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Are these substances moving across the membrane by active or passive transport?

Are these substances moving across the membrane by active or passive transport?-example-1
User Irae Carvalho
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1 Answer

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Passive transport: It is given when a molecule can cross through the membrane without any waste of energy, it is in favor of the concentration gradient. There are different types of passive transport, the most known is osmosis (the transport of water molecules from a zone of less solute concentration to a zone of more solute concentration).

Active transport: It is given with a waste of energy, and against the concentration gradient of the respective molecule.

In the first case:

Glucose: It is moving from a zone of 20% concentration to a zone of 10% concentration, i.e from one zone with more glucose to a zone with less glucose, so it is passive transport.

Water: It's the same as glucose in this case. It is moving by passive transport, specifically osmosis.

Second case:

Glucose: It is moving from a zone of 20% glucose to a zone with none, so it is passive transport.

Water: It is moving from a zone with no solute to a zone with solute (glucose), so it's by osmosis.

Third case:

In this case, both zones have the same concentration of glucose and water. This is what we call a dynamic equilibrium, where the molecules move from one zone to another constantly but concentrations of both do not change.

User Ensminger
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