HBO’s film adaptation of journalist Rebecca Skloot’s best-selling book “The Immortal Life of Henrietta Lacks” is a fine if somewhat formulaic lesson in how to pare a very complicated and often technical story down to its emotional essence. It also sends a clear message to those who fall back on science to answer any question or moral qualm, even when it comes to matters of the soul. We may be only a collection of cells, but beyond the microscope, the mystery of life is more elusive.

Or something like that. The film (airing Saturday) stars Rose Byrne as Rebecca, a freelance science writer determined to learn more about the deceased, anonymous woman whose cancerous cells, extracted without consent in 1951 at Baltimore’s Johns Hopkins Hospital, became a scientific legend. Easily reproduced, the “HeLa” cells played a vital role in decades of medical breakthroughs. Tracing their origin to Henrietta Lacks is easy enough, Rebecca discovers (it was more or less an open secret in scientific circles), but finding out more about Lacks’s life sends her on a difficult journey that will take more than a decade to finish.

Her first obstacle is the Lacks family itself — including Henrietta’s children, whose distrust and anger about the use of their mother’s cells has simmered for years. The youngest, a daughter named Deborah (Oprah Winfrey), doubts Rebecca’s sincerity and repeatedly accuses her of trying to profit off her mother’s story. As journalist and source, they reach an uneasy accord, with Deborah extracting a promise from Rebecca: “You ain’t gonna lie and you ain’t gonna keep nothing from me.”

The film — shepherded by Winfrey and directed by George C. Wolfe (“Lackawanna Blues”) from a screenplay by Wolfe, Peter Landesman and Alexander Woo — briskly skims over the copious amounts of medical sleuthing required to write the book, favoring the family narrative that begins and ends in the nearly nonexistent town of Clover, Va., where Henrietta grew up and had children. Through the recollections of older relatives, Deborah and Rebecca learn more about Henrietta’s past and her struggles.

As a parallel to the indifference with which Hopkins helped itself to her mother’s cells, Deborah is obsessed with tracking down the records of a sibling who was institutionalized. The film successfully conveys the triumph the women feel when they turn up scraps of information long thought to be lost; in a quieter way, “The Immortal Life of Henrietta Lacks” is another one of those heroic journalism movies — a lesson in sticking with a story long past the point that others would sensibly give up.

As far back as her Oscar-nominated film debut in 1985’s “The Color Purple,” Winfrey has been a reluctant actress, appearing here and there in projects that appealed to her, sometimes just to play a cameo version of her media-magnate self. Her performance here as Deborah is a reminder of how just how powerfully she can inhabit a character, even a difficult one. She empathetically shows us Deborah’s lifelong sense of violation, combined with her explosive temper and bouts of anxiety. It’s proof positive that Winfrey should make time in her schedule to take more acting jobs. (Unless she wants to run for president, which sounds a lot more plausible than it used to.)

“The Immortal Life of Henrietta Lacks” is beautifully shot, economically told (if anything it feels too rushed) and respectful to the legacy of the HeLa cells. At its heart, however, is a central misunderstanding. Doctors in the 1950s were concerned only with harvesting the cancer cells — a selfishly banal act — while Deborah and her family struggle throughout the story to grasp the basic science. When they hear that their mother’s cancer cells have been injected into monkeys or shot into space, they think that it’s literally her, that she can feel her cells interacting with the AIDS virus and other diseases.

Rebecca finally realizes the value in this line of magical thinking and rather than snuff Henrietta out of this process with clinical explanations, she gives the Lacks family the freedom to lend a spiritual aspect to their mother’s countless blessings to modern medicine.

Though it delves deeply into the Lacks’s pain, the film clearly intends to smooth over some rougher edges, perhaps in search of a peaceful ending. The real Deborah Lacks died in 2009, just before the book was released; the Lacks family continues to bicker over a sense of ownership to their mother’s legacy. But Henrietta’s gift (stolen or borrowed or however you want to perceive it) lives on.

The Immortal Life of Henrietta Lacks (95 minutes) airs Saturday at 8 p.m. on HBO, with encores.