Unit 3: Active & Bulk Membrane Transport

Question 1

Describe

3 general features of active transport

Answer 1

1. Require energy
2. Move solutes from regions of LOWER concentration to regions of HIGHER concentration
3. Establish / maintain a concentration gradient

Question 2

Compare and contrast

Active molecular transport (pumps)
VS
Facilitated diffusion using carrier proteins

Answer 2

Both use carrier proteins (although pumps have evolved to move solutes in opposite direction and using energy), which change shape to move particles
Both move solutes across the membrane
Active transport requires energy and goes against the concentration gradient
Facilitated diffusion does not require energy and goes with the concentration gradient

Question 3

Which direction are sodium and potassium ions moved with the Na+/K+ pump?

Answer 3

Three sodium ions out
for each
Two potassium ions in

Mnemonic to remember: think of toucans (the birds). 2 - K - IN

Question 4

Describe the process

Sodium Potassium Pump

Answer 4

1. Na+ from cytoplasm binds to pump
2. Cellular “battery” binds
3. Energy from battery enables pump to change shape, opening toward extracellular environment
4. Sodium are released out of cell and potassium ions bind to pump
5. Pump changes shape again, opening toward cytosol
6. Potassium are released into cytosol

Question 5

Define

Voltage

Answer 5

Electrical potential energy or a separation of electrical charges (positive from negative)

Question 6

Define

Membrane potential

Answer 6

Voltage across a cell membrane

Inside of cell is more negative compared to extracellular environment

Question 7

What two forces drive the movement of ions across a membrane?

Answer 7

Chemical gradients
and
Electrical forces

Combined, this makes the electrochemical gradient

Question 8

What is the importance of

Cotransport

Answer 8

Allows cells to use one substance’s concentration gradient (formed by active transport) to power the movement of another substance

Question 9

Compare and contrast

Bulk Transport and Other Transport

Answer 9

Most transport types (diffusion, facilitated diffusion/ osmosis, and pumps) move particles across the cell membrane
Bulk transport does NOT include the movement across the membrane but instead packages the materials into vesicles

Question 10

Describe the process of

Exocytosis

Answer 10

A vesicle fuses with the plasma membrane
Contents of the vesicle get released into extracellular space
Membrane of the vesicle fuses with / adds to the plasma membrane

Question 11

Describe the process of

Endocytosis

Answer 11

Membrane extends around a substance (requires a lot of cytoskeleton action)
The membrane folds into a pocket, which pinches off to become its own vesicle

Question 12

List the

Purpose(s) of Exocytosis

Answer 12

Note that these may seem similar, but WHY a cell does them still differs!
-To move products out of a cell to be used by other nearby cells or be used in the ECM
-To expel waste products or excess water from a cell
-To move, such as by rapidly expelling water (think: paramecia)
-To add more membrane to the plasma membrane
-To add specific proteins into the plasma membrane

Question 13

List the

Purpose(s) of Endocytosis

Answer 13

Note that these may seem similar, but WHY a cell does them still differs!
-To take in large quantities of material from the environment very rapidly (esp in pinocytosis)
-To take in material that is too large to pass the membrane (esp in phagocytosis)
-To take a substance that the cell has bound to it into the cell
-To remove proteins that are on the plasma membrane