Biology / Unit 2 Bio 0345 short lesson, about 20 seconds
Carrier Proteins
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The idea
A carrier protein binds a specific substance and changes shape to move it across the membrane, saturating once every carrier is occupied.
In practice
When blood glucose exceeds what the kidney's glucose carriers can reabsorb, the excess passes into the urine.
Where people slip
Once saturated, raising the gradient further does not raise the transport rate — the carriers become the limit.
Your place on the trail
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