Ch. 7 Membrane Support & Function

Question 1

what is the function of the plasma membrane?

Answer 1

-provide protection for a cell
-keep organelles inside and regulate the entry/exit of foreign materials

Question 2

why are phospholipids amphipathic?

Answer 2

-they have a hydrophilic phosphate head and two hydrophobic fatty acid tails

Question 3

what is the function of cholesterol in the cell?

Answer 3

maintains cell fluidity: if temperature goes up, fluidity goes up, so cholesterol brings it back down, and vice

Question 4

what are the fluid properties of the cell membrane?

Answer 4

lateral movement = 10^7 times a second
vertical movement = once a month

Question 5

what does the fluid mosaic model of the cell describe?

Answer 5

it describes the cell membrane as flexible, fluid, and composed of many different structures [proteins, carbs, phospholipids)

Question 6

what is an integral protein?

Answer 6

a protein that is transmembrane = it goes through both sides of the cell membrane

Question 7

what is a peripheral protein?

Answer 7

a protein that is on one side of the cell membrane = loosely bound to proteins or phospholipids (or cytoskeleton on the cytoplasmic side)

Question 8

what are the six major functions of plasma membrane proteins?

Answer 8

1. transport - Na/K pump
2. enzymes - lactase
3. signal transduction - neurotransmitters
4. cell-cell recognition - blood types
5. intercellular joining - desmosomes
6. ECM/cytoskeleton attachment - integrins

Question 9

what are aquaporins?

Answer 9

protein channels for water to enter / exit cell

Question 10

what molecules are permeable to the cell membrane?

Answer 10

oxygen, co2, small amounts of water, small lipids

Question 11

how do aquaporins affect the rate of water transport?

Answer 11

by providing an open channel for large amounts of water to enter/exit the cell

Question 12

what membrane factors affect the selective permeability of membranes? [how do things get in/out of the membrane?]

Answer 12

-membrane proteins & vesicles

Question 13

what is passive transport?

Answer 13

movement of a particle across a membrane with no energy spent

Question 14

what is diffusion?

Answer 14

the movement of molecules from a high concentration to a low concentration

Question 15

what is facilitated diffusion?

Answer 15

diffusion with the aid of a membrane protein [gated channel], such as an aquaporin

Question 16

what is active transport?

Answer 16

transport of a solute against its gradient using ATP

Question 17

how do concentration gradients create potential energy?

Answer 17

the energy released by solutes moving down a gradient can be used to power other functions in the cell

Question 18

what is osmosis?

Answer 18

the diffusion of water across a selectively permeable membrane [moves from high solute [] to low solute []]

Question 19

what happens to a cell placed in hypotonic solution?

Answer 19

-water moves into cell, cell bursts/lyses
-in plant cells - cell becomes turgid, which is normal and healthy

Question 20

what happens to a cell placed in an isotonic solution?

Answer 20

water enters and exits at the same rate - no change

Question 21

what happens to a cell placed in a hypertonic solution?

Answer 21

animal cells: water leaves cell, cell shrivels up
plant cell: becomes plasmolyzed

Question 22

what is membrane potential?

Answer 22

the electrical potential difference between the inside and outside of a cell, established by active transport (Na/K pump)

Question 23

what is co-transport?

Answer 23

when two different molecules or ions are moved across a cell membrane at the same time - established by concentration gradients [one moves down, one moves against]

Question 24

what is the function of the sodium potassium pump? how many molecules of each does it pump in/out of the cell?

Answer 24

-creates electrochemical gradient by pumping 3Na+ OUT of the cell and 2K+ INTO the cell

Question 25

what is the function of a proton pump?

Answer 25

to create H+ gradients that are used to transport many other nutrients, commonly found in plants, fungi, and bacteria