NEET MDS Lessons
Biochemistry
Regulation of PTH secretion
Secretion of parathyroid hormone is controlled chiefly by serum [Ca2+] through negative feedback. Calcium-sensing receptors located on parathyroid cells are activated when [Ca2+] is low.
Hypomagnesemia inhibits PTH secretion and also causes resistance to PTH, leading to a form of hypoparathyroidism that is reversible.
Hypermagnesemia also results in inhibition of PTH secretion.
Stimulators of PTH includes decreased serum [Ca2+], mild decreases in serum [Mg2+], and an increase in serum phosphate.
Inhibitors include increased serum [Ca2+], severe decreases in serum [Mg2+], which also produces symptoms of hypoparathyroidism (such as hypocalcemia), and calcitriol.
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.
These cannot be synthesized by the body and must be obtained from food.
| Essential Amino Acids | Key Functions |
|---|---|
| Histidine | Growth, tissue repair, precursor for histamine |
| Isoleucine | Muscle metabolism, immune function |
| Leucine | Muscle repair, protein synthesis |
| Lysine | Collagen formation, calcium absorption |
| Methionine | Antioxidant, methyl group donor |
| Phenylalanine | Precursor for neurotransmitters (dopamine, epinephrine) |
| Threonine | Tooth enamel, collagen, immune function |
| Tryptophan | Precursor for serotonin and melatonin |
| Valine | Muscle energy, tissue repair |
Found in: Meat, eggs, dairy, soy, legumes, quinoa
The pH scale
An acidic solution is one in which [H+ ] > [OH- ]
•In an acidic solution, [H+ ] > 10-7 , pH < 7.
•A basic solution is when [OH- ] > [H+ ].
•In a basic solution, [OH- ] > 10-7 , pOH < 7, and pH >7.
• When the pH = 7, the solution is neutral.
•Physiological pH range is 6.5 to 8.0
Riboflavin: Vitamin B2
Riboflavin, or vitamin B2, helps to release energy from foods, promotes good vision, and healthy skin. It also helps to convert the amino acid tryptophan (which makes up protein) into niacin.
RDA Males: 1.3 mg/day; Females: 1.1 mg/day
Deficiency : Symptoms of deficiency include cracks at the corners of the mouth, dermatitis on nose and lips, light sensitivity, cataracts, and a sore, red tongue.
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.
Monosaccharides: Aldoses (e.g., glucose) have an aldehyde at one end
They are classified acc to the number of carbon atoms present
Trioses, tetroses, pentose ( ribose, deoxyribose), hexoses (glucose, galactose, fructose) Heptoses (sedoheptulose)
Glyceraldehyde simplest aldose
Ketoses (e.g., fructose) have a keto group, usually at C 2.
Dihydroxyacetone simplest Ketoses
The higher sugar exists in ring form rather than chain form
Furan : 4 carbons and 1 oxygen
Pyrans : 5 carban and 1 oxygen
These result from formation of hemiacital linkage b/w carbonyl and an alcohol group