NEET MDS Lessons
Biochemistry
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.
These are normally non-essential but become essential during stress, illness, or in infants.
| Conditionally Essential | When Needed |
|---|---|
| Arginine | Growth, trauma, immune stress |
| Cysteine | Liver disease, oxidative stress |
| Glutamine | Critical illness, burns |
| Tyrosine | PKU (phenylketonuria) patients |
| Proline, Glycine | Wound healing, collagen synthesis |
Enzyme assays measure the activity or concentration of specific enzymes in blood or tissue samples. Elevated or reduced levels often indicate organ dysfunction or cellular damage.
Enzyme Groups & Their Clinical Significance
| Enzyme Group | Function | Clinical Relevance |
|---|---|---|
| Oxidoreductases | Catalyze oxidation-reduction reactions | Liver, cardiac, and muscle injury markers |
| Transferases | Transfer functional groups between molecules | Liver and muscle enzymes (e.g., AST, ALT) |
| Hydrolases | Break chemical bonds using water | Pancreatic enzymes (e.g., amylase, lipase) |
| Lyases | Break bonds without hydrolysis or oxidation | Less commonly used in diagnostics |
| Isomerases | Rearrange molecular structures | Rarely used clinically |
| Ligases | Join molecules using ATP | Mostly research-based, not routine diagnostics |
Vitamin B12: Cobalamin
Vitamin B12, also known as cobalamin, aids in the building of genetic material, production of normal red blood cells, and maintenance of the nervous system.
RDA The Recommended Dietary Allowance (RDA) for vitamin B12 is 2.4 mcg/day for adult males and females
Vitamin B12 Deficiency
Vitamin B12 deficiency most commonly affects strict vegetarians (those who eat no animal products), infants of vegan mothers, and the elderly. Symptoms of deficiency include anemia, fatigue, neurological disorders, and degeneration of nerves resulting in numbness and tingling.
Anaerobic organisms lack a respiratory chain. They must reoxidize NADH produced in Glycolysis through some other reaction, because NAD+ is needed for the Glyceraldehyde-3-phosphate Dehydrogenase reaction (see above). Usually NADH is reoxidized as pyruvate is converted to a more reduced compound, that may be excreted.
The complete pathway, including Glycolysis and the re-oxidation of NADH, is called fermentation.
For example, Lactate Dehydrogenase catalyzes reduction of the keto group in pyruvate to a hydroxyl, yielding lactate, as NADH is oxidized to NAD+.
Skeletal muscles ferment glucose to lactate during exercise, when aerobic metabolism cannot keep up with energy needs. Lactate released to the blood may be taken up by other tissues, or by muscle after exercise, and converted via the reversible Lactate Dehydrogenase back to pyruvate
Fermentation Pathway, from glucose to lactate (omitting H+):
glucose + 2 ADP + 2 Pi → 2 lactate + 2 ATP
Anaerobic catabolism of glucose yields only 2 “high energy” bonds of ATP.
Enzyme Kinetics
Enzymes are protein catalysts that, like all catalysts, speed up the rate of a chemical reaction without being used up in the process. They achieve their effect by temporarily binding to the substrate and, in doing so, lowering the activation energy needed to convert it to a product.
The rate at which an enzyme works is influenced by several factors, e.g.,
- the concentration of substrate molecules (the more of them available, the quicker the enzyme molecules collide and bind with them). The concentration of substrate is designated [S] and is expressed in unit of molarity.
- the temperature. As the temperature rises, molecular motion - and hence collisions between enzyme and substrate - speed up. But as enzymes are proteins, there is an upper limit beyond which the enzyme becomes denatured and ineffective.
- the presence of inhibitors.
- competitive inhibitors are molecules that bind to the same site as the substrate - preventing the substrate from binding as they do so - but are not changed by the enzyme.
- noncompetitive inhibitors are molecules that bind to some other site on the enzyme reducing its catalytic power.
- pH. The conformation of a protein is influenced by pH and as enzyme activity is crucially dependent on its conformation, its activity is likewise affected.
The study of the rate at which an enzyme works is called enzyme kinetics.
Clinical significance
Primary hyperparathyroidism is due to autonomous, abnormal hypersecretion of PTH in the parathyroid gland
Secondary hyperparathyroidism is an appropriately high PTH level seen as a physiological response to hypocalcemia.
A low level of PTH in the blood is known as hypoparathyroidism and is most commonly due to damage to or removal of parathyroid glands during thyroid surgery.