Text Structure and Purpose: SAT Practice Questions & Study Guide

The following text is adapted from a 2020 biology textbook excerpt. Mitochondria are often called the "powerhouses of the cell," a description that captures their primary function: generating the adenosine triphosphate (ATP) that fuels cellular activity. But mitochondria do more than produce energy. They regulate the cell's calcium levels, contribute to thermogenesis, and play a central role in apoptosis—the programmed cell death that is essential to development and immune function. Understanding the full scope of mitochondrial function requires moving beyond the familiar powerhouse metaphor. What is the main purpose of the text?

The following text is adapted from a 2019 profile of linguist Noam Chomsky. Chomsky's theory of universal grammar—the idea that all human languages share a common underlying structure encoded in the human brain—transformed the study of linguistics in the 1960s. By proposing that language acquisition was innate rather than entirely learned, Chomsky gave linguists a new explanatory framework and set the agenda for cognitive science for decades. Today, however, some researchers question whether evidence from newly documented languages supports universal grammar's core claims, suggesting that grammatical universals may be far more limited than Chomsky proposed. The underlined sentence ("Today, however, some researchers...") primarily serves to

The following text is adapted from a 2021 essay on the history of public health. The campaign to add fluoride to public water supplies in the mid-twentieth century is often cited as one of public health's great triumphs: a low-cost, population-wide intervention that dramatically reduced tooth decay across all socioeconomic groups. Less frequently acknowledged is the campaign's contentious reception. Fluoridation was opposed by a coalition ranging from libertarians concerned about involuntary medication to some scientists who questioned whether the benefits outweighed the risks of systemic fluoride exposure. Understanding both the success and the controversy of fluoridation offers a more complete picture of how public health interventions are negotiated in democratic societies. What is the main purpose of the text?

The following text is adapted from a 2023 article on materials science. For decades, researchers believed that glass was thermodynamically a very viscous liquid—a material perpetually flowing, though far too slowly to observe. Museum guides routinely cited thicker window glass at the bottom of old church windows as evidence of this slow downward flow. This claim, while evocative, is now known to be incorrect. Medieval glassmakers installed panes with the thicker edge at the bottom as a deliberate construction choice, not as evidence of any flow. The glass in those windows has not moved measurably in five hundred years. The sentence "This claim, while evocative, is now known to be incorrect" primarily serves to

The following text is adapted from a 2022 philosophical essay on moral luck. Consider two drivers who are equally negligent—both run red lights, both are distracted, both are objectively equally blameworthy in their intentions. One driver reaches his destination without incident; the other strikes and injures a pedestrian. Our moral and legal practices treat these two individuals very differently, though their inner states and choices were identical. The philosopher Thomas Nagel called this asymmetry "moral luck"—the influence of factors outside an agent's control on how we assess their moral responsibility. Whether moral luck is a genuine feature of ethics or merely an artifact of our unreflective practices remains deeply contested. What is the main purpose of the text?

The following text is adapted from a 2021 review of climate adaptation literature. The adaptation literature in climate science has long been dominated by what scholars call the "impacts-first" framework: researchers identify projected climate impacts, then ask what policies could reduce harm. Recently, a growing group of scholars has proposed inverting this framework. Rather than beginning with impacts and working toward solutions, they argue for starting with the social vulnerabilities that make communities susceptible to harm in the first place—poverty, weak governance, inadequate infrastructure—and addressing those vulnerabilities directly. From this perspective, climate adaptation is less a technical exercise in managing projected futures than a continuation of longstanding social justice work. The final sentence of the passage primarily serves to

The following text is adapted from a 2019 article on the psychology of habit formation. Habit researchers have identified a three-part structure underlying most automatic behaviors: a cue that triggers the behavior, a routine (the behavior itself), and a reward that reinforces it. This "habit loop," first described by Ann Graybiel's neuroscience laboratory and later popularized by journalist Charles Duhigg, explains why habits are so resistant to elimination through willpower alone. Simply deciding to stop a habit does nothing to disrupt the cue-routine-reward cycle. Effective habit change, researchers argue, requires inserting a new routine between the existing cue and reward, leaving the loop's structure intact while replacing its core behavior. What is the main purpose of the text?

The following text is adapted from a 2023 essay on Victorian literary culture. Victorian lending libraries played a role in shaping the novel that literary historians have only recently begun to appreciate. Because lending libraries purchased books in bulk, publishers catered directly to their preferences—and the libraries' preferences were conservative. Mudie's Select Library, the largest in England, refused to stock novels with sexually explicit content or challenges to Christian orthodoxy, effectively setting the moral parameters of respectable fiction. Authors who wished to reach a mass audience had to negotiate with these gatekeepers, sometimes sanitizing their manuscripts after initial rejection. The result was a mainstream Victorian fiction that was, in part, an artifact of commercial constraint rather than purely artistic vision. The final sentence primarily serves to