MDS PREP
Glycine is a:
1. Glycogenic amino acid, only
2. Ketogenic only
3. Glucogenic and ketogenic
4. Since It Is optically inactive therefore none of the above
Biochemistry
Answer: 1
Glycine is a Glycogenic amino acid, only
Which of the following vitamins is MOST likely to be involved with bone loss in the elderly?
1. Vitamin A
2. Niacin
3. Thiamine
4. Vitamin D
Biochemistry
Answer: 4
Vitamin D is crucial for the maintenance of bone health as it aids in the
absorption of calcium from the digestive tract and facilitates the incorporation
of calcium into bones. A deficiency in vitamin D can lead to osteoporosis, a
condition characterized by weak and porous bones that are more susceptible to
fractures, which is common in the elderly. While vitamin A (Answer 1) is
important for vision and skin health, and niacin (Answer 2) and thiamine (Answer
3) have roles in energy metabolism and nerve function, respectively, vitamin D's
primary role in calcium homeostasis makes it most relevant to bone loss in older
individuals.
Hyperuricemia in Lesch-Nyhan syndrome is due to a defect in which of the following pathways?
1) Purine biosynthesis
2) Pyrimidine biosynthesis
3) Purine salvage
4) Pyrimidine salvage
Biochemistry Answer: 3
Uric acid is a purine derivative, increased by purine salvage reactions that convert purines, purine ribonucleosides, and purine deoxyribonucleoside to mononucleotides (incorrect answer 4).
Such salvage reactions require much less energy than de novo synthesis (incorrect answers 1, 2). The liver is the major site of purine nucleotide biosynthesis and provides excess purines for other tissues that cannot synthesize purines.
A defect in hypoxanthine-guanine phosphoribosyl transferase, one of the enzymes of purine salvage, is responsible for purine overproduction and subsequent hyperuricemia observed in Lesch-Nyhan syndrome.
Aromatic amino acid is:
1. Tyrosine 2. Histidine
3. Arginine 4. Lysine
Biochemistry
Answer: 1
Tyrosine is Aromatic amino acid
An important rate limiting step of Kreb's cycle is catalysed by
1. pyruvate dehydrogenase
2. isocitrate dehydrogenase
3. succinate dehydrogenase
4. citrate synthetase
Biochemistry Answer: 2
Rate limiting step of Kreb's cycle is catalysed by isocitrate dehydrogenase
The biochemical defect in Osteogenesis Imperfecta, type II is:
1. a mutation in the alpha 1 chain of Type I collagen.
2. a deficiency in collagenase.
3. a deficiency in lysyl oxidase.
4. a deficiency in lysyl hydroxylase.
Biochemistry
Answer: 4
The biochemical defect in Osteogenesis Imperfecta, type II is a deficiency in lysyl hydroxylase.
Which of the following amino acids is a
precursor for epinephrine?
1. Valine
2. Leucine
3. Tyrosine
4. Cysteine
Biochemistry
Answer: 3
Epinephrine, also known as adrenaline, is a hormone and neurotransmitter that
is synthesized in the body from the amino acid tyrosine. Tyrosine is a
non-essential amino acid, which means that it can be synthesized in the body
from phenylalanine, another essential amino acid. The synthesis of epinephrine
occurs in two main steps:
1. Hydroxylation of tyrosine: Tyrosine is converted into dihydroxyphenylalanine
(DOPA) by the enzyme tyrosine hydroxylase. This is the rate-limiting step in the
synthesis of epinephrine.
2. Decarboxylation and further hydroxylation: DOPA is then decarboxylated to
form dopamine, which is further hydroxylated to produce norepinephrine.
Norepinephrine is the immediate precursor of epinephrine.
3. Formation of epinephrine: Norepinephrine is methylated by the enzyme
phenylethanolamine N-methyltransferase (PNMT) and converted into epinephrine.
The other amino acids listed are not directly involved in the synthesis of
epinephrine:
1. Valine and Leucine are branched-chain amino acids that are primarily involved
in the metabolism of muscles and energy production.
2. Cysteine is a sulfur-containing amino acid that is important for the
synthesis of proteins with disulfide bridges and is a precursor for other
molecules like glutathione and taurine, but not directly involved in the
synthesis of epinephrine.
Symptoms from a riboflavin deficiency can be:
1. Cracks in the corner of the mouth (angular stomatitis)
2. Inflammation of the tongue (glossitis)
3. Eye and skin changes
4. All of the above
Biochemistry
Answer: 4
The eye change include an increase in blood vessels and inflammation of the conjunctivae, cornea is invaded by capillaries, producing opaque areas and even ulceration. Dermatitis characterized by a greasy and scaly reddened lesion develops on the skin around the nasolabial folds and may extend to a butterfly shape on the cheeks. There many also be lesions at the corners (canthi) of the eyes and lobes of the mouth.