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Grade 9 · unit review

Review: Cell Transport and Boundaries

Model exchange across cell membranes and connect it to gradients.

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Bring the unit skills together

Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.

Unit review questions
1. Which scientific label fits the specifically described step or feature? Supplied case: Particles spread down their concentration gradient.
Need a hint?
  • Look for the described feature: net particle movement down concentration gradient.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.
2. Supplied case 5: higher concentration (mmol/L)=25; lower concentration (mmol/L)=10, using the explicitly named quantities. Concentration difference equals higher millimoles per liter minus lower millimoles per liter. What result follows?
Need a hint?
  • Concentration difference equals higher millimoles per liter minus lower millimoles per liter.
  • Net movement differs from each individual path.
3. Which scientific label fits the specifically described step or feature? Supplied case: No net change despite microscopic motion.
Need a hint?
  • Look for the described feature: opposing flows balance on average.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.
4. Which scientific label fits the specifically described step or feature? Supplied case: Boundary size available for transport.
Need a hint?
  • Look for the described feature: boundary available for exchange.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Create a four-panel explanation for “Cell Transport and Boundaries” using one supplied case from each lesson. Include the observation, scientific mechanism or calculation, result and a limitation. You may draw and speak your explanation; all inputs are supplied.

Work on paper or in your own document. Explain the choices you made.

  • Use one supplied case from each of the four lessons.
  • Name the relevant structure, quantity or process in every panel.
  • Show calculations with units or a causal evidence chain.
  • Distinguish source facts from fictional classroom data.
  • State a model limit or a condition that would change the result.
Compare with a model response

Panel 1: A permeable membrane separates solute at 6 and 1 mmol/Lwithout a pump. What net tendency fits? Which inference or prediction is best supported? Result: Net passive solute movement is high-to-low while particles can move both ways.. Reasoning: Random microscopic motion plus the gradient produces a net tendency, not one-way individual paths. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 2: Supplied case 1: higher concentration (mmol/L)=12; lower concentration (mmol/L)=4, using the explicitly named quantities. Concentration difference equals higher millimoles per liter minus lower millimoles per liter. What result follows? Result: 8 mmol/L. Reasoning: Substitute the supplied values: (12)-(4) = 8 mmol/L. Use the same concentration unit. Gradient direction depends on the measured substance. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 3: At equal solute concentration, ten modeled particles move each way per interval. What follows? Which inference or prediction is best supported? Result: Net movement is zero while microscopic movement continues.. Reasoning: Balanced opposite flows create dynamic equilibrium without ending individual motion. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 4: A cube model doubles side length from 1 to 2 units. Which comparison follows? Which inference or prediction is best supported? Result: Area/volume falls from 6/1=6 to 24/8=3.. Reasoning: Area scales with length squared and volume with length cubed, reducing ratio for similar larger shapes. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.