Inquiry Into Life Chapter 4

Sodium-Potassium Pump

A carrier protein that changes shape after the attachment of the phosphate group, and after its detachment, allows the carrier to combine alternately with sodium ions and potassium ions.

Desmosomes

A form of adhesion junctions where internal cytoplasmic plaques, firmly attached to the intermediate filament cytoskeleton within each cell, are joined by integral membrane proteins called cadherins between cells. The result is a sturdy but flexible sheet of cells.

Receptor-Mediated Endocytosis

A form of pinocytosis that occurs when molecules bind to specific receptor proteins, which migrate to or are already in a coated pit. The vesicle that forms contains the molecules and their receptors.

Selectively Permeable

A function of the plasma membrane where only certain substances can move across the membrane while others cannot.

Osmosis

The diffusion of water across a selectively permeable membrane due to concentration differences.

Middle Lamella

A layer of adhesive substances that holds the cells together.

Extracellular Matrix (ECM)

A meshwork of proteins and polysaccharides in close association with the cell that produced them.

Phagocytosis

A method of endocytosis that occurs when the substance to be transported into the cell is large, such as a food particle or another cell.

Endocytosis

A portion of the plasma membrane invaginates to envelop the substance going in, and then the membrane pinches off to form an intracellular vesicle.

Exocytosis

A vesicle fuses with the plasma membrane as secretion occurs.

Carrier Proteins

An integral protein that is involved in the passage of molecules through the membrane by combining with a substance and helping it to move.

Channel Proteins

An integral protein that is involved in the passage of molecules through the membrane.

Peripheral Proteins

Reside on one side of the plasma membrane. They help stabilize and shape the plasma membrane.

Tight Junctions

Brings cells even closer than desmosomes by the junction's proteins connecting plasma membranes between adjacent cells together, producing a zipperlike fastening.

Cell Recognition Proteins

Glycoproteins that help the body recognize when it is being invaded by pathogens so that an immune reaction can occur.

Enzymatic Proteins

Integral proteins that directly carry out metabolic reactions.

Receptor Proteins

Integral proteins that have a shape that allows a specific molecule to bind to it. The binding of this molecule causes a protein to change its shape and thereby bring about a cellular response.

Gap Junctions

Junctions that are formed when two identical plasma membrane channels join, enabling the cells to communicate, lend strength to the cells, and allow small molecules and ions to pass between them.

Active Transport

Molecules or ions move through the plasma membrane, accumulating either inside or outside the cell.

Glycolipids

Phospholipids that have attached carbohydrate (sugar) chains which only occur on the outside surface of the plasma membrane.

Glycoproteins

Proteins that have attached carbohydrate (sugar) chains which only occur on the outside surface of the plasma membrane.

Hypertonic Solutions

Solutions that cause cells to shrink or shrivel due to loss of water.

Hypotonic Solutions

Solutions that cause cells to swell, or burst, due to an intake of water.

Integral Proteins

Span the plasma membrane and can protrude from one or both sides.

Aquaporins

Special channel proteins that allow water to quickly cross the membrane.

Factors That Influence Diffusion

Temperature, pressure, electrical currents, and molecular size. [As the temperature increases, the rate of diffusion increases]

Fluid-Mosaic Model

The combination of proteins, steroids, and phospholipids in the plasma membranes.

Solvent

The liquid substance of a solution.

Adhesion Junctions

The most common type of intercellular junction between skin cells that serve to mechanically attach adjacent cells.

Diffusion

The movement of molecules from a higher to a lower concentration

Facilitated Transport

The passage of such molecules as glucose and amino acids across the plasma membrane even though they are not lipid-soluble.

Osmotic Pressure

The pressure that develops in a system due to osmosis.

Homeostasis

The process of regulating the entrance and exit of molecules in a cell to maintain a steady internal environment of a cell and organism.

Pinocytosis

The process that occurs when vesicles form around a macromolecule, such as a liquid or around very small particles and is continually occurring.

Crenation

The shriveling of a cell in a hypertonic solution.

Solute

The solid substance of a solution.

Isotonic Solutions

The solute concentration and the water concentration both inside and outside the cell are equal, and therefore there is no net gain or loss of water.

Cytolysis

The term used to refer to disrupted cells.

Hemolysis

The term used to refer to disrupted red blood cells.

Bulk Transport

Vesicle formation transports macromolecules into and out of the cell because the molecules are too large to be transported by carrier proteins.

Turgor Pressure

What is created when a plant cell swells in a hypotonic solution.

Concentration Gradient

When molecules move from an area where their concentration is high to an area where their concentration is low.