Active transport: uptake against the gradient needs energy
| English | 中文 | Pinyin |
|---|---|---|
| mineral ion/ˈmɪnərəl ˈaɪɒn/ | 矿物离子 | kuàng wù lí zi |
| active transport/ˈæktɪv ˈtrænspɔːt/ | 主动运输 | zhǔ dòng yùn shū |
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.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
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?
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.
Match each technical term to its precise meaning.
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.
- 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?
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.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- 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.
A model root absorbs 0.30 mg ions in 15 min. Calculate mean uptake rate. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model root absorbs 0.30 mg ions in 15 min. Calculate mean uptake rate.
The result is 0.02 mg/min. 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.
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.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Active transport requires no energy from respiration. This claim is false: “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.
Active transport: uptake against the gradient needs energy: 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.
Active transport requires no energy from respiration.
“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.
Movement of a substance against its concentration gradient using energy: write the technical term.
active transport means Movement of a substance against its concentration gradient using energy.