Membrane Structure and Function: Chp 7

Question 1

plasma membrane

Answer 1

is selectively permeable and allows some substances to cross it more easily than others

Question 2

fluid mosaic model

Answer 2

describes the membrane as fluid, with proteins embedded in or associated with the phospholipid bilayer

Question 3

phospholipids

Answer 3

present in the membrane and provide a hydrophbic barrier that separates the cell from its liquid environment. Hydrophilic molecules cannot easily enter the cell, but hydrophobic molecules can enter much more easily

Question 4

integral proteins

Answer 4

are completely embedded in the membrane, some of which are transmembrane proteins that span the membrane completely

Question 5

peripheral proteins

Answer 5

are loosely bound to the membrane’s surface

Question 6

carbohydrates

Answer 6

on the membrane are crucial in cell-cell recognition (which is necessary for proper immune function) and in developing organisms ( for tissue differentiation). Cell-surface carbohydrates varyfromspecies to species and are the reason that blood transfusions much be type-specific

Question 7

nonpolar molecules

Answer 7

are hydrophobic and can dissolve in the phospholipid bilayer and cross the membrane easily EX: hydrocarbons, carbon dioxide, and oxygen

Question 8

transport proteins

Answer 8

span the membbrane and allows hydrophilic substances to avoid the lipid bilayer and pass through the membrane

Question 9

aquaporins

Answer 9

special transport proteins that allow water molecules to move across the membrane and accelerates the speed

Question 10

passive diffusion

Answer 10

when a substance travels from where it is more concentrated to where it is less concentrated. No energy is required

Question 11

osmosis

Answer 11

the diffusion of water across a selectively permeable membrane

Question 12

isotonic solution

Answer 12

there will be no net movement of water across the plasma membrane. Water crosses the membrane, but at the same rate in both directions

Question 13

hypertonic solutions

Answer 13

the cell will lose water to its surroundings. The hyper- prefix refers to more solutes in the water around the cell causing a movement of water to the higher concentration of solutes meaning the cell loses water to the environment, shrivels, and might die.

Question 14

hyoptonic solutions

Answer 14

water will enter the cell faster than it leaves causing the cell to swell and possibly burst. The hypo= prefix refers to fewer solutes in the water around the cell which is why the movement of water is into the cell because more solutes are present in the cell

Question 15

flaccid

Answer 15

limp plant cell

Question 16

plasmolyzed

Answer 16

a plant cell that has lost water and is shrivelled

Question 17

turgid

Answer 17

plant cells that have full vacuoles and are very firm

Question 18

facilitated diffusion

Answer 18

process by which ions and hydrophilic substances diffuse across the cell membrane with the help of transport proteins that are specific for the substances they transport and works by:

• providing a hydrophilic channel through which the molecules such as ions and polar molecules can pass
• they bind loosely to the ions and polar molecules and carry them trhough the membrane

Question 19

active transport

Answer 19

when substances are moved against their concentration gradient (from less concentrated to more concentrated). requires energy

Question 20

sodium-potassium pump

Answer 20

a type of active transport. this transmembrane protein pumps sodium out of the cell and potassium into the cell. the sodium-potassium pump is necessary for proper nerve transmission and is a major energy consumer in your body

Question 21

membrane potential

Answer 21

the difference in electric charge across a membrane that is expressed in voltage. the inside of the cell is negatively charged compared with outside the cell

Question 22

two forces that drive the diffusion of ions across a membrane are:

Answer 22

chemical force (which is the ions concentration gradient) and voltage gradient (which attracts positively charged ions and repels negatively charged ions)

Question 23

electrochemical gradient

Answer 23

the combination of chemical force and voltage gradient action on ions

Question 24

electrogenic pump

Answer 24

a transport protein that generates voltage across the membrane

Question 25

cotransport

Answer 25

an ATP pump that transports a specific solute indirectly drives the active transport of oter substances. In this process, the substance that was initially pumped across the membrane can do work as it moves back across the membrane by diffusion and brings with it a second compound against its gradient

Question 26

exocytosis

Answer 26

vesicles from the cell’s interior fuse with the cell membrane, expelling their contents

Question 27

endocytosis

Answer 27

the cell forms new vesicles from the plasma membrane; this allows the cell to take in macromolecules.

Question 28

phagocytosis

Answer 28

“cellular eating” occurs when the cell wraps pseudopodia around a solid particle and brings it into the cell

Question 29

pinocytosis

Answer 29

“cellular drinking” is when the cell takes in small droplets of extracellular fluid within small vesicles. It is not specific, beacause any and all included solutes are taken into the cell

Question 30

receptor-mediated endocytosis

Answer 30

certain substances (generally referred to as ligands) bind to specific receptors on the cell’s surface and this causes a vesicle to form around the substance and then to pinch off into the cytoplasm