Passive Transport across the Membrane

Question 1

What is Passive Transport?

Answer 1

-Cells moving in & out of a cell without using energy

Question 2

What is a Concentration Gradient?

Answer 2

-The difference between concentration on the inside of the membrane & the outside of the membrane

Question 3

What is Diffusion?

Answer 3

-The random motion of molecules & ions dissolved in water that moves from regions of high concentration to low concentration

Question 4

What is the major to crossing a biological membrane?

Answer 4

-The hydrophobic interior= repels polar molecules but not non-polar molecules

Question 5

What is the plasma membrane permeable to?

Answer 5

• Limited permeability to Small polar molecules

- Very limited permeability to larger polar molecules & ions

Question 6

What is Facilitated Diffusion?

Answer 6

-Diffusion mediated by a membrane protein

Question 7

What are the 2 proteins that aid in Facilitated Diffusion?

Answer 7

• Channel Proteins

- Carrier Proteins

Question 8

How do Channel proteins allow for Facilitated Diffusion?

Answer 8

-They have a hydrophilic interior that provides an aqueous channel where polar molecules can through when the channel is open

Question 9

How do Carrier Proteins allow for Facilitated Diffusion?

Answer 9

-They bind specifically to the molecule they assist

Question 10

Since 2 proteins aid for facilitated diffusion, the Cell Membrane is…

Answer 10

Selectively Permeable

Question 11

Why can’t Ions move between the cytoplasm of the cell & the extrcellular fluid without help?

Answer 11

-Ions are repelled by non-polar molecules= present in the interior of the plasma membrane

Question 12

What are Ion Channels?

Answer 12

• They aid in the diffusion of ions bc ion channels posess a hydrated interior= allowing ions to diffuse in either direction depending on the relative concentration across the membrane
• Plays essential role in signaling by the nervous system

Question 13

What are Gated Channels?

Answer 13

-They are channel proteins that can be opened or closed in response to a stimulus (electrical or chemical)

Question 14

What are the 3 conditions that determine the net movement of ions?

Answer 14

• Their relative concentration on either side of the membrane
• The voltage difference across the membrane & gated channels
• The stage of the gated channels (open or closed)

Question 15

What is Membrane potential?

Answer 15

-A voltage difference= electrical potential difference across the membrane

Question 16

What does changes in the Membrane potential form?

Answer 16

-It forms the basis for transmission signals in the nervous system & other tissues

Question 17

What do Carrier Proteins help transport?

Answer 17

-Ions & other solutes (sugars, amino acids)

Question 18

for Carrier Proteins, what is the relationship between concentration & rate of transport?

Answer 18

• Concentration increase=more of the carriers are bound to the transport molecule
• So at high enough concentration, all of the carriers will be occupied= rate of transport will be constant= carriers exhibit saturation

Question 19

in Simple dffusion, what is the relationship between concetration & rate of transport?

Answer 19

-As concetration increases, transport is linearly increasing

Question 20

What is an Aqueous Solution?

Answer 20

-The mixture of the ions & molecules (sugars & amino acids) that are dissolved in water

Question 21

What does water & solutes have in common?

Answer 21

-They both tend to diffuse from regions of high concentration to ones of low concentration
(down their concentration gradients)

Question 22

What is Osmosis?

Answer 22

-The net diffusion of water across the membrane toward a higher concentration

Question 23

What determines the Osmotic Concentration?

Answer 23

-The concentration of all solutes in a solution

Question 24

What is a Hypotonic Solution & what happens to the cell?

Answer 24

• Lower concetrations of solutes

- Water moves into the cell & causes cell to burst= Hydrostatic pressure increases

Question 25

What is a Hypertonic Solution & what happens to the cell?

Answer 25

• Higher concentrations of solutes

- Water moves out of the cell & causes the cell to shrivel up= Hydrostatic pressure decreases

Question 26

What is a Isotonic Solution & what happens to the cell?

Answer 26

• Same concentration of solutes inside & outside

- Cells are at a “balanced” state= don’t gain or lose water

Question 27

What are Aquaporins?

Answer 27

-Specialized channels for water= facilitates water flow in living cells

Question 28

How many types of Aquaporins have been found in mammals?

Answer 28

-More than 11 types

Question 29

What are the 2 general classes of Aquaporins?

Answer 29

• Those that are specific to only water

- Those that allow other small hydrophyllic molecules (glycerol & urea) to cross the membrane

Question 30

What is Hydrostatic Pressure?

Answer 30

-The pressure of the cytoplasm pushing out against cell membrane

Question 31

What is Osmotic Pressure?

Answer 31

-The force needed to stop osmotic flow

Question 32

Why won’t the cells of prokaryotes, fungi, plants & many protists burst in a Hypotonic solution?

Answer 32

-They each have cell walls that can withstand high internal pressures without bursting

Question 33

What are the 3 strategies for having a steady influx when exposed to a Hypotonic solution?

Answer 33

• Extrusion
• Isosmotic regulation
• Turgor

Question 34

What is Extrusion?

Answer 34

-Some single celled eukaryotes use contractile vacuoles to remove water by collecting it from various parts of the cytoplasm & transporting it the central part of the vacuole near the cells surface

Question 35

What is Isomotic Regulation?

Answer 35

• Organisms that live in ocean= adjust internal concentration to match the concetration of the sea water
• Terrestial animals= circulate fluid through their bodies that bathes cell in isotonic solution

Question 36

What is Turgor?

Answer 36

-The Turgor Pressure (internal hydrostatic pressure) presses the plasma membrane against the interior of the cell wall= makes cell ridgid

Question 37

What are the 3 passive transport processes?

Answer 37

• Simple diffusion
• Facilitated diffusion
• Osmosis