NEET MDS Lessons
Biochemistry
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.
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.
Applications of the Henderson-Hasselbalch equation
• Calculate the ratio of CB to WA, if pH is given
• Calculate the pH, if ratio of CB to WA is known
• Calculate the pH of a weak acid solution of known concentration
• Determine the pKa of a WA-CB pair
• Calculate change in pH when strong base is added to a solution of weak acid. This is represented in a titration curve
• Calculate the pI
VITAMINS
Based on solubility Vitamins are classified as either fat-soluble (lipid soluble) or water-soluble. Vitamins A, D, E and K are fat-soluble
Vitamin C and B is water soluble.
B-COMPLEX VITAMINS
Eight of the water-soluble vitamins are known as the vitamin B-complex group: thiamin (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), vitamin B6 (pyridoxine), folate (folic acid), vitamin B12, biotin and pantothenic acid.
Weak Acids and pKa
• The strength of an acid can be determined by its dissociation constant, Ka.
• Acids that do not dissociate significantly in water are weak acids.
• The dissociation of an acid is expressed by the following reaction: HA = H+ + A- and the dissociation constant Ka = [H+ ][A- ] / [HA]
• When Ka < 1, [HA] > [H+ ][A- ] and HA is not significantly dissociated. Thus, HA is a weak acid when ka < 1.
• The lesser the value of Ka, the weaker the acid.
• Similar to pH, the value of Ka can also be represented as pKa.
• pKa = -log Ka.
• The larger the pKa, the weaker the acid.
• pKa is a constant for each conjugate acid and its conjugate base pair.
• Most biological compounds are weak acids or weak bases.
Factors regulating blood calcium level
(i) Vitamin D
(a) Vitamin D and absorption of calcium: Active form of calcium is calcitriol. Calcitriol enters intestinal wall and binds to cytoplasmic receptor and then binds with DNA causes depression and consequent transcription of gene code for calbindin. Due to increased availability of calbindin, absorption of calcium increases leading to increased blood calcium level.
(b) Vitamin D and Bone: Vitamin D activates osteoblast, bone forming cells & also stimulates secretion of alkaline phosphatase. Due to this enzyme, calcium and phosphorus increase.
(c) Vitamin D and Kidney: Calcitriol increase reabsorption of calcium and phosphorus by renal tubules.
(ii) Parathyroid hormone (PTH)
Normal PTH level in serum is 10-60ng/l.
(a) PTH and bones: In bone, PTH causes demineralization. It also causes recreation of collagenase from osteoclast leads to loss of matrix and bone resorption. As a result, mucopolysacharides and hydroxyproline are excreted in urine.
(b) PTH and Kidney: In kidney, PTH causes increased reabsorption of calcium but decreases reabsorption of phosphorus from kidney tubules.
(iii) Calcitonin Calcitonin decreases serum calcium level. It inhibits resorption of bone. It decreases the activity of osteoclasts and increases osteoblasts.
Hyper Calcemia When plasma Ca2+ level is more than 11mg/dl is called Hypercalcemia. It is due to parathyroid adenoma or ectopic PTH secreting tumor. calcium excreted in urine decreases excretion of chloride causing hyperchloremic acidosis.
Hypocalcemia Plasma calcium level less than 8mg/dl is called hypocalcemia. Tetany due to accidental surgical removal of parathyroid glands or by autoimmune disease. In tetany, neuromuscular irritability is increased. Increased Q-7 internal in ECG is seen. Main manifestation is carpopedal spasm. Laryngismus and stridor are also observed.
These can be synthesized by the body from other compounds.
| Non-Essential Amino Acids | Key Functions |
|---|---|
| Alanine | Energy production, glucose metabolism |
| Asparagine | Nervous system development |
| Aspartic acid | DNA synthesis, neurotransmission |
| Glutamic acid | Brain function, neurotransmitter |
| Serine | Cell membranes, metabolism |
The body makes these from carbohydrates and other amino acids.