Podcast
Questions and Answers
Which of the following describes the effect of a hypotonic solution on a cell?
Which of the following describes the effect of a hypotonic solution on a cell?
- The cell will maintain its size with no change in volume.
- The cell will shrink as water exits.
- The cell will increase its size as water enters. (correct)
- The cell will burst due to excessive water intake. (correct)
What is the primary reason for the swelling of cells placed in an isosmotic urea solution?
What is the primary reason for the swelling of cells placed in an isosmotic urea solution?
- Urea cannot cross the cell membrane.
- Water follows urea into the cell. (correct)
- Osmolarity is equal on both sides of the membrane.
- The concentration of electrolytes is higher inside the cell.
What condition occurs if red blood cells are placed in a hypertonic solution?
What condition occurs if red blood cells are placed in a hypertonic solution?
- The cells will maintain their shape and volume.
- The cells will experience shrinkage as water leaves. (correct)
- The cells will fill with excess electrolyte ions.
- The cells will swell and potentially burst.
What potential consequence might result from low plasma protein levels?
What potential consequence might result from low plasma protein levels?
What is a potential consequence of cerebral edema?
What is a potential consequence of cerebral edema?
What is osmolarity defined as?
What is osmolarity defined as?
What is the primary driving force for osmosis?
What is the primary driving force for osmosis?
Which of the following statements about cell membranes is correct?
Which of the following statements about cell membranes is correct?
If a solution in a cell has a higher concentration of sucrose compared to the surrounding solution, the solution in the cell is classified as:
If a solution in a cell has a higher concentration of sucrose compared to the surrounding solution, the solution in the cell is classified as:
In a solution with 1 mol/L NaCl, how many osmoles per liter does it produce?
In a solution with 1 mol/L NaCl, how many osmoles per liter does it produce?
Which characteristic of aquaporins contributes to osmosis?
Which characteristic of aquaporins contributes to osmosis?
What term best describes a solution with low solute concentration relative to another?
What term best describes a solution with low solute concentration relative to another?
What will happen to a cell placed in a hyperosmotic sucrose solution?
What will happen to a cell placed in a hyperosmotic sucrose solution?
Which of the following best defines osmotic pressure?
Which of the following best defines osmotic pressure?
How does a hypoosmotic solution affect a cell?
How does a hypoosmotic solution affect a cell?
What is the approximate osmolarity of body fluid compartments?
What is the approximate osmolarity of body fluid compartments?
What happens to water movement when two solutions are compared as isosmotic?
What happens to water movement when two solutions are compared as isosmotic?
If the intracellular fluid (ICF) has an osmolarity of 300 mOsm/L, what would the osmolarity be in a solution that causes the cell to swell?
If the intracellular fluid (ICF) has an osmolarity of 300 mOsm/L, what would the osmolarity be in a solution that causes the cell to swell?
Which term describes the condition when a cell neither swells nor shrinks in an external solution?
Which term describes the condition when a cell neither swells nor shrinks in an external solution?
What is the effect of an increase in solute concentration on osmotic pressure?
What is the effect of an increase in solute concentration on osmotic pressure?
Why does sucrose not cross the cell membrane during osmotic processes?
Why does sucrose not cross the cell membrane during osmotic processes?
During osmotic equilibrium, which process maintains the balance of fluids between compartments?
During osmotic equilibrium, which process maintains the balance of fluids between compartments?
Flashcards
Tonicity
Tonicity
The ability of a solution to cause water to move across a semipermeable membrane.
Hypotonic Solution
Hypotonic Solution
A solution with a lower solute concentration than the inside of a cell, causing water to move into the cell, leading to swelling.
Isotonic Solution
Isotonic Solution
A solution with the same solute concentration as the inside of a cell, resulting in no net movement of water.
Hypertonic Solution
Hypertonic Solution
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Oedema
Oedema
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Osmolarity
Osmolarity
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Osm/L
Osm/L
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Osm/kg
Osm/kg
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Osmosis
Osmosis
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Osmotic Pressure
Osmotic Pressure
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Semi-permeable Membrane
Semi-permeable Membrane
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Aquaporins
Aquaporins
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Osmotic Equilibrium
Osmotic Equilibrium
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Isosmotic
Isosmotic
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Hyposmotic
Hyposmotic
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Hyperosmotic
Hyperosmotic
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Intracellular Fluid (ICF)
Intracellular Fluid (ICF)
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Extracellular Fluid (ECF)
Extracellular Fluid (ECF)
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Study Notes
Objectives
- Define osmotic pressure
- Calculate osmolarity and osmolality
- Understand terms hyposmotic, hyperosmotic, isosmotic
- Understand the difference between osmolarity and tonicity
- Understand the effects of osmosis at the cellular and capillary levels
Osmolarity (Osmotic Concentration)
- Osmolarity is the concentration of all solutes in a solution
- Units of osmolarity are Osm/L (Osmoles per Litre)
- Osmolarity is similar to molar concentration (M)
- Units of osmolality are Osm/kg
- Osmolarity values are usually similar to osmolality; however, osmolality accounts for solutes that contribute to the osmotic pressure of a solution
- Some substances dissociate in solution
- 1 mol/L glucose = 1 Osm/L
- 1 mol/L NaCl = 2 Osm/L
- 1 mol/L CaClâ‚‚ = 3 Osm/L
Cell Membranes
- Cell membranes are selectively permeable
- Allow hydrophobic (lipid-soluble) substances to pass easily
- Allow some small hydrophilic (polar) substances to pass easily
- Prevent the free passage of larger polar substances (e.g., glucose, ions)
Movement of Water Across Cell Membranes
- Water is a polar molecule (+/-)
- Small amounts of water pass through the lipid bilayer via simple passive diffusion
- Membrane permeability to water can be increased by aquaporins
- Aquaporins are specialized water channels
Osmosis
- Osmosis is a passive transport mechanism
- Water moves from an area of high water concentration (high water potential) to an area of low water concentration (low water potential) across a semipermeable membrane
- High solute concentration = low water concentration
- Low solute concentration = high water concentration
- Osmosis must occur through a semipermeable membrane that allows water but not other substances to pass
- Osmosis is driven by osmotic pressure, the pressure required to prevent osmosis
- The greater the solute concentration, the greater the osmotic pressure
Osmosis in Cells
- A cell with a higher concentration of a solute will have a lower water concentration
- Water will move from areas of higher water concentration to areas of lower water concentration
- This will cause the cell to swell or shrink depending on the relative concentrations
Body Fluid Compartments
- In the body, all compartments are normally in osmotic equilibrium (~300 mOsm)
- Changes in the concentration of intracellular fluid (ICF) or extracellular fluid (ECF) result in fluid shifts between compartments
Comparing Osmolarity
- Comparing osmolarity of solutions can be done using terms such as: isosmotic, hyposmotic, or hyperosmotic
Tonicity
- Tonicity describes how a solution affects cell volume
- Osmolarity is affected by all solutes present, while tonicity is only affected by solutes that cannot cross the membrane
- A hypotonic solution will cause cells to swell
- An isotonic solution will cause no change in cell volume
- A hypertonic solution will cause cells to shrink
Comparing Tonicity
- Consider the case of urea, which can cross the membrane, influencing the cell's water balance, despite similar osmolarity conditions
Osmotic Behaviour of Cells
- RBCs placed in isotonic solutions (e.g., 0.9% NaCl) maintain normal shape and volume
- RBCs placed in hypotonic solutions (e.g., water) swell and may burst (hemolysis)
- RBCs placed in hypertonic solutions (e.g., 2% NaCl) shrink
How this Relates to Cells in the Body
- Cell membranes are permeable to water, moving in and out by osmosis, influenced by solute concentration gradients across the ECF and ICF
- Electrolytes contribute to body fluid osmolarity
- ECF and ICF must have similar osmolarity to maintain balance
- Osmosis occurs if water is lost from one compartment
Oedema (UK) / Edema (US)
- Plasma proteins maintain osmotic pressure within blood vessels
- Low plasma proteins can result in fluid leaving circulation and entering tissues, causing oedema
- Causes include hypoproteinaemia conditions like liver or kidney disease, malabsorption, or nutritional lack
Cerebral Oedema
- Cerebral oedema involves fluid accumulation in the brain, increasing intracranial pressure
- Causes include stroke, tumors, head trauma
- Severe consequences can include hypoxia, damage, and possibly death
- Treatment includes hypertonic solutions like mannitol administered intravenously (IV)
Glossary of Terms
- Includes definitions for isotonic, hypertonic, hypotonic, isoosmotic, hyperosmotic, hypoosmotic, relevant to osmolarity and tonicity
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