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Step-by-step solution for: Transport Across the Cell Membrane Worksheet student copy (3 ...
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Step-by-step solution for: Transport Across the Cell Membrane Worksheet student copy (3 ...
You've uploaded a worksheet titled "Transport Across the Cell Membrane" that explores osmosis and diffusion across a semi-permeable membrane using diagrams of bags in beakers with different concentrations of water and glucose. The student has already completed most of the questions, but let's go through the correctness, explanations, and clarifications for each section to ensure full understanding.
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Each diagram shows a bag (representing a cell or semi-permeable membrane) submerged in a beaker. The membrane is permeable to both water (H₂O) and glucose (G). The concentration of water and glucose differs between the inside of the bag and the solution in the beaker.
We analyze based on tonicity:
- Hypertonic: Higher solute concentration outside → water moves out.
- Hypotonic: Lower solute concentration outside → water moves in.
- Isotonic: Equal solute concentration → no net movement.
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## ✔ Detailed Answers & Explanations
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✔ Answer (already done):
- A: Water moves out of the bag → arrow from bag to beaker; Glucose moves into the bag → arrow from beaker to bag.
- B: Water moves into the bag → arrow from beaker to bag; Glucose moves out of the bag → arrow from bag to beaker.
- C: No net movement of water or glucose → balanced arrows or none.
> ✔️ Correct! These reflect concentration gradients.
---
✔ Student Answer:
- A: Hypertonic
- B: Hypotonic
- C: Isotonic
> ✔️ Correct!
#### Explanation:
- A: Bag = 80% H₂O, 20% Glucose → Beaker = 90% H₂O, 10% Glucose
→ Beaker has less glucose, so it’s hypertonic relative to the bag? Wait — this needs correction!
Wait — let’s double-check tonicity.
Tonicity compares solute concentration. Higher solute concentration = more concentrated.
Let’s re-analyze:
#### 🧪 Diagram A:
- Bag: 80% H₂O → 20% Glucose (high solute)
- Beaker: 90% H₂O → 10% Glucose (low solute)
→ So the bag has higher solute concentration than the beaker → the beaker is hypotonic to the bag.
But the student labeled it "Hypertonic", which is incorrect.
✘ Mistake here!
✔ Correction:
- A: The beaker is hypotonic to the bag (lower solute), so the bag is hypertonic.
- But the question asks: *"Is the solution in the beaker...?"* → So we label the beaker’s tonicity relative to the bag.
So:
- A: Beaker is hypotonic to the bag.
- B: Beaker is hypertonic to the bag.
- C: Beaker is isotonic to the bag.
➡️ Student got A wrong, B wrong, C correct.
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#### Re-labeling:
| Diagram | Bag | Beaker | Tonicity of Beaker Relative to Bag |
|--------|-----|--------|------------------------------------|
| A | 80% H₂O, 20% Glucose | 90% H₂O, 10% Glucose | Hypotonic |
| B | 100% H₂O, 0% Glucose | 80% H₂O, 20% Glucose | Hypertonic |
| C | 90% H₂O, 10% Glucose | 90% H₂O, 10% Glucose | Isotonic |
✔ So correct labels should be:
- A: Hypotonic
- B: Hypertonic
- C: Isotonic
✘ Student swapped A and B.
---
✔ Student Answer: Passive transport. An example is water diffusion.
✔️ Correct!
Water and glucose move down their concentration gradients without energy input → passive transport (diffusion). Osmosis is passive.
---
✔ Student Answer: The bag will shrink after time due to the water leaving.
✔️ Correct!
Because the beaker is hypotonic (lower solute), water leaves the bag → bag shrinks.
---
✔ Student Answer: The bag is going to extend due to the water traveling into the bag.
✔️ Correct!
Beaker is hypertonic → high solute → water enters the bag → bag swells/extends.
---
✔ Student Answer: The bag is going to stay the same due to the isotonic solution.
✔️ Correct!
Equal solute concentrations → no net movement → volume unchanged.
---
✔ Student Answer: The solution will be isotonic at the 'same strength'.
✔️ Partially correct, but needs refinement.
Better answer:
> At equilibrium, there is no net movement of water or glucose. Molecules still move randomly, but the rate in equals rate out. The solutions are isotonic.
---
✔ Student Answer: The red blood cells in your blood must constantly be in an isotonic condition. A 0.9% salt solution is isotonic to red blood cells.
✘ Incorrect. This is not answering the question.
The question asks: What molecule is largely responsible for the changes in volume?
Answer: Water (H₂O)
Because osmosis (movement of water) causes the swelling or shrinking of the bag. Glucose may diffuse, but it's water movement that changes volume.
✔ Correct answer: Water (H₂O)
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✔ Student Answer: The amount of water going into the cell is the same as the amount going out of the cell. The salt inside the cell is the same as the solution outside.
✔️ Correct concept, though no sketch is drawn.
Explanation: In isotonic solution:
- Salt concentration inside = outside
- Water movement is balanced
- Cell maintains normal shape
Example: 0.9% NaCl is isotonic to human RBCs.
---
## ✔ Final Summary of Corrections
| Question | Student Answer | Correctness | Correction Needed? |
|--------|----------------|-------------|--------------------|
| 1 | Arrows drawn | ✔️ Correct | ✔ |
| 2 | A: Hypertonic, B: Hypotonic, C: Isotonic | ✘ Incorrect | Swap A and B → A: Hypotonic, B: Hypertonic |
| 3 | Passive transport | ✔️ Correct | ✔ |
| 4 | Bag shrinks | ✔️ Correct | ✔ |
| 5 | Bag extends | ✔️ Correct | ✔ |
| 6 | Bag stays same | ✔️ Correct | ✔ |
| 7 | Isotonic at same strength | ⚠️ Partially correct | Add: "No net movement" |
| 8 | Red blood cell info | ✘ Incorrect | Answer: Water (H₂O) |
| 9 | Concept correct | ✔️ Correct | Needs sketch (not provided) |
---
## ✍️ Recommended Revision for Student
Label the beaker’s tonicity relative to the bag:
- A: Hypotonic (beaker has lower solute → water leaves bag)
- B: Hypertonic (beaker has higher solute → water enters bag)
- C: Isotonic
> Answer: Water (H₂O) is largely responsible for the changes in volume because its movement by osmosis causes the bag to swell or shrink.
---
## 🎯 Key Takeaways
- Tonicity depends on solute concentration.
- Water moves from low solute to high solute (osmosis).
- Passive transport occurs for both water and glucose.
- Equilibrium means no net movement.
- Volume changes are due to water movement, not glucose alone.
---
Let me know if you'd like a corrected version of the worksheet or a sketch for question 9!
---
🔬 Overview of the Diagrams
Each diagram shows a bag (representing a cell or semi-permeable membrane) submerged in a beaker. The membrane is permeable to both water (H₂O) and glucose (G). The concentration of water and glucose differs between the inside of the bag and the solution in the beaker.
We analyze based on tonicity:
- Hypertonic: Higher solute concentration outside → water moves out.
- Hypotonic: Lower solute concentration outside → water moves in.
- Isotonic: Equal solute concentration → no net movement.
---
## ✔ Detailed Answers & Explanations
---
1. Draw arrows indicating the net movement of each material.
✔ Answer (already done):
- A: Water moves out of the bag → arrow from bag to beaker; Glucose moves into the bag → arrow from beaker to bag.
- B: Water moves into the bag → arrow from beaker to bag; Glucose moves out of the bag → arrow from bag to beaker.
- C: No net movement of water or glucose → balanced arrows or none.
> ✔️ Correct! These reflect concentration gradients.
---
2. Is the solution in the beaker isotonic, hypertonic, or hypotonic to the solution in the bag? Label each solution under the picture.
✔ Student Answer:
- A: Hypertonic
- B: Hypotonic
- C: Isotonic
> ✔️ Correct!
#### Explanation:
- A: Bag = 80% H₂O, 20% Glucose → Beaker = 90% H₂O, 10% Glucose
→ Beaker has less glucose, so it’s hypertonic relative to the bag? Wait — this needs correction!
Wait — let’s double-check tonicity.
Tonicity compares solute concentration. Higher solute concentration = more concentrated.
Let’s re-analyze:
#### 🧪 Diagram A:
- Bag: 80% H₂O → 20% Glucose (high solute)
- Beaker: 90% H₂O → 10% Glucose (low solute)
→ So the bag has higher solute concentration than the beaker → the beaker is hypotonic to the bag.
But the student labeled it "Hypertonic", which is incorrect.
✘ Mistake here!
✔ Correction:
- A: The beaker is hypotonic to the bag (lower solute), so the bag is hypertonic.
- But the question asks: *"Is the solution in the beaker...?"* → So we label the beaker’s tonicity relative to the bag.
So:
- A: Beaker is hypotonic to the bag.
- B: Beaker is hypertonic to the bag.
- C: Beaker is isotonic to the bag.
➡️ Student got A wrong, B wrong, C correct.
---
✘ Let's fix this:
#### Re-labeling:
| Diagram | Bag | Beaker | Tonicity of Beaker Relative to Bag |
|--------|-----|--------|------------------------------------|
| A | 80% H₂O, 20% Glucose | 90% H₂O, 10% Glucose | Hypotonic |
| B | 100% H₂O, 0% Glucose | 80% H₂O, 20% Glucose | Hypertonic |
| C | 90% H₂O, 10% Glucose | 90% H₂O, 10% Glucose | Isotonic |
✔ So correct labels should be:
- A: Hypotonic
- B: Hypertonic
- C: Isotonic
✘ Student swapped A and B.
---
3. Are these substances moving across the membrane by active or passive transport? Explain.
✔ Student Answer: Passive transport. An example is water diffusion.
✔️ Correct!
Water and glucose move down their concentration gradients without energy input → passive transport (diffusion). Osmosis is passive.
---
4. Describe how the appearance of the bag at “A” might change after a period of time has passed.
✔ Student Answer: The bag will shrink after time due to the water leaving.
✔️ Correct!
Because the beaker is hypotonic (lower solute), water leaves the bag → bag shrinks.
---
5. Describe how the appearance of the bag at “B” might change after a period of time has passed.
✔ Student Answer: The bag is going to extend due to the water traveling into the bag.
✔️ Correct!
Beaker is hypertonic → high solute → water enters the bag → bag swells/extends.
---
6. Describe how the appearance of the bag at “C” might change after a period of time has passed.
✔ Student Answer: The bag is going to stay the same due to the isotonic solution.
✔️ Correct!
Equal solute concentrations → no net movement → volume unchanged.
---
7. What will happen to the movement of water and glucose when both sides of the membrane have reached equilibrium?
✔ Student Answer: The solution will be isotonic at the 'same strength'.
✔️ Partially correct, but needs refinement.
Better answer:
> At equilibrium, there is no net movement of water or glucose. Molecules still move randomly, but the rate in equals rate out. The solutions are isotonic.
---
8. What molecule is largely responsible for the changes in volume of these bags?
✔ Student Answer: The red blood cells in your blood must constantly be in an isotonic condition. A 0.9% salt solution is isotonic to red blood cells.
✘ Incorrect. This is not answering the question.
The question asks: What molecule is largely responsible for the changes in volume?
Answer: Water (H₂O)
Because osmosis (movement of water) causes the swelling or shrinking of the bag. Glucose may diffuse, but it's water movement that changes volume.
✔ Correct answer: Water (H₂O)
---
9. Draw a simple sketch of a red blood cell in an isotonic solution. Label the inside and the outside of the cell with the correct concentrations of salt and water.
✔ Student Answer: The amount of water going into the cell is the same as the amount going out of the cell. The salt inside the cell is the same as the solution outside.
✔️ Correct concept, though no sketch is drawn.
Explanation: In isotonic solution:
- Salt concentration inside = outside
- Water movement is balanced
- Cell maintains normal shape
Example: 0.9% NaCl is isotonic to human RBCs.
---
## ✔ Final Summary of Corrections
| Question | Student Answer | Correctness | Correction Needed? |
|--------|----------------|-------------|--------------------|
| 1 | Arrows drawn | ✔️ Correct | ✔ |
| 2 | A: Hypertonic, B: Hypotonic, C: Isotonic | ✘ Incorrect | Swap A and B → A: Hypotonic, B: Hypertonic |
| 3 | Passive transport | ✔️ Correct | ✔ |
| 4 | Bag shrinks | ✔️ Correct | ✔ |
| 5 | Bag extends | ✔️ Correct | ✔ |
| 6 | Bag stays same | ✔️ Correct | ✔ |
| 7 | Isotonic at same strength | ⚠️ Partially correct | Add: "No net movement" |
| 8 | Red blood cell info | ✘ Incorrect | Answer: Water (H₂O) |
| 9 | Concept correct | ✔️ Correct | Needs sketch (not provided) |
---
## ✍️ Recommended Revision for Student
🔁 Fix Question 2:
Label the beaker’s tonicity relative to the bag:
- A: Hypotonic (beaker has lower solute → water leaves bag)
- B: Hypertonic (beaker has higher solute → water enters bag)
- C: Isotonic
🔁 Fix Question 8:
> Answer: Water (H₂O) is largely responsible for the changes in volume because its movement by osmosis causes the bag to swell or shrink.
---
## 🎯 Key Takeaways
- Tonicity depends on solute concentration.
- Water moves from low solute to high solute (osmosis).
- Passive transport occurs for both water and glucose.
- Equilibrium means no net movement.
- Volume changes are due to water movement, not glucose alone.
---
Let me know if you'd like a corrected version of the worksheet or a sketch for question 9!
Parent Tip: Review the logic above to help your child master the concept of cell membrane transport worksheet.
