Bio Ch 5

Question 1

Cholesterol

Answer 1

lipid found in the animal plasma membrane; helps modify the fluidity of the membrane over a range of temperatures

Question 2

Extracellular matrix (ECM)

Answer 2

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

Question 3

Fluid-Mosaic Model

Answer 3

cells are pliable because the phospholipid bilayer is fluid; fluidity of membrane also prevents it from solidifying as external temperatures drop

Question 4

Glycolipids & glycoproteins

Answer 4

phospholipids and proteins that have attached carbohydrate (sugar) chains

Question 5

Channel proteins

Answer 5

involved in passing molecules through the membrane; allow a substance to move from one side to the other

Question 6

Carrier proteins

Answer 6

involved in passing molecules through the membrane; receive a substance and change their shape; this change serves to move the substance across the membrane

Question 7

Cell recognition proteins

Answer 7

glycoproteins; help the body recognize when it is being invaded by pathogens so that an immune response can occur

Question 8

Receptor proteins

Answer 8

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

Question 9

Enzymatic proteins

Answer 9

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

Question 10

Junction proteins

Answer 10

involved in forming various types of connections between animal cells; allow the cilia of cells that line your respiratory tract to beat in unison

Question 11

Selectively permeable

Answer 11

allowing only certain substances into the cell while keeping others out

Question 12

Concentration gradient

Answer 12

gradual change in chemical concentration between 2 areas of differing concentrations

Question 13

Transduction pathway

Answer 13

series of relay proteins that ends when a protein is activated

Question 14

Aquaporins

Answer 14

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

Question 15

Bulk transport

Answer 15

a way that large particles can exit or enter a cell

Question 16

Diffusion

Answer 16

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

Question 17

Solution

Answer 17

solute (usually solid) + solvent (usually liquid)

Question 18

Solute

Answer 18

substance that is dissolved in a solvent, forming a solution

Question 19

Solvent

Answer 19

liquid portion of a solution that serves to dissolve a solute

Question 20

Osmosis

Answer 20

diffusion of water across a selectively permeable membrane from high to low concentration

Question 21

Osmotic pressure

Answer 21

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

Question 22

Isotonic solutions

Answer 22

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

Question 23

Tonicity

Answer 23

the strength of the solution

Question 24

Hypotonic solutions

Answer 24

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

Question 25

Cytolysis

Answer 25

disrupted (burst) cells

Question 26

Hemolysis

Answer 26

disrupted red blood cells

Question 27

Turgor pressure

Answer 27

swelling of a plant cell in a hypotonic solution creates this

Question 28

Hypertonic solutions

Answer 28

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

Question 29

Crenation

Answer 29

in animal cells, the shriveling of the cell due to water leaving the cell when the environment is hypertonic

Question 30

Plasmolysis

Answer 30

shrinking of the cytoplasm due to osmosis

Question 31

Facilitated transport

Answer 31

explains how molecules such as glucose and amino acids are rapidly transported across the plasma membrane; does not require energy

Question 32

Active transport

Answer 32

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

Question 33

Sodium-potassium pump

Answer 33

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

Question 34

Exocytosis

Answer 34

an intracellular vesicle fuses with the plasma membrane as secretion occurs

Question 35

Endocytosis

Answer 35

cells take in substances by forming vesicles around the material; occurs in 3 ways (phagocytosis, pinocytosis, or receptor-mediated endocytosis)

Question 36

Phagocytosis

Answer 36

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)

Question 37

Pinocytosis

Answer 37

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

Question 38

Receptor-mediated endocytosis

Answer 38

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

Question 39

Adhesion junctions

Answer 39

serve to mechanically attach adjacent cells; two types; most common type of intercellular junction between skin cells

Question 40

Desmosomes

Answer 40

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

Question 41

Hemidesmosome

Answer 41

intermediate filaments of the cytoskeleton are attached to the ECM through integrin proteins

Question 42

Tight junctions

Answer 42

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

Question 43

Gap junction

Answer 43

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

Question 44

Cell wall

Answer 44

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

Question 45

Plasmodesmata

Answer 45

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