Medical Science Test 1 Nddc Scholarship

Fabry's disease is a rare lysosomal storage disorder caused by a mutation in the GLA gene, leading to deficient levels of the enzyme alpha-galactosidase A. This causes the abnormal accumulation of a fatty substance called ceramide trihexoside (globotriaosylceramide) in various organs. It follows an X-linked inheritance pattern. Key symptoms include episodes of severe pain in the hands and feet (acroparesthesia), skin rashes (angiokeratomas), and kidney or heart issues. Profound muscular weakness is not a hallmark of Fabry's; it is more characteristic of glycogen storage diseases or muscular dystrophies.

Sickle Cell Anaemia is an autosomal recessive disorder, meaning an individual must inherit two copies of the mutated gene (one from each parent) to manifest the disease. It is caused by a specific point mutation in the beta-globin chain of haemoglobin, resulting in 'Haemoglobin S'. This causes red blood cells to become sickle-shaped, leading to 'pain crises' (intense chronic and acute pain) and anaemia. While it is highly prevalent in people of African descent, the statement that it is 'autosomal dominant' is genetically incorrect.

The Southern blot is a molecular biology technique used specifically for the detection of a specific DNA sequence in DNA samples. It involves electrophoresis to separate DNA fragments, transferring them to a filter membrane, and using DNA hybridization with a labelled probe to identify specific sequences. Film is then used for detection (autoradiography). Antigen/antibody reactions are the hallmark of the Western blot (for proteins) or ELISA, not the Southern blot, which relies entirely on nucleic acid base-pairing.

S-adenosyl-methionine (SAM) is the primary methyl group donor in the body, essential for various biochemical reactions including the synthesis of neurotransmitters and the conversion of guanidinoacetate to phosphocreatine. It is synthesized from the amino acid methionine and ATP. However, it is a co-factor/substrate, not an enzyme. The rate-limiting enzyme of glycolysis is phosphofructokinase-1 (PFK-1). SAM has no direct role in regulating the glycolytic pathway.

Activated carriers are molecules that store energy or chemical groups in easily exchangeable forms. Examples include ATP (carries phosphate), SAM (carries methyl groups), and TPP (thiamine pyrophosphate, carries aldehyde groups). GMP (Guanosine monophosphate) is a nucleotide used in the synthesis of RNA and as a signalling molecule, but it is not an 'activated carrier' in the sense of being a high-energy donor for metabolic reactions, unlike its triphosphate counterpart, GTP.

During a single turn of the TCA cycle, three specific oxidation-reduction reactions occur that result in the reduction of \(NAD^+\) to NADH. These occur at the following steps:
1. Isocitrate to alpha-ketoglutarate
2. Alpha-ketoglutarate to succinyl-CoA
3. Malate to oxaloacetate
Thus, for every molecule of Acetyl-CoA that enters the cycle, 3 NADH molecules are produced. (Note: Since one glucose produces two pyruvates, a full glucose molecule results in 6 NADH from the TCA cycle itself).

Gluconeogenesis is an energetically expensive process. To synthesize one molecule of glucose from two molecules of pyruvate, the following energy-consuming steps occur (multiplied by 2 for the two pyruvates):
1. 2 ATP are used by Pyruvate Carboxylase to convert pyruvate to oxaloacetate.
2. 2 GTP (ATP equivalents) are used by PEP Carboxykinase to convert oxaloacetate to phosphoenolpyruvate (PEP).
3. 2 ATP are used by Phosphoglycerate Kinase to convert 3-phosphoglycerate to 1,3-bisphosphoglycerate.
The total energy requirement is \(2 + 2 + 2 = 6\) ATP equivalents.

Tryptophan is the metabolic precursor for serotonin (a neurotransmitter) and melatonin (a hormone regulating sleep). It can also be converted into Niacin (Vitamin B3) via the kynurenine pathway. Creatine, however, is synthesized primarily from the amino acids Arginine, Glycine, and Methionine. It has no structural or metabolic link to Tryptophan.

Pompe's disease is classified as Glycogen Storage Disease Type II. Unlike other GSDs that affect the cytoplasm, Pompe's is unique because it involves the accumulation of glycogen within lysosomes. This leads to progressive muscle weakness and, in its infantile-onset form, massive cardiomegaly (enlarged heart). Type I is Von Gierke's, Type III is Cori's, and Type IV is Andersen's disease.

Duodenal ulcers are almost never malignant (cancerous), which distinguishes them from gastric (stomach) ulcers that require biopsy to rule out cancer. They are more common in younger populations (30–50 years old) rather than those primarily over 65, though they can occur at any age. Interestingly, patients often experience weight gain because eating food buffers the stomach acid and relieves the pain, leading to frequent snacking. Malignancy is a characteristic typically reserved for the clinical assessment of gastric ulcers, not duodenal ones.