Unit 1 Section 2:Exchange accross plasma membranes

Question 1

diffusion

Answer 1

movement of small non-polar molecules or water down the concentration gradient. molecules will diffuse both ways. this continues until the particles are evenly distributed. diffusion is a passive process meaning no energy is required. as long as particles can move freely through the membrane they can diffuse across it.

Question 2

<p>

| rate of diffusion</p>

Answer 2

<p>
three main factors: * the higher the concentration gradient the faster the rate of diffusion</p>

<p>
*the thinner the exchange surface the faster the rate.</p>

<p>
*the larger the surface area the faster the rate of diffusion.</p>

Question 3

Osmosis

Answer 3

diffusion of water molecules across a partially permeable membrane, from higher water potential to lower water potential.

Question 4

water potential

Answer 4

the potential of water molecules to diffuse in or out of a solution.

• pure water hase water potential of 0
• adding solutes lowers its water potential
• water potential of any solution is always negative.
• the more negatine the water potential the higher the concentration of solutes in the solution

Question 5

isotonic solutions

Answer 5

• have same water potential
• wont lose or gain water because no difference in water potential
• Plant cells don’t change
• animal cells wont change

Question 6

hypotonic

Answer 6

• solution has higher water potential than cell
• water will move into the cell by osmosis
• Plant cell : vacuole will swell, cellmembrane will psh against the cell wall, cell will become turgid
• Animal cell will swell and eventually burst

Question 7

hypertonic

Answer 7

cell has higher water potential

• water will move out of cell by osmosis
• plant cell becomes flaccid
• animal cell will shrink
• called PLASMOLYSIS

Question 8

facilitated diffusion

Answer 8

large molecules, most polar molecules and ions canont difuse through the bilayer directly.
they difuse through carrier or channel proteins.
*particles move down the concentration gradient
*passive process

Question 9

carrier/transport Proteins

Answer 9

large molecules including polar molecules and ions in or out of the cell membrane. different carrier proteins facilitate the movement of different molecules.

• a large molecule attaches to a carrier protein
• the protein changes shape
• realeases the molecule on the opposite side of the membrane

Question 10

channel Proteins

Answer 10

form pores in the membrane for smaller ions and polar molecules. different channel proteins facilitate the diffusion of different molecules.

Question 11

active transport

Answer 11

moves molecules up the concentration gradient requiring energy.
uses carries proteins

Question 12

endocytosis

Answer 12

molecules that are too large to be taken in by carrier proteins can be surrounded by a section of the cell’s plasma membrane. this pinches off inside the cell to form a vesicle. this can also be used to take in microorganisms

Question 13

exocytosis

Answer 13

substances produced need to be realeased from the cell e.g. digestive enzymes, hormones. vesicles containing these substances pinch off from the Golgi apparatus and move towards the plasma membrane, it then fuses with the membrane and releases their contents outside.

Question 14

summary diffusion

Answer 14

net movement of particles down the concentration gradient, not requiring energy

Question 15

summary osmosis

Answer 15

movement pf water molecules across a partially permeable membrane from high to low water potential, not requiring energy.

Question 16

summary facilitated diffusion

Answer 16

movement of particles down the concentration gradient. uses carrier proteins for large ions and polar molecules, channel proteins for smaller ions and polar molecules.
doesn’t require energy

Question 17

summary active transport

Answer 17

movement of particles up the concentration gradient, using carrier proteins requiring energy

Question 18

summary endocytosis

Answer 18

movement of large molecules into a cell, plasma membrane surrounds the substance then pinches off forming a vesicle incide the cell.
requires energy

Question 19

summary exocytosis

Answer 19

movement of molecules out of a cell, vesicles fuse with plasma membrane and releases contents, requires energy