Q.28 What are the basic properties of Gram positive (+ve) bacteria
(A). Thick peptidoglycan layer is present
(B). Teichoic acids are present
(C). Periplasmic space is negligible
(D). Outer membrane is present
Choose the correct answer from the options given below:
1. (A), (B) and (D) only.
2. (A), (B) and (C) only.
3. (A), (B), (C) and (D).
4. (B), (C) and (D) only.
Gram-positive bacteria have a thick cell wall that defines their key properties in microbiology exams. The correct answer is option 2: (A), (B), and (C) only.
Correct Properties
Gram-positive (+ve) bacteria feature a thick peptidoglycan layer (20-80 nm, 60-90% of wall), teichoic acids for structure and antigenicity, and negligible periplasmic space, lacking an outer membrane.
| Property | True for Gram +ve? | Explanation |
|---|---|---|
| (A) Thick peptidoglycan | Yes | Multiple layers for rigidity |
| (B) Teichoic acids | Yes | Polymers in wall/membrane |
| (C) Periplasmic negligible | Yes | No distinct space |
| (D) Outer membrane | No | Gram -ve trait |
Option Breakdown
Option 1Â errs by including (D) outer membrane, absent in Gram +ve.
Option 2Â is correct: (A), (B), (C) match Gram +ve structure precisely.
Option 3Â wrongly adds (D), characteristic of Gram -ve bacteria.
Option 4Â omits (A), the hallmark thick peptidoglycan.
This guide clarifies cell wall differences for biology students, emphasizing exam-ready facts on Gram staining and structure.
