Active Transport

• Sometimes organisms require certain substances and therefore need to move dissolved substances from a region of low concentration to a region where they are at a higher concentration.
• This process is of course opposite to the direction in which particles would normally move in diffusion. This is active transport.
• In Active Transport particles move against the concentration gradient and therefore require energy which must be supplied by the cell.
• Carrier proteins that are found in the cell membrane of cells use energy to transport molecules or ions across the membrane, against the concentration gradient.
• When organisms utilize active transport the energy for the process come from respiration. Due to this the cells capable of active transport usually have more mitochondria, in which respiration takes place, than other cells.
• Active transport is the movement of particles from an area of low concentration to an area of high concentration against a concentration gradient.

Active Transport in Plant cells

• Plants require mineral salts such as nitrates for growth
• The concentration of nitrates is higher on the plant root cell than it is in the soil solution surrounding it.
• The plant cannot rely on diffusion as the nitrates would diffuse out of the cell and into the soil.
• Hence the cells utilize energy to actively transport nitrates across the cell membrane into the root cell, against the concentration gradient.

Active Transport in Animal Cells

• The process of active transport takes place in the human during digestion of food in the ileum (small intestine).
• Once food has been absorbed by the villi, after some time the concentration of food molecules inside the villi increases, at this point no more food can diffuse in.
• As more food is still required, simple sugars, amino acids, vitamins & minerals are actively transported into the villi from an area of low concentration against the concentration gradient.

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