Biology Test 5 - Water Potential

Why is water called the 'universal solvent'?

Because it can dissolve many different molecules.

What causes water molecules to be dipolar?

Oxygen is more electronegative than hydrogen, creating slight charges on each atom.

What type of bond forms between water molecules?

Hydrogen bonds.

Why are hydrogen bonds important for water's properties?

They create networks that give water its unique properties like high specific heat capacity.

Why are hydrogen bonds hard to detect?

They are weak and constantly forming and breaking.

How was the existence of hydrogen bonds confirmed?

Through indirect experiments and theoretical models, and directly detected in 2017.

What are ions?

Atoms that have gained or lost electrons, resulting in a charge.

How does water dissolve ionic compounds?

By surrounding ions with hydration shells and separating them.

What attracts water molecules to ions?

The slight positive charge of hydrogen attracts negative ions, and the slight negative charge of oxygen attracts positive ions.

What is a hydration shell?

A layer of water molecules surrounding an ion in solution.

What is dissolution?

The process of solute particles separating and spreading uniformly in a solution.

Can covalent compounds dissolve in water?

Yes, through intermolecular interactions without dissociating into ions.

What is a solute?

A substance that dissolves in a solvent.

What is a solvent?

A substance that dissolves a solute.

What is a solution?

A homogeneous mixture of solute and solvent.

What is the 'memory of water' theory?

The idea that water retains a memory of substances it was in contact with even after dilution.

Is the 'memory of water' theory scientifically supported?

No, it lacks empirical evidence and is considered pseudoscience.

How does water move between solutions of different concentrations?

From regions of lower solute concentration to higher solute concentration.

What is osmosis?

The movement of water across a selectively permeable membrane from low to high solute concentration.

What is a hypertonic solution?

A solution with a higher solute concentration compared to another.

What is a hypotonic solution?

A solution with a lower solute concentration compared to another.

What is an isotonic solution?

Two solutions with equal solute concentrations.

In which direction does water move during osmosis?

From hypotonic to hypertonic regions.

What happens to an animal cell in a hypertonic solution?

It shrinks and becomes crenated.

What happens to a plant cell in a hypertonic solution?

It undergoes plasmolysis.

What happens to an animal cell in a hypotonic solution?

It swells and may burst (lysis).

What happens to a cell in an isotonic solution?

Water moves equally in and out, maintaining the cell's size and shape.

What is diffusion?

The movement of particles from high to low concentration without needing a membrane.

How is osmosis different from diffusion?

Osmosis specifically involves water moving across a membrane.

What happens to a cell bathed in a solution that is not isotonic to the cell?

Water will move into or out of the cell by osmosis, changing the cell's size and structure.

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

Plant tissue loses water, resulting in a loss of length and mass.

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

Plant tissue gains water, resulting in an increase in length and mass.

How can you determine the isotonic solute concentration of a plant tissue?

By measuring the percentage change in mass and/or length after placing the tissue in various solute concentrations.

What does a high standard deviation indicate about a data set?

It indicates high variability in the data set.

What does a low standard deviation indicate about a data set?

It indicates low variability in the data set.

What does standard error measure?

It measures the variability between multiple data sets and indicates precision.

What happens to a cell without a cell wall placed in a hypotonic solution?

Water moves into the cell, causing it to swell and potentially burst (lysis).

What happens to a cell without a cell wall placed in a hypertonic solution?

Water moves out of the cell, causing it to shrink and crenate.

What structures help freshwater unicellular organisms survive in hypotonic environments?

Contractile vacuoles.

Why is maintaining isotonic tissue fluids important in multicellular organisms?

To prevent harmful changes to cellular processes and maintain overall health.

What organ in humans helps maintain isotonic tissue fluids?

The kidney.

What happens to a plant cell placed in a hypotonic solution?

Water enters the cell, increasing turgor pressure and making the cell turgid.

What happens to a plant cell placed in a hypertonic solution?

Water leaves the cell, causing plasmolysis and loss of turgor pressure.

What is turgor pressure?

The pressure exerted by the cytoplasm against the cell wall in a plant cell due to water intake.

Why are isotonic solutions used for organ transplantation?

To prevent water loss or gain by cells, reducing damage and increasing transplantation success.

Why are isotonic fluids administered intravenously?

To rapidly deliver medications, fluids, or nutrients without disrupting the osmotic balance of cells.

What does haemolysis refer to?

The rupture of red blood cells placed in hypotonic solutions, releasing haemoglobin into the surrounding fluid.

What is water potential?

Water potential is a measure of the potential energy of water per unit volume relative to pure water under standard conditions.

What units is water potential usually measured in?

Water potential is usually measured in kilopascals (kPa).

What is the water potential of pure water at standard conditions?

0 kPa.

What happens to water movement as water potential becomes more negative?

It becomes harder for water to move.

What are the two factors that influence water potential?

Solute potential and pressure potential.

What is the equation for water potential?

Ψw = Ψs + Ψp.

What is solute potential?

The attraction of water molecules to solute particles, reducing the number of free water molecules and limiting water movement.

What is pressure potential?

The physical pressure exerted on a system, which can be positive or negative.

How does positive pressure potential affect water potential?

It increases water potential.

How does negative pressure potential affect water potential?

It decreases water potential.

How does water move in relation to water potential?

Water moves by osmosis from areas of higher water potential to areas of lower water potential.

What effect does a bigger difference in water potential have on water movement?

It increases the speed of water movement.

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

Water moves into the tissue, causing an increase in turgor pressure.

Why does water move into plant tissue in a hypotonic solution?

Because the solute potential inside the tissue is more negative than the solute potential of the solution.

What is turgor pressure?

The outward pressure exerted by the cytoplasm against the cell wall in plant cells.

How is equilibrium reached when plant tissue is in a hypotonic solution?

Positive pressure potential offsets negative solute potential, equalizing water potentials inside and outside the tissue.

Why can't animal cells generate significant pressure potential?

Because animal cells lack cell walls.

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

Water moves out of the tissue, leading to a loss of turgor and plasmolysis.

Why does water move out of plant tissue in a hypertonic solution?

Because the solute potential of the solution is more negative than the solute potential of the tissue.

What happens to pressure potential when water leaves plant cells?

It becomes negative, indicating lower internal pressure compared to external pressure.

What is the resulting water potential when both solute potential and pressure potential are negative?

A highly negative water potential, encouraging water to move out of the tissue.