NEET MDS Lessons
Biochemistry
LIPOPROTIENS
Lipoproteins Consist of a Nonpolar Core & a Single Surface Layer of Amphipathic Lipids
The nonpolar lipid core consists of mainly triacylglycerol and cholesteryl ester and is surrounded by a single surface layer of amphipathic phospholipid and cholesterol molecules .These are oriented so that their polar groups face outward to the aqueous medium. The protein moiety of a lipoprotein is known as an apolipoprotein or apoprotein,constituting nearly 70% of some HDL and as little as 1% of Chylomicons. Some apolipoproteins are integral and cannot be removed, whereas others can be freely transferred to other lipoproteins.
There re five types of lipoproteins, namely chylomicrons, very low density lipoproteins(VLDL) low density lipoproteins (LDL), high density Lipoproteins (HDL) and free fatty acid-albumin complexes.
Pantothenic Acid
Pantothenic Acid is involved in energy production, and aids in the formation of hormones and the metabolism of fats, proteins, and carbohydrates from food.
RDA The Adequate Intake (AI) for Pantothenic Acid is 5 mg/day for both adult males and females.
Pantothenic Acid Deficiency
Pantothenic Acid deficiency is uncommon due to its wide availability in most foods.
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
Niacin: Vitamin B3, Nicotinamide, Nicotinic Acid Niacin, or vitamin B3,
is involved in energy production, normal enzyme function, digestion, promoting normal appetite, healthy skin, and nerves.
RDA Males: 16 mg/day; Females: 14 mg/day
Niacin Deficiency : Pellagra is the disease state that occurs as a result of severe niacin deficiency. Symptoms include cramps, nausea, mental confusion, and skin problems.
ZINC
The enzyme RNA polymerase, which is required for transcription, contains zinc and it is essential for protein bio synthesis.
Deficiency in Zinc leads to poor wound healing, lesions of skin impaired spermatogenesis, hyperkeratosis, dermatitis and alopecia
Glycogen Storage Diseases are genetic enzyme deficiencies associated with excessive glycogen accumulation within cells.
- When an enzyme defect affects mainly glycogen storage in liver, a common symptom is hypoglycemia (low blood glucose), relating to impaired mobilization of glucose for release to the blood during fasting.
- When the defect is in muscle tissue, weakness and difficulty with exercise result from inability to increase glucose entry into Glycolysis during exercise.
Various type of Glycogen storage disease are
|
Type |
Name |
Enzyme Deficient |
|
I |
Von Geirke’s Disease |
Glucose -6-phosphate |
|
II |
Pompe’s Disease |
(1, 4)glucosidase |
|
III |
Cori’s Disease |
Debranching Enzymes |
|
IV |
Andersen’s Disease |
Branching Enzymes |
|
V |
McArdle’s Disease |
Muscles Glycogen Phosphorylase |
ISO-ENZYMES
Iso-enzymes are physically distinct forms of the same enzyme activity. Higher organisms have several physically distinct versions of a given enzyme, each of which catalyzes the same reaction. Isozymes arise through gene duplication and exhibit differences in properties such as sensitivity to particular regulatory factors or substrate affinity that adapts them to specific tissues or circumstances.
Isoforms of Lactate dehydrogenase is useful in diagnosis of myocardial infarction. While study of alkaline phosphatase isoforms are helpful in diagnosis of various bone disorder and obstructive liver diseases.