DAT Question of the Day

Correct Answer: D. Stimulate sodium reabsorption by the kidneys.

When the adrenal cortex secretes glucocorticoids, many actions are initiated. Cortisol, for example, is released during times of stress. Gluconeogenesis (the process of creating glucose from non-carbohydrates) and lipolysis (the breakdown of fats) are both activated to generate more energy for the both during times of stress. Immunologic response, inflammatory response, glucose uptake by muscle and fat tissues, and protein construction are all restricted as these are energetically expensive and the body needs to place its energy reserves into other areas. Sodium reabsorption by the kidneys is regulated by secretion of mineralocorticoids of the adrenal cortex, such as aldosterone.

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Correct Answer: B. The gap between the myelin sheath segments

The correct answer is B. The gap between the axon terminal and dendrite of the next neuron is called the synaptic cleft. The lipid-based coating that covers the neurons is the myelin sheath, and this sheath covers segments along the axon called internodes and the gaps between these internodes are called the Nodes of Ranvier.

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Correct Answer: D. enteropeptidase and trypsin

After releasing trypsinogen from the pancreas, enteropeptidase cleaves the inactive protein at specific sites. As a consequence of this action trypsin is generated. This enzyme has ability to generate trypsinogen on its own and to release an active enzyme.

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Correct Answer: B. They are responsible for the supercoiling of DNA.

Histones are not responsible for methylating DNA(A) or helping topoisomerase enzymes bind. Histones interact with DNA through ELECTROSTATIC interactions, and an octet of histones plus a length of DNA forms a NUCLEOSOME and causes the DNA to form its tertiary structure and become supercoiled.

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Correct Answer: B. Blood

The three primary germ layers of the embryo include: the ectoderm, endoderm, and mesoderm. The endoderm differentiates to form the gastrointestinal tract, the lungs, the pharynx and parts of the urinary system. The ectoderm is the outer layer of the three germ layers and results in the formation of the epidermis and related structures like hair, nails, and external sense organs. The ectoderm also forms the spinal cord and the brain. The mesoderm is the middle layer of the three germ layers and eventually develops into connective tissues (including bone), cartilage, muscle, and the blood vessels. Blood is considered a type of connective tissue, thus the correct answer is [B].

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Correct Answer: A. Testes

This is a great example of a conceptual question on the DAT. There are many pieces of information here, but if we take it one step at a time, it really isn’t that bad.

First, we have to explain why Cell Type 2 has such a low intracellular concentration compared to the other Cell Types. Recall that steroid hormones are lipid-soluble, which means they freely diffuse through the cell membrane.

In contrast, peptide hormones are stored in granules and are only released when stimulated. So from this information, we can deduce that Cell Type 2 must be synthesizing a steroid hormone, and the other Cell Types must be a variant of a peptide hormone.

As Cell Type 2 was synthesizing its steroid hormone, it was just freely diffusing out, and not building up in concentration inside the cell, so when the researcher measured the intracellular concentration, she barely found any steroid hormone at all. In contrast, Cell Type’s 1, 3, 4, and 5 were synthesizing peptide hormones and building up their concentrations because they store peptide hormones in granules.

Lastly, the question asks where Cell Type 2 possibly came from. Cell Type 2 would need to be harvested from a part of the body that produces steroids, of which there are three main centers, and those are:

1. Adrenal cortex, which produces mineralocorticoids and glucocorticoids like aldosterone and cortisol. It also is a secondary site for androgen synthesis.

2. Testes, which mainly secrete testosterone in relation to hormone synthesis.

3. Ovaries, which mainly secrete estrogen and progesterone in relation to hormone synthesis.

Note: The placenta also produces steroid hormones during pregnancy.

Thus, the correct answer to this question is [A], the testes, as it is the only organ listed that synthesizes steroid hormones.
All of the other answer choices describe organs that do not produce steroid hormones, and are therefore incorrect.

B. Adrenal medulla – Composed mainly of chromaffin cells, which synthesize catecholamines (epinephrine, norepinephrine, and dopamine) from tyrosine.

C. Anterior pituitary – Produces FSH, LH, ACTH, TSH, Prolactin and GH. (Remember the acronym FLAT PiG).

D. Pineal gland – The pineal gland is responsible for synthesizing melatonin.

E. Pancreas – Synthesizes several important peptide hormones, including insulin, glucagon, and somatostatin.

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Correct Answer: C. archaebacteria

The bacteria were found in a hot spring where most bacteria would not be able to grow. Also, the cell wall of the bacteria is composed of a polysaccharide. Eubacteria would not be present in harsh conditions and would also have a cell wall composed of peptidoglycan. Archaebacteria are able to withstand harsh conditions and generally have cell walls made of polysaccharides or lipid based substances. Deuterostome and protostomes are biology terms but refer to the differentiation of the first opening in the blastopore for animals, not bacteria. Eukaryotes do not as a general group all have cell walls and most cannot live in harsh environments.

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Correct Answer: D. plasmodesmata

Tight junctions create a tight seal between adjacent cells, whereas desmosomes serve to adhere cells together anchoring them to one another. Gap junctions allow for adhesion and transport of cytoplasmic materials between neighboring animal cells. The question refers to plant cells and this specialized cellular junction is referred to as the plasmodesmata.

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Correct Answer: B. chromatin

In interphase the DNA is scattered throughout the nucleus. It is during prophase of mitosis and meiosis that the DNA becomes tightly packed, wrapping around histones and forming the tightly coiled chromosomes. A nucleosome is a unit of DNA wrapped around a histone. It is these nucleosomes that wrap around each other to make the super coiled DNA structure. Sister chromatids are formed when the chromosome condenses in prophase.

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Correct Answer: A. Golgi Body

The golgi body assists in the processing of proteins by modifying and sorting the protein. In addition, the golgi body is responsible for tagging and dispersing proteins that are destined to leave the cell. These proteins are packaged in transport vesicles that are then taken to the cell membrane, where the vesicle fuses with the membrane and ejects the protein outside of the cell. The ribosome and rough endoplasmic reticulum both help with protein synthesis but are not responsible for vesicle production. The mitochondria is the site of ATP production during cellular respiration and does not directly form vesicles. The smooth endoplasmic reticulum is essential in lipid production and detoxifying the cell.

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