Cell Membranes

Endocytosis

The process of bringing large particles into a cell through the folding inward of its cell membrane

Three types include phagocytosis, pinocytosis, and receptor-mediated endocytosis

Phagocytosis

The process by which a cell folds its cell membrane around large particles or other cells, creating a vesicle, and then 'eats' them; for example, a white blood cell devouring a bacterium

Active Transport

A type of transport across cell membranes that requires the use of energy due to ions or molecules moving against their concentration gradient, from areas of low to high solute concentration

Cytoplasm

The space inside a cell that holds the different parts that work together in order for a cell to function

Phospholipid

A component of a cell membrane composed of a phosphate group, which is hydrophilic and polar, and a lipid, which is hydrophobic and nonpolar

Pinocytosis

Process by which a cell's membrane surrounds liquids and small dissolved molecules and brings them into a vesicle, where the cell 'drinks' them; e.g., cells by capillaries 'drink' blood

Types of Membrane Proteins Used in Active Transport

Uniport: moves a substance in one direction

Antiport: moves two substances in opposite directions

Symport: moves two substances in the same direction

Lysosome

A structure within a cell responsible for breaking down food, foreign objects, and old cellular components found within the cell using digestive enzymes for reuse or recycling by the cell

Concentration Gradient

The gradual difference in the concentration of a solute between two areas

Vesicle

A circular bud made of membrane that is formed during the process of endocytosis when a cell surrounds an object with its cell membrane

Cell Membrane

A membrane that separates the intracellular and extracellular environments using a phospholipid bilayer

Hypotonic Solution

A solution that contains less solutes inside a cell membrane compared to outside the membrane

Selectively Permeable Membrane

A barrier that allows some materials to pass through it but not all

Cholesterol

Hydrophobic material that floats in phospholipid bilayers; helps preserve the fluidity of membranes and works as a barrier against unwanted molecules

Passive transport

A type of transport across cell membranes that does not involve the use of energy

Sodium-Potassium Pump

In nerve cells; an antiport that moves sodium ions outside the cell and potassium ions into the cell to maintain a concentration gradient (more sodium outside the cell, more potassium inside)

Diffusion

A type of passive transport in which solutes move along their concentration gradient, from an area of high concentration to an area of low concentration