Nokea
The compound that enters the Krebs cycle and combines with oxaloacetic acid is
- A. citric acid.
- B. pyruvic acid.
- C. acetyl-CoA.
- D. phosphoglyceraldehyde.
Correct Answer: C
Rationale: The correct answer is C: acetyl-CoA. Acetyl-CoA is the compound that combines with oxaloacetic acid at the beginning of the Krebs cycle to form citric acid. This step is essential for the cycle to proceed, making acetyl-CoA the correct choice.
A: Citric acid is formed after acetyl-CoA combines with oxaloacetic acid, so it is a product of the reaction, not the compound that enters the cycle.
B: Pyruvic acid is converted to acetyl-CoA in a separate process before entering the Krebs cycle.
D: Phosphoglyceraldehyde is not involved in the Krebs cycle; it is a compound in glycolysis.
You may also like to solve these questions
A patient presented with fever and cough. A sputum sample stained by Gram's method revealed Gram-positive diplococci with a capsule. What is the likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive diplococci with a capsule is characteristic of S. pneumoniae. This bacterium is a common cause of pneumonia, especially in patients with fever and cough. It is also known for causing infections such as otitis media and sinusitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form diplococci or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus commonly associated with meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative rod, not a diplococcus, and is more commonly associated with pneumonia in immunocompromised patients.
Which of the following bacteria is responsible for causing the disease known as whooping cough?
- A. Bordetella pertussis
- B. Clostridium tetani
- C. Haemophilus influenzae
- D. Staphylococcus aureus
Correct Answer: A
Rationale: Step 1: Bordetella pertussis is the causative agent of whooping cough, also known as pertussis.
Step 2: This bacterium produces toxins that damage the respiratory tract, leading to severe coughing fits.
Step 3: Clostridium tetani causes tetanus, Haemophilus influenzae causes respiratory infections, and Staphylococcus aureus causes skin infections.
Step 4: Therefore, A is the correct answer as it is the only bacterium directly associated with whooping cough.
Which of the following bacteria is associated with the disease tuberculosis?
- A. Mycobacterium leprae
- B. Mycobacterium tuberculosis
- C. Streptococcus pneumoniae
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: Step 1: Mycobacterium tuberculosis is a bacterium known to cause tuberculosis.
Step 2: Mycobacterium leprae causes leprosy, not tuberculosis.
Step 3: Streptococcus pneumoniae causes pneumonia, not tuberculosis.
Step 4: Neisseria gonorrhoeae causes gonorrhea, not tuberculosis.
Conclusion: Mycobacterium tuberculosis is the correct answer as it is the only bacterium associated with tuberculosis among the choices provided.
A wound smear revealed Gram-negative rods producing blue-green pigment. The bacteria had a fruity odor. What is the causative agent?
- A. Pseudomonas aeruginosa
- B. Escherichia coli
- C. Klebsiella pneumoniae
- D. Proteus mirabilis
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known to produce a blue-green pigment called pyocyanin, which is characteristic of the organism. Additionally, it has a distinct fruity odor due to the production of certain volatile compounds. Escherichia coli (B) does not produce blue-green pigment or have a fruity odor. Klebsiella pneumoniae (C) and Proteus mirabilis (D) also do not exhibit these specific characteristics associated with Pseudomonas aeruginosa.
All bacteria are __________ cells.
- A. eukaryotic
- B. prokaryotic
- C. diploid
- D. haploid
Correct Answer: B
Rationale: The correct answer is B: prokaryotic. Bacteria are prokaryotic cells because they lack a true nucleus and membrane-bound organelles. They have a simple cell structure with genetic material floating freely in the cytoplasm. Choice A (eukaryotic) is incorrect because eukaryotic cells have a nucleus and membrane-bound organelles. Choice C (diploid) is incorrect as bacteria do not have a defined ploidy level like diploid organisms do. Choice D (haploid) is also incorrect as bacteria do not have a true haploid or diploid state due to their lack of a defined nucleus.