Active transport: uptake against the gradient needs energy
הוצג| English | משמעות |
|---|---|
| mineral ion/ˈmɪnərəl ˈaɪɒn/ | יוני מינרלים |
| active transport/ˈæktɪv ˈtrænspɔːt/ | הובלה פעילה |
What would explain this observation?
- A root can absorb mineral ions 矿物离子 even when their concentration is lower in soil solution than inside its cells. Net diffusion alone would not explain this uptake.
Build the model
- Active transport 主动运输 moves substances from a more dilute region to a more concentrated one, against their concentration gradient.
- It requires energy from respiration.
- Root hair cells use it to absorb mineral ions needed for healthy growth from dilute soil solution.
- Sugar can also be absorbed from a lower concentration in the gut into blood with a higher sugar concentration.
- active transport: Movement of a substance against its concentration gradient using energy.
- mineral ion: A dissolved charged mineral species used by an organism.
Which observation requires active transport in the stated model?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Active transport is required when net movement goes AGAINST the gradient - ions entering a cell that already holds a higher concentration. Diffusion down a gradient and water balance need no energy from respiration.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Compare three processes.
- Diffusion gives net movement of particles down their gradient.
- Osmosis concerns water crossing a partially permeable membrane from dilute toward more concentrated solution.
- Active transport can move selected solutes against their gradient using respiratory energy.
- The same membrane can support more than one process for different substances.
In the lab: Interpret a provided concentration diagram: label the substance and both concentrations before choosing the process. Use school-approved plant observations or model data to examine the effect of conditions limiting respiration. Control tissue condition and time; reduced uptake may have several causes and does not alone reveal a complete transport mechanism.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a model uptake observation transfers 0.24 milligrams of a mineral ion in 12 min.
- Mean uptake rate =0.24/12=0.020 mg/min.
- If uptake is into a cell already at higher mineral-ion concentration, its direction supports an active-transport explanation.
- Rate alone does not identify whether the gradient is favourable or unfavourable.
Your turn: A model root absorbs 0.30 mg ions in 15 min. Calculate mean uptake rate.
A model root absorbs 0.30 mg ions in 15 min. Calculate mean uptake rate.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 0.02 mg/min. Known: 0.30 mg absorbed in 15 min. Use mean rate = amount / time. Rate = 0.30/15 = 0.02 mg per minute. The rate alone does not show the direction relative to the gradient.
Check the conclusion and its limits
- “Active” does not mean faster under every condition.
- Energy comes from respiration, not from the mineral ion automatically being nutritious.
- Water movement by osmosis is not defined as active transport of water against a gradient.
Not true: Active transport requires no energy from respiration. "Active" means energy-dependent: moving substances against their gradient requires energy released by respiration, usually via transport proteins. Without respiration, active transport stops.
- Active transport moves substances from a more dilute region to a more concentrated one, against their concentration gradient.
- Compare three processes.
- Watch for: “Active” does not mean faster under every condition.
Active transport requires no energy from respiration.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
"Active" means energy-dependent: moving substances against their gradient requires energy released by respiration, usually via transport proteins. Without respiration, active transport stops.
Movement of a substance against its concentration gradient using energy: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
active transport means Movement of a substance against its concentration gradient using energy.