Exercise 4: Membrane Transport

Vocabulary practice flashcards covering cellular membrane transport mechanisms, laboratory tests for diffusion and osmosis, tonicity effects on erythrocytes, and filtration.

Membrane Transport

The movement of nutrients and water from the extracellular fluid (ECF) across the plasma membrane into the cell, and the transfer of waste materials from the intracellular fluid (ICF) out of the cell.

Extracellular Fluid (ECF)

The fluid located outside the cell membrane.

Intracellular Fluid (ICF)

The fluid located inside the cell, also called the cytosol.

Simple Diffusion

The passive movement of molecules down their concentration gradient from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Lipid-Soluble Substances

Substances such as oxygen ($\text{O}_2$) and carbon dioxide ($\text{CO}_2$) that diffuse directly through the lipid bilayer of the plasma membrane without requiring protein channels.

Facilitated Diffusion

The passive transport of water-soluble molecules across the plasma membrane down their concentration gradient using helper membrane proteins, such as channels or pores.

Conformation

The specific three-dimensional shape of a carrier protein that shifts or changes to move a bound solute from one side of the membrane to the other.

Active Transport

A process that uses metabolic energy stored in $\text{ATP}$ to transport molecules against their concentration gradient from an area of low concentration to high concentration.

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+\,\text{Pump}$)

An active transport carrier protein driven by the hydrolysis of $\text{ATP}$ that pumps $3\,\text{Na}^+$ out of the cell and $2\,\text{K}^+$ into the cell against their respective concentration gradients.

Osmosis

The diffusion of water across a selectively permeable membrane.

Dialysis Tubing

A selectively permeable artificial membrane that allows small molecules to diffuse through microscopic pores while blocking larger molecules.

Lugol's Iodine

A chemical indicator solution that yields a blue-black color in the presence of starch.

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

A chemical reagent used to detect the presence of salt ($\text{NaCl}$) by forming a cloudy white precipitate streak.

Benedict Reagent

A diagnostic reagent used to test for the presence of sugar that changes color from blue to green, yellow, orange, or red after heating in a boiling water bath.

Tonicity

The ability of an extracellular solution to change the volume or internal pressure of a cell by driving the osmotic movement of water.

Isotonic Solution

A solution whose solute and water concentrations equal those inside the cell, causing water to move inward and outward at equal rates with no change in cell volume.

Hypotonic Solution

A solution that has a lower solute concentration and a higher water concentration than the intracellular fluid, driving net water movement into the cell.

Hemolysis

The swelling and eventual rupturing of red blood cells resulting from net water entry when exposed to a hypotonic solution.

Hypertonic Solution

A solution with a higher solute concentration and lower water concentration than the intracellular fluid, causing net water movement out of the cell.

Crenation

The shrinkage and crinkling of red blood cells caused by net water loss when exposed to a hypertonic solution.

Filtration

A passive process driven by gravity where a porous filter allows particles smaller than the pore diameter to pass through while trapping larger particles.

Filtrate

The liquid and dissolved substances that successfully pass through a filter.