Question
What property of antibiotics makes them effective in the treatment of infectious diseases?
A. They stimulate the production of antibodies.
B. They block metabolic pathways in prokaryotes.
C. They block the metabolic processes in viruses.
D. They inhibit mitosis in eukaryotes.
▶️Answer/Explanation
Answer: B. They block metabolic pathways in prokaryotes.
Explanation:
Antibiotics are effective because they target and block specific metabolic pathways that are unique to prokaryotic cells (bacteria). For example, many antibiotics inhibit bacterial cell wall synthesis or protein synthesis, processes that do not occur in human cells, making them selective and effective against bacterial infections.
Option Evaluation:
A. Incorrect — Antibiotics do not stimulate antibody production; that is the role of the immune system.
B. Correct — Antibiotics interfere with bacterial metabolism or structures, stopping bacterial growth or killing bacteria.
C. Incorrect — Viruses lack metabolic pathways and rely on host cells, so antibiotics are ineffective against viruses.
D. Incorrect — Antibiotics do not inhibit mitosis in eukaryotic cells; this would harm human cells.
Question
Which cells are subject to attack by HIV?
A. Lymphocytes
B. Erythrocytes
C. Platelets
D. Phagocytes
▶️Answer/Explanation
Answer: A. Lymphocytes
Explanation:
HIV (Human Immunodeficiency Virus) specifically targets lymphocytes, particularly a type called T-helper cells (CD4+ T cells). These cells play a crucial role in the immune system by helping to activate other immune cells. When HIV infects and destroys these lymphocytes, it weakens the immune system, making the body vulnerable to infections.
Options Evaluation:
A. Correct — Lymphocytes, especially T-helper cells, are the primary target of HIV.
B. Incorrect — Erythrocytes (red blood cells) do not have nuclei or the receptors HIV needs to infect cells.
C. Incorrect — Platelets are involved in blood clotting and are not targets of HIV.
D. Incorrect — Phagocytes engulf pathogens but are not the main cells infected by HIV.
Question
A combination of antibiotics and bioengineered antibodies to bacterial antigens is now being used in hospitals to treat bacterial infections. What makes this method more effective than just using antibiotics alone?
A. Increases selective pressure on bacteria to evolve antibiotic resistance
B. Bacteria become noticeable to phagocytes
C. Antibodies can be cloned by the immune system
D. Blocks metabolic pathways in bacteria
▶️Answer/Explanation
Answer: B. Bacteria become noticeable to 
phagocytes
Explanation:
Using a combination of antibiotics and bioengineered antibodies enhances treatment effectiveness because the antibodies bind specifically to bacterial antigens. This tagging makes bacteria more recognizable to phagocytes, the immune cells that engulf and destroy pathogens. This process, called opsonization, helps the immune system clear infections more efficiently than antibiotics alone.
Options Evaluation:
A. Incorrect — Increasing selective pressure on bacteria would actually encourage antibiotic resistance, which is undesirable.
B. Correct — Antibodies mark bacteria, making them easier targets for phagocytes.
C. Incorrect — Antibodies themselves are not cloned by the immune system; B cells produce antibodies. Bioengineered antibodies provide immediate assistance.
D. Incorrect — Blocking metabolic pathways is how antibiotics work, but the addition of antibodies improves immune recognition rather than blocking metabolism.
Question
The diagram shows the major events involved in the formation of a blood clot.
What is Factor Y?
A. Fibrin
B. Prothrombin
C. Fibrinogen
D. Thrombin
▶️Answer/Explanation
Answer: D. Thrombin
Explanation:
This diagram represents the blood clotting cascade, which involves a series of enzymatic activations to ultimately form a blood clot. Let’s break down the key components:
Key Steps in Blood Clotting:
Tissue Damage triggers release of clotting factors from:
Platelets
Damaged cells
Plasma (e.g., calcium, vitamin K)
This initiates an enzymatic cascade, activating clotting factors in a specific order.
Factor W and Factor X are upstream activators (Factor X is often Stuart-Prower factor).
Factor Y is Thrombin, which:
Is formed from prothrombin
Converts fibrinogen (Factor Z) into fibrin, forming the clot
Factor Z (the final step before clot formation) is fibrin.
Mapping the Options:
| Option | Substance | Role in Cascade | Likely Label |
|---|---|---|---|
| A | Fibrin | Forms the clot mesh | Factor Z |
| B | Prothrombin | Inactive precursor of thrombin | Precursor to Y |
| C | Fibrinogen | Converted into fibrin by thrombin | Not Y |
| D | Thrombin | Converts fibrinogen to fibrin (active enzyme) | Factor Y |