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What is it correct answer according to mdcat exam
The question asks: "Which two structures play a direct role in permitting bacteria to adhere to each other, or to other surfaces?"
The options are:
- Capsules
- Endospores
- Fimbriae
- Plasmids
- Flagella
The correct answer is A. 1 and 2... wait - let me re-read.
The structures listed are:
- Capsules - help bacteria adhere to surfaces (e.g., teeth, tissues)
- Endospores - dormant survival structures, NOT involved in adhesion
- Fimbriae - hair-like projections specifically designed for adhesion to host cells and surfaces
- Plasmids - genetic elements, not adhesion structures
- Flagella - used for motility/locomotion, not adhesion
The two structures that play a direct role in adhesion are:
- Capsules (1) - sticky polysaccharide layer that helps bacteria attach to surfaces
- Fimbriae (3) - primary adhesion structures in bacteria
The correct answer is B. 1 and 3 (Capsules and Fimbriae)
From the table visible in the image, fimbriae are described as being "involved in attachment with host" and capsules also aid in adherence. Flagella are for locomotion/motility, endospores are for survival, and plasmids carry genetic material.
So for the MDCAT exam, the answer is B. 1 and 3.
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Answer these correctly from mdcat
Here are the answers to both questions:
Question 2
"Bacteria that cause nosocomial infections produce extra cellular substances that allow them to stick firmly to medical devices, such as intra venous catheters. Which one of the following is the name of this extra cellular substance?"
Options: A. Axial filament | B. Endotoxin | C. Flagella | D. Glycocalyx
✅ Correct Answer: D. Glycocalyx
Explanation: The glycocalyx is the extracellular sticky substance (made of polysaccharides) that surrounds bacteria. It allows bacteria to adhere firmly to surfaces like IV catheters, prosthetic devices, and tissues. When it is firmly attached and organized, it is called a capsule; when loosely attached, it is called a slime layer. Both are forms of glycocalyx. This is the key structure responsible for nosocomial (hospital-acquired) infections on medical devices.
- Axial filament = part of spirochete flagella (motility)
- Endotoxin = lipopolysaccharide in gram-negative cell walls (not adhesion)
- Flagella = locomotion, not adhesion
Question 3
"Which of the following requires ATP to function, and permits some species to respond to taxes (plural of taxis)?"
Options: A. Endospore | B. Sex pilus | C. Flagellum | D. Capsule
✅ Correct Answer: C. Flagellum
Explanation: Flagella are the only bacterial structures that:
- Require ATP (via a proton motive force-driven motor, consuming cellular energy) to rotate and function
- Enable taxis - both chemotaxis (movement toward/away from chemicals) and phototaxis (movement toward light)
- Endospores are dormant structures requiring no ATP for their function
- Sex pilus transfers DNA but does not drive taxis
- Capsule is a passive sticky layer requiring no ATP
Summary:
| Q | Answer |
|---|---|
| 2 | D - Glycocalyx |
| 3 | C - Flagellum |
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