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RELEVANT LEARNING OUTCOME:
(c) Explain how and why different substances move across membranes through simple diffusion, osmosis, facilitated diffusion, active transport, endocytosis and exocytosis.
Active transport is the movement of ions/molecules across a membrane against a concentration gradient (i.e., from a region of lower concentration to a region of higher concentration). It involves the a protein pump and the expenditure of energy by the cell, usually in the form of ATP.
The three main ways in which active transport occurs in cells are through:
Coupled carriers
ATP-driven pumps
Light-driven pumps
👁️🗨️Watch the video to learn about active transport through
ATP-driven sodium-potassium pump (until 4:18)
Coupled carriers (from 5:46 - 'secondary active transport')
Why would cells need to move particles against a concentration gradient? What do you think is the advantage of having coupled carriers?
🖊️Check Your Understanding: Learning Goals Checkpoint
🖊️Check Your Understanding: Learning Goals Checkpoint
List the similarities between active transport and facilitated diffusion.
They both require proteins to assist the transport over particles across the membrane.
In the case of facilitated diffusion through a carrier protein, both processes require a conformational change in the protein involved.
List the differences between active transport and facilitated diffusion.
Active transport vs facilitated diffusion
Requires energy expenditure in the form of ATP hydrolysis vs does not require additional expenditure of energy from ATP (energy required is from the kinetic energy of the particles themselves).
Involves one type of protein (carrier protein) vs involves one of two types of proteins (carrier or channel proteins).
Requires a conformational change of the (carrier) protein vs may not necessarily involve the conformational change of the protein (in the case of channel proteins).
Transports particles against a concentration gradient vs transports particles down a concentration gradient.
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