Microbiology Quiz Chapter 4

The main distinctions between prokaryotic and eukaryotic cells are the absence of organelles and the structure of cell walls and membranes. Prokaryotic cells are simpler and lack membrane-bound organelles, such as mitochondria and nucleus, while eukaryotic cells have these organelles. Additionally, prokaryotic cells have a different structure of cell walls and membranes compared to eukaryotic cells. Therefore, the statement is true.

Mycoplasmas are resistant to antibiotics that interfere with cell wall synthesis because they have no cell wall. Unlike other bacteria, mycoplasmas lack a rigid cell wall, making them naturally resistant to antibiotics that target this structure. Instead, they have a plasma membrane that contains sterols, which provides them with protection. This unique characteristic allows mycoplasmas to survive and thrive in various environments, including the presence of antibiotics that would typically inhibit bacterial growth by targeting the cell wall.

The correct answer is B and E are false. This is because the statement in option B, "B, C and E are false," contradicts the given characteristics. The characteristics mentioned in the question clearly state that prokaryotic cells do not have their DNA enclosed within a nucleus and that the cell walls of prokaryotes contain many nutrients like polysaccharides. Therefore, option B is false. Similarly, option E, "None is false," is also incorrect as there are indeed false statements in the given characteristics.

The correct answer is "Glycocalyx, biofilms". Glycocalyx is a structure external to the cell wall that is composed of polysaccharide and/or polypeptide. It can be described as either a capsule or a slime layer. Biofilms are a collection of microorganisms that are held together by the glycocalyx. The glycocalyx in biofilms is a very important component as it helps protect the microorganisms from environmental stresses and enhances their ability to adhere to surfaces.

The given answer correctly identifies the different shapes and characteristics of bacteria. Streptococci are spherical bacteria that remain attached in chainlike patterns. Bacillus refers to rod-shaped bacteria. Cocci can have various shapes such as oval, elongated, round, or flattened on one side. Staphylococci are associated with grapelike clusters or broad sheets. Environmental conditions can alter the shape of a bacterium. Coccobacillus is a bacterium with an intermediate shape between a coccus and a bacillus.

The endosymbiotic theory explains that eukaryotes originate from prokaryotes, meaning that larger bacterial cells lost their cell walls and engulfed smaller bacterial cells.

Passive processes involve the movement of substances across the membrane from an area of high concentration to an area of low concentration without the use of ATP energy by the cell. Simple diffusion is a type of passive process that is especially used for the transportation of small molecules across the cell membrane. Osmotic pressure refers to the pressure required to prevent the movement of pure water into a solution containing solutes. Group translocation is a process that occurs exclusively in prokaryotes, where the substance being transported is chemically altered during transport, making the plasma membrane impermeable to the altered substance, causing it to remain inside the cell.

The false statements regarding glycocalyx's functions are: Slime layer can contribute to bacterial virulence, Capsules can protect viruses from phagocytosis by the cells of the host, and A glycocalyx's viscosity will enhance the movement of nutrients out of the cell.