D2.3 Water potential

What is solvation?

Solvation is the combination of a solvent with the molecules or ions of a solute.

What property of water makes it an effective solvent?

Water’s polarity, with a partial negative charge at the oxygen pole and partial positive charge at the hydrogen pole.

Why do polar solutes dissolve in water?

Polar solutes dissolve due to attraction between the partial positive and negative charges on water molecules and solute molecules.

What attracts positively charged ions in water?

Positively charged ions are attracted to the partial negative oxygen pole of water.

What attracts negatively charged ions in water?

Negatively charged ions are attracted to the partial positive hydrogen pole of water.

What prevents ions from clumping together in water?

Water molecules form shells around ions and charged molecules, preventing them from precipitating by clumping together.

What is cytoplasm?

Cytoplasm is a complex mixture of dissolved substances in which the chemical reactions of metabolism occur.

Why are solutions more viscous than pure water?

Intermolecular attractions between solutes and water restrict the movement of water molecules, making solutions more viscous.

What determines the net movement of water between two solutions?

Water moves from the less concentrated solution to the more concentrated solution due to solute–water attractions.

What is osmosis?

Osmosis is the net movement of water across a membrane due to the attractions between solutes and water.

What makes solutes osmotically active?

Solutes are osmotically active if intermolecular attractions form between them and water.

What is a hypotonic solution?

A solution with a lower concentration of osmotically active solutes.

What is a hypertonic solution?

A solution with a higher concentration of osmotically active solutes.

What happens between isotonic solutions?

There is no net movement of water because the concentrations of osmotically active solutes are equal.

What is dynamic equilibrium?

When there is no net movement of water between two isotonic solutions.

What is concentration?

Concentration is the amount of solute per unit volume of solution.

How is solute concentration measured?

It is measured in moles per cubic decimeter (moles/dm³).

What separates the cytoplasm inside a cell from extracellular fluids?

The plasma membrane separates the cytoplasm inside a cell from extracellular fluids.

Why is osmosis a passive process?

Osmosis does not require energy because water moves naturally from a hypotonic to a hypertonic solution.

How can cells change the direction of water movement?

By raising or lowering the concentration of osmotically active solutes inside the cell.

Why do root cells absorb water from soil?

The cytoplasm of root cells is hypertonic compared with water in the soil.

What is the result of bathing an animal cell in a hypotonic solution?

Water enters the cell, making it swell and potentially burst.

What happens when an animal cell is placed in a hypertonic solution?

Water leaves the cell by osmosis, causing the cytoplasm to shrink.

What causes plant cells to become turgid?

High pressures due to water entry by osmosis.

What is wilting in plants?

Wilting occurs when plant cells lose water, become flaccid, and stems and leaves bend downwards.

What is plasmolysis?

Plasmolysis is the process where the plasma membrane pulls away from the cell wall due to water loss.

Why are isotonic solutions important for medical procedures?

Isotonic solutions prevent cells from swelling or dehydrating during medical treatments.

What is normal saline?

Normal saline is an isotonic sodium chloride solution containing 9 g of NaCl per cubic decimeter of solution.

How does normal saline benefit medical procedures?

It can be used for intravenous drips, wound rinses, and organ preservation, among others.

What is water potential?

Water potential is a measure of the potential energy per unit volume of water.

What is the water potential of pure water at standard atmospheric pressure?

Pure water has a water potential of zero.

What factors influence water potential in living systems?

Solute concentrations and hydrostatic pressure influence water potential.

How does hydrostatic pressure affect water potential?

Higher hydrostatic pressure increases the potential energy of water.

What happens when solutes dissolve in water?

Solutes reduce the potential energy of water, making water potential more negative.

What is the formula for water potential?

Water potential (Ψw) = solute potential (Ψs) + pressure potential (Ψp).

What is the solute potential of pure water?

The solute potential of pure water is zero.

Why is pressure potential important?

It can be positive or negative, depending on whether pressure is above or below atmospheric pressure.

What happens when plant tissue is bathed in a hypotonic solution?

Water enters the cells, increasing their water potential and making them turgid.

What happens when plant tissue is bathed in a hypertonic solution?

Water leaves the cells, decreasing their water potential and making them flaccid.

What does it mean when cells are plasmolysed?

It means the plasma membrane has detached from the cell wall due to water loss.

What is the relationship between solute concentration and water potential?

As solute concentration increases, water potential becomes more negative.

How is dynamic equilibrium achieved in plant cells?

Water movement stops when the solute potential and pressure potential are balanced.

What happens to plant cells in pure water?

Plant cells become fully turgid as water potential reaches zero.

What is turgidity in plant cells?

Turgidity is the swollen state of plant cells due to water entry.

What is the importance of turgid plant tissue?

Turgid tissue provides structural support to non-woody plants.

What happens to the plasma membrane during plasmolysis?

It pulls away from the cell wall as the cytoplasm volume decreases.

What causes wilting in plants?

Wilting occurs when plant cells lose turgor pressure due to water loss.

What is the effect of hypertonic solutions on human cells?

Hypertonic solutions dehydrate human cells, causing them to shrink.

What is the effect of hypotonic solutions on human cells?

Hypotonic solutions cause human cells to swell and burst.

Why are isotonic solutions ideal for human cells?

Isotonic solutions maintain equal water movement, keeping cells healthy.

What is the role of normal saline in organ transplants?

It is used to cool and preserve donor organs during transport.

What is the water potential of plant cells in a hypertonic solution?

Water potential becomes more negative as water leaves the cells.

How does bathing plant tissue in pure water affect pressure potential?

Pressure potential increases as cells become fully turgid.

What is the solute potential of a 1 mol/dm³ NaCl solution?

It is −4,540 kPa.

What causes cells to become flaccid?

Water loss reduces pressure potential, making cells flaccid.

How does water move between cells with different water potentials?

Water moves from higher to lower water potential to minimize energy.

What happens to solute potential during water movement?

Solute potential becomes less negative as water enters the cells.

What happens to pressure potential during water movement?

Pressure potential becomes more positive as water enters the cells.

What is the effect of solute potential on water potential?

Higher solute concentration makes water potential more negative.

What happens to water potential when hydrostatic pressure increases?

Water potential becomes more positive.

What happens to water potential when solutes dissolve?

Water potential becomes more negative.

What does a negative water potential indicate?

A negative water potential indicates lower potential energy of water.

What is the relationship between solute potential and osmotic potential?

Solute potential is sometimes called osmotic potential.

What happens to plant cells in a hypertonic solution?

Water leaves the cells, causing plasmolysis and cell death.

How do plants avoid further water loss during droughts?

Plants close stomata to reduce transpiration.

What is the importance of water potential in plants?

Water potential predicts the direction of water movement.

What happens to water potential when solutes dissolve?

Water potential decreases as solutes dissolve.

What happens to pressure potential when water enters plant cells?

Pressure potential increases as cells become turgid.

Why is water potential important in living systems?

Water potential helps explain water movement in cells and tissues.