone.
- Promote protein synthesis as well as phospholipids, cholesterol, etc. The synthesis of all these nutrients require thousand of molecules of ATP.
- Supply energy needed during muscle contraction.
Because of all these important functions, ATP must always be available to release its energy rapidly and almost explosively whenever it is needed in the cell. To replace ATP used by the cell other much slower chemical reactions break down carbohydrates, fats and proteins and use the energy derived from these to form new ATP (2).
ATP keeps the heart beating. With each heartbeat ions of potassium, sodium, and calcium move in and out of the cell and in and out of different organelles inside the cell. The continual flow of ions keeps the heart beating rhythmically and allows the heart to fully relax between beats and able to refill with blood for each contraction.
ATP also allows the heart to build important cellular constituents such as proteins and genetic material. These allow the heart to be repaired whenever there is enough wear.
Mitochondria, the cellular energy powerhouse
The mitochondria is considered the powerhouse because it produces most of the energy needed by the cell. Mitocondria generates more than 90% of the body’s need for energy to sustain life and they take approximately 35% of the space within the heart cell.
The way energy is produced is called ‘respiration’because it requires oxygen. It happens as follows: carbon fragments like fats and pyruvate are oxidized by oxygen that is delivered by the blood and used to make ATP. This process releases electrons, which recycle ADP back into ATP, thereby restoring energy to the cell.
ATP formed inside the mitochondria must be moved into the cytosol of the cell to release its life-giving energy. ADP from the cytosol must be moved into the michochondria, where it can recycle to ATP. Because the mitochondrial membrane is permeable to both ATP and ADP, they can be exchanged across the mitochondrial membrane, with ATP moving out and ADP moving in. Then an enzyme called ‘ATP-ADP translocase’ moves ATP and ADP across the mitochondrial membrane, keeping ATP flowing to the cell and ADP flowing to the mitochondria. This process supplies the vital energy needed to sustain life.
Oxygen does not contribute to the process directly, but acts as a metabolic garbage can, gathering up the spent electrons after they have flowed through the process, then releasing carbon dioxide (CO2) and water. Some of this is released when we exhale, and the rest is transported by the blood to the kidneys to be excreted as urine.
Around 2-5% of this oxygen is turned into free radicals. These free radicals are formed inside the mitochondrial membrane and they can accumulate rapidly because oxygen utilization occurs constantly within the mitochondria.
While an abundance of free radicals can accelerate aging and degenerative diseases,and be the major unexplained cause of congestive heart failure, research has shown that a small percentage of free radicals may play an important part in supporting life processes, like mitochondrial respiration.
Recent research has shown that we can enrich our mitochondria with nutrients. Since our diets are not balanced, supplementation has become ‘ necessary way of life’ (1). Dr. Stephen Sinatra, considers mitochondria to be the key to how we age, why we get disease any why we die prematurely.
Something else important about mitochodria is that they contain their own set of DNA, from 2 to 10 copies of DNA called mtDNA. All of this genetic material is obtained from the mother , not the father. Mitochondrial DNA makes the proteins needed for energy metabolism. Because this mitochondrial DNA is not isolated from its environment by a membrane, it is exposed to free radicals, rendering it unable to pass on genetic information. It it for this reason that we must supplement with antioxidant nutrients.
Roles of the mitochondria
The majority of the ATP is formed in the mitochondria.This is how it happens, step by step: When glucose enters the cell it is acted on by enzymes and becomes ‘pyruvic acid’ by a process known as ‘glycolysis’. The pyruvic acid derived from carbohydrates, fatty acids and amino acids are all converted into a compound known as ‘acetyl-CoA’. Another set of enzymes act on this compound in order to extract its energy through a process known as ‘Krebs cycle’.
In the ‘citric acid cycle’, acetyl-CoA is split into its components: hydrogen atoms and carbon dioxide, the latter eventually comes out of the cell, while the hydrogen atoms are highly reactive and combine with oxygen. This releases a tremendous amount of energy which is used by the mitochondria to convert large amounts of ADP to ATP. The newly formed ATP is transported out of the mitochondria into all parts of the cell and used as energy for the cell functions.
Hearts need a constant supply of energy
As long as the cell is supplied with two basic ingredients: food and oxygen, the cycle of energy use and supply goes on unimpeded millions of times per second in every cell in the body. Since the amount of ATP available is small compared with the demand, the cells must continue manufacturing energy. The continual supply of ATP is necessary to maintaining cardiac function.
In heart cells most of the ATP is present in the cell in two cellular structures: the cytosol and the mitochondria. The cytosol is the fluid portion of the cell that contains main constituents of the cell including the mitochondria.Each heart cell can contain as many as 5,000 mitochondria, If the heart works extra hard, like it is the case of ischemic heart disease, the ATP pool may increase in order to get more energy (1).
Once ATP releases its energy most of the ADP that is generated returns to the mitochondria to be recycled back into ATP. After ATP forms again it leaves the mitochondria and moves to the region of the cell needing energy. A small amount of the ADP remains in the cytosol, where it is reformed into ATP more slowly. This ATP is generally associated with cell membranes and provides the energy needed to control ion movement into and out of the cell (1).
There is ATP also outside the cell that is important for cell energy but it is small compared with the amount of ATP found inside the cell. In diseased hearts, the amount of ATP found outside the cell can be up to ten times higher than in healthy hearts.This extracellular ATP has a major function of forming adenosine, a strong vasodilator. ‘In ischemic heart conditions, the vasodilatory effect of adenosine helps open blood vessels, allowing more blood and oxygen to flow to the heart’(1).
Measuring cellular energy
In the cell there are hundreds of different enzymes whose job is to accelerate biochemical reactions. For this reason, they can be compared to spark plugs in a car, and the amount of energy generating material available to gasoline. Enough energy is needed for the spark to act on it and speed up these reactions. Enzymes that release the chemical energy in ATP are called ‘ATPases’.
How energy translates to work in the body
The human heart has four chambers, two upper chambers, called ‘left and right atria’, two lower chambers, called ‘left and right ventricles’. When the heart beats there are several stages that involve energy within the ventricular muscles.
‘Systolic function’ refers to the stage of the heartbeat when the lower chambers contract, squeezing blood out of the arteries . This requires adequate ATP energy in cells of the heart muscle and a strong muscle to respond and contract effectively. Contraction empties most of the blood out of the heart chambers, but requires the least amount of cellular energy.This means that even in cases of exhaustion there is still energy left in the heart to allow our body to rest. In terms of blood pressure, contraction corresponds to the upper number in blood pressure measurement.
After the contraction phase there is a brief period of rest, 1/3 of a second long. This is the ‘relaxation’ or ‘diastolic phase’, where the heart refills with blood for the next contraction.The relaxation stage also depends on energy and on the ability of the heart to ‘stretch without sagging, fill and accommodate adequate blood volume. (1)’ A lot more energy is needed for the heart to relax than to force it to contract for two reasons:
- A lot of energy is needed to separate the bonds (called ‘rigor bonds’)formed during contraction in order to allow the muscle to return to its relaxed state.
- During relaxation, energy is also needed to remove the calcium ions from the cell following contraction. This is how it works: When the heart is preparing to contract, large amounts of calcium rush into the cell, helping the heart contract. When contraction is over, calcium must be pumped out of the cytosol, this requires ATP. The calcium pump has two sites for ATP and both have to be attached to ATP before the pump can work. This process is similar to what is known as ‘writer’s cramp in which the muscles of the finger get so tight after being used without pause that they cannot relax. This is caused by the fact that all the energy has been used to contract the muscle holding the pencil. Because there is no energy left, calcium cannot be discharged from the cytosol and the rigor bonds formed in the muscle fibers cannot be broken. In the case of the heart, the heart will not be able to fully relax, which means that it cannot be filled with blood properly and pump it to the whole body.This is what is called ‘dyastolic dysfunction’. It is characterized by a thickening and stiffening of the walls of the ventricles, which increases blood pressure, reduces the amount of blood discharged from the heart and makes it harder for the heart to fill.It is an early sign of cardiac problems that around 25% of the population over the age of 45, both male and female have. Around 50% of this percentage does not know they have this condition which puts them at risk for congestive heart failure.
Concluding, the heart needs a constant supply of energy. A key player in this supply of energy is a circulatory system that is fluid enough to deliver nutrients and oxygen to the heart cells. Only when this is the case can cells manufacture ATP to keep the cycle of energy use and supply unimpeded millions of times per second in every cell in the body to keep the cell fully charged, no matter how hard the heart is working.
The ‘Heart and Body Extract’, because of its role in improving circulation can help carry oxygen and nutrients to the cell. Make sure you add ‘Heart and Body Extract’ to your health protocol today!
Thank you for reading.
- Sinatra, Stephen T. The Sinatra Solution: Metabolic Cardiology. Laguna Beach, CA: Basic Health, 2011. Print.
- Guyton, Arthur C., and John E. Hall. Textbook of Medical Physiology. Philadelphia, PA: Saunders, 1996. Print.