MDS PREP
Which of the following dental tissues is most likely to be effected by Vit-A
deficiency
1. enamel
2. dentin
3. cementum
4. pulp
Biochemistry Answer: 1
Enamel most likely effected by deficiency of vitamin A
Glycolysis occurs in:
1. Cytoplasm
2. Mitochondrion
3. Both In cytoplasm and mitochondria
4. Only in presence of O2
Biochemistry
Answer: 1
Glycolysis is a metabolic process that occurs in the cytoplasm of the cell.
The process is central to the conversion of glucose into energy in the form of
adenosine triphosphate (ATP) and is a fundamental part of cellular respiration.
1. Cytoplasm: Glycolysis takes place in the cytoplasm of the cell. The cytoplasm
is the fluid-filled space between the cell membrane and the nucleus (and other
organelles in eukaryotes) where various metabolic reactions occur. This process
involves a series of enzymatic reactions that break down one molecule of glucose
into two molecules of pyruvate, yielding two net molecules of ATP and two
molecules of NADH (a reduced form of nicotinamide adenine dinucleotide) along
with some other byproducts.
2. Mitochondrion: Although glycolysis does not occur in the mitochondrion, the
mitochondrion plays a crucial role in the subsequent stages of glucose
metabolism. After glycolysis, the pyruvate molecules produced in the cytoplasm
can be transported into the mitochondria, where they are further processed in
the citric acid cycle (also known as the Krebs cycle or TCA cycle) and the
electron transport chain to produce more ATP.
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.
The essential. sulphur containing amino acid is:
1. Methionine 2. Cystetne
3. Cystine 4. Valine
Biochemistry
Answer: 1
Methionine is sulphur containing AminoAcid
Urea formation take place in liver by:
1. Salvage pathway
2. Krebs cycle
3. Krebs Henseleit cycle
4. none
Biochemistry
Answer: 3
The synthesis of urea takes place in the liver by the process called ''Ornithine
cycle'' or "Urea cycle"
This cycle was discovered by Hans Krebs and Kurt Henseleit in the year 1932.
The Ornithine cycle is completed in 5 steps:
1. Conversion of ammonia into carbamoyl phosphate
2.The transfer of carbamoyl group from carbamoyl phosphate to ornithine
3. Releasing of the formed citrulline into the cytosol
4. Cleavage of argininosuccinate
5. Hydrolysis of Arginine: The final step involves the hydrolysis of Arginine
into urea and ornithine
Arginase is the sixth and final enzyme of this cycle.
All of the following statements are true for the acetylcholinesterase receptor
EXCEPT that it
1). opens an ion channel.
2). binds to succinylcholine.
3). undergoes irreversible conformational changes when exposed to carbamates
4). is inactivated in myasthenia gravis
Biochemistry
Answer: 2
Acetylcholinesterase receptor opens an ion channel, undergoes irreversible conformational changes when exposed to carbamates , it is inactivated in myasthenia gravis
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.
The concentration of ketones is increased in body due to:
1. Starvation
2. High fat diet
3. Diabetes mellitus
4. All of the above
Biochemistry
Answer: 4
The concentration of ketones is increased in body due to:
1. Starvation
2. High fat diet
3. Diabetes mellitus