Membrane Transport

Question 1

What factors affect permeability? 4

Answer 1

Size, shape, electrical charge, and lipid solubility

Question 2

What 7 factors affect diffusion?

Answer 2

1. Distance: closer is faster
2. Size: smaller is faster
3. Temperature: higher is faster
4. Concentration: higher is faster
5. Electrical Forces: opposite charges attract
6. Solubility
7. Permeability

Question 3

What are the 4 modes of transport?

Answer 3

Diffusion, filtration, carrier-mediated, and vesicular

Question 4

What modes of transport require energy?

Answer 4

Carrier mediated (passive or active), vesicular (active)

Question 5

What modes of transport do not require energy?

Answer 5

Diffusion (passive), filtration (passive), carrier mediated (active or passive)

Question 6

What is diffusion?

Answer 6

Passive transport

Movement of ions across a membrane through a channel from [high] to [low] (down a concentration gradient)

it is believed that some lipid-soluble molecules can diffuse directly across the plasma membrane

Question 7

What is osmosis?

Answer 7

Passive transport; diffusion of water

Movement of water across a membrane using aquaporins until water and solute concentrations are equal on both sides

rate depends on #

Question 8

What molecules are lipid soluble and which are lipid insoluble?

Answer 8

Fatty acids, steroids, alcohol, O2, and CO2 are lipid soluble

H2O, Na+, and Ca2+ are lipid insoluble

Question 9

In what environments does osmotic flow occur?

Answer 9

Isotonic, hypotonic, hypertonic solutions

Question 10

What happens if a cell is placed in an isotonic solution?

Answer 10

No osmotic flow occurs and the cell appears normal in size and shape

Question 11

What happens if a cell is placed in a hypotonic solution? (lower solute concentration than within the cell)

Answer 11

Water flows into the cell and will swell and continue until the plasma membrane ruptures or lyses

Question 12

What happens if a cell is placed in a hypertonic solution? (higher solute concentration than within the cell)

Answer 12

Water flows out of the cell and will crenate (shrivel)

Question 13

What type of open channels do red blood cells have?

Answer 13

Aquaporins

Question 14

What is filtration?

Answer 14

Passive transport

Hydrostatic pressure (HP, blood pressure) forces water and small molecules across a membrane

about 80% of fluid entering tissues on arteriole end are reabsorbed on venous side of an artery

Question 15

What is carrier-mediated transport: facilitated transport?

Answer 15

Passive movement of molecules along a concentration gradient, requiring a transporter (a protein) to facilitate this movement across the membrane

different from diffusion because the maximum transport rate is determined by the number of transporters

Question 16

What is carrier-mediated transport: primary active transport?

Answer 16

Active movement of molecules against the concentration gradient across the membrane requiring energy (from low to high)

energy is supplied in the form of ATP and required specialized proteins called ion pumps

ex. Na+/K+ pump which actively pumps Na+ out and K+ into cells

this protein is present in most cells in the body and uses 25% of all ATP produced at rest

Question 17

What is the difference between diffusion and facilitated transport?

Answer 17

Facilitated transport is different from diffusion because the maximum transport rate is determined by the number of transporters

Question 18

What is carrier-mediated transport: secondary active transport?

Answer 18

Occurs when the Na+ concentration created by the Na+/K+ pump is used to aid in the transport of other molecules

ATP is still used but is used indirectly, or secondary to the transportation of the molecule

ex. sodium dependent glucose transporter where glucose is absorbed along with the Na+ entering the channel to go through the cycle

Question 19

What are antiporters and symporters?

Answer 19

Antiporters: one comes in, the other goes out

Symporters: going in the same direction/together

Question 20

What are the types of vesicular transportation?

Answer 20

Endocytosis, phagocytosis, pinocytosis, and exocytosis

Question 21

What is endocytosis?

Answer 21

The process of transporting substances across the plasma membrane into the cell by forming a vesicle

substances that are transported in this way are too large or complex to use a transporter or channel

Question 22

What is phagocytosis?

Answer 22

Cell eating, type of endocytosis where cells or debris are consumed and destroyed

white blood cells do this to invading bacteria

Question 23

What is pinocytosis?

Answer 23

Cell drinking, type of endocytosis where small particles are absorbed into the cell

Question 24

What is exocytosis?

Answer 24

Occurs when a substance is exported from a cell using a vesicle. The vesicle fuses with the plasma membrane and expels the vesicle contents into the extracellular fluid

hormones and extracellular proteins are transported in this manner
-mucus and waste