MCAT Biology : Biology
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Example Questions
Example Question #11 : Biology
Which fo the following marks a distinct quality of smooth muscle?
It contains striations and intercalated discs
It contains specialized gap junctions
It develops tension quickly, but maintains contractions longer
It fatigues rapidly
It develops tension slowly, but maintains contractions longer
It develops tension slowly, but maintains contractions longer
Smooth muscle varies from other muscle types because it has the capacity to develop tension slowly, but maintain contractions for a longer period. The autorhythmic cells within smooth muscle generate slow wave or pacemaker potentials that allow tension to develop slowly. Think, for example, of the smooth muscle that surrounds the bladder and generates tension slowly or of the smooth muscle that controls the size of the pupil and must maintain contractions for extended periods.
Example Question #12 : Biology
A man must have his duodenum completely removed. During the surgery, the stomach will be connected to the jejunum. As a result of the surgery, the patient will likely suffer from which of the following conditions?
Deficiency in water absorption
Inability to produce bile
Inability to digest lipids
Inability to convert polysaccharides to disaccharides
Inability to synthesize vitamin K
Inability to digest lipids
The duodenum and jejunum are two adjacent regions of the small intestine. The duodenum is the region in which the majority of chemical digestion occurs. The pancreas secretes several critical digestive enzymes into the duodenum. One of these enzymes is lipase, which is responsible for lipid digestion. Removal of this region would result in an inability to digest lipids.
Production of vitamin K mostly occurs in the large intestine, digestion of polysaccharides to disaccharides is accomplished with salivary amylase, water absorption occurs in the large intestine, and bile is produced by the liver.
Example Question #6 : Other Biology Concepts
A vitamin is defined as an organic molecule that is required to be obtained from the diet because it cannot be synthesized by the organism. Based on this definition, which of the following is not a true vitamin?
Vitamin C
Vitamin A
Vitamin E
Vitamin D
Vitamin D
Although there are recommended intake values for vitamin D, this "vitamin" can be synthesized by the body with the help of UV radiation from the sun.
Example Question #13 : Biology
Certain inhibitors bind enzymes irreversibly through covalent bonding. Would the kinetics (V vs. [S] curve) of this be similar to that of a reversible noncompetitive inhibitor? Why?
Yes, since the 
None of these
Yes, since the total effect would result in a loss of usable enzymes for the reaction
No, since the total effect would result in a loss of usable enzymes for the reaction
No, since the 
Yes, since the total effect would result in a loss of usable enzymes for the reaction
An irreversible noncompetitive inhibitor permanently deactivates some enzyme function. Therefore, the effective enzyme concentration will be reduced, which is also what is observed through using a reversible noncompetitive inhibitor. 
Example Question #14 : Biology
Which of the following types of enzymes irreversibly modifies its substrate?
Protease
All of these
Kinase
Ligase
Phosphatase
Protease
Proteases are enzymes that cleave substrates at certain locations. This permanently removes a part of the protein and thus is irreversible. Kinases catalyze the phosphorylation of proteins. Since phosphatases do the opposite, we know that phosphate groups can be reversibly added to proteins. Ligases catalyze the joining of two molecules together, which is reversible since large dimers and polymers are broken down all the time.
Example Question #15 : Biology
The parietal cells of the stomach are vital for both food digestion and as a defense mechanism against pathogens. When the parietal cells are not functioning properly, diseases such sepsis due to Clostridium difficile and malnutrition may occur. To keep the digestive system healthy, proper nutrition as well as a balanced diet is vital.
The parietal cells of the stomach secrete hydrochloric acid via the hormone gastrin. Gastrin is released when the stomach distends, via the presence of proteins and/or indirectly by the vagus nerve from the parasympathetic nervous system. Hydrochloric acid breaks down certain ingested food as well as activates certain zymogens for further digestion of macromolecules. The high acidity of the stomach due to the release of hydrochloric acid by parietal cells also destroys most pathogens. When the parietal cell is not functioning properly, opportunistic pathogens may create health problems.
Parietal cells also secrete intrinsic factor, a glycoprotein which binds to vitamin B12 to prevent destruction of the vitamin by the hydrochloric acid. Down the gastrointestinal tract, the vitamin is absorbed by the ileum of the small intestine. Vitamin B12 is essential for red blood cell production. A diet low in vitamin B12 may lead to anemia.
When the acidity of the stomach is too high, somatostatin is secreted by the D cells of the stomach. somatostatin inhibits the parietal cells from releasing more hydrochloric acid. What type of feedback is this?
Forward
Positive
Negative
Backward\
Neutral\
Negative
The increase in acidity of the stomach will activate the D Cells in the stomach to secrete somatostatin. somatostatin will then inhibit the parietal cells from releasing hydrochloric acid. This is a form of negative feedback since a downstream
Example Question #12 : Other Concepts
The cellular membrane is a very important structure. The lipid bilayer is both hydrophilic and hydrophobic. The hydrophilic layer faces the extracellular fluid and the cytosol of the cell. The hydrophobic portion of the lipid bilayer stays in between the hydrophobic regions like a sandwich. This bilayer separation allows for communication, protection, and homeostasis.
One of the most utilized signaling transduction pathways is the G protein-coupled receptor pathway. The hydrophobic and hydrophilic properties of the cellular membrane allows for the peptide and other hydrophilic hormones to bind to the receptor on the cellular surface but to not enter the cell. This regulation allows for activation despite the hormone’s short half-life. On the other hand, hydrophobic hormones must have longer half-lives to allow for these ligands to cross the lipid bilayer, travel through the cell’s cytosol and eventually reach the nucleus.
Cholesterol allows the lipid bilayer to maintain its fluidity despite the fluctuation in the body’s temperature due to events such as increasing metabolism. Cholesterol binds to the hydrophobic tails of the lipid bilayer. When the temperature is low, the cholesterol molecules prevent the hydrophobic tails from compacting and solidifying. When the temperature is high, the hydrophobic tails will be excited and will move excessively. This excess movement will bring instability to the bilayer. Cholesterol will prevent excessive movement.
Epinephrine binds to its receptor on the surface of the cell. Molecule B also binds to the same receptor but when bound, all of the receptors on the cell's surface are upregulated. What type of regulation is this?
Positive feedback
None of these
Cooperation
Allosteric inhibition
Negative feedback
Cooperation
This is an example of cooperation because the activation of one will positively regulate others.
Example Question #1 : Systems Biology And Tissue Types
Follicle-stimulating hormone (FSH) stimulates the growth of a follicle in the ovary, a process that occurs __________.
between birth and puberty
between puberty and menopause
only before the female is born
between fertilization and birth
between puberty and menopause
At puberty, the oocytes arrested at birth in meiosis I resume growth. This most often happens once a month, if fertilization has not occurred, and continues from puberty until menopause. The oocytes arrested at birth complete meiosis I, and are then arrested in meiosis II until fertilization occurs. During ovulation, the follicle ruptures and develops into the corpus luteum. Without fertilization, the endometrium is shed and the cycle continues. Once menopause is reached, this cycle ceases and most often women are no longer fertile.
Example Question #1 : Reproductive System
The hormones FSH and LH are involed in oogenesis in women. When LH surges in the ovarian cycle, what event will result?
Menstruation
Corpus luteum degradation
Endometrium proliferation
Ovulation
None of the above
Ovulation
Follicles are stimulated to grow when FSH level rises. The follicles produce estrogen that exerts a positive feedback on LH, whose levele begin to rise. When LH levels peak on the 14th day of the cycle, the follicle ruptures, releasing the egg from the ovary and leaving the corpus luteum behind in the ovary. After ovulation, the corpus luteum secretes both estrogen and progesterone to inhibit GnRH. When GnRH is inhibited, FSH and LH will also be inhibited.
Example Question #1 : Reproductive System And Development
An environmental toxin has been found to directly disrupt normal gamete production in women. What tissue or organ is the toxin likely localizing to?
Oviduct
Ovaries
Endometrium
None of these
Uterus
Ovaries
The most likely localization of the toxin would be to the ovaries, since this is where gamete production begins for females. For males, gametes are produced in the testes. The incorrect answers are all parts of the female reproductive system. The oviduct is where fertilization takes place. The endometrium (the lining of the uterus) is where the embryo will eventually implant.
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