AP Biology Unit 2.5: Membrane Transport Flashcards

A set of vocabulary flashcards reviewing cellular transport mechanisms, passive and active transport, membrane structures, and bulk transport processes for AP Biology Unit 2.5.

Selective Permeability

The property of cellular membranes that acts as a selective barrier, allowing the formation of solute concentration gradients and maintaining an internal environment distinct from the external environment.

Passive Transport

The net movement of molecules from regions of high concentration to low concentration across a membrane without the direct input of metabolic energy ($\text{ATP}$).

Simple Diffusion

The passive transport of small, nonpolar molecules, such as oxygen ($\text{O}_2$) and carbon dioxide ($\text{CO}_2$), down their concentration gradient directly through the lipid bilayer.

Facilitated Diffusion

The passive movement of polar or charged molecules across a membrane down their concentration gradient utilizing specialized transport proteins.

Aquaporins

Specialized channel proteins that facilitate the rapid transport of water across biological membranes compared to slow transport through the lipid bilayer.

Osmosis

The diffusion of water across a selectively permeable membrane from an area of high water potential (low solute) to low water potential (high solute).

Active Transport

The movement of molecules against their concentration gradient (from low to high concentration) requiring the direct input of metabolic energy ($\text{ATP}$) and membrane protein pumps.

$\text{Na}^+/\text{K}^+$ Pump

An active transport pump that uses $\text{ATP}$ to transport 3 Sodium ions ($\text{Na}^+$) out of the cell and 2 Potassium ions ($\text{K}^+$) in, generating an electrochemical gradient vital for nerve signal transmission.

Endocytosis

A process of bulk transport where the cell takes in large molecules or materials by folding the plasma membrane inward to form new vesicles.

Exocytosis

A bulk transport process in which internal vesicles release material outside the cell by fusing with the plasma membrane.

Phagocytosis

A specific form of endocytosis known as 'cell eating,' in which the cell engulfs solid particulate matter.

Pinocytosis

A specific form of endocytosis known as 'cell drinking,' in which the cell takes in extracellular fluids and dissolved solutes.

Fluid Mosaic Model

A framework depicting the cell membrane as a mosaic of proteins, cholesterol, and carbohydrates drifting in a fluid phospholipid bilayer that allows vesicles to form and fuse.

Concentration Gradient

A spatial difference in solute concentration across a membrane that represents stored potential energy used by biological systems to perform work and maintain dynamic homeostasis.