Cellular Transport - Active Transport (OCR GCSE Combined Science A (Gateway))

Active Transport

• Diffusion and osmosis rely upon the passive (no energy is required) transport of substances down concentration gradients

• Cells also need to be able to transport substances across the cell membrane against a concentration gradient.

  • This requires the input of energy (in the form of ATP) released from cellular respiration

• Active transport moves substances from a more dilute solution to a more concentrated solution

Active transport across the cell membrane involves protein carrier molecules embedded in the cell membrane

Plants

• Root hair cells lining the surface of plant roots need to move minerals such as magnesium ions from a region of lower concentration (the very dilute solution of minerals in the soil surrounding the roots) to a region of higher concentration (inside the cytoplasm of the cell)

• Mineral ions are needed by plants to function healthily

  • Magnesium ions are needed to make chlorophyll

  • Nitrate ions are needed to make amino acids and therefore for protein synthesis (and subsequently growth)

Animals

• Nutrients (e.g. glucose) can diffuse into the bloodstream from the small intestine (the gut)

• But this is dependent on a concentration gradient existing between the small intestine and the bloodstream

  • i.e. a higher concentration of glucose in the small intestine compared to the bloodstream

• Active transport allows nutrients like glucose to be transported into the bloodstream from the small intestine even when the concentration gradient is in the wrong direction

  • i.e. when the concentration of sugar molecules in the bloodstream is higher

  • This is essential to stop us from starving as glucose can continuously be transported to the bloodstream