AP Biology Chapter 5 - Cell Membrane Structure and Function Vocabulary

phospholipid bilayer

a thin, fluid membrane made up of two layers of phospholipid molecules that forms a barrier around all cells.

embedded proteins

a protein that is permanently fixed within or spanning the cell membrane's phospholipid bilayer

fluid mosaic model

A model from 1972 that describes the cell membrane as a flexible layer where proteins float in a fluid phospholipid bilayer.

Recognition protein

A specialized protein, often a glycoprotein, on the surface of a cell that helps it identify its type to other cells

Receptor protein

Specialized proteins that recognize and bind to specific molecules or substances outside the cell.

Transport protein

Membrane proteins that help substances move across the cell membrane

Enzyme

proteins that catalyze specific chemical reactions in living organisms without being consumed in the process

peripheral protein

A type of membrane protein that is loosely attached to the surface of the membrane

integral protein

Membrane proteins that are embedded within the lipid bilayer of the cell membrane and penetrate the hydrophobic core.

Diffusion

process of random movement toward a state of equilibrium

Concentration

the amount of solute relative to the amount of solvent

Solvent

a liquid that has dissolved or can dissolve one or more substances

Solute

a substance that is dissolved in a liquid

Solution

a solvent and its dissolved solutes

Concentration gradient

a difference in concentration of a substance across the space

Equilibrium

condition in which the concentration of a substance is equal throughout

plasma membrane

a thin, flexible barrier that surrounds every cell, separating the cell's interior from its external environment.

selectively permeable

A property that means a barrier allows certain molecules or ions to pass though while blocking others.

Passive transport

movement of molecules across a cell membrane from an area of high concentration to an area of low concentration.

simple diffusion

random movement of molecules through the phospholipid bilayer

osmosis

a special kind of diffusion that involves the movement of H₂O through membrane

Hypertonic

an adjective describing a solution that has a higher solute concentration than another solution.

Crenation

The process in which a cell shrinks and shrivels in a hypertonic solution

Hypotonic

an adjective describing a solution that has a lower solute concentration than another solution.

Isotonic

an adjective describing a solution that has an equal solute concentration as another solution.

Facilitated Diffusion

A type of passive transport that moves large or charged molecules across a cell membrane with the help of transmembrane proteins.

Facilitated Diffusion by Channel Proteins

A type of passive transport where molecules move across a cell membrane through a channel protein that goes completely through the membrane and provides safe passage through a polar pore.

Facilitated Diffusion by Carrier Proteins

A type of passive transport in which molecules are shielded from the interior of the membrane.

Active Transport

the transport of material across the cell membrane against the concentration gradient

Sodium Potassium Pump

a carrier protein that uses ATP to actively transport Na⁺  out of a cell and K⁺ into the cell

Bulk Transport

moving large quantities of materials into or out of cell

Endocytosis

process by which material is brought into a cell by invagination  of the plasma membrane and the formation of a vesicle

Phagocytosis

“Cell eating”  type of endocytosis in which large particles are taken in by the cell

Pinocytosis

“cell drinking”  type of endocytosis in which liquids or very small particles are taken in by the cell

Receptor Mediated Endocytosis

type of pinocytosis that in which very efficient, specific molecules can be brought into cell, determined by receptors.

Cell Junctions

Specialized membranes that allow cells to attach to one another, communicate with one another, and exchange materials with one another.

Desmosome

a strong cell junction that attaches adjacent cells to one another

Tight Junction

leak-proof cell junctions that create a tight seal between cells

Gap Junction

cell junctions that form channels between adjacent cells and allow communication between cells w/ the exchange of materials.

Cell surface area to volume ratio (SA:V)

The measurement of a cell’s surface area compared to its volume, calculated by dividing the surface area by the volume.

Energy

The capacity to do work

Kinetic energy

Energy of motion

Potential energy

Stored energy

chemical energy

Energy stored in organic molecules

Thermodynamics

The study of energy, heat, and work, and how they relate to the properties of matter.

Law of Conservation of Energy (1st Law of Thermodynamics)

A principle that states that energy cannot be created or destroyed

2nd Law of Thermodynamics

A principle that states that energy cannot be changed from one form to another without a loss of usable energy

Entropy

The relative amount of disorganization

Free energy

How much energy is available to do work

Endergonic reactions

Reactions that consume energy

Catabolic Reactions

Reactions that break down complex molecules into smaller subunits

Exergonic reaction

a reaction that releases energy

Anabolic reactions

Reactions that link simple molecules together to form more complex ones