Microbiology Quiz 2 - Chapter 5

The correct answer is Symbiosis. Biologists have found evidence that eukaryotic cells evolved from prokaryotic organisms through a process called symbiosis. This process involves a mutually beneficial relationship between two different organisms, where both organisms live together and benefit from each other. In the case of eukaryotic cells, it is believed that a prokaryotic organism was engulfed by another prokaryotic cell, leading to a symbiotic relationship and eventually giving rise to eukaryotic cells. This theory is supported by the presence of organelles, such as mitochondria and chloroplasts, in eukaryotic cells, which are thought to have originated from engulfed prokaryotic organisms.

The cytoskeleton is a network of protein filaments that provides structural support to the cell and helps maintain its shape. It also plays a role in cell movement by facilitating the movement of the cytoplasm and organelles within the cell. Therefore, all of the given choices - anchoring organelles, providing support, functioning in cytoplasmic movements, and helping maintain cell shape - are correct functions of the cytoskeleton.

When a eukaryotic cell is not undergoing mitosis, the DNA and its associated proteins appear as a visible thread-like mass called chromatin. Chromatin is the relaxed form of DNA that is found in the nucleus of a cell. It consists of DNA wrapped around histone proteins, forming a complex called a nucleosome. This thread-like mass of chromatin allows for the efficient packaging and organization of the DNA within the nucleus, while still allowing for accessibility and transcription of genes.

The endosymbiotic theory proposes that eukaryotic cells evolved from a symbiotic relationship between different types of prokaryotic cells. According to this theory, a larger prokaryotic cell engulfed a smaller prokaryotic cell, forming a symbiotic relationship where the smaller cell provided beneficial functions such as energy production. Over time, the smaller cell became an organelle within the larger cell, giving rise to the complex structure of eukaryotic cells. Therefore, the emergence of eukaryotes is explained by the endosymbiotic theory.

Ribosomes in eukaryotic cells are found in two locations: scattered in the cytoplasm and on the surface of the endoplasmic reticulum. The cytoplasm is the fluid-filled region of the cell where many cellular processes occur, including protein synthesis. The endoplasmic reticulum is a network of membranes involved in protein synthesis and transport. Therefore, ribosomes are present in both the cytoplasm and the endoplasmic reticulum in eukaryotic cells.

Mitochondria are the correct answer because they have their own DNA, similar to bacterial cells, and can replicate independently within the eukaryotic cell. They also have a double membrane structure, similar to the cell membrane of bacterial cells. Additionally, mitochondria have their own ribosomes and can produce some of their own proteins, just like bacterial cells. These characteristics make mitochondria the organelle that most resembles a bacterial cell within a eukaryotic cell.

The eukaryotic cell's glycocalyx is mostly polysaccharide. The glycocalyx is a layer of carbohydrates that surrounds the cell membrane. It serves various functions such as cell recognition, cell adhesion, and protection against osmotic lysis. The majority of the glycocalyx is composed of polysaccharides, which are long chains of sugar molecules. These polysaccharides provide structural support and help in cell-cell communication. While the glycocalyx is involved in many metabolic reactions, it is not the site where most of these reactions occur. The cell wall is a separate structure from the glycocalyx.

Most fungi obtain nutrients from dead plants and animals, which means they decompose organic matter. Fungi that decompose dead organic material are called saprobes. They play a crucial role in the ecosystem by breaking down dead organic matter and recycling nutrients back into the environment. Parasites, on the other hand, obtain nutrients from living organisms, substrates refer to the material on which fungi grow, nonseptate refers to a type of hyphae structure, and dimorphic refers to fungi that can exist in two different forms.

Mitochondria is the correct answer because it is the organelle that contains cristae, which are the folds in the inner membrane where enzymes and electron carriers for aerobic respiration are found. These enzymes and electron carriers are essential for the production of ATP, the main energy source for the cell. Lysosomes, Golgi apparatus, Chloroplasts, and Endoplasmic reticulum do not contain cristae or play a role in aerobic respiration.

The nucleolus is responsible for ribosomal RNA synthesis. Ribosomal RNA is a crucial component of ribosomes, which are the cellular structures responsible for protein synthesis. The nucleolus is located within the nucleus of a cell and is involved in the assembly of ribosomes. It contains the genes and enzymes necessary for the synthesis of ribosomal RNA. Therefore, the nucleolus is the site where ribosomal RNA is synthesized, making it the correct answer.