Experiment No. 2: Effect of Salt Concentration on Onion Cell Morphology

Vocabulary flashcards covering key membrane transport concepts, osmosis, diffusion, plasmolysis, and related terms from the onion cell experiment notes.

Cell membrane

A thin, flexible boundary that separates the interior from the exterior of the cell and controls which substances can cross it; composed of a lipid bilayer with embedded proteins.

Permeability

The ability of a material or membrane to allow liquids or gases to pass through it.

Lipids solubility and membrane permeability

Membrane permeability depends on how soluble a substance is in lipids, not on its size.

Carrier-mediated transport

Movement of molecules across the membrane via specific carrier proteins; can be active or facilitated, depending on the molecule.

Water-soluble compounds impermeable

Water-soluble (polar) substances generally cannot cross the lipid bilayer without transport proteins.

Osmosis

Diffusion of water across a semipermeable membrane from higher water concentration to lower water concentration.

Endosmosis

Inflow of water into a cell when placed in distilled water or a dilute solution.

Exosmosis

Outward flow of water from a cell into a more concentrated solution (hypertonic).

Diffusion

Movement of particles from an area of high concentration to an area of low concentration without energy input or transport proteins.

Simple diffusion

Diffusion of substances across the cell membrane directly through the lipid bilayer without transport proteins.

Facilitated diffusion

Diffusion that uses specific transport proteins or channels; does not require energy and can be bidirectional.

Active transport

Movement of substances across the membrane that requires energy (ATP) and transport proteins; is unidirectional.

Uniport

Transport of a single type of solute in one direction across a membrane.

Symport

Co-transport of two different solutes in the same direction across a membrane.

Antiport

Transport of two different solutes in opposite directions across a membrane.

Endocytosis

Bulk transport of materials into the cell by engulfment of the substance with the plasma membrane; requires ATP.

Phagocytosis

Engulfment and ingestion of large particles (e.g., bacteria) by cells; forms a phagosome that fuses with lysosomes.

Pinocytosis

“Drinking” phase; uptake of extracellular fluid by the cell; a nonselective form of endocytosis.

Receptor-mediated endocytosis

Selective endocytosis where specific molecules (e.g., LDL) bind to receptors and are internalized.

Exocytosis

Process by which vesicles fuse with the plasma membrane to release their contents outside the cell.

Bulk transport

Endocytosis and exocytosis; large-scale movement of substances via vesicles.

Plasmolysis

Process in which a plant cell loses water in a hypertonic solution, causing cytoplasm to shrink and the plasma membrane to pull away from the cell wall.

Isotonic solution

A solution with the same solute concentration as the cell interior; no net water movement.

Hypertonic solution

A solution with a higher solute concentration outside the cell, causing water to leave the cell and potential plasmolysis.

Hypotonic solution

A solution with a lower solute concentration outside the cell, causing water to enter the cell.

Distilled water control

Neutral baseline condition used to observe natural cell behavior without added solutes.

Aquaporin

Protein channels in the cell membrane that facilitate rapid water movement (osmosis).

Cytoplasm

The fluid inside the cell where organelles are suspended; may shrink during plasmolysis.

Cell wall

Rigid boundary in plant cells that remains intact during plasmolysis and helps maintain structure.

Permeability

The ability of a material or membrane to allow liquids or gases to pass through it.

Lipids solubility and membrane permeability

Membrane permeability depends on how soluble a substance is in lipids, not on its size.

Carrier-mediated transport

Movement of molecules across the membrane via specific carrier proteins; can be active or facilitated, depending on the molecule.

Water-soluble compounds impermeable

Water-soluble (polar) substances generally cannot cross the lipid bilayer without transport proteins.

Osmosis

Diffusion of water across a semipermeable membrane from higher water concentration to lower water concentration.

Channel proteins

Pores in the cell membrane that allow specific ions or small molecules to pass through rapidly; a type of transport protein used in facilitated diffusion.

Concentration gradient

The difference in the concentration of a substance between two regions, which drives diffusion from high to low concentration.

Turgor pressure

The pressure exerted by the cell's protoplast against the cell wall in plant cells due to elastic distension, maintaining rigidity; high in hypotonic solutions.

Fluid mosaic model

A widely accepted model describing the structure of the cell membrane as a dynamic, fluid arrangement of phospholipids and proteins, where components can move laterally.

Glycocalyx

A layer of carbohydrate chains on the outer surface of the cell membrane, formed by glycolipids and glycoproteins, involved in cell recognition, adhesion, and protection.