Ch 7 - Membranes

Question 1

fluid mosaic model

Answer 1

• Currently accepted model of the arrangement of molecules in the plasma membrane. A mosaic of protein molecules bobbing in a fluid bilayer of phospholipids. Proteins are not randomly distributed. Groups of proteins are often associated in long-lasting specialized patches, where they carry out common functions.
• Membranes must be fluid to work properly.
• Somewhat like a tile mosaic, a membrane is a collage of different proteins, often clustered together in groups, embedded in the fluid matrix of the lipid bilayer.

Question 2

passive transport

Answer 2

• transport of a substance across a membrane with no energy investment
• diffusion, facilitated diffusion, osmosis
• moves DOWN the gradient concentration

Question 3

diffusion

Answer 3

the movement of particles of any substance so that they spread out into the available space

selective permeability/the cell is able to take up some small molecules and ions and exclude others

Question 4

facilitated diffusion

Answer 4

Many polar molecules and ions blocked by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane

Question 5

osmosis

Answer 5

diffusion of water across a membrane. water wants to achieve equilibrium, so if the solute cannot cross the membrane the water will move anyway to achieve equilibrium

Question 6

isotonic solution

Answer 6

concentration of solutes in the solution is the same as inside of the cell

Question 7

hypotonic solution

Answer 7

concentration of solutes in the solution is lower than inside the cell

Question 8

hypertonic solution

Answer 8

concentration of solutes in the solution is higher than inside the cell

Question 9

animal cell reactions in isotonic, hypertonic, and hypotonic solutions

Answer 9

• isotonic: stable/water diffuses across the membrane at the same rate in both directions
• hypertonic: cell will lose water, shrivel, and die
• hypotonic: cell will swell and lyse (burst)

Question 10

plant cell reactions in isotonic, hypertonic, and hypotonic solutions

Answer 10

• isotonic: there is no net tendency for water to enter and the cells become flaccid (plant will wilt)
• hypertonic: the cell will lose water and shrink. As it shrivels, its plasma membrane pulls away from the cell wall at multiple places (plasmolysis)
• hypotonic: stable/cell wall helps maintain the cell’s water balance, cells are turgid

Question 11

bulk transport

Answer 11

Large molecules, such as proteins and polysaccharides, generally don’t cross the membrane by diffusion or transport proteins. Instead, they usually enter and leave the cell in bulk, packaged in vesicles.