Final answer:
Passive transport occurs without energy while active transport requires energy. Osmosis is a form of passive transport where water moves across a membrane without energy use. Selective permeability of the plasma membrane is crucial for maintaining homeostasis through these transport processes.
Step-by-step explanation:
Differences Between Passive and Active Transport
The main difference between passive transport and active transport is that passive transport does not require the cell to expend energy, whereas active transport requires energy, often in the form of ATP, to move substances across the cell membrane.
Examples of Passive Transport
Diffusion: A perfume molecule spreading out in a room.
Osmosis: Water moving through a semipermeable membrane to balance solute concentration.
Facilitated Diffusion: Glucose entering a cell via a specific carrier protein.
All these passive transport processes share the commonality of moving substances down their concentration gradient, from areas of higher concentration to lower concentration, without the use of cellular energy.
Active Transport
Active transport, on the other hand, moves substances against their concentration gradient, from an area of lower concentration to higher concentration. This process often involves transport proteins such as pumps, and an example includes the sodium-potassium pump which exchanges Na+ for K+ across the cell membrane.
Osmosis as a Form of Passive Transport
Osmosis is a special type of diffusion where water moves across a semipermeable membrane. Since osmosis occurs without the expenditure of cellular energy, it is considered a form of passive transport.
Importance of Plasma Membrane Selective Permeability
The plasma membrane's selective permeability is essential for maintaining the cell's homeostasis by regulating the entry and exit of different compounds, and thus is closely related to both active and passive transport mechanisms.