Free Test Prep MCAT Exam Questions

Section: Physical Sciences 

Our sense of smell is arguably the most powerful of our five senses, but it also the most elusive. It plays a vitalyet mysterious role in our lives. Olfaction is rooted in the same part of the brain that regulates such essentialfunctions as body metabolism, reaction to stress, and appetite. But smell relates to more than physiologicalfunction: its sensations are intimately tied to memory, emotion, and sexual desire. Smell seems to liesomewhere beyond the realm of conscious thought, where, intertwined with emotion and experience, it shapesboth our conscious and unconscious lives.The peculiar intimacy of this sense may be related to certain anatomical features. Smell reaches the brain moredirectly than do sensations of touch, sight, or sound. When we inhale a particular odor, air containing volatileodiferous molecules is warmed and humidified as it flows over specialized bones in the nose called turbinates.As odor molecules land on the olfactory nerves, these nerves fire a message to the brain. Thus olfactoryneurons render a direct path between the stimulus provided by the outside environment and the brain, allowingus to rapidly perceive odors ranging from alluring fragrances to noisome fumes.Certain scents, such as jasmine, are almost universally appealing, while others, like hydrogen sulfide (whichemits a stench reminiscent of rotten eggs), are usually considered repellent, but most odors evoke differentreactions from person to person, sometimes triggering strong emotional states or resurrecting seeminglyforgotten memories. Scientists surmise that the reason why we have highly personal associations with smells isrelated to the proximity of the olfactory and emotional centers of our brain. Although the precise connectionbetween emotion and olfaction remains a mystery, it is clear that emotion, memory, and smell are all rooted in apart of the brain called the limbic lobe.Even though we are not always conscious of the presence of odors, and are often unable to either articulate orremember their unique characteristics, our brains always register their existence. In fact, such a large amountof human brain tissue is devoted to smell that scientists surmise the role of this sense must be profound.Moreover, neurobiological research suggests that smell must have an important function because olfactoryneurons can regenerate themselves, unlike most other nerve cells. The importance of this sense is furthersupported by the fact that animals experimentally denied the olfactory sense do not develop full and normalbrain function.The significance of olfaction is much clearer in animals than in human beings. Animal behavior is stronglyinfluenced by pheromones, which are odors that induce psychological or behavioral changes and often providea means of communicating within a species. These chemical messages, often a complex blend of compounds,are of vital importance to the insect world. Honeybees, for example, organize their societies through odor: thequeen bee exudes an odor that both inhibits worker bees from laying eggs and draws drones to her when sheis ready to mate. Mammals are also guided by their sense of smell. Through odors emitted by urine and scentglands, many animals maintain their territories, identify one another, signal alarm, and attract mates.Although our olfactory acuity can’t rival that of other animal species, human beings are also guided by smell.Before the advent of sophisticated laboratory techniques, physicians depended on their noses to help diagnoseillness. A century ago, it was common medical knowledge that certain bacterial infections carry the musty odorof wine, that typhoid smells like baking bread, and that yellow fever smells like meat. While medical science hasmoved away from such subjective diagnostic methods, in everyday life we continue to rely on our sense ofsmall, knowingly or not, to guide us.It can be inferred from the passage that the emotional element of human olfaction would be better understoodthrough investigation into:Section: Verbal Reasoning 

For the last two decades many earth scientists have supported the notion that the Mediterranean was once ahuge, dry desert, lying 3,000 meters below sea level. This “death valley” was thought to have existed at the endof Miocene time, about 6 to 5.5 million years ago……From a geological point of view, the Mediterranean is a tectonically mobile land-enclosed depression – small(about 3,000,000 square kilometers) in comparison to the major world oceans…Immediately obvious on allcharts is the highly variable topography and relief of both the seafloor and adjacent borderland. The coastline ishighly irregular and continental shelves, though generally narrow, are well developed off the major river deltas(Nile, Rhone, Po, and Ebro). Moreover, the deep-sea basins and trenches have distinctive relief, with basinplains ranging in depth from less than 1,000 meters to more than 4,000…Observation that rocks dredgedoffshore are similar to those on land raised a fundamental concept – the key to understanding Mediterraneanhistory lies in the adjacent emerged land masses, and vice-versa……Early paleographic reconstructions showed that the once-open communication with the Atlantic deterioratedduring the upper Miocene. Water-mass exchange continued for a while in the Rif Strait, but then ceasedcompletely prior to the beginning of the Pliocene……High relief near what is now the Strait of Gibraltar served as a barrier to the exchange of waters with theAtlantic. Exposed to a hot and dry climate, water evaporated and the then-dry basin elicited comparison with agigantic Death Valley…Microfossil studies suggested that the depth of the Mediterranean basin at these timeshad been “deep.” Estimates suggested a dry seafloor as far as 2,000 meters below ocean level… As aresponse to suddenly lowered sea level, rivers feeding the Mediterranean and canyons on the now-dry seafloorbegan a geologically dramatic phase of erosion. Deep, Grand Canyon-like gorges of the Nile and Rhone rivers,presently buried on land, were apparently cut during a great drawdown of water – when the Mediterranean floorlay exposed 1,000 meters or more below its present level…The sudden flooding through a gigantic waterfall atGibraltar drowned the exposed basin floor. These falls would have been 1,000 times bigger than NiagaraFalls…This flooding event is recorded by the Miocene Pliocene boundary, a time when open marine faunalassemblages were suddenly reintroduced from the Atlantic……Geological theories usually fall at a glacial pace into a sea of controversy, and this one is no exception. Today– charging that proof for the theory is lacking – many scientists believe that the Med always contained saltwater,with only the depth of the seafloor and the water being in question… Some of the tenets on which the theorywas formulated are, if not defective, very seriously in question. To interpret their findings, a respectable numberof geologists studying the surrounding emerged borderland as well as subsea sections indicate that alternative,more comprehensive concepts must be envisioned……It is not realistic to envision the Mediterranean seafloor of about 5 million years ago as a desert at 3,000meters below present ocean level. Several years ago…the Mediterranean [was compared] to a complexpicture-puzzle that comprises numerous intricate pieces, many of which are already in place. A general imageis emerging, although gaps in some areas of the picture remain fuzzy and indistinct.All of the following are features of the “desert theory” EXCEPT:

Suppose an α-particle starting from rest is accelerated through a 5 megavolt potential difference. What is thefinal kinetic energy of the α-particle? Section: Physical Sciences 

Figure 1Myoglobin facilitates transport in muscle and serves as a reserve store of O2. Mb is a single polypeptide chaincontaining a heme group, with a molecular weight of 18 kd. As can be seen in Figure 1, Mb (Curve D) has agreater affinity for than Hb.A sample of human adult Hb is placed in an 8 M urea solution, resulting in the disruption of noncovalentinteractions. After this procedure, the α chains of Hb are isolated. Which of the four curves most closelyresembles the O2-dissociation curve for the isolated α chains? [Note: Assume that Curve B represents the O2-dissociation curve for human adult Hb in vivo.]Section: Biological Sciences