Ch 4 Biology Vocabulary
Terms
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- the smallest unit of life
- cell
- 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
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- 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
- cytoplasm
- double layer within the plasma membrane which phospholipids spontaneously arrange themselves into
- phospholipid bilayer
- membrane proteins and their attached carbohydrates
- glycoproteins
- 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
- fluids
- the number of molecules in a given unit of volume
- concentration
- a physical difference in properties such as temperature, pressure, electrical charge, or concentration of a particular substance between two adjoining regions
- gradient
- 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
- diffusion
- 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 disper
- 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
- osmosis
- 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
- endocytosis
- 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
- exocytosis
- property of the membrane that allows some molecules to pass through, or *permeate*
- selectively permeable
- a barrier that prevents the passage of all molecules
- impermeable
- (during osmosis) the equal movement of water into and out of cells
- isotonic
- (during osmosis) the net water movement out of cells
- hypertonic
- (during osmosis) the net water movement into cells
- hypotonic
- a membranous sac
- vesicle
- (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
- pinocytosis
- (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
- phagocytosis
- (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-boun
- receptor-mediated endocytosis
- junction made of protein strands that holds cells together
- desmosomes
- 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
- plasmodesmata
- 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
- glycolipid