Chapter 8 Biology Vocabulary

cell membrane

cell membrane

separates the inside of a cell from its surroundings, is semi-permeable and made of phospholipids, is thin and flexible and surrounds all cells, regulates what enters and leaves the cell

cell wall

a structural layer surrounding cells, outside the cell membrane, can be tough, flexible, and sometimes rigid, a layer of polysaccharides in plants, fungi, and bacteria, is only in some cells

selectively permeable

allows only specific molecules to pass through the cell membrane, which are gases and water

hydrophobic

a property where something is repelled by water

hydrophilic

a property where something is attracted to water

fluid mosaic model

describes the structure of the cell membrane as a compilation of components, including phospholipids, cholesterol, proteins, and carbohydrates

homeostasis

constant conditions that organisms need to maintain (to gain equilibrium)

diffusion

a process where particles move from an area where they are more concentrated to an area where they are less concentrated

facilitated diffusion

a process of diffusion where molecules pass through the cell membrane using its channels

aquaporin

a water channel protein in a cell

osmosis

the diffusion of water through a semi-permeable membrane

isotonic

when the concentration of two solutions are the same

hypertonic

a solution with a greater concentration of solutes (when compared to another)

hypotonic

a solution with less concentration of solutes (when compared to another)

osmotic pressure

the minimum pressure needed to prevent the flow of solvent molecules through a semi-permeable membrane

passive transport

a type of membrane transport that does not require energy to move substances across cell membranes, passes from an area of high concentration to low concentration

active transport

the movement of materials against a concentration difference (low concentration to high concentration), requires energy

protein pumps

energy from ATP is used to release small molecules and ions across the cell membranes, active transport proteins change during this process, also binds substances on one side of the membrane and releasing them on the other.

bulk transport

larger molecules and even solid clumps of material can be transported by this transport, can take several forms, depending on the size and shape of the material moved in or out of the cell

endocytosis

when a cell internalizes any substance from the outside, the taking in of matter by a living cell in order to form a vacuole

exocytosis

process by which cells move materials from within the cell into the extracellular fluid, contents of a cell vacuole are released to the exterior through the vacuole membrane and cell membrane fusing

phagocytosis

when a cell engulfs a particle and digests it, the ingestion of bacteria or other material