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43 Cards in this Set

  • Front
  • Back
the smallest unit of life
the gatekeeper of the cell, which allows only specific substances in or out and passes chemical messages from the external environment to the cell's interiror
plasma membrane
- selectively isolates the cell's contents from the external environment
- regulates the exchange of essential substances between the cell's contents and the external environment
- communicates with other cells
functions of the plasma membrane
model of the plasma membrane
fluid mosaic model
consists of all of a cell's internal contents, including all the organelles except the nucleus, in eukaryotes; mostly water
double layer within the plasma membrane which phospholipids spontaneously arrange themselves into
phospholipid bilayer
membrane proteins and their attached carbohydrates
regulates the movement of hydrophilic molecules through the plasma membrane
transport proteins
forms pores or channels that allow small water-soluble molecules to pass through the membrane
channel proteins
binding sites that can temporarily attach to specific molecules on one side of the membrane to change the protein's shape and move the molecule across the membrane
carrier proteins
trigger cellular responses when specific molecules in the extracellular fluid bind to them
receptor proteins
serve as identification tags and cell-surface attachment sites
recognition proteins
any substance that can move or change shape in response to external forces without breaking apart
the number of molecules in a given unit of volume
a physical difference in properties such as temperature, pressure, electrical charge, or concentration of a particular substance between two adjoining regions
a difference in concentration of those substances between one region and another
concentration gradient
the net movement of molecules from regions of high concentration to regions of low concentration
occurs when no factors, such as electrical charge, pressure differences, or physical barriers, are opposing the movement of diffusion; the moevement of molecules from regions of high to low concentration will continue until the substance is evenly dispersed through the fluid or the air
dynamic equilibrium
movement of substances across a membrane, going down a gradient of concentration, pressure, or electrical charge. does not require the cell to expend energy
passive transport
diffusion of water, dissolved gasses, or lipid-soluble molecules through the phospholipid bilayer of a membrane
simple diffusion
diffusion of usually water-soluble molecules through a channel or carrier protein
facilitated diffusion
diffusion of water across a selectively permeable membrane - that is, a membrane that is more permeable to water than to dissolved molecules
movement of substances into or out of a cell using cellular energy
energy-requiring transport
movement of individual small molecules or ions through membrane-spanning proteins, using cellular energy, usually ATP
active transport
movement of large particles, including large molecules or entire microorganisms, into a cell by engulfing extracellular material, as the plasma membrane forms membrane-bound sacs that enter the cytoplam
movement of materials out of a cell by enclosing the material in a membranous sac that moves to the cell surface, fuses with the plasma membrane, and opens to the outside, allowing its contents to diffuse away
property of the membrane that allows some molecules to pass through, or *permeate*
selectively permeable
a barrier that prevents the passage of all molecules
(during osmosis) the equal movement of water into and out of cells
(during osmosis) the net water movement out of cells
(during osmosis) the net water movement into cells
a membranous sac
(type of endocytosis) a dimple forms in the plasma membrane, which deepens and surrounds the extracellular fluid; the membrane encloses the fluid, forming a vesicle
(type of endocytosis) the plasma membrane extends pseudopods toward an extracellular particle (for example, food); the ends of the pseudopods fuse, encircling the particle; a vesicle called a food vacuole is formed containing the engulfed particle
(type of endocytosis) receptor proteins for specific molecules or complexes of molecules are localized at coated pit sites; the receptors bind the molecules and the membrane dimples inward; the coated pit region of the membrane encloses the receptor-bound molecules; a vesicle containing the bound molecules is released into the cytoplasm
receptor-mediated endocytosis
junction made of protein strands that holds cells together
junction formed by strands of protein that seal cells together by wrapping around them and making them leak-proof
tight junctions
junction made of pairs of channels that connect the insides of adjacent cells and allows cells to communicate by allowing the flow of certain substances from cell to cell; found in animal cells
gap junctions
juction that connects the inside of adjacent cells and allows communication and the transfer of certain materials between cells; found in plant cells
the outer surfaces of the cells of bacteria, plants, fungi, and some protists
cell wall
the part of the cell wall that is formed by cellulose
primary cell wall
the part of the cell wall that is formed by lignin
secondary cell wall
carbohydrate attached to the head of a phospholipid