Concept 7.2: Membrane structure results in selective permeability

Question 1

—many molecules ordered into a higher level of organization—with emergent properties beyond those of the individual molecules.

Answer 1

supramolecular structure

Question 2

Sugars, amino acids, and other nutrients enter the cell, and metabolic

Answer 2

waste products leave it.

Question 3

cell takes in O2 for use in cellular respiration and expels

Answer 3

CO2

Question 4

the cell regulates its concentrations of inorganic ions, such as Na+, K+, Ca2, and C1-, by shuttling them one way or the other across the

Answer 4

plasma membrane.

Question 5

Nonpolar molecules, such as hydrocarbons,CO2, and O2, are

Answer 5

hydrophobic, as are lipids

Question 6

hydrophobic interior of the membrane impedes direct passage through the membrane of ions and polar molecules, which are

Answer 6

hydrophilic.

Question 7

the lipid bilayer is only one aspect of the ____________________ responsible for a cell’s selective permeability

Answer 7

gatekeeper system

Question 8

hydrophilic substances can avoid contact with the lipid bilayer by passing through _________________ that span the membrane.

Answer 8

transport proteins

Question 9

function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane

Answer 9

channel proteins

Question 10

a channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane

Answer 10

aquaporins

Question 11

hold onto their passengers and change shape in a way that shuttles them across the membrane

Answer 11

carrier proteins

Question 12

is so selective that it even rejects fructose, a structural isomer of glucose.

Answer 12

“glucose transporter”

Question 13

membranes exhibit selective permeability, meaning that they allow some substances to

Answer 13

cross more easily than others

Question 14

consider oxygen which enters the cell and used in cellular respiration and carbon dioxide, which exits the cell as a

Answer 14

waste product

Question 15

the plasma membrane, especially its hydrophobic center, small nonpolar molecules, such as oxygen and carbon dioxide can easily

Answer 15

diffuse across that layer

Question 16

what substances do you think would have a hard time crossing a membrane?

Answer 16

larger polar molecules, such as glucose, and charged ions, such as sodium, can’t cross on their own. they need the help of specific transport proteins to pass through a membrane.

Question 17

transport proteins may be carrier proteins that shuttle a molecule such as

Answer 17

glucose across the membrane by changing shape

Question 18

other transport proteins provide channels through which specific molecules or ions such as ________ can diffuse.

Answer 18

sodium