Membrane Transport

Question 1

What are the two types of transport (in terms of energy) and their subtypes

Answer 1

1) Passive transport
a) Unaided (diffusion)
b) Facilitated

2) Active transport
a) Primary (uses energy directly)
b) Secondary (use energy indirectly)

Question 2

Describe passive diffusion

Answer 2

The process of small molecules making their way across a membrane along the concentration gradient (high to low concentration). These molecules must be polar uncharged, or hydrophobic (e.g benzene)

Question 3

Describe facilitated diffusion

Answer 3

Polar and charged molecules can pass across the membrane by using carrier proteins (undergo conformational changes when ligand binds), or protein channels. Net flow is still down the concentration gradient

Question 4

What important functions does active transport allow within the cell?

Answer 4

Allows uptake of things which are moving against the concentration gradient, like:

1) Uptake of essential nutrients
2) Removal of waste
3) Maintenance of non-equilibrium concentrations of certain ions

Question 5

Describe the process of active transport

Answer 5

Energy is required, provided by another coupled reaction. The flow can either be up or down a concentration gradient.

Question 6

Describe primary active transport

Answer 6

Directly uses energy stored in ATP to move solutes across the plasma membrane. Movement is UNIDIRECTIONAL, and proteins are often referred to as pumps. This can often creates an electrochemical gradient. Example is the Na+/K+ pump

Question 7

Describe secondary active transport

Answer 7

Utilizes the electrochemical created by primary active transport to move solutes across the membrane.

Question 8

Name three types of transport proteins

Answer 8

1) ATP-powered pumps
2) Channel proteins (ion channels)
3) Carrier proteins

Question 9

Name the three types of carrier proteins

Answer 9

1) Uniporter
2) Symporter
3) Antiporter

• 2/3 are cotransporters