Domain: Healthcare — Digestive Physiology
Target concept: Pepsin Activity Assay (Protein Digestion Method)

Video generation prompt: Equal volumes of protein samples were placed into two tubes separately. An acid-containing pepsin solution was added to one tube, while water was added to the other. Both tubes were kept at a warm temperature. After heating, the tubes were gently shaken and compared, focusing only on the procedural steps.

Evaluation guide:
(i) Target concept: Enzymatic protein digestion by pepsin under acidic, warm conditions results in measurable physical state change (reduced turbidity/viscosity) distinguishable from control.
Minimum mechanism: Protein substrate must be initially insoluble/opaque; pepsin must be co-delivered with acid (HCl) to activate; warmth must be sufficient for enzymatic activity (≥37°C); time must allow catalytic turnover; absence of enzyme (water control) must preserve initial state.
(ii)Storyline: [Phase 1: Setup] Two identical tubes enter frame side-by-side; equal opaque protein suspension is dispensed into each. [Phase 2: Intervention] Distinct liquids added: one visibly differentiated (amber-tinted/labeled) pepsin+acid, one colorless/unlabeled water. [Phase 3: Incubation] Tubes remain still on warm surface (steam/hotplate cue), no action, no change. [Phase 4: Test] Simultaneous gentle shake applied, motion identical in timing/amplitude. [Phase 5: Readout] Side-by-side freeze-frame or slow pan reveals differential flow behavior: pepsin tube liquid moves uniformly; water tube shows suspended particulates resisting motion. Perspective: Fixed frontal view, eye-level, centered framing; all phases fully visible, no occlusion.

Manual:
Experimental Procedure
1. Place equal volumes of opaque white protein suspension into two identical transparent tubes.
2. Add acid-containing pepsin solution to first tube; add water to second tube.
3. Place both tubes on warm surface; wait briefly.
4. Gently shake both tubes simultaneously.
5. Compare side-by-side.
Observation of Experimental Phenomena
The pepsin tube becomes less opaque and flows freely; the water tube remains thick, cloudy, and resistant to flow.
Summary of Experimental Principles
Pepsin, activated by acid and warmth, hydrolyzes proteins into smaller peptides, reducing viscosity and turbidity; water causes no enzymatic digestion.

Prompt Grounding rubric:
level_1: Neither tube is shown, or only one tube appears in frame; no protein suspension is placed into any tube; no pepsin-and-acid solution or water is added to either tube; there is no cue suggesting a warm incubation step (no hot plate, steam, or similar warmth indicator); the two tubes are never shown together for a final comparison.
level_2: Two containers appear but are mismatched in size or shape; the protein suspension is placed into only one tube, or the amounts clearly differ between the two tubes; a liquid is added to both tubes or to neither, rather than one tube receiving the pepsin-acid solution and the other receiving water; the two added liquids look identical, with no color, tint, or other visual cue distinguishing which tube received which liquid.
level_3: Two matching transparent tubes are shown side by side, each holding an equal amount of an opaque white protein suspension (e.g., an egg-white mixture); one tube then receives a visibly distinct liquid (such as a pale-yellow-tinted solution) while the other receives a clear, colorless liquid; both tubes sit undisturbed near an implied warm surface (hot-plate glow, rising steam, or a similar cue); the recording ends with both tubes shown together in the same frame for a final comparison.
level_4: Everything required at the 3-point level is present, and additionally the two added liquids keep a clearly distinguishable visual identity (for instance a faint amber tint versus fully colorless) rather than looking like the same liquid; the protein suspension in both tubes looks identically opaque and uniform before any liquid is added; no extra actions such as stirring or swapping tubes occur before the warm/incubation phase; and the two-tube layout stays fixed and centered in frame throughout.
level_5: Everything at the 4-point level holds for the entire recording with no lapses: the visual distinction between the two liquids remains identifiable in every frame from the moment they are added through the final comparison; equal amounts of protein suspension are placed in both tubes before either liquid is introduced; which tube received which liquid never becomes unclear or swapped; and there is no camera movement, cut, occlusion, or lighting change at any point in the recording.

Scientific and Causal Correctness rubric:
level_1: No discernible change occurs in either tube; both tubes look identical before and after the incubation; no digestion-related phenomenon is visible; there is no consistent link between which liquid was added and what happens to the tube's contents.
level_2: Only one tube shows any change (e.g., cloudiness, settling, or a color shift) with no consistent pattern relating it to the added liquid; the change occurs in the wrong tube (e.g., the water tube clears while the pepsin tube thickens); or the observed change contradicts pepsin's digestive role (e.g., the pepsin tube solidifies rather than becoming more fluid).
level_3: Both tubes start out as a uniform opaque white suspension; after the warm incubation period, the pepsin tube shows reduced opacity and increased fluidity (e.g., visible flow when gently shaken, partial clearing, or even thinning), while the water tube keeps its original opacity and thickness (no flow, clumping or settling unchanged); this difference only appears after the liquids are added and the warm period has passed, not before.
level_4: Building on the 3-point distinction, the pepsin tube's clearing and thinning progress in one direction only, without re-thickening or separating back into layers; the water tube shows no clearing, no increase in flow, and no loss of its original clumped texture at any point; neither tube shows behavior at odds with pepsin's digestive role, such as bubbling or a solid curd forming only in the pepsin tube.
level_5: The distinction from the 4-point level holds throughout, and additionally: when both tubes are shaken at the same time, the pepsin tube's contents swirl and flow as a single uniform liquid with no visible particles resisting the motion, while the water tube's contents show visible particulate matter that settles or clumps and resists flowing freely; at no point in the sequence does either tube's behavior reverse or become ambiguous.

Spatiotemporal Consistency rubric:
level_1: One or both tubes appear to jump to a different position between frames; the room lighting switches abruptly from bright to dark with no transition; a tube, its liquid, or the warm surface flickers, vanishes, or visibly distorts in shape; or the liquid level inside a tube changes amount from one frame to the next with no addition or shake shown to cause it.
level_2: One tube rotates or shifts sideways relative to the other partway through the sequence; the liquid being poured appears to miss the tube's opening or the resulting liquid level doesn't match what was poured; the gentle shake looks jerky in one tube but smooth in the other, or is missing from one tube entirely; or the warm-surface background (hot plate, steam) appears and disappears between phases without explanation.
level_3: Both tubes stay in the same relative position and plane throughout, whether the footage is one continuous shot or has cuts that preserve this alignment; each poured liquid visibly enters its tube's opening rather than spilling past it; the final shake is applied to both tubes at the same time; each tube's cast shadow and the scene's overall brightness stay recognizably similar in strength and direction from setup through the final comparison, but one minor spatial slip is present, such as a brief single-frame jump in a tube's edge position or a short blur that makes it hard to tell exactly when the shake starts.
level_4: All the continuity described at the 3-point level holds with no exceptions; in addition, any visible text or marking on a tube stays legible and upright throughout, neither tube appears to shift closer to or farther from the camera relative to the other during the shake, and the tube rims and liquid surfaces show no visible drift out of alignment between frames, except for a brief moment of motion blur during the shake itself that doesn't obscure the final side-by-side comparison.
level_5: The entire sequence is filmed from one fixed, front-facing viewpoint with no camera panning, rotation, or zoom at any point; both tubes' rims show no visible drift or misalignment across the whole recording; each liquid's surface stays level and undisturbed during the still (non-shake) phases; and the final shake is smooth, symmetric, and matched in speed and extent between the two tubes, so the only motion difference visible is in how each liquid behaves once shaken.