MCAT Biology : Other Microbiology Concepts

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Other Microbiology Concepts

Which of the following types of microscopy is best for the visualization of living organisms?

Possible Answers:

Phase contrast microscope

Electron microscope

Scanning electron microscope

Light microscope

Compound light microscope

Correct answer:

Phase contrast microscope

Explanation:

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. 

Example Question #2 : Other Microbiology Concepts

All of the following are examples of asexual reproduction, except __________.

Possible Answers:

budding

fission

induction

parthenogenesis

Correct answer:

induction

Explanation:

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. 

Example Question #1 : Other Microbiology Concepts

Which of the following can be considered extra-genomic DNA in eukaryotic cells?

Possible Answers:

Mitochondria DNA

Introns

Cytosolic chromosomes during mitosis

DNA in the nucleus after envelope breakdown

DNA in the nucleolus

Correct answer:

Mitochondria DNA

Explanation:

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.

Example Question #2 : Other Microbiology Concepts

The cell is the most basic functional unit of life.  Everything that we consider to be living is made up of cells, and while there are different kinds of cells, they all have some essential features that link them all together under the category of "life."  One of the most important parts of a cell is the membrane that surrounds it, seperating it from the rest of the environment.

While organisms from the three main domains live in incredibly different environments, they all possess similar cell membranes.  This phospholipid bilayer protects the cell, giving it a way to allow certain things in while keeping other things out.  Though organisms from different domains have different kinds of fatty linkages in their membranes, they all serve this essential purpose.

Membranes contain all kinds of essential proteins and signal molecules that allow the inside of the cell to respond to the outside of the cell.  In a multicellular eukaryote, this ability can be used to allow cells to communicate.  In a bacterial colony, an extracellular signal could be used to signal other bacteria.  Signals cascade through a series of molecular pathways that go from the outside of the cell all the way to the nucleus and back out again, giving the cell control on a genetic level.  This allows cellular responses to be quick and effective, and it also allows the cell to control how long it stays in that state.

What characteristic of a cell could a scientist use to determine what domain to which an unknown cell belonged?

Possible Answers:

If the genetic material in the cell's nucleus was DNA or RNA

The environment of the cell

The presence of a cellular membrane

The kind of membrane fatty linkages

The presence of a cell wall

Correct answer:

The kind of membrane fatty linkages

Explanation:

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.

Example Question #5 : Other Microbiology Concepts

What should a scientist look for if he is trying to determine whether a certain organism is a bacteria rather than a virus?

Possible Answers:

Whether the organism can be killed by antibiotics

Whether the organism causes disease

Whether the organism is smaller than a eukaryotic cell

Whether the organism has a nucleus

Whether the organism contains genetic material

Correct answer:

Whether the organism can be killed by antibiotics

Explanation:

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.

Example Question #3 : Other Microbiology Concepts

Which of the following leukocytes is not a participant in the innate immune response?

Possible Answers:

Neutrophils

T-lymphocytes

Macrophages

Basophils

Correct answer:

T-lymphocytes

Explanation:

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.

Example Question #7 : Other Microbiology Concepts

The following processes occur both in eukaryotes and prokaryotes except for which answer choice?

Possible Answers:

mRNA processing

Regulation of intracellular osmoles

Oxidative phosphorylation

Regulation of transcription

Correct answer:

mRNA processing

Explanation:

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.

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