Cell Biology: Membrane Transport Concepts

Small, hydrophobic molecules crossing the cell membrane without energy, following a concentration gradient.

Polar or charged molecules crossing the cell membrane with help from proteins (channels or carriers), still following a concentration gradient.

Membrane proteins that bind to a molecule and change shape to move it across the cell membrane.

Membrane proteins creating a channel through the cell membrane for molecules to pass.

Water, ions, and small organic molecules (like sugars, vitamins)

The cell membrane allows certain molecules to pass through while blocking others.

Moving molecules against a concentration gradient using cell energy (ATP).

Movement of small inorganic ions, water, and small organic molecules in and out of cells.

A carrier protein that transports a single type of molecule down its concentration gradient.

Water channel proteins that allow rapid water movement across the membrane.

Channel proteins that transport ions across the membrane.

The narrow pores in the channel only allow ions of the correct size and charge to pass.

Ion channels that open in response to specific signals (e.g., ligands, voltage, pressure).

Uses energy (like ATP hydrolysis) to move molecules against their concentration gradient.

Uses energy stored in an electrochemical gradient to transport molecules.

A network of interconnected internal membranes within eukaryotic cells, involved in protein synthesis, modification, transport, and other cellular processes.

A network of interconnected membrane sacs studded with ribosomes, involved in protein synthesis, folding, modification, and transport.

A network of interconnected membrane tubules without ribosomes, involved in lipid synthesis, steroid hormone production, and detoxification.

A stack of flattened membrane sacs called cisternae, involved in protein sorting, modification, packaging, and secretion.

Membrane-bound organelles containing hydrolytic enzymes, responsible for cellular digestion and waste disposal.

A selectively permeable phospholipid bilayer that forms the outer boundary of cells, regulating the movement of molecules in and out of the cell.

Molecules with both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, forming the basis of the plasma membrane structure.

The most abundant class of lipids in membranes, containing a glycerol backbone, phosphate group, and an alcohol, forming the hydrophilic head and hydrophobic tails.

A phospholipid has a hydrophilic head (phosphate group) and a hydrophobic tail (fatty acid chain).

These lipids are derived from sphingosine and contain a fatty acid attached to the amino group. Glycosphingolipids are a type of sphingolipid with sugar head groups.

Sterols are four-ring hydrocarbons, with cholesterol being the most abundant in mammalian cell membranes.

These proteins span the entire phospholipid bilayer, having hydrophilic regions facing the aqueous environment and hydrophobic regions embedded in the membrane.

These proteins are attached to the membrane by covalent bonds with one or more lipid molecules.

These proteins do not interact with the hydrophobic core of the membrane and are localized to the cytosolic or exoplasmic face.

Transmembrane proteins can have carbohydrate chains attached, always located on the exoplasmic face. These chains interact with the extracellular environment.

The plasma membrane provides compartmentalization, acts as a scaffold for biochemical activities, controls molecule movement, transports solutes, and responds to external stimuli.

Large, complex molecules like proteins, nucleic acids, carbohydrates, and lipids. They are too big for transport proteins or pumps.

A process by which eukaryotic cells take in large molecules or particles from their surroundings by forming vesicles from the plasma membrane.

A type of endocytosis where the cell takes in soluble materials from the environment and packages them in vesicles for digestion. It's not specific about what it takes in.

Specific type of endocytosis where cells take in molecules by binding to receptors on the cell surface. Receptors are concentrated in clathrin-coated pits.

A type of endocytosis where cells engulf large particles, like microorganisms or dead cells, by forming large vesicles called phagosomes. It involves the extension of pseudopodia (actin-based movement) to enclose the particle.

Macrophages, neutrophils, and dendritic cells in mammals are specialized white blood cells that engulf and destroy foreign particles.

Specific regions of the plasma membrane where proteins are concentrated, forming coated vesicles during receptor-mediated endocytosis.

Vesicles formed by the fusion of phagosomes (containing engulfed particles) with lysosomes (containing digestive enzymes).

A type of lipoprotein particle that carries cholesterol in the bloodstream, important for delivering cholesterol to cells.

A genetic disorder where individuals have extremely high cholesterol levels due to mutations in the LDL receptor gene, increasing risk of heart disease.

Small, spherical sacs formed by the inward budding of clathrin-coated pits, carrying molecules into the cell.

A continuous process by which cells release molecules from the Golgi apparatus to the cell surface, without specific signals.

The release of molecules from cells in response to specific signals, like hormones, neurotransmitters, or changes in cell conditions.