Question

*Which of the following statements is true?

a. peptidoglycan is comprised of cross-linked fatty acids

b. the cell walls of most bacteria are composed of peptidoglycan

c. Gram-negative bacteria have a relatively thick layer of peptidoglycan

d. peptidoglycan is found mainly in the cell walls of fungi, algae and plants

e. answers (a) and (b) are both correct

* The cell membrane of bacteria

a. is semi-permeable.

b. is usually a lipid bilayer

c. prevents cell lysis due to high intracellular osmotic pressure

d. answers (a) and (b) are correct e. answers (a) and (c) are correct

* A bacterial species has a generation time of 15 minutes and is growing exponentially. If there are 2 cells initially how many cells are there after 90 minutes?

a. 256 b. 128 c. 64 d. 32 e. none of the above

*Most bacterial cells reproduce by

a. the budding of daughter cells from a mother cell

b. forming spores that later germinate

c. binary fission

d. production of gametes and sexual reproduction

  

Answer 1

1.   Peptidoglycan is found in the cell wall of bacteria and is made of sugars and amino acids (N-acetyl glucosamine and N-acetyl muramic acid). Gram positive bacteria have a thick peptidoglycan layer when compared to Gram negative bacteria. So, the correct option is option B, the cell walls of most bacteria are composed of peptidoglycan.
2.   Similar to all cell membranes the bacterial cell membrane is also a bilayer membrane made of phospholipids. It is also semi permeable in nature thus allowing only certain substances to pass through it. So, the correct option is option D, answers a and B are correct.
3.   Generation time G = t/n
Where t is the time per generation
N is the number of generations
Therefore
n = G/t
= 90/15 = 6
Number of cells present initially = 2
Since the bacterial species is growing exponentially
Number of cells after 6 generations = 2ⁿ = 2⁶ = 64.
So, the correct option is option C, 64.

4.   Bacterial cells reproduce by binary fission. In the process of binary fission, a single bacterial cell divides into two identical daughter cells. Under unfavourable conditions some bacteria form spores known as the endospores that later germinate. Yeast usually reproduce by the process of budding. Production of gametes and reproduction by the fusion of gametes through conjugation occurs in eukaryotes. So, the correct option is option C binary fission.