Chapter 3, Problem 9RQ

Summary Introduction

To review:

The subcellular structures present in certain cells having various functions like magnetotaxis or photosynthesis.

Introduction:

The subcellular structures are the simple structures that are present inside the cell. These structures can be easily visualized by transmission electron microscope or scanning electron microscope. A few examples of subcellular structures are mitochondria, endoplasmic reticulum, Golgi apparatus, and nucleus.

In cells, there are several major structures that are involved in content organization, DNA (deoxyribonucleic acid) maintenance, and in the synthesis of new parts. In order to adapt to the diverse environment and metabolic processes, various species evolve some subcellular structures like thylakoids, storage granules, and carboxysomes. Photosynthetic bacteria or organisms are associated with the formation of their own food.

Thylakoids are membrane-bound sections that lie in cyanobacteria and chloroplasts. Photosynthetic bacteria evolve this subcellular structure to increase the collecting surface of membranes involved in photosynthesis. These structures carry out light reactions for energy storage and absorption of photons. This energy is used for carbon dioxide fixation that takes place inside the covered polyhedral bodies which are carboxysomes along with the Rubisco enzyme for fixation. Phycobilisomes are also found in association with the thylakoid membrane in order to harvest sunlight.

Storage granules are generated by nonphototrophic bacteria of soil. These granules store essential metabolites and reserved energy. Magnetotaxis is a form of chemotaxis that possesses the ability to respond toward magnetism. The magnetotactic bacteria sense magnetism and get oriented along with the magnetic field. The subcellular structure is flagella that moves clockwise and anticlockwise on the basis of the magnetism.