Practice: AP Biology water potential

What is water potential?

Water potential ($\displaystyle Ψ$) is the measure of the potential energy in water, driving its movement.

Equation for water potential

$\displaystyle Ψ = Ψs + Ψp$, where Ψs = solute potential, Ψp = pressure potential.

Define solute potential (Ψs)

Solute potential is the effect of solute concentration on water potential, typically negative.

True or false: Ψp is always positive.

False, because pressure potential can be zero or negative in some conditions.

Difference between Ψs and Ψp

Ψs is due to solute concentration; Ψp is the physical pressure on water.

What happens to plant cells in a hypertonic solution?

They lose water and undergo plasmolysis, leading to wilting.

Fill in the blank: Pure water has a water potential of _____

0 MPa.

Effect of increased solute concentration on Ψs

It decreases Ψs, resulting in lower overall water potential.

What is osmotic potential?

Osmotic potential is synonymous with solute potential, reflecting water movement towards solutes.

True or false: Water moves from high to low water potential.

True, because water always moves towards areas of lower potential.

Describe turgor pressure.

Turgor pressure is the pressure of the cell contents against the cell wall, maintaining cell rigidity.

Function of aquaporins

Aquaporins are channel proteins that facilitate rapid water transport across cell membranes.

What is the impact of pressure on water potential?

Increased pressure increases Ψp, potentially increasing overall water potential.

Define isotonic solution

An isotonic solution has equal solute concentrations on both sides of a membrane.

What does a negative Ψs indicate?

A negative Ψs indicates the presence of solutes, which lowers water potential.

Difference between osmosis and diffusion

Osmosis specifically refers to water movement, while diffusion is the movement of any substance.

True or false: Water potential is only relevant for plant cells.

False, it applies to all cells, influencing their hydration states.

What does it mean if a cell is flaccid?

A flaccid cell has low turgor pressure and is not firm due to water loss.

Role of the cell wall in plants

The cell wall helps maintain turgor pressure and provides structural support.

Effect of environmental drought on plants

Drought leads to decreased water potential, affecting water uptake and cell turgor.

Calculate Ψ in a plant cell with Ψs = -0.5 MPa, Ψp = 0.3 MPa

$\displaystyle Ψ = -0.5 + 0.3 = -0.2 MPa$.

What occurs during active transport?

Active transport moves substances against their concentration gradient, requiring energy.

Importance of maintaining water potential

Maintaining water potential is crucial for cell function, nutrient transport, and overall homeostasis.

How does transpiration affect water potential?

Transpiration creates negative pressure, helping pull water upward in plants.