BIOL 1000 Exercise 7: Membrane Transport Study Guide

Vocabulary flashcards based on BIOL 1000 Exercise 7 study guide covering solution terminology, SA:V ratios, molecular diffusion rates, tonicity effects on plant/animal cells, and dialysis membrane transport.

Solution

A liquid mixture composed of two or more substances (solute dissolved within a solvent).

Solute

The substance that is dissolved in a solution (salt, glucose, or starch).

Solvent

The dissolving agent of a solution, usually present in the greatest amount (e.g., water in biological systems).

Diffusion

Passive movement of solute particles from an area of higher concentration to lower concentration until equilibrium.

Osmosis

Specialized passive diffusion of water molecules across a selectively permeable membrane that moves from a higher to a lower solute concentration.

Equilibrium

State where solute molecules are uniformly distributed; net movement ceases, but individual particle movement continues equally in all directions.

Surface Area to Volume (SA:V) Ratio Principle

As a cell increases in size, its volume grows much faster than its surface area. Smaller cells maintain a higher SA:V ratio, providing sufficient cell membrane area to efficiently exchange nutrients and wastes for the internal volume.

Molecular Weight vs. Rate of Movement Principle

Smaller, lighter molecules move faster and diffuse across a medium at a higher velocity than larger, heavier molecules at equal temperatures, which leads to more efficient transport. The diffusion rate is inversely proportional to the molecular size (weight).

Hypertonic Solution

A solution with a solute concentration higher than the cytoplasm causes water to move out of the cell, resulting in crenation in animal cells and plasmolysis in plant cells.

Isotonic Solution

A solution with a solute concentration equal to that of the cytoplasm, resulting in no net water movement, maintaining the normal/viable biconcave disc shape in both animal and plant cells.

Hypotonic Solution

A solution with a solute concentration lower than the cytoplasm, causing water to move into the cell, resulting in lysis/hemolysis (bursting) in animal cells (RBCs) and turgidity in plant cells.

Crenation

The shrinking or shriveling of animal cells (such as red blood cells) when placed in a hypertonic solution.

Plasmolysis

The process in plant cells placed in a hypertonic solution (e.g., $10\%\,\text{NaCl}$) where water leaves the central vacuole by osmosis, causing the plasma membrane and cytoplasm to shrink away from the rigid cellulose cell wall.

Deplasmolysis

The reversal of plasmolysis that occurs when a plasmolyzed plant cell is placed back into pure water.

Turgor Pressure

Internal pressure created in plant cells in hypotonic environments as water flows in and pushes against the rigid cellulose cell wall, preventing bursting and maintaining structural uprightness.

Silver Nitrate ($\text{AgNO}_3$) Indicator Test

Reagent used to test for salt/chloride ($\text{NaCl}$); produces a clear solution for a negative result and a cloudy white precipitate ($\text{AgCl}$) for a positive result indicating diffusion out of the membrane.

Iodine Reagent ($\text{I}_2\text{KI}$) Indicator Test

Reagent used to test for starch; has a blue-black color for a positive result and a yellow/amber/brown color for a negative result

Molecules that can cross the membrane

Salt and water (not starch)

Surface area to volume rule

A smaller cube/cell has a higher surface area to volume ratio, which means its more efficient

Concentration clostest to Isotonic (Carrot Experiement)

10% sucrose because it is already at equilibrium

Concentration that is hypertonic (Carrot Experiement)

20% and 30%

Concentration closest to hypotonic (Carrot Experiement)

0% because the water has less sucrose in it, which means the water goes into the carrot

Carrot that lossed the most weight

30% because it has the most sucrose in the water

Carrot that gained the most weight

0% because it has the less sucrose and the water went into the cell thus making the carrot gain weight