Chapter 6: 6.4 Membrane Transport

Question 1

What are the types of membrane transport?

Answer 1

1. Passive transport
2. Active transport

Question 2

What are characteristics of passive transport?

Answer 2

• Molecules moves with a concentration gradient
• No energy is required

Question 3

What are the two types of passive transport?

Answer 3

• Simple diffusion
• Facilitated diffusion

Question 4

What is the difference between simple diffusion vs. facilitated diffusion?

Answer 4

Simple diffusion:
* No transport protein

Faciliatated diffusion:
* Requires transport protein

Question 5

Where does facilitated diffusion occur through?

Answer 5

Occurs through:
* Protein channels that form a pore in the membrane
* Carrier proteins that physically bind to molecules and guide them through the membrane

Question 6

What are the characteristics of active transport?

Answer 6

• Molecules move against the concentration gradient
• Requires an input of energy

Question 7

What are the two types of active transport?

Answer 7

1. Primary active transport
2. Secondary active transport

Question 8

Describe:

Osmosis

Answer 8

A form of passive/simple diffusion
* Water moves down its concentration gradient across a selectively permeable membrane

Question 9

Describe the movement of water:

In an isotonic solution

Answer 9

Movement of water is even across the membrane in either direction

Question 10

Describe the movement of water:

In a hypertonic solution

Answer 10

A gradient created by a molecule (e.g. too much salt outside the cells) results in a net movement of water out of the cell
* Results in shrivelling

Question 11

Describe the movement of water:

In a hypotonic solution

Answer 11

A gradient created by a molecule (e.g. too much salt inside the cells) results in a net movement of water into the cell
* Results in swelling

Question 12

In selective permeability:

What affects the permeability of molecules through the phospholipid bilayer?

Answer 12

Size and polarity
* The smaller the molecule, the easier it can cross the membrane
* Non-polar molecules are more permeable than polar molecules

Question 13

In selective permeability:

What are non-polar molecules are more permeable than polar molecules?

Answer 13

The lipid bilayer has a largely non-polar interior, thus non-polar molecules are favoured

Question 14

In selective permeability:

What is the exception to the polarity rule in permeability? Explain why

Answer 14

Water
* There are numerous aquaporin (water channels) in the membrane, allowing polar water to cross the membrane very quickly

Question 15

Osmosis and Selective Permeability are forms of…

Answer 15

Passive/Simple Diffusion

Question 16

True or False:

Facilitated diffusion requires energy

Answer 16

False, it only requires the help of a membrane protein, no energy required

Question 17

Does facilitated diffusion go towards or away from the concentration gradient?

Answer 17

Towards (i.e. from high to low concentration)

Question 18

What membrane proteins are used in facilitated diffusion?

Answer 18

• Channel proteins
• Carrier proteins

Question 19

Compare:

Channel proteins vs. Carrier proteins

Answer 19

Channel proteins:
* Less selective

Carrier proteins:
* Selective towards on particular molecule

Question 20

Describe:

Primary Active Transport

Answer 20

Uses energy for transport of a molecules against its concentration gradient
* Energy comes from ATP

Question 21

What purpose does primary active transport have?

(Besides transporting against concentration gradient)

Answer 21

Can be used to generate an electrochemical gradient
* This may then be used as an energy source for secondary active transport

Question 22

Give an example of:

Primary Active Transport

Answer 22

Na+/K+ pump

Question 23

Describe:

Secondary Active Transport

Answer 23

Uses energy for transport of a molecules against its concentration gradient
* Energy comes from an electrochemical gradient generated by primary active transport

Question 24

Explain:

The movement of molecules in secondary active transport

Answer 24

Movement of two molecules across membrane is coupled
* Molecule moving with its concentration gradient provides the energy for the one moving against its concentration gradient

Question 25

What are the two types of secondary active transport? Explain them

Answer 25

1. Symport: When both molecules move in the same direction
2. Antiport: When the two molecules move in opposite directions