Hole's Chapter 3: Cell Movement Flashcards

Terms Definitions
physical (or passive) processes
diffusion, osmosis, facilitated diffusion, and filtration.
physiological (or active) processes
active transport, endocytosis, and exocytosis.
diffusion
the tendency of atoms, molecules, and ions in a liquid or air solution to move from areas of higher concentration to areas of lower concentration (become more distributed - more diffuse).
diffusion
occurs because atoms, molecules, and ions are in constant motion.
concentration gradient
difference in concentration
diffusional equilibrium
when concentration of substance becomes uniform throughout solution and there is no net movement.
requirements for diffusion
1. cell membrane is permeable to that substance, 2. concentration gradient exists such that the substance is at a higher concentration on one side of membrane or the other.
physiological steady state
concentrations of diffusing substances are unequal but stable, more appropriate in reference to organisms
most important factors in diffusion rate
distance, the concentration gradient, and temperature.
facilitated diffusion
movement that follows concentration gradient but uses membrane proteins as "carriers" , very important to ions and other larger water-soluble molecules
facilitated diffusion
moves molecules from higher to lower concentration BUT number of carrier molecules in cell membrane limits rate
osmosis
the movement of water across a selectively permeable membrane into a compartment containing solute that cannot cross the same membrane
osmosis rule
greater concentration of impermeant solute particles, the lower the water concentration of that solution, the greater osmotic pressure
isotonic
solutions with the same osmotic pressure as body fluids, cells do not change size in this solution
hypertonic
solutions with a higher osmotic pressure than body fluids, if cells put into this solution there will be net movement of water by osmosis out of cell into surrounding solution - cells shrink
hypotonic
solutions with lower osmotic pressure than body fluids, gain water by osmosis and swell or possibly even burst
filtration
molecules are forced through membranes by this process
filtration
commonly used to separate solids from water
filtration
a passive process since gravity can be the applied force
filtration
tissue fluid forms when water and dissolved substances are forced out through the walls of capillaries, but cells and large molecules are left inside
active transport
movement against a concentration gradient from lower to higher concentration, requires energy derived from cellular metabolism
active transport
uses carrier molecules within cell membrane that have binding sites that combine with specific particles being transported - triggers release of cellular energy - alters shape of carrier protein - "passenger" molecules can move through membrane
endocytosis
moves molecules or other particles that are too large to enter a cell by diffusion or active transport; conveyed in a vesicle that forms from a section of the cell membrane
3 forms of endocytosis
pinocytosis, phagocytosis, receptor-mediated endocytosis
pinocytosis
intake of liquid droplets
pinocytosis
cell takes in tiny droplets of liquid, small portion of cell membrane indents, open end of tubelike part seals off and produces vesicle, sac detaches from surface and moves into cytoplasm, cell is able to take in water and particles dissolved in it
phagocytosis
intake of solids, often with the fusion of lysosomes which digest the material
phagocytes
certain types of cells that can take in solid particles such as bacteria and cellular debris, ex. some white blood cells
phagocytosis
important line of defense against infection
phagocytosis
phagocyte encounters solid particle, particle attaches to cell membrane, portion of membrane projects outward surrounding particle and slowly draws it inside cell, part of membrane surrounding solid detaches forming vesicle, lysosome usually joins vesicle and lysosome enzymes decompose contents
receptor-mediated endocytosis
moves specific kinds of particles into the cell
receptor-mediated endocytosis
process involves protein molecules that extend through cell membrane and are exposed on its outer surface
receptor-mediated endocytosis
protein-receptors present on cell membrane bind to specific ligands
ligands
molecules that bind specifically to receptors
low-density lipoproteins (LDL)
spherical particles where cholesterol molecules are synthesized in liver cells and packaged
apolipoprotein-B
coating on LDL particle containing binding protein
receptor-mediated endocytosis
molecules that can bind to receptor sites selectively enter cell; other types of molecules left outside
receptor-mediated endocytosis
provides specificity
exocytosis
reverse of endocytosis, expels the residue after lysosomal enzymes have digested solids brought in through phagocytosis
exocytosis
allows cell to secrete material produced by cell, for example nerve cells use this to release neurotransmitters chemicals
transcytosis
combines exocytosis and endocytosis to selectively and rapidly transport a substance/particle from one end of a cell to the other
transcytosis
enables substances to cross barriers formed by tightly connected cells; occurs in normal physiology and in disease
transcytosis
enables healthy immune system to monitor pathogens in small intestine, protecting against some forms of food poisoning
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