Question

Which of the following extensions of the cell membrane is responsible for the storage of respiratory pigments?
(a) Mesosome
(b) Lomasome
(c) Chloroplast
(d) Thylakoids

Answer 1

Hint: In the case of bacteria, they don't have a specialized respiratory system. However, like our mitochondria, they have certain structures in the plasma membrane that contains respiratory pigments and enzymes. The structures are similar to mitochondria but don't have an outer membrane.

Complete step by step answer:
In some gram-positive bacteria, there are some extensions of the plasma membrane that become invigilated and folded structures. These are known as mesosomes. At first, mesosomes were considered equivalent to mitochondria, but soon it was proven that unlike mitochondria, the mesosomes don't have an outer membrane. However, it contains some respiratory pigments spread throughout the plasma membrane.
So, the correct answer is, 'Mesosomes.'

Additional Information: Here's an explanation to each term mentioned in the question-
- Mesosome: It is formed by the extension of the plasma membrane into the cell wall. This forms some uneven folded shapes, such as vesicles, tubules, and lamellae. Mesosomes are found in some bacteria, mainly gram- positive bacteria. These are important in various processes like cell wall synthesis, DNA replication, distribution to daughter cells, respiration, secretions, etc. The mesosome contains respiratory pigments that take part in respiration in the bacteria.
- Lomasome: These were first discovered by Berlin and Bowen. Lomasomes are sac- like and found in between the cell wall and plasmalemma. These are present in the haustoria of fungal hyphae.
- Chloroplasts: We all know the name of chloroplasts as it is an essential part of photosynthesis. These contain photosynthetic pigment chlorophyll that helps the plant to capture sunlight to carry out the process of photosynthesis. They are found mainly in green plants and algae. Like mitochondria, they are also double- membrane organelle.
- Thylakoids: Thylakoids are membranous sacs that construct the thylakoid system in chloroplasts. The chlorophyll pigments are found in these membranes. The thylakoid system is the place where the light-dependent reaction of photosynthesis takes place.

Note: Mesosomes are present in gram- positive bacteria and it contains the pigments required for their respiration. Lomasome, chloroplasts, and thylakoids are present in other organisms like plants, fungi, and algae.