Question

Water moves across a selectively permeable membrane: From (a) Region of higher water potential \(\quad\) Region of lower water potential (b) Lower water concentration Higher water concentration (c) Higher solute concentration Lower solute concentration (d) Region of higher osmotic potential Region of lower osmotic potential

Short answer

(a) From Region of higher water potential to Region of lower water potential, (b) From Higher water concentration to Lower water concentration, (c) From Lower solute concentration to Higher solute concentration, (d) From Region of higher osmotic potential to Region of lower osmotic potential

Step-by-step solution

Understand Water Potential Direction

In osmosis, water moves from a region of higher water potential to a region of lower water potential. So, the answer to (a) is `From Region of higher water potential to Region of lower water potential`.

Comprehend Water Concentration Direction

Water concentration and water potential are directly related. Therefore, in osmosis, water moves from an area of higher water concentration to an area of lower water concentration. Thus, the answer to (b) is `From Higher water concentration to Lower water concentration`.

Identify the Solute Concentration Direction

In osmosis, water moves from an area of lower solute concentration to an area of higher solute concentration. This is because the solute concentration negatively impacts the water potential, i.e., the higher the solute concentration, the lower the water potential. Hence, the answer to (c) is `From Lower solute concentration to Higher solute concentration`.

Distinguish Osmotic Potential Direction

Osmotic potential is another name of the solute potential, hence just like in step 3, osmosis moves water from a region of higher osmotic potential to a region of lower osmotic potential. Therefore, the answer to (d) is `From Region of higher osmotic potential to Region of lower osmotic potential`.

Key concepts

Water Potential

Water potential is a critical concept in understanding osmosis, which is the movement of water across a membrane. Simplified, water potential measures the potential energy of water in a system and determines the direction in which water will flow. Water moves from areas of high water potential, which usually have more pure water, to areas of low water potential, where water is less pure because it contains more solutes.

Consider water potential as a driving force: water under high potential is like a stored energy ready to move to an area of lower potential. This is why during osmosis, you'll see water traveling from a wet, spongy soil (high water potential) to a drier one (lower water potential), aiming to reach a balance. To help students grasp this idea, imagine a crowd of people (water molecules) in one room (higher water potential) moving towards an adjacent less crowded room (lower water potential) to spread out evenly.

Selectively Permeable Membrane

A selectively permeable membrane is a gatekeeper in the world of cells, deciding what may enter or leave. This type of membrane allows certain substances, like water, to pass through while blocking others, such as various solutes and ions. The selectivity is crucial for maintaining a stable internal environment in cells, called homeostasis.

In the context of osmosis, the selectively permeable membrane is what lets water molecules flow through while preventing solute particles from doing the same. This is why a raisin will plump up in a glass of water: water passes into the raisin through its selectively permeable skin, and since the inside has a higher solute concentration, water flows in to balance this out. A useful analogy for students is to think of the membrane as a security checkpoint, where water is like VIP guests with all-access passes and solutes are stopped at the gate.

Solute Concentration

Solute concentration refers to the amount of dissolved substances, such as salts or sugars, present in a solution. Understanding solute concentration is vital for grasping osmosis, as it inversely affects water potential: as the solute concentration increases, the water potential decreases, prompting water to move towards the higher solute concentration region.

A real-life example could be making lemonade: the more sugar (solute) added to the water, the lower its water potential becomes, and if there was a way for water to move, it would go into the lemonade mixture. Students can envision this by imagining themselves mixing different amounts of salt in water and seeing how the mixtures with more salt could 'pull' the water towards themselves.

Osmotic Potential

Osmotic potential, also known as solute potential, is a specific term used to describe the component of water potential that is due to the presence of solutes. It is always a negative value because solutes lower the water potential of a system. The greater the concentration of solutes in a solution, the more negative the osmotic potential becomes. In osmosis, water moves from an area with higher (less negative) osmotic potential to one with lower (more negative) osmotic potential.

Analogous to a financial analogy, if pure water has a 'wealth' of zero (high osmotic potential), adding solutes is like a 'debt' that lowers the 'wealth' (more negative osmotic potential). Understanding this concept helps students predict the flow of water: it migrates towards the 'debt' area to 'pay it off' and balance the books, so to speak, creating an equilibrium.