1.4 Membrane Transport

Question 1

What is the concentration gradient?

Answer 1

When material moves from a high concentration to a low concentration.

Question 2

What are the key qualities of cellular membranes?

Answer 2

They are semi-permeable, large and charged particles are usually blocked.
They are selective, membrane proteins may regulate the passage of material that cannot freely cross.

Question 3

What is passive transport?

Answer 3

Movement of material that moves along the concentration gradient (high–>low).

Question 4

What is diffusion?

Answer 4

The net movement of molecules from a high to low concentration until equilibrium.

Question 5

What are the three types of passive transport?

Answer 5

Simple diffusion, osmosis, and facilitated diffusion.

Question 6

What is simple diffusion?

Answer 6

Movement of small or lipophilic molecules. (ex. O2 and CO2 in cellular respiration)

Question 7

What is osmosis?

Answer 7

Movement of FREE water molecules and occurs from low solute concentration regions.

Question 8

What is facilitated diffusion?

Answer 8

Movement of large or charged molecules with the help of membrane proteins

Question 9

What is active transport?

Answer 9

Movement of material that moves against the concentration gradient (low–>high), requiring ATP energy.

Question 10

What are the types of active transport?

Answer 10

Primary direct and secondary indirect active transport.

Question 11

What is primary active transport?

Answer 11

Involves the direct use of ATP energy to transport (ex. from ATP hydrolysis).

Question 12

What is secondary active transport?

Answer 12

Involves coupling the molecule with another moving along an electrochemical gradient.

Question 13

What influences the rate of diffusion?

Answer 13

-temperature, affects the kinetic energy of particles
-molecular size, large molecules=greater resistance in fluid
-gradient steepness, greater rate=higher gradient

Question 14

What is osmolarity?

Answer 14

The measure of solute concentration in # of osmoles per liter of solute (osmol/L).

Question 15

What is a hypertonic solution?

Answer 15

Solutions with a higher osmolarity (solute concentration), so it gains water.

Question 16

What is a hypotonic solution?

Answer 16

Solutions with a lower osmolarity (solute concentration), so it loses water.

Question 17

What is an isotonic solution?

Answer 17

Solutions that have the same osmolarity, so no net water flow.

Question 18

What will happen to cells in hypertonic solutions?

Answer 18

Water will leave the cell causing it to shrivel; crenation.

Question 19

What will happen to cells in hypotonic solutions?

Answer 19

Water will enter the cell causing it to potentially burst; lysis.

Question 20

What is the effect of hypertonic and hypotonic solutions in plant cells?

Answer 20

Hypertonic: cytoplasm will shrink, but cell wall will maintain its structure
Hypotonic: cytoplasm will expand but cannot rupture because of the cell wall–>turgor pressure

Question 21

What are channel proteins?

Answer 21

They help transport large molecules along the gradient during facilitated diffusion and have a hydrophilic interior pore for water-soluable materials to pass through.

Question 22

What are carrier proteins?

Answer 22

They can be used during facilitated diffusion or active transport to move molecules along/against the concentration gradient in the presence of ATP. They will only bind a specific molecule unlike the pores of channel proteins.

Question 23

What is endocytosis?

Answer 23

Large substances (or bulk amts) enter the cell without crossing the membrane.

Question 24

What are the types of endocytosis?

Answer 24

Phagocytosis—solid substances are ingested
Pinocytosis—liquid/dissolved substances are ingested

Question 25

What is exocytosis?

Answer 25

Large substances (or bulk amts) exit the cell without crossing the membrane using vesicles.