BIOL 1103 Lab 7 on Diffusion and Osmosis review

This set of flashcards covers key concepts from the BIOL 1103 lab notes, focusing on diffusion, osmosis, tonicity, and lab procedures.

What is the primary function of the plasma membrane?

Acts as a selectively permeable barrier, regulating the precise movement of specific substances both into and out of the cell to maintain cellular homeostasis.

What are the 2 overarching mechanisms by which substances move across the plasma membrane?

1. Passive Transport, which does not require cellular energy.

2. Active Transport, which relies on cellular energy (ATP) to move substances.

What’s Osmosis?

The specialized diffusion of water molecules across a semi-permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration), aiming to equalize solute concentrations on both sides.

What’s a hypotonic solution?

• Is an extracellular solution that possesses a lower concentration of solute particles compared to the cytoplasm inside the cell.

• When a cell is placed in a hypotonic environment, water tends to move into the cell via osmosis.

What’s the consequence for an animal cell when it is placed in a hypertonic solution?

• Water will osmotically move out of the cell.

• Causes the cell to lose volume, shrivel, and undergo a process called crenation.

What defines active transport?

• Process by which a cell moves substances across its plasma membrane against their concentration gradient (from an area of lower concentration to an area of higher concentration).

• This uphill movement necessitates the direct expenditure of cellular energy, typically in the form of ATP.

What is the difference between endocytosis and exocytosis?

• Endocytosis is the cellular process of taking large substances, fluids, or particles into the cell by engulfing them within a vesicle formed from the plasma membrane.

• Conversely, exocytosis is the process by which a cell releases substances, such as waste products or signaling molecules, to the exterior by fusing vesicles containing these substances with the plasma membrane.

What is the biological significance of tonicity?

The measure of the effective solute concentration of a solution relative to another solution (typically the cytoplasm of a cell), which determines the direction and extent of water movement across a semi-permeable membrane and, consequently, its effect on cell volume and shape.

What happens to plant cells when they are in hypotonic surroundings?

• Absorb water through osmosis and the incoming water fills their large central vacuoles, causing the cell membrane to press firmly against the cell wall.

• Creating turgor pressure, making the plant cell (and the entire plant) stiff and rigid, a state known as turgid.

In the context of diffusion, what is equilibrium?

• Is achieved when the net movement of molecules across a permeable barrier or throughout a system ceases.

• At this point, the concentration of the molecules of interest is uniformly distributed throughout the system, though individual molecules continue to move randomly.

What is the utility of the mnemonic 'Water wants to go where the party is'?

• Illustrates the principle of osmosis: water molecules preferentially move to areas where the concentration of solute particles is higher.

• This movement occurs to dilute the higher solute concentration, thereby balancing the concentration gradient across a semi-permeable membrane.

What specific condition is physiologically ideal for typical animal cells?

• Isotonic conditions because there is no net movement of water into or out of the cell.

• This allows the cell to maintain its normal volume and shape, which is crucial for proper cellular function.

What are 3 primary mechanisms categorized under passive transport?

1. Simple Diffusion (direct movement across the membrane)

2. Facilitated Diffusion (movement aided by membrane proteins),

3. Filtration (movement driven by hydrostatic pressure).

What is the relationship between a solute and a solvent within a solution?

• In any solution, the solute is defined as the substance that is dissolved, typically present in a lesser amount, while the solvent is the substance, usually present in a greater amount, in which the solute is dissolved.

• For example, in saltwater, salt is the solute and water is the solvent.

What are the outcomes for cells when they are situated in isotonic solutions?

• When cells are placed in an isotonic solution, the extracellular solute concentration is equal to the intracellular solute concentration.

• Consequently, there is an equal rate of water movement into and out of the cell, resulting in no net water movement, and thus the cell maintains its normal shape and volume, neither shriveling nor bursting.

What fundamental biological concept does the lab class primarily aim to investigate and compare?

Investigate and compare the fundamental biological mechanisms of passive transport and active transport across cell membranes.

Which would be a molecule NOT moving along with its concentration gradient?

a hydrogen ion being pumped across the membrane by a protein expending energy

Which method for crossing the cell membrane requires energy?

Active Transport

What is facilitated diffusion?

molecules carried by proteins across the membrane into the cell, not requiring energy

What happens to a red blood cell in an isotonic solution?

Nothing, it's fine and in equilibrium.

What describes a solution if the salt concentration is higher outside the cell than inside the cell?

hypertonic solution