NEET MDS Lessons
Biochemistry
Folate: Folic Acid, Folacin Folate, also known as folic acid or folacin, aids in protein metabolism, promoting red blood cell formation, and lowering the risk for neural tube birth defects. Folate may also play a role in controlling homocysteine levels, thus reducing the risk for coronary heart disease.
RDA for folate is 400 mcg/day for adult males and females. Pregnancy will increase the RDA for folate to 600 mcg/day.
Folate Deficiency
Folate deficiency affects cell growth and protein production, which can lead to overall impaired growth. Deficiency symptoms also include anemia and diarrhea.
A folate deficiency in women who are pregnant or of child bearing age may result in the delivery of a baby with neural tube defects such as spina bifida.
| Enzyme | Clinical Use | Indicates |
|---|---|---|
| CK (Total) | Muscle injury, rhabdomyolysis | Trauma, statin-induced myopathy |
| CK-MM | Skeletal muscle-specific | Muscular dystrophies |
| AST | Also elevated in muscle damage | Used alongside CK |
| LDH | Non-specific marker | Muscle, liver, or cardiac damage |
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
| Enzyme | Clinical Use | Timing |
|---|---|---|
| Troponin I/T | Gold standard for myocardial infarction | Rises in 3–6 hrs, peaks at 12–24 hrs |
| CK-MB | Specific to cardiac muscle damage | Rises in 4–6 hrs, peaks at 24 hrs |
| LDH (Isoenzyme 1) | Used historically for MI diagnosis | Peaks at 48–72 hrs |
Troponins remain elevated for up to 10 days—ideal for late diagnosis.
Titration of a weak acid with a strong base
• A weak acid is mostly in its conjugate acid form
• When strong base is added, it removes protons from the solution, more and more acid is in the conjugate base form, and the pH increases
• When the moles of base added equals half the total moles of acid, the weak acid and its conjugate base are in equal amounts. The ratio of CB / WA = 1 and according to the HH equation, pH = pKa + log(1) or pH = pKa.
• If more base is added, the conjugate base form becomes greater till the equivalance point when all of the acid is in the conjugate base form.
Protein folding is essential for proper biological function. When folding goes wrong, it can trigger a cascade of pathological effects. Here are three key examples:
1. Alzheimer’s Disease
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Misfolded Protein: Amyloid-β (Aβ) and tau
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Mechanism:
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Aβ peptides misfold and aggregate into amyloid plaques in the brain.
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Tau proteins form neurofibrillary tangles inside neurons.
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Impact:
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Neuronal death, memory loss, cognitive decline.
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Progressive neurodegeneration.
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Fun Fact: These plaques can be seen in brain imaging and are a hallmark of Alzheimer’s pathology.
2. Prion Diseases (e.g., Mad Cow Disease, Creutzfeldt-Jakob Disease)
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Misfolded Protein: Prion protein (PrP^Sc)
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Mechanism:
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Normal prion protein (PrP^C) misfolds into a pathogenic form (PrP^Sc).
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PrP^Sc induces other prion proteins to misfold, creating a chain reaction.
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Impact:
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Rapid brain degeneration, motor dysfunction, fatal outcomes.
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No immune response—prions are host proteins, not foreign invaders.
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Unique Feature: Prions are infectious proteins—no DNA or RNA involved.
3. Sickle Cell Anemia
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Misfolded Protein: Hemoglobin (HbS mutation)
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Mechanism:
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A single amino acid substitution (valine for glutamic acid) in β-globin.
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Causes hemoglobin to polymerize under low oxygen, distorting red blood cells into a sickle shape.
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Impact:
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Blocked blood flow, pain crises, organ damage.
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Reduced oxygen-carrying capacity.
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Note: Unlike amyloid diseases, this is a structural misfolding due to a genetic mutation.
Function of Calcium
The major functions of calcium are
(a) Excitation and contraction of muscle fibres needs calcium. The active transport system utilizing calcium binding protein is called Calsequestrin. Calcium decreases neuromuscular irritability.
(b) Calcium is necessary for transmission of nerve impulse from presynaptic to postsynaptic region.
(c) Calcium is used as second messenger in system involving protein and inositol triphosphate.
(d) Secretion of insulin, parathyroid hormone, calcium etc, from the cells requires calcium.
(e) Calcium decrease the passage of serum through capillaries thus, calcium is clinically used to reduce allergic exudates.
(f) Calcium is also required for coagulation factors such as prothrombin.
(g) Calcium prolongs systole.
(h) Bone and teeth contains bulk quantity of calcium.