Chapter 5: Cell Membranes and Transport

Question 1

phospholipid

Answer 1

lipid bilayer

Question 2

Describe the structure, and common components, of eukaryotic membranes.

Answer 2

consists of proteins embedded in an asymmetric fluid of lipid molecules

Question 3

Explain what is meant by membrane asymmetry

Answer 3

Proteins of one half of the bilayer are structurally and functionally distinct from the other half

Question 4

Describe how the “fluid mosaic model” fits what is known about the plasma membrane with respect to membrane structure/characteristics.

Answer 4

• membranes are fluid in which proteins are embedded and float freely
• membrane asymmetry: particles on either side of the membrane differ in size, number and shape (two sides are distinctly different)

Question 5

Describe the factors affecting membrane fluidity

Answer 5

• lipid density/composition: the more unsaturated, the more fluid
• temperature: high temp reduces the fluidity of the membrane

Question 6

Explain how the plasma membrane structure provides selective permeability.

Answer 6

only allows certain molecules or ions to pass through it by means of active or passive transport

Question 7

What are the two distinct categories of membrane proteins?

Answer 7

intergral membrane proteins and peripheral membrane proteins

Question 8

intergral membrane proteins

Answer 8

interact with the membrane hydrophobic core

Question 9

peripheral membrane proteins

Answer 9

interact with the membrane hydrophilic surface

Question 10

active transport

Answer 10

The transport of molecules across a membrane against a concentration gradient that requires the expenditure of energy

Question 11

amphipathic

Answer 11

contains a region that is hydrophobic and hydrophilic

Question 12

passive transport

Answer 12

The movement of a substance across a membrane without the need to expend chemical energy a such as ATP.

Question 13

What drives passive transport?

Answer 13

diffusion

Question 14

diffusion

Answer 14

the net movement of a substance (solute) from a region of high concentration to a region of lower concentration

Question 15

simple diffusion

Answer 15

the movement of molecules directly across a membrane without the involvement of a transporter

Question 16

facilitated diffusion

Answer 16

the diffusion of molecules across a membrane through the aid of a transporter

Question 17

Facilitated diffusion is carried out by two types of transport proteins:

Answer 17

-channel proteins and carrier proteins

Question 18

channel proteins

Answer 18

-form hydrophilic pathways in the membrane through which molecules can pass

Question 19

carrier proteins

Answer 19

binds a single specific solute and transports it across the lipid bilayer

Question 20

primary active transport

Answer 20

-the same protein that transports the molecules also hydrolyzes ATP to power the transport directly (moves positively charged ions)

Question 21

secondary active transport

Answer 21

the transport is indirectly driven by ATP (moves both ions and organic molecules)

Question 22

electrochemical gradient

Answer 22

• Both a concentrations (of the ions) and electrical charge difference on the two sides of the membrane
• store energy that is used for other transport mechanisms

Question 23

osmosis

Answer 23

the diffusion of water molecules across a selectively permeable membrane from a solution of lower solutes concentration to a solution of higher solute concentration
-passive diffusion of water

Question 24

hypertonic solution

Answer 24

solution surrounding the cell has a higher concentration; water leaves

Question 25

isotonic solution

Answer 25

concentration in and out of the cell are equal; no net movement

Question 26

hypotonic solution

Answer 26

solution in the cell is higher than the surrounding; water enters

Question 27

aquaporin

Answer 27

Selectively conduct water molecules in and out of the cell (integral membrane pore protein; aka water channels)

Question 28

Describe the importance of osmoregulation in organisms.

Answer 28

-maintaining balance

methods of expelling what they do not need and conserving what is in short supply

Question 29

Secondary active transport occurs by two mechanisms:

Answer 29

symport and antiport

Question 30

symport/cotransport

Answer 30

the transport of two molecules in the same direction across a membrane

Question 31

antiport/exchange diffusion

Answer 31

a molecule moves through a membrane channel into a cell and powers the active transport of a second molecule out of the cell

Question 32

desaturases

Answer 32

Produce unsaturated fatty acids

Question 33

sterols

Answer 33

also influence membrane fluidity;