MCAT Biology › MCAT Biological Sciences
Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
The apicoplast that defines the phylum Apicomplexa is a membrane bound organelle. Which of the following is true of membrane-bound organelles?
I. They are only present in eukaryotes
II. They are bound by a single phospholipid layer
III. They do not have membrane-associated proteins attached
Which of the following statements about mitochondria could be used as support for the endosymbiotic theory?
Which of the following statements about mitochondria could be used as support for the endosymbiotic theory?
During muscle contraction, which parts of a sarcomere change in length?
In the human body, the colon primarily absorbs __________.
Which of the following is a correct description of the sympathetic and parasympathetic nervous systems?
Sarin gas is a potent nerve agent that quickly causes serious physiological effects if ingested, even in very small quantities. It inhibits acetylcholinesterase, an enzyme that degrades acetylcholine. Acetylcholinesterase generally acts at the neuromuscular junction.
Sarin gas may cause which of the following?
Which of the following is true regarding a transmembrane receptor?
Which of the following is true of intestinal function?
Which two muscles do humans use primarily for inhalation?