Illustration of red blood cell and plant cell responses to different tonicity conditions.

This question asks you to label the environments (isotonic, hypotonic, hypertonic) based on how red blood cells and plant cells appear in each.

Let’s break this down by understanding what happens to each cell type in different osmotic environments:

---

🧬 Osmosis Basics:

- Isotonic: Same solute concentration inside and outside the cell → no net water movement → cell maintains normal shape.
- Hypotonic: Lower solute concentration outside → water enters cell → cell swells (may lyse in animal cells; turgid in plant cells).
- Hypertonic: Higher solute concentration outside → water leaves cell → cell shrinks (crenates in animal cells; plasmolyzes in plant cells).

---

## 🔴 RED BLOOD CELL (Animal Cell — no cell wall)

a. Normal, round, smooth shape → Isotonic

- Water moves in and out equally → cell is in equilibrium.

b. Shriveled, spiky appearance → Hypertonic

- Water has left the cell due to higher solute concentration outside → crenation.

c. Swollen, possibly about to burst → Hypotonic

- Water entered the cell → swelling (lysis may occur if too much water enters).

---

## 🌿 PLANT CELL (Has rigid cell wall)

d. Cell membrane pulled away from cell wall, cytoplasm shrunken → Hypertonic

- Water left the cell → plasmolysis occurs (cell membrane detaches from cell wall).

e. Normal, but not fully swollen → Isotonic

- Cell is flaccid (not turgid), but not plasmolyzed → typical in isotonic environment.

> *Note: In many diagrams, plant cells in isotonic solution look slightly less full than in hypotonic, but still intact without plasmolysis.*

f. Turgid — cytoplasm pressed against cell wall → Hypotonic

- Water entered → vacuole expands → cell becomes firm/turgid (healthy state for plants).

---

## ✔ Final Answers:

RED BLOOD CELL
- a. Isotonic
- b. Hypertonic
- c. Hypotonic

PLANT CELL
- d. Hypertonic
- e. Isotonic
- f. Hypotonic

---

✔ This matches the expected behavior of cells under osmotic stress. Plant cells are protected from bursting by their cell wall, while animal cells like RBCs can lyse in hypotonic solutions.