Membrane Structure and Function

Flashcards about Membrane Structure and Function, covering topics such as membrane components, fluidity, permeability, transport mechanisms, and bulk transport.

Lipids and Proteins

The main components of membranes, along with proteins; important for cell structure and function.

Amphipathic molecules

Molecules containing both hydrophobic and hydrophilic regions.

Fluid mosaic model

A model that depicts the membrane as a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.

Membranes

Held together mainly by weak hydrophobic interactions, allowing lipids and some proteins to move sideways within the membrane.

Cholesterol

A membrane component in animal cells that affects membrane fluidity differently at different temperatures, reducing fluidity at moderate temperatures and hindering solidification at low temperatures.

Peripheral proteins

Proteins bound to the surface of the membrane.

Integral proteins

Proteins that penetrate the hydrophobic core of the membrane.

Transmembrane proteins

Integral proteins that span the membrane.

Glycolipids

Carbohydrates bonded to lipids on the cell surface. Function as markers for cell identification.

Glycoproteins

Carbohydrates bonded to proteins on the cell surface. Function as markers for cell identification.

Selective permeability

The ability of a membrane to allow some substances to cross more easily than others.

Transport proteins

Proteins that facilitate the passage of hydrophilic substances across the membrane.

Aquaporins

Channel proteins that greatly increase the rate of passage of water molecules across the membrane.

Diffusion

The movement of particles of any substance so that they spread out evenly into the available space.

Concentration gradient

The region along which the density of a chemical substance increases or decreases.

Osmosis

The diffusion of free water across a selectively permeable membrane.

Tonicity

The ability of a surrounding solution to cause a cell to gain or lose water.

Isotonic solution

A solution with the same solute concentration as that inside the cell; water diffuses at the same rate in both directions.

Hypertonic solution

A solution with a solute concentration greater than that inside the cell; water tends to leave the cell.

Hypotonic solution

A solution with a solute concentration less than that inside the cell; water tends to enter the cell.

Osmoregulation

Control of solute concentration and water balance, especially important for organisms in hypotonic or hypertonic environments.

Turgor pressure

The pressure exerted back on the cell by the inelastic cell wall when a plant cell takes up water in a hypotonic solution.

Turgid

The state of being very firm in a plant cell, the healthy state for most plant cells.

Flaccid

The state of being limp in a plant cell in an isotonic solution.

Plasmolysis

A phenomenon in plant cells in a hypertonic environment where the cell membrane pulls away from the cell wall.

Facilitated diffusion

Transport proteins speed the passive movement of molecules across the plasma membrane. Requires no energy.

Gated channels

Ion channels that open or close in response to a stimulus.

Active transport

Uses energy to move solutes against their concentration gradients; all proteins involved are carrier proteins.

Membrane potential

The voltage across a membrane, created by differences in the distribution of positive and negative ions.

Electrogenic pump

The transport protein that generates voltage across a membrane, storing energy that can be used for cellular work.

Cotransport

Occurs when active transport of a solute indirectly drives transport of other substances.

Exocytosis

Transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell.

Endocytosis

Macromolecules are taken into the cell in vesicles.

Phagocytosis

A cell engulfs a particle by extending pseudopodia around it and packing it in a membranous sac called a food vacuole.

Pinocytosis

Molecules are taken up when extracellular fluid is gulped into tiny vesicles.

Receptor-mediated endocytosis

Vesicle formation is triggered by solute binding to receptors.