Bio Ch 5 Flashcards
Cholesterol
lipid found in the animal plasma membrane; helps modify the fluidity of the membrane over a range of temperatures
Extracellular matrix (ECM)
only in animal cells; contains various protein fibers and very large, complex carbohydrate molecules; many functions, including lending external support to the plasma membrane and assisting in communication between cells
Fluid-Mosaic Model
cells are pliable because the phospholipid bilayer is fluid; fluidity of membrane also prevents it from solidifying as external temperatures drop
Glycolipids & glycoproteins
phospholipids and proteins that have attached carbohydrate (sugar) chains
Channel proteins
involved in passing molecules through the membrane; allow a substance to move from one side to the other
Carrier proteins
involved in passing molecules through the membrane; receive a substance and change their shape; this change serves to move the substance across the membrane
Cell recognition proteins
glycoproteins; help the body recognize when it is being invaded by pathogens so that an immune response can occur
Receptor proteins
have a shape that allows only a specific molecule to bind to it; the binding of this molecule causes the protein to change its shape and thereby bring about a cellular response; totally dependent on signaling molecules
Enzymatic proteins
carry out metabolic reactions directly; some are attached to the various membranes of the cell; without these, a cell would never be able to perform the chemical reactions needed to maintain its metabolism
Junction proteins
involved in forming various types of connections between animal cells; allow the cilia of cells that line your respiratory tract to beat in unison
Selectively permeable
allowing only certain substances into the cell while keeping others out
Concentration gradient
gradual change in chemical concentration between 2 areas of differing concentrations
Transduction pathway
series of relay proteins that ends when a protein is activated
Aquaporins
allow water to cross a membrane more quickly than expected; allow cells to equalize water pressure differences between their interior and exterior environments so their membranes don’t burst from environmental pressure changes
Bulk transport
a way that large particles can exit or enter a cell
Diffusion
movement of molecules from a higher to a lower concentration (that is, down their concentration gradient - until equilibrium is achieved and the molecules are distributed equally); results from random molecular motion that can be observed with any type of molecule
Solution
solute (usually solid) + solvent (usually liquid)
Solute
substance that is dissolved in a solvent, forming a solution
Solvent
liquid portion of a solution that serves to dissolve a solute
Osmosis
diffusion of water across a selectively permeable membrane from high to low concentration
Osmotic pressure
pressure that develops in a system due to osmosis; the greater the possible osmotic pressure, the more likely it is that water will diffuse in that direction
Isotonic solutions
the solute concentration and the water concentration both inside and outside the cell are equal, and there is no net gain or loss of water
Tonicity
the strength of the solution
Hypotonic solutions
solutions that cause cells to swell, or burst, due to an intake of water; a solution with a lower concentration of solute (higher concentration of water) than inside the cell
Cytolysis
disrupted (burst) cells
Hemolysis
disrupted red blood cells
Turgor pressure
swelling of a plant cell in a hypotonic solution creates this
Hypertonic solutions
solutions that cause cells to shrink/shrivel due to loss of water; a solution with a higher percentage of solute (lower concentration of water) outside of the cell
Crenation
in animal cells, the shriveling of the cell due to water leaving the cell when the environment is hypertonic
Plasmolysis
shrinking of the cytoplasm due to osmosis
Facilitated transport
explains how molecules such as glucose and amino acids are rapidly transported across the plasma membrane; does not require energy
Active transport
transporting a molecule against its concentration gradient; requires energy; molecules/ions move through the plasma membrane, accumulating either inside or outside the cell; moving from lower to higher concentration
Sodium-potassium pump
carrier protein in the plasma membrane that moves sodium ions out of and potassium ions into cells; important in the function of nerve and muscle cells in animals
Exocytosis
an intracellular vesicle fuses with the plasma membrane as secretion occurs
Endocytosis
cells take in substances by forming vesicles around the material; occurs in 3 ways (phagocytosis, pinocytosis, or receptor-mediated endocytosis)
Phagocytosis
when the material taken in by endocytosis is large (like a food particle or another cell); common in unicellular organisms such as amoebas; also occurs in humans (necessary toward the development of our immunity to bacterial diseases)
Pinocytosis
occurs when vesicles form around a liquid or around very small particles; blood cells, cells that line the kidney tubules or the intestinal wall, and plant root cells use this
Receptor-mediated endocytosis
form of pinocytosis that is quite specific because it uses a receptor protein to recognize compatible molecules and bring them into the cell; uses coated pit; selective, much more efficient than ordinary pinocytosis; involved in the uptake and also in the transfer and exchange of substances between cells
Adhesion junctions
serve to mechanically attach adjacent cells; two types; most common type of intercellular junction between skin cells
Desmosomes
internal cytoplasmic plaques, firmly attached to the intermediate filament cytoskeleton within each cell, are joined by integral membrane proteins called cadherins between cells; result = sturdy but flexible sheet of cells
Hemidesmosome
intermediate filaments of the cytoskeleton are attached to the ECM through integrin proteins
Tight junctions
type of adhesion junction between adjacent cells; bring cells even closer than desmosomes; connect plasma membranes between adjacent cells together, producing a zipperlike fastening; tissues that serve as barriers are held together in this way
Gap junction
allows cells to communicate; formed when 2 identical plasma membrane channels join; important in heart muscle and smooth muscle because they permit a flow of ions that is required for the cells to contract as a unit
Cell wall
plant cells surrounded by this; varies in thickness, depending on the function of the cell; contains cellulose fibrils in which microfibrils are held together by noncellulose substances; pectin allows wall to stretch when cell is growing; noncellulose polysaccharides harden this when the cell is mature
Plasmodesmata
numerous narrow membrane-lined channels that pass through the cell wall; in a plant, the cytoplasm of living cells is connected by this; allows only water and small solutes to pass freely from cell to cell; allows plant cells to maintain their own concentrations of larger substances and differentiate into particular cell types
