Test: Prokaryotes - MCAT MCQ

Prokaryotes are unicellular organisms that lack membrane-bound organelles such as a nucleus, mitochondria, or endoplasmic reticulum. Instead, their genetic material is present in a single circular chromosome located in the nucleoid region.

Prokaryotes have a cell wall that provides structural support and protection. The cell wall composition varies among different types of prokaryotes, with bacteria having peptidoglycan in their cell wall, while archaea have different types of cell wall structures.

Prokaryotes reproduce through binary fission, a process in which a single prokaryotic cell divides into two identical daughter cells. This process allows for rapid population growth in prokaryotic organisms.

Prokaryotes are classified into two domains: Bacteria and Archaea. The domain Eukarya includes organisms with eukaryotic cells, which have a true nucleus and membrane-bound organelles.

Prokaryotes do not perform endocytosis, which is a process by which eukaryotic cells engulf external materials. Instead, prokaryotes obtain nutrients through processes such as photosynthesis, cellular respiration, or fermentation.

Prokaryotes exhibit genetic diversity through genetic recombination. This occurs through processes such as horizontal gene transfer, transformation, transduction, and conjugation, which allow for the exchange of genetic material between prokaryotic cells.

Certain prokaryotes, such as nitrogen-fixing bacteria, have the ability to convert atmospheric nitrogen gas (N₂) into ammonia (NH₃) through a process called nitrogen fixation. This ammonia can then be used by other organisms in the ecosystem.

Prokaryotes are incredibly diverse and can be found in various habitats, including soil, freshwater, and extreme environments such as hot springs and deep-sea vents. They have adapted to survive and thrive in a wide range of conditions.

Conjugation is a process in which genetic material, usually in the form of plasmids, is transferred between two prokaryotic cells. This transfer occurs through a pilus, a structure that connects the two cells, allowing for the exchange of genetic information.

Prokaryotes have essential ecological roles, including decomposing organic matter, producing oxygen through photosynthesis (in certain prokaryotes), and cycling nutrients such as carbon and nitrogen. These processes are fundamental for the balance and functioning of ecosystems.