NEET MDS Lessons
Biochemistry
COENZYMES
Enzymes may be simple proteins, or complex enzymes.
A complex enzyme contains a non-protein part, called as prosthetic group (co-enzymes).
Coenzymes are heat stable low molecular weight organic compound. The combined form of protein and the co-enzyme are called as holo-enzyme. The heat labile or unstable part of the holo-enzyme is called as apo-enzyme. The apo-enzyme gives necessary three dimensional structures required for the enzymatic chemical reaction.
Co-enzymes are very essential for the biological activities of the enzyme.
Co-enzymes combine loosely with apo-enzyme and are released easily by dialysis. Most of the co-enzymes are derivatives of vitamin B complex
MAGNESIUM
The normal serum level of Magnesium is 1.8 to 2.2. mg/dl.
Functions of Magnesium
(a) Irritability of neuromuscular tissues is lowered by Magnesium
(b) Magnesium deficiency leads to decrease in Insulin dependent uptake of glucose
(c) Magnesium supplementation improves glucose tolerance
Causes such as liver cirrhosis, protein calorie malnutrition and hypo para thyroidism leads to hypomagnesemia
The main causes of hypermagnesemia includes renal failure, hyper para thyroidism, rickets, oxalate poisoning and multiple myeloma.
CLASSIFICATION OF LIPIDS
Lipids are classified as follows:
1. Simple lipids: Esters of fatty acids with various alcohols.
(a) Fats: Esters of fatty acids with glycerol. Oils are fats in the liquid state. A long-chain carboxylic acid; those in animal fats and vegetable oils often have 12–22 carbon atoms.
(b) Waxes: Esters of fatty acids with higher molecular weight monohydric alcohols. Waxes are carboxylic acid esters, RCOOR’ ,with long, straight hydrocarbon chains in both R groups
2. Complex lipids: Esters of fatty acids containing groups in addition to an alcohol and a fatty acid.
(a) Phospholipids: Lipids containing, in addition to fatty acids and an alcohol, a phosphoric acid residue. They frequently have nitrogen containing bases and other substituents,
Eg glycerophospholipids the alcohol is glycerol
sphingophospholipids the alcohol is sphingosine.
(b) Glycolipids (glycosphingolipids): Lipids containing a fatty acid, sphingosine, and carbohydrate. These lipids contain a fatty acid, carbohydrate and nitrogenous base. The alcohol is sphingosine, hence they are also called as glycosphingolipids. Clycerol and phosphate are absent
e.g., cerebrosides, gangliosides.
(c) Other complex lipids: Lipids such as sulfolipids and aminolipids. Lipoproteins may also be placed in this category.
3. Precursor and derived lipids: These include fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, and ketone bodies, hydrocarbons, lipid soluble vitamins, and hormones. Because they are uncharged, acylglycerols (glycerides), cholesterol, and cholesteryl esters are termed neutral lipids
4. Miscellaneous lipids: These include a large number of compounds possessing the characteristics of lipids e.g., carotenoids, squalene, hydrocarbons such as pentacosane (in bees wax), terpenes etc.
NEUTRAL LIPIDS: The lipids which are uncharged are referred to as neutral lipids. These are mono-, di-, and triacylglycerols, cholesterol and cholesteryl esters.
HORMONES
A hormone is a chemical that acts as a messenger transmitting a signal from one cell to another. When it binds to another cell which is the target of the message, the hormone can alter several aspects of cell function, including cell growth, metabolism, or other function.
Hormones can be classified on three primary ways as following:
1. Autocrine: An autocrine hormone is one that acts on the same cell that released it.
2. Paracrine: A paracrine hormone is one that acts on cells which are nearby relative to the cell which released it. An example of paracrine hormones includes growth factors, which are proteins that stimulate cellular proliferation and differentiation.
3. Endocrine: An endocrine hormone is one that is released into the bloodstream by endocrine glands. The receptor cells are distant from the source. An example of an endocrine hormone is insulin, which is released by the pancreas into the bloodstream where it regulates glucose uptake by liver and muscle cells.
Glycogenolysis
Breakdown of glycogen to glucose is called glycogenolysis. The Breakdown of glycogen takes place in liver and muscle. In Liver , the end product of glycodgen breakdown is glucose where as in muscles the end product is Lactic acid Under the combined action of Phosphorylase (breaks only –α-(1,4) linkage )and Debranching enzymes (breaks only α-(1,6) linkage )glycogen is broken down to glucose.
The basic characteristics of enzymes includes
(i) Almost all the enzymes are proteins and they follow the physical and chemical reactions of proteins (ii) Enzymes are sensitive and labile to heat
(iii) Enzymes are water soluble
(iv) Enzymes could be precipitated by protein precipitating agents such as ammonium sulfate and trichloroacetic acid.
Biotin
Biotin helps release energy from carbohydrates and aids in the metabolism of fats, proteins and carbohydrates from food.
RDA The Adequate Intake (AI) for Biotin is 30 mcg/day for adult males and females
Biotin Deficiency Biotin deficiency is uncommon under normal circumstances, but symptoms include fatigue, loss of appetite, nausea, vomiting, depression, muscle pains, heart abnormalities and anemia.