Active transport:
- the movement of particles through a cell membrane
- from a region of lower concentration
- to a region of higher concentration
- using energy from respiration
*Attn!: this is against the concentration gradient. It is like swimming against the current of water, and therefore, requires energy.
Animals and plants rely on active transport to move substances (when the concentration gradient is not set up to favor diffustion).
Cells need to provide energy for active transport ('active' being the operative word here).
- energy is supplied by respiration using ATP
- at the mitochondria
Protein molecules called carrier proteins in the cell membrane transport molecules across the membrane.
- the protein binds with ATP
- ATP breaks down to release energy
- the protein changes shae
- particles are moved against the concentration gradient.
Active transport is important for the movement of substances across membranes e.g. ion uptake by root hairs and uptake of glucose by epithelial cells of villi and kidney tubules
Tip!
2 main differences between diffusion and active transport:
- direction of movement (down or up a gradient)
- whether or not energy is needed for the movement
Practice question
Figure above shows root hair cells.
b)Explain why respiration rates may increase in root hair cells during the uptake of mineral ions [1 mark]- Explain how the presence of root hair cells on roots enables the efficient absorption of water and minerals. [2 marks]
- Root hair cells can absorb mineral ions by diffusion and active transport.
Answers
1. - Large number of root hair cells give a large surface area to the root.
- Mitochondria are present to provide energy for active transport.
2. a) active transport is absorption of a substance into a cell or across a membrane
- against (up) a concentration gradient.
- using energy
b) active transport requires energy
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