The human body is the most wonderful machine consisting of 10000 billion cells and each of these cells has the capability of producing energy by burning food that we eat. The major sources of energy to the body are – Carbohydrates, Protein, and Fats. To produce energy, foods have to be provided to the cells in their simplest form i.e. Glucose for Carbohydrates, Amino Acids for Protein, and Triglycerides (Fatty Acids) for Fats. The powerhouse of the cells is called the Mitochondria carries out the job to convert this Glucose, Amino Acids, and Fatty Acids to Calories.
When we eat food in the form of thousands of dishes – these items have to be broken in the food pipe (medically called Gastrointestinal Tract) to their simplest forms. This is done is steps called – Digestion, and Absorption. Each of the food that we eat is first chewed, and digested in the stomach by acids and gastric juices, then further digested in the intestine by bile juice (secreted by the liver) and also juice secreted by the intestine and pancreas. The enzymes present in these juices break the food into Glucose, Amino Acids, and Fatty Acids (triglycerides). This process is called digestion.
The next step is absorption. These simplest forms of food are taken up from the intestine to the bloodstream. As soon as it is done the blood level of Glucose, Amino Acids and Triglycerides goes up. The blood – which is pumped to the whole of the body by the heart takes these absorbed products to the billions of cells and there they are assimilated (further break down) to produce energy.
Fats (also called lipids) that are present in the food or blood can be divided into three categories – Cholesterol, Triglycerides (called the natural fats), and phospholipids. Cholesterol is a type of fatty acid consisting of 27 carbon atoms and performs three important functions in our body:
1. They help in the formation of the wall of all the cells in the body.
2. Produce sex hormones – which help in the formation of sex organs of the body and allow them to work, and
3. Help in the digestion – absorption of fats in the intestine as a part of Bile juice.
About 97% of cholesterol groups secreted in the bile juice are absorbed back into the bloodstream. Apart from the cholesterol consumed in the form of food (non-vegetarian food, milk, and milk products) a considerable amount of Cholesterol is also manufactured by our liver. The cholesterol is an indispensable chemical of the body – as without it the body will die.
The oils that we consume in our food consist of fatty acids – which can be saturated or unsaturated (depending on the possibility of the addition of further Hydrogen). All these fats are absorbed in the form of triglycerides and small chain fatty acids from the intestine. The blood level of triglycerides beyond 160 mg is very bad – as it helps deposit fat inside the heart arteries. The liver also manufactures a lot of triglycerides and releases them in the blood in the form of VLDL.
Cholesterol and Triglycerides mostly travel in the blood in combination with proteins and phospholipids. Different combinations of these chemicals circulating in the blood are known as LDL (Low Density Lipoprotein) Cholesterol, HDL (High-Density Lipoprotein) Cholesterol, and VLDL (Very Low-Density Lipoprotein) Cholesterol. LDL contains 53% cholesterol in it.
In the liver – cholesterol is manufactured from Acetyl Co A, which in turn is converted into HMG (Hydroxy Methyl Glutaryl) Co A is then converted into Mevalonic acid by an enzyme called HMG Co A reductase. Mevalonic acid is then converted into cholesterol in the next few steps.
Cholesterol and Triglycerides are broken down inside the cells – and their uptake depends on a protein LDL receptor. Drugs that can influence this LDL receptor hold a lot of promise in the future and can offer a permanent solution to Heart Disease. Triglycerides are broken down to fatty acids and Glycerol by an enzyme called Lipo-protein lipase, inside the cells. Most of the triglycerides are stored inside the fat cells and can be used when less calorie (less than 1600/day) are provided to the body.
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