Osmosis and Tonicity Flashcards

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Questions and Answers

What is an aquaporin?

Creates special water channels through which water can freely move into and out of nearly every cell in the body

Which of the following factors influence body water content? (Select all that apply)

Height

Metabolism

Gender (correct)

Age (correct)

What is the distribution of water among body compartments?

67% intracellular, 33% extracellular (75% interstitial, 25% plasma)

What is osmosis?

The movement of water across a membrane in response to a solute concentration gradient Signup and view all the answers

What is osmotic pressure?

The pressure that must be applied to oppose osmosis (atm or mm Hg) Signup and view all the answers

What does osmolarity refer to?

Number of osmotically active particles per liter of solution Signup and view all the answers

What is the formula for calculating osmolarity?

osmolarity (osmol/L) = molarity (mol/L) X #particles/molecule (osmol/mol) Signup and view all the answers

What is the normal osmolarity of the human body?

300 mOsM (or a little less) Signup and view all the answers

What is osmolality?

Osmoles of solute per kilogram of water Signup and view all the answers

What does isosmotic mean?

Describes two solutions with the same number of solute particles per unit volume Signup and view all the answers

What does hyperosmotic describe?

A solution with more solute particles per unit volume than another solution Signup and view all the answers

What does hyposmotic mean?

A solution with fewer solute particles per unit volume than another solution Signup and view all the answers

What is the definition of hypotonic?

If a cell placed in the solution gains water at equilibrium and swells, the solution is hypotonic to the cell Signup and view all the answers

What does hypertonic mean?

If a cell placed in the solution loses water and shrinks at equilibrium, the solution is hypertonic to the cell Signup and view all the answers

What is the difference between tonicity and osmolarity?

Tonicity describes a comparative term focused on cell volume changes, while osmolarity is a measurable concentration of solute particles Signup and view all the answers

What are penetrating solutes?

Solutes that can enter the cell Signup and view all the answers

What are nonpenetrating solutes?

Solutes that can't enter the cell Signup and view all the answers

Tonicity depends on the concentration of ____.

nonpenetrating solutes only Signup and view all the answers

What is the most important nonpenetrating solute?

NaCl Signup and view all the answers

How can you figure out the tonicity of a solution without actually putting a cell in it?

By knowing the concentrations of nonpenetrating solutes in the cell and in the solution Signup and view all the answers

Why can an isosmotic solution be isotonic or hypotonic, but not hypertonic?

An isosmotic solution cannot have a higher concentration of nonpenetrating solutes than the cell Signup and view all the answers

What are the rules for osmolarity and tonicity?

<ol> <li>Assume that all intracellular solutes are nonpenetrating. 2. Compare osmolarities before the cell is exposed to a solution. 3. Tonicity describes the volume change of a cell at equilibrium. 4. Determine tonicity by comparing nonpenetrating solute concentrations. 5. Hyposmotic solutions are always hypotonic.</li> </ol> Signup and view all the answers

Study Notes

Aquaporin

Facilitates water movement across cell membranes by creating specific water channels.

Factors Influencing Body Water Content

Body water content varies by gender: males generally have higher water content than females.
Age affects water content, with infants having more body water than adults.

Distribution of Water Among Body Compartments

Intracellular fluid makes up 67% of total body water.
Extracellular fluid accounts for 33%, divided into:
- 75% interstitial fluid
- 25% plasma

Osmosis

Defined as the movement of water through a membrane driven by differences in solute concentration.

Osmotic Pressure

Refers to the pressure required to prevent osmosis, measured in atmospheres (atm) or millimeters of mercury (mm Hg).

Osmolarity

Measures the concentration of osmotically active particles in a solution, usually expressed in osmoles per liter (osmol/L or OsM), distinct from molarity.

Calculation of Osmolarity

Osmolarity can be calculated using the formula: osmolarity (osmol/L) = molarity (mol/L) x #particles/molecule (osmol/mol).

Dissociation Factor

Indicates the extent of molecular dissociation in a solution, with sodium chloride (NaCl) having a dissociation factor of 1.8 at body temperature.

Normal Osmolarity of the Human Body

Typical osmolarity is around 300 mOsM, slightly less than this value.

Osmolality

Refers to the concentration of solute in osmoles per kilogram of water; the terms osmolarity and osmolality are often used interchangeably in biological contexts.

Isosmotic Solutions

Two solutions are isosmotic if they have the same concentration of solute particles per unit volume.

Hyperosmotic Solutions

Solutions with a higher number of solute particles per unit volume compared to another solution.

Hyposmotic Solutions

Solutions that contain fewer solute particles per unit volume than another solution.

Tonicity

Hypotonic solutions cause a cell to gain water, leading to cell swelling.
Hypertonic solutions lead to water loss from a cell, causing it to shrink.
Isotonic solutions maintain the cell's size, with no net water movement.

Differences Between Tonicity and Osmolarity

Osmolarity quantifies solute particles in a solution, while tonicity is a comparative term that does not have units and specifically pertains to the effect on cell volume.
Tonicity always relates a solution's effect on a cell, while osmolarity can compare any two solutions.

Solute Penetration

Penetrating solutes can freely enter cells, while nonpenetrating solutes cannot.

Tonicity Dependence

Tonicity is determined by the concentration of nonpenetrating solutes within the solution.

Most Important Nonpenetrating Solute

Sodium chloride (NaCl) is the key nonpenetrating solute in physiological contexts.

Tonicity Assessment Without Cell Exposure

Tonicity can be inferred by comparing the concentrations of nonpenetrating solutes in the cell versus those in the solution.

Isosmotic Solution Characteristics

An isosmotic solution cannot be hypertonic as it can't have a higher concentration of nonpenetrating solutes than the cell.
If all solutes are nonpenetrating, the isosmotic solution is isotonic; if penetrating solutes are present, it becomes hypotonic.

Rules for Analyzing Osmolarity and Tonicity

Assume all intracellular solutes are nonpenetrating when evaluating tonicity.
Assess osmolarities before exposing a cell to any solution, noting that equilibrium results in isosmotic conditions.
Tonicity specifies how cell volume will change at equilibrium.
Determine tonicity by comparing concentrations of nonpenetrating solutes, as water moves toward higher solute concentrations.
Always remember that hyposmotic solutions are equivalently hypotonic.

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Description

Test your understanding of osmosis and tonicity with these flashcards. Learn about essential terms like aquaporin, factors influencing body water content, and the distribution of water in body compartments. Perfect for biology students looking to reinforce their knowledge!