Nokea
Ribosomes take part in:
- A. protein synthesis
- B. break down of different substances
- C. oxidative phosphorylation
- D. inactivation of antibiotics
Correct Answer: A
Rationale: Ribosomes are responsible for protein synthesis, where they translate the genetic information from mRNA into specific amino acid sequences to form proteins. This process occurs in both prokaryotic and eukaryotic cells. Ribosomes do not participate in the breakdown of substances, which is mainly carried out by lysosomes or proteasomes. Oxidative phosphorylation involves the generation of ATP in mitochondria, not ribosomes. Ribosomes do not inactivate antibiotics; this is typically done by enzymes or chemical modifications. Therefore, the correct answer is A as ribosomes play a crucial role in protein synthesis.
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After a prolonged isoniazid treatment, the patient developed polyneuritis, paresthesia, memory disorders, and convulsions. What is the most likely mechanism of the described isoniazid side-effects?
- A. Disruption of cell membrane synthesis
- B. Inhibition of protein synthesis
- C. Inhibition of RNA-synthesis
- D. Inhibition of pyridoxal phosphate synthesis
Correct Answer: D
Rationale: The correct answer is D. Isoniazid inhibits pyridoxal phosphate synthesis, which is the active form of vitamin B6. Pyridoxal phosphate is essential for various enzymatic reactions, including neurotransmitter synthesis and myelin formation. Therefore, isoniazid-induced pyridoxal phosphate deficiency can lead to neurological symptoms like polyneuritis, paresthesia, memory disorders, and convulsions.
A: Disruption of cell membrane synthesis - This is not the mechanism of isoniazid side-effects.
B: Inhibition of protein synthesis - Isoniazid does not directly inhibit protein synthesis.
C: Inhibition of RNA-synthesis - Isoniazid does not inhibit RNA synthesis; it affects vitamin B6 metabolism.
Anticodon is:
- A. Produced during the process of replication
- B. A nucleotide triplet on the molecule of mRNA
- C. A nucleotide DNA triplet defining the amino acid which has a specific sequence on the polypeptide chain during the translation
- D. A nucleotide triplet forming a unit of genetic code in a transfer RNA molecule corresponding to a complementary codon on messenger RNA
Correct Answer: D
Rationale: The correct answer is D because an anticodon is a nucleotide triplet in a tRNA molecule that pairs with a complementary codon on mRNA during translation. Step 1: Anticodons are found in tRNA, not in DNA or mRNA. Step 2: Anticodons specifically bind to codons on mRNA to ensure correct amino acid incorporation into the growing polypeptide chain, making option D the most accurate choice. Option A is incorrect as replication does not involve anticodons. Option B is incorrect because codons, not anticodons, are found on mRNA molecules. Option C is incorrect as it describes a codon on DNA, not an anticodon on tRNA.
Which is the most prominent immunoglobulin class present in external secretions
- A. IgG
- B. IgM
- C. IgA
- D. IgE
Correct Answer: C
Rationale: The correct answer is C: IgA. IgA is the most prominent immunoglobulin class present in external secretions like saliva, tears, and mucus. It plays a crucial role in mucosal immunity by preventing pathogens from entering the body. IgG is mainly found in the blood and tissues, IgM is the first antibody produced in response to an infection, and IgE is involved in allergic reactions. IgA's presence in external secretions helps protect the body from infections at mucosal surfaces, making it the correct choice in this context.
Family Reoviridae does not include:
- A. Orthoreovirus type 3
- B. Orthomyxovirus type 1
- C. Orthoreovirus type 1
- D. Orthoreovirus type 2
Correct Answer: B
Rationale: The correct answer is B: Orthomyxovirus type 1. Family Reoviridae includes Orthoreovirus types 1, 2, and 3. Orthomyxovirus belongs to a different family, Orthomyxoviridae. Therefore, B is the correct answer. Orthoreovirus types 1, 2, and 3 are part of the Reoviridae family. Choice A, C, and D are incorrect because they are all part of the Reoviridae family which includes Orthoreoviruses.
The catarrhal stage of the whooping cough is characterized by:
- A. Decrease in paroxysms of coughing
- B. Subsequent respiratory infection for many months after the onset of pertussis
- C. Uncontrollable coughing followed by a high pitched 'whoop' sound
- D. Mild respiratory symptoms (mild coughing, sneezing or a runny nose)
Correct Answer: D
Rationale: The correct answer is D because the catarrhal stage of whooping cough is characterized by mild respiratory symptoms such as mild coughing, sneezing, or a runny nose. During this stage, the cough may start to worsen but is not yet severe.
A: Incorrect - Decrease in paroxysms of coughing is not seen in the catarrhal stage; it occurs later in the paroxysmal stage.
B: Incorrect - Subsequent respiratory infection for many months after the onset of pertussis is not a characteristic of the catarrhal stage.
C: Incorrect - Uncontrollable coughing followed by a high pitched 'whoop' sound is typical of the paroxysmal stage, not the catarrhal stage.