Microbiology - MCAT Biological and Biochemical Foundations of Living Systems

Bacteria can be killed by antibiotics, whereas viruses cannot.

Both bacteria and viruses have genetic material, can cause disease, and are smaller than eukaryotic cells. Neither of them has a nucleus.

The passage tells us that the type of fatty linkages in cell membranes can tell us what domain an organism belongs to. For example, bacteria have ester linkages while archea have ether linkages. The other answers are wrong for a few reasons. All cells have DNA as their primary genetic material. Viruses have RNA sometimes, but they aren't considered alive. Both bacteria and plants have cell walls, so that won't tell us for sure what the domain is. As stated in the passage, all cells have cellular membranes. While the environment can tell us a bit about the cell, the passage doesn't say it is a sure way to know, so we can't make an assumption based on that.

A phase contrast microscope is best for the visualization of living things because the other types of microscopy require methods of mounting onto a slide that can kill the organisms.

Organisms have the ability to reproduce in various ways outside of sexual reproduction. Mechanisms of asexual reproduction include binary fission, budding, regeneration, and parthenogenesis. Binary fission refers to mitotic division, leading to independent daughter offspring. Budding refers to the growth of a viable offspring from the main organism, before becoming mature and detaching. Regeneration refers to the ability to reproduce from a severed appendage. Parthenogenesis refers to development of an embryo without being fertilized.

Induction is involved in cell-cell communication during embryogenesis, causing one group of cells to change an adjacent group's behavior. It is not a method of asexual reproduction, and is therefore the correct answer.

Extra-genomic DNA is DNA that does not originate from the nuclear genome. DNA from mitochondria is passed down from generation to generation from the mother to the offspring. It is considered extra-genomic because the genome for mitochondria comes from the actual cell constituent rather than the nucleus of the cell.

Other examples of extra-genomic DNA are plasmids and viral genomes that may become incorporated during the lysogenic viral cycle.

Any chromosomal DNA is considered genomic, and is contained in the organismal genome.

Both bacteria and eukaryotic cells regulate their cytosolic osmoles in order to both maintain the integrity of their cell membranes and to maintain proper functioning of cytosolic proteins. Although bacteria have the added protection of a cell wall, they still rely on ion gradients to regulate the uptake and release of nutrients. Both regulate transcription using transcription factors and undergo aerobic respiration. Bacteria do NOT process their mRNA. Rather, it can be transcribed and translated simultaneously.

T-lymphocytes are members of the adaptive immune system, and are only activated after the innate immune system fails to eliminate the antigen. The adaptive immune system is a more specified response to the antigen, requiring previous exposure to the foreign pathogen and involving the secretion of antibodies. In contrast, the innate immune response does not require previous exposure or involve antibody release.

Both plants and fungi consist of eukaryotic cells. Their cells contain membrane-enclosed nuclei and organelles which is a defining characteristic of eukaryotic cells.

Fungi do not photosynthesize. While seedless plants and fungi use spores, this trait is not common to all plants. Plant cell walls are composed of collagen, while fungi use chitin.

The antifungal compound is likely specific to chitin, as it is a common material of many fungi cell wall structures. Chitin is resistant to breakdown, and is actually found in insect exoskeletons. The incorrect answers are found in skin cells as well as fungal cells, and would harm the skin if the chemical attacked these structures.

Fungi are typically characterized based on reproductive methods and structures. All fungi can reproduce asexaully, but only deuteromycetes lack a sexual reproduction phase, only reproducing asexually.

Most fungi reproduce by creating microscopic spores, which are reproductive cells than can be dispersed by wind, water, or animals. Spores can be generated sexually or asexually. If the scientist disrupts spore formation, the fungus will not be able to spread spores to other areas of the laboratory.

Inhibition of spore formation would limit the fungus's ability to reproduce over distance, however fungi have multiple methods of reproduction and would still be able to generate progeny even if spore production is disabled.

Most fungi have a life cycle that consists of both sexual and asexual periods. Spores can be produced sexually or asexually, depending on the availability of male or female gametes. This has provided an advantage to fungi to be able to spread and propagate in a variety of environments.

Congregation of hyphae form mycelium, the tissue that allows fungi to absorb nutrients from surrounding food sources. Often, the majority of mycelium mass is not visible to the observer. "Fungal roots" is a misleading answer, even though mycelium looks similar to root structures of plants. Gametangia is where gametes are produced in the fungus.

Binary fission occurs in prokaryotes and is a form of asexual reproduction. Fungi are considered haploid eukaryotes and undergo reproduction through processes like asexual spore release, vegetative reproduction, and sexual spore release. Asexual spores do not have DNA mixing, while sexual spores do have DNA mixing. Vegetative reproduction is when part of the fungus breaks off and forms a new fungus.

Organelles are only found in eukaryotic cells which set them apart from prokaryotic cells.

Gram-positive bacteria are able to retain the crystal violet stain found in gram stain because of their thick peptidoglycan cell walls. Consequently, these bacteria stain dark blue or purple by gram staining. Alternatively, gram-negative bacteria appear red or pink because they are unable to retain the dye due to thinner cell walls and less peptidoglycan.

E. Coli is a type of bacteria. Because bacteria are prokaryotes, they do not contain membrane-bound organelles. A nucleus is a membrane-bound organelle and therefore would not be found in bacteria.

Bacilli is a genus of bacteria that are characterized by their rod-shaped cells. Bacilli can be either gram positive, such as Bacillus anthracis, or gram negative, such as Salmonella enterica. Bacilli bacteria can be either aerobic (require oxygen) or facultative anaerobes (can thrive in both oxygen rich and oxygen poor environment). Bacilli are not exclusively aerobic, nor are they exclusively gram positive.

The technique explained in the question is the "Gram stain". Bacteria that are Gram-positive will stain a bluish-purple color, while Gram-negative bacteria will stain a red or pink color. This difference in color occurs because of the large cell wall present on Gram-positive bacteria, and is a response to increased peptidoglycan expression. Additionally, some bacteria (such as mycobacteria and helicobacter) are not easily stained using this method.

In order for the bacteria to be distributed throughout the liquid, it must be able to survive in either the presence or absence of oxygen. Facultative anaerobic bacteria can surive in both cases, although, they prefer oxygen. In the absence of oxygen, they can produce energy through fermentation. Both microaerophiles and obligate aerobic bacteria require oxygen to survive and, in this experiment, would be found near the top of the tube. Oxygen is toxic to obligate anaerobic bacteria, which would be found at the bottom.