Cell Membrane and Transport Vocabulary

Vocabulary flashcards covering cell membrane composition, membrane proteins, transport mechanisms (passive vs. active), osmosis solution types, and cellular homeostasis based on Unit 2 (Part 1) lecture notes.

Cell

The smallest functional unit of organisms.

Cell membrane

A structure composed of a double layer of phospholipids (phospholipid bilayer) surrounding all cells that regulates the entry and exit of molecules.

Homeostasis

The process of maintaining or regulating a stable internal environment despite changes in external conditions.

Integral proteins

Proteins that span across the entire membrane from one phospholipid head to another to assist the movement of large molecules.

Carrier protein

A type of transport protein that changes shape to allow water molecules, small ions, or other materials to move across the membrane.

Channel protein

A type of transport protein with a tunnel-like pore in the middle that allows specific molecules to pass through.

Receptor protein

A membrane protein that binds to specific extracellular signaling molecules, such as hormones.

TRACIE

An acronym for the six main jobs of membrane proteins: Transport, Receptors, Anchorage, Cell Recognition, Intercellular Joining, and Enzyme Activity.

Peripheral proteins

Proteins located on the interior or exterior surface edges of the membrane that function in cell recognition and hormone recognition.

Cholesterol

A steroid composed of a 4-fused carbon ring structure that acts as a temperature buffer and provides membrane stability by physically limiting phospholipid movement.

Oligosaccharides

Linked chains of a few monosaccharides attached to membrane lipids or proteins that serve as identification markers for cell-to-cell recognition.

Glycolipids

Carbohydrate chains attached directly to lipids within the phospholipid bilayer.

Glycoproteins

Carbohydrate chains attached to integral or peripheral membrane proteins.

Fluid Mosaic Model

A model describing the cell membrane as a flexible layer where components move freely ('fluid') and consist of a mixture ('mosaic') of lipids, proteins, and carbohydrates.

Amphipathic

Having both hydrophobic (water-fearing) and hydrophilic (water-loving) properties, such as a phospholipid molecule.

Equilibrium

A state achieved when there is an equal concentration of solutes on both sides of a cell membrane.

Passive transport

The movement of molecules down a concentration gradient from an area of high concentration to low concentration without requiring energy.

Simple diffusion

A type of passive transport where fluid or gas molecules move unassisted from an area of high concentration to low concentration until equilibrium is reached.

Osmosis

The simple diffusion of water molecules across a cell membrane from an area of high water potential (low solute) to low water potential (high solute).

Isotonic solution

A solution having an equal solute concentration relative to the inside of a cell, resulting in no net movement of water.

Hypotonic solution

A solution with a lower solute concentration than the inside of a cell, causing water to rush into the cell.

Hypertonic solution

A solution with a higher solute concentration than the inside of a cell, causing water to move out of the cell.

Cytolysis

The swelling and bursting of an animal cell when placed in a hypotonic solution.

Plasmolysis

The shriveling or shrinking of a cell caused by water loss when exposed to a hypertonic solution.

Contractile vacuoles

Organelles found in freshwater protists, such as Amoeba, that actively push out excess water to prevent cytolysis.

Turgor pressure

The pressure exerted within a plant cell by fluid pushing the cell membrane against the rigid cell wall.

Turgid

The firm, swollen condition of a plant cell when well-watered in a hypotonic environment.

Facilitated diffusion

The passive movement of molecules down their concentration gradient with the assistance of channel or carrier transport proteins.

Aquaporins

Specialized channel proteins that permit water molecules to pass across the membrane faster than simple diffusion.

Active transport

The movement of molecules against or up their concentration gradient from an area of low concentration to high concentration, requiring energy in the form of $\text{ATP}$.

Exocytosis

A form of active transport requiring $\text{ATP}$ where bulk quantities of materials are secreted out of a cell via vesicles that fuse with the plasma membrane.

Endocytosis

An active transport process requiring $\text{ATP}$ where bulk materials are brought into the cell by forming vesicles from the plasma membrane.

Pinocytosis

A form of endocytosis ('cell-drinking') where the cell internalizes small droplets of extracellular fluid containing dissolved molecules.

Phagocytosis

A form of endocytosis ('cell-eating') where the cell extends pseudopodia to engulf large particles, such as food or bacteria, into a food vacuole.

Receptor-mediated endocytosis

A selective type of endocytosis where specific target molecules bind to receptor proteins in coated pits before being engulfed into vesicles.

Sodium-potassium pump

An active transport protein that uses $\text{ATP}$ to pump $3\,Na^+$ ions out of the cell for every $2\,K^+$ ions pumped in, maintaining a net negative charge inside the cell.