OCR A Level Biology:复习笔记2.5.5 Active Transport

Active Transport

  • Active transport is the movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
  • Active transport requires carrier proteins (each carrier protein being specific for a particular type of molecule or ion)
  • Although facilitated diffusion also uses carrier proteins, active transport is different as it requires energy
  • The energy is required to make the carrier protein change shape, allowing it to transfer the molecules or ions across the cell membrane
  • The energy required is provided by ATP (adenosine triphosphate) produced during respiration. The ATP is hydrolysed to release energy

A carrier protein changing shape during active transport

  • Active transport is important in:
    • The reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules
    • The absorption of some products of digestion from the digestive tract
    • The loading of sugar from the photosynthesising cells of leaves into the phloem tissue for transport around the plant
    • The loading of inorganic ions from the soil into root hairs

     

Exam Tip

Be careful not to get carrier proteins and channel proteins confused when answering questions on active transport. Active transport requires carrier proteins (transmembrane transport proteins that undergo conformational change) not channel proteins.

 

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