Domain: Healthcare — Digestive Physiology
Target concept: Maltase Activity Assay (Maltose Hydrolysis Method)

Video generation prompt: Place maltose solution into two labeled test tubes; add maltase to one tube and leave the other as a no-enzyme control, then incubate both in a water bath at the same temperature. Add Benedict's reagent to both tubes and heat them gently side by side for the same short duration. Demonstrate clear steps, labeled test tubes, controlled temperature, and simple manual operation.

Evaluation guide:
(i) Target concept: Enzymatic hydrolysis of maltose by maltase, monitored by comparing Benedict's-reagent reduction against an untreated control.
Minimum mechanism: Maltase (an alpha-glucosidase, not amylase) cleaves the glycosidic bond of maltose into two glucose units. Maltose itself already carries one free (reducing) anomeric carbon, so an untreated control tube will also eventually give some positive Benedict's reaction on heating. The assay therefore cannot rely on precipitate presence or absence alone. What maltase's action changes is the amount of free reducing sugar: hydrolysis roughly doubles the number of free reducing ends per original maltose molecule, so the maltase-treated tube reaches a denser brick-red Cu2O precipitate sooner and more intensely than the control tube within the same fixed, short heating interval. Benedict's reagent supplies Cu2+ in an alkaline tartrate complex that is reduced to Cu2O on heating in the presence of a reducing sugar.
(ii) Storyline: [0-2s] Two labeled test tubes, each with clear maltose solution, shown side by side. [2-3s] Maltase is added to one tube only; the other tube is left as a no-enzyme control (or receives an equal volume of plain solution). [3-5s] Both tubes are placed into the same water bath at a stable temperature, side by side, with contents continuously visible. [5-6s] Benedict's reagent is added to both tubes as a second, distinct liquid addition. [6-10s] Both tubes are gently heated together for the same short duration; any resulting precipitate settles gradually from the bottom upward. All steps occur from a fixed frontal lab-bench perspective with both tubes visible throughout.

Manual:
Experimental Procedure
1. Place equal volumes of clear maltose solution into two labeled test tubes (Tube A: plus maltase; Tube B: no-enzyme control).
2. Add maltase solution to Tube A only; add an equal volume of plain solution with no enzyme to Tube B.
3. Incubate both tubes together in a water bath at the same stable temperature.
4. Add Benedict's reagent to both tubes.
5. Gently heat both tubes together for the same short, fixed duration.
Observation of Experimental Phenomena
Both tubes may eventually show some brick-red or orange precipitate on heating, because maltose itself is already a reducing sugar. However, Tube A (maltase-treated) develops a denser, more complete precipitate sooner than Tube B (control) within the same heating window, since maltase hydrolysis roughly doubles the amount of free reducing sugar available to react with Benedict's reagent. No precipitate forms in either tube before Benedict's reagent is added and heat applied.
Summary of Experimental Principles
Maltase hydrolyzes maltose into two glucose units. Because maltose already has one free reducing (hemiacetal) group, both the enzyme-treated and control tubes are capable of giving a positive Benedict's test on heating — the difference maltase produces is in the rate and intensity of color and precipitate development (denser, faster in the treated tube), not in a simple positive-versus-negative result. Benedict's reagent (Cu2+ in alkaline tartrate) is reduced by reducing sugars on heating to form insoluble brick-red Cu2O.

Prompt Grounding rubric:
level_1: No test tube is shown; neither maltose solution, maltase, nor Benedict's reagent appears at any point; there is no water bath; no hand action of adding, incubating, or heating anything is shown.
level_2: A test tube or a reagent container appears, but no actual pouring or adding action ever happens, or the two tubes are not distinguishable from one another, with no labels and no visible difference in what is added to each.
level_3: Two test tubes are shown, each labeled or otherwise visually distinguishable, and each contains a clear liquid; maltase is visibly added to one tube while the other tube visibly receives no such addition, or receives a plain solution instead; both tubes are placed into a shared water bath that shows a steady temperature, such as visible steam or a stable liquid level.
level_4: Both tubes are shown side by side throughout incubation; after incubation, Benedict's reagent is visibly added to both tubes as a distinct second liquid addition; both tubes are then gently heated together, with visible signs of heat such as steam or gentle bubbling around both; the maltase tube and the control tube go through every step in the same order and at the same time as each other.
level_5: The maltase tube and the control tube are each clearly labeled and stay visually distinguishable throughout; each step (placing maltose solution, adding maltase to only one tube, incubating both, adding Benedict's reagent to both, and heating both) happens in the correct order for both tubes at once; both tubes remain fully visible with a fixed camera viewpoint and stay in a stable side-by-side arrangement for the entire clip, with neither tube leaving the frame or being fully blocked from view at any point.

Scientific and Causal Correctness rubric:
level_1: Neither tube shows any color change after heating, or both tubes develop the identical brick-red precipitate at the same time with no visible difference between them, or a color change happens before Benedict's reagent has even been added.
level_2: A color change happens at the wrong stage, for example immediately upon adding maltase before Benedict's reagent or heat is involved, or the control tube rather than the maltase tube is the one that reacts faster or more strongly.
level_3: Both tubes are colorless-to-blue before heating and only begin changing color after Benedict's reagent has been added and heat applied; the maltase tube's brick-red or orange precipitate appears sooner or looks more developed than the control tube's by the end of the heating window, even if the control eventually shows a faint version of the same color change.
level_4: The maltase tube consistently reaches a denser, more developed brick-red or orange precipitate than the control tube within the same heating time, with the control's color change, if any, clearly lagging behind or staying visibly fainter; the color development in both tubes looks like it comes from the bottom of the liquid rather than appearing instantly throughout.
level_5: Within the same fixed heating interval, the maltase tube visibly develops a denser, more complete brick-red or orange precipitate than the control tube, and this gap between the two tubes is visible and holds for the remainder of the clip; neither tube shows an implausible color, such as black char or purple/magenta; the precipitate in both tubes, where present, settles toward the bottom rather than floating or dispersing through the liquid.

Spatiotemporal Consistency rubric:
level_1: A test tube is hidden from view for a moment and then shown suddenly full again with no visible transition, a hand adding a reagent disappears mid-pour and reappears elsewhere, a tube's orientation snaps to a different angle with no motion shown getting there, or the lighting on the bench changes drastically from one moment to the next.
level_2: There is a visible jump cut between steps, a hand's motion looks jerky at the start or end of a pour, the water bath's surface ripples in a way that doesn't match anything touching it, or a tube visibly wobbles hard during a phase when it should be sitting still.
level_3: Both tubes stay in the same position relative to each other throughout; hand motion during each addition looks like one continuous motion rather than a series of jumps; the tubes stay upright and still during incubation; the water bath's surface shows only small, steady ripples rather than sudden disturbances.
level_4: The camera viewpoint doesn't pan, tilt, or zoom at any point; no hand or object fully blocks the view of either tube's contents during an addition or during heating; both tubes keep the same orientation across every phase of the procedure; neither tube's liquid surface flickers or strobes at any point.
level_5: Liquid poured into each tube follows a smooth, continuous arc rather than jumping or teleporting; heating produces a gradual, even shimmer above each tube rather than an instant change; any precipitate that forms visibly settles downward over several moments rather than snapping into place; a hand and a tube never appear to pass through one another; no motion anywhere in the clip runs backward or repeats itself.