Tonicity

​Tonicity & Homeostasis

Module C: Cell Transport & Energy

​Review

Osmosis

• Osmosis is the movement of water from areas of high concentration to low concentration.

• Water moves across the cell membrane without the use of energy (ATP).

• This balance/movement of water is extremely important to cellular structure.​

Module C: Cell Transport & Energy

Lesson Guiding Questions

What is a solution? How do we describe them?

How does water move in different solutions?

What is a solution?

Solutions

• Solutions are made when solutes are added to solvents.

• For example, salt (solute) added to water (solvent) = salt water (solution)

• Solutions are described by their solute concentrations.​

• Solutions can be classified in 3 different ways: isotonic, hypotonic, or hypertonic.

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Module C: Cell Transport & Energy

• In isotonic solutions, the solute concentration is equal on both sides of the cell membrane.

• Water moves in both directions equally.

• The cell's structure (in animals) remains intact.​

Module C: Cell Transport & Energy

Isotonic Solutions

• In hypotonic solutions, the solute concentration is LOWER (water concentration is HIGHER) outside of the cell than inside the cell.

• Water moves into the cell (down the concentration gradient).

• The cell gets larger.

• "Hypo" = "hippo"​

Module C: Cell Transport & Energy

Hypotonic Solutions

• In hypertonic solutions, the solute concentration is HIGHER (water concentration is LOWER) outside of the cell than inside the cell.

• Water moves out of the cell (down the concentration gradient).

• The cell gets smaller.

Module C: Cell Transport & Energy

Hypertonic Solutions

Open Ended

Explain why animal cells function best in isotonic environments.

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Mr. Buie