Vitamin B6: Pyridoxine, Pyridoxal, Pyridoxamine

Aids  in protein metabolism and red blood cell formation. It is also involved in the body’s production of chemicals such as insulin and hemoglobin.

Vitamin B6 Deficiency Deficiency symptoms include skin disorders, dermatitis, cracks at corners of mouth, anemia, kidney stones, and nausea. A vitamin B6 deficiency in infants can cause mental confusion.

The Phosphate Buffer System

This system, which acts in the cytoplasm of all cells, consists of H₂PO₄^–  as proton donor and HPO₄ ^2– as proton acceptor :

H₂PO₄^–  = H⁺ + H₂PO₄^–

The phosphate buffer system works exactly like the acetate buffer system, except for the pH range in which it functions. The phosphate buffer system is maximally effective at a pH close to its pKa of 6.86 and thus tends to resist pH changes in the range between 6.4 and 7.4. It is, therefore, effective in providing buffering power in intracellular fluids.

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.

TRIGLYCEROL

Triacylglycerols (formerly triglycerides) are the esters of glycerol with fatty acids. The fats and oils that are widely distributed in both  plants and animals are chemically triacylglycerols.

They are insoluble in water and non-polar in character and commonly known as neutral fats.

Triacylglycerols are the most abundant dietary lipids. They are the form in which we store reduced carbon for energy. Each triacylglycerol has a glycerol backbone to which are esterified 3 fatty acids. Most triacylglycerols are "mixed." The three fatty acids differ in chain length and number of double bonds

Structures of acylglycerols :

Monoacylglycerols,  diacylglycerols and triacylglycerols, respectively consisting of one, two and three molecules of fatty acids esterified to

a molecule of glycerol

Lipases hydrolyze triacylglycerols, releasing one fatty acid at a time, producing  diacylglycerols, and eventually glycerol

Glycerol arising from hydrolysis of triacylglycerols is converted to the Glycolysis intermediate dihydroxyacetone phosphate, by reactions catalyzed by:
(1) Glycerol Kinase
(2) Glycerol Phosphate Dehydrogenase

Free fatty acids, which in solution have detergent properties, are transported in the blood bound to albumin, a serum protein produced by the liver.
Several proteins have been identified that facilitate transport of long chain fatty acids into cells, including the plasma membrane protein CD36

During fasting or carbohydrate starvation, oxaloacetate is depleted in liver because it is used for gluconeogenesis. This impedes entry of acetyl-CoA into Krebs cycle. Acetyl-CoA then is converted in liver mitochondria to ketone bodies, acetoacetate and b-hydroxybutyrate.

 Three enzymes are involved in synthesis of ketone bodies:

b-Ketothiolase. The final step of the b-oxidation pathway runs backwards, condensing 2 acetyl-CoA to produce acetoacetyl-CoA, with release of one CoA.

HMG-CoA Synthase catalyzes condensation of a third acetate moiety (from acetyl-CoA) with acetoacetyl-CoA to form hydroxymethylglutaryl-CoA (HMG-CoA).

HMG-CoA Lyase cleaves HMG-CoA to yield acetoacetate plus acetyl-CoA.

 b-Hydroxybutyrate Dehydrogenase catalyzes inter-conversion of the ketone bodies acetoacetate and b-hydroxybutyrate.

Ketone bodies are transported in the blood to other tissue cells, where they are converted back to acetyl-CoA for catabolism in Krebs cycle

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