Which answer choice is an enantiomer of the molecule shown below?

A mystery compound has only one chiral carbon. The enantiomers of this molecule are placed in separate beakers. Which of the following statements is false?

Shown above is the chemical structure for penicillin, a common prescription drug. How many chiral carbons does penicillin have?

How many chiral centers does the following molecule contain?

Ephedrine has the IUPAC name of 2-(methylamino)-1-phenylpropan-1-ol.

The stereochemical assignments for carbons 1 and 2 are __________ and __________, respectively.

An isomer exists such that half of its chiral centers have opposite configurations compared to the original compound. What is the relationship between the isomer and the original compound?

Prionsare the suspected cause of a wide variety of neurodegenerative diseases in mammals. According to prevailing theory, prions are infectious particles made only of protein and found in high concentrations in the brains of infected animals. All mammals produce normal prion protein, PrP^C, a transmembrane protein whose function remains unclear.

Infectious prions, PrP^Res, induce conformational changes in the existing PrP^Cproteins according to the following reaction:

PrP^C+ PrP^Res→ PrP^Res+ PrP^Res

The PrP^Resis then suspected to accumulate in the nervous tissue of infected patients and cause disease. This model of transmission generates replicated proteins, but does so bypassing the standard model of the central dogma of molecular biology. Transcription and translation apparently do not play a role in this replication process.

This theory is a major departure from previously established biological dogma. A scientist decides to test the protein-only theory of prion propagation. He establishes his experiment as follows:

Homogenized brain matter of infected rabbits is injected into the brains of healthy rabbits, as per the following table:

Rabbit 1 and 2: injected with normal saline on days 1 and 2

The above trials serve as controls.

Rabbit 3 and 4: injected with homogenized brain matter on days 1 and 2

The above trials use unmodified brain matter.

Rabbit 5 and 6: injected with irradiated homogenized brain matter on days 1 and 2

The above trials use brain matter that has been irradiated to destroy nucleic acids in the homogenate.

Rabbit 7 and 8: injected with protein-free centrifuged homogenized brain matter on days 1 and 2

The above trials use brain matter that has been centrifuged to generate a protein-free homogenate and a protein-rich homogenate based on molecular weight.

Rabbit 9 and 10: injected with boiled homogenized brain matter on days 1 and 2

The above trials use brain matter that have been boiled to destroy any bacterial contaminants in the homogenate.

A scientist claims that he has discovered how PrPRes propagates. He claims that the PrPRes interacts with the PrPC by using its own partially negative oxygen atoms to interact with partially positive hydrogen atoms on PrPC. What is true of these bonds?

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 includesPlasmodium, Babesia,andToxoplasma.

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, oroocyst. 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 whereToxoplasma gondiiwas growing with intestinal epithelial cells. A second plate ofToxoplasma gondiiwas grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.

A scientist is conducting a follow up experiment to the one described above. She is attempting to determine how cryptosporidium adheres to the gastrointestinal mucosa. She determines that the key step is a binding of a surface protein ligand to a receptor. Which of the following forces are common patterns for protein-protein interaction?

I. Hydrogen bonding

II. Coordinate covalent bonding

III. Polar covalent

IV. Metallic bonding

One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.

In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.

Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.

下图显示了在bloo单核细胞移动d vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.

Which of the following is likely true about the interactions between selectins and the "rolling" monocytes?

Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is callednegative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.

As the figure below shows, immune cells typically originate in the bone marrow. Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.

In the process of negative selection described in the passage, the interaction of T-cells and normal body proteins happens via brief and easily broken biochemical bonds. What type of bonding is most probably involved?