Ch. 12

Question 1

Which type of transport protein forms tiny hydrophilic pores through which solutes can pass by diffusion?

Answer 1

passive transport

Question 2

In mammalian cells, what is the most plentiful positively charged ion on the outside of cells and what is the most plentiful positively charged ion on the inside of cells?

Answer 2

Potassium (K+) is high inside the cell and Sodium (Na+) is the most plentiful outside the cell. (Salty Bananas)

Question 3

What is the main ion that balances the Na+ ions on the outside of the cell

Answer 3

Chloride ions (Cl-)

Question 4

If you are moving ions against their concentration gradient (say Na+ from inside to outside the cell) does this require active transport?

Answer 4

Yes, it requires ATP hydrolysis

Question 5

Uniport

Answer 5

one type of molecule transported one way

Question 6

Antiport:

Answer 6

two types of molecules transported opposite directions, one against its gradient.

Question 7

Is the Na+/K+ ATPase an anti porter?

Answer 7

Yes, does active transport.

Question 8

Symport

Answer 8

two types of molecules transported one way

Question 9

Are K+ or Na+ ions flowing down their electrochemical gradient through an ion channel with passive or active transport?

Answer 9

passive

Question 10

Why do K+ and Na+ ions need to be transported through ion channels to get across the plasma membrane

Answer 10

Because they are highly charged and cannot get across the hydrophobic fatty acid tails of the phospholipids bilayer

Question 11

What inhibits these ions from passing through the lipid bilayer freely?

Answer 11

The hydrophobic fatty acid tails make it hard for the ions to pass through the lipid bilayer, so they need the ion channel to pass through freely

Question 12

What type of molecule will diffuse most rapidly across the lipid bilayer

Answer 12

small non polar

Question 13

True or false or true or true. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind to their solutes with great specificity in the same way an enzyme binds its substrate?

Answer 13

True as the northern wind

Question 14

The movement of an ion down its electrochemical gradient is called: passive or active?

Answer 14

Passive

Question 15

The movement of an ion against its electrochemical gradient is called: passive or active transport?

Answer 15

active

Question 16

What type of membrane transport protein can perform active or passive transport: channels or transporters?

Answer 16

Channels: always passive
Transporters: can be active or passive

Question 17

Does Na+ or K+ have a larger electrochemical gradient across the cell?

Answer 17

3 Na+ out for every 2 K+ in, so Na+ is stronger

Question 18

An electrochemical gradient has a voltage component and an electrical component: true or false?

Answer 18

true

Question 19

If the inner plasma membrane has a net negative charge (although the cell overall is electrically neutral), then what type of ions will the cell tend to pull in: positive or negative solutes?

Answer 19

Positive ions like Na+ ions

Question 20

Why do plant cells not burst due to osmotic swelling?

Answer 20

Plant cells are surrounded by a thick cell wall that can contain the pressure built up due to osmotic forces

Question 21

Is calcium kept low or high in the cytosol?

Answer 21

Ca2+ levels are kept low in the cytosol because when Ca2+ flows into the cell, it causes signals to trigger intracellular events (muscle contractions, secretion of signal molecules)

Question 22

Is calcium kept low or high in extracellular fluid?

Answer 22

Ca2+ is left high in extracellular fluid to be available to flow in at any moment

Question 23

What organelle is critical in controlling the concentration of calcium in the cytosol?

Answer 23

Endoplasmic Reticulum

Question 24

What does bacteriorhodopsin use as an energy source to pump H+ ions out of the cell to create an electrochemical gradient of protons?

Answer 24

Bacteria (procaryotes) use H+ ATPase to pump ions out of the cell. Uses H+ gradient instead of Na+ gradient.

Question 25

Solute movement through channels is active or passive?

Answer 25

passive (diffuses through down its concentration gradient)

Question 26

Is there a membrane potential that can be formed across the plasma membrane with negatively charged ions on the cytosolic side and positively charged ions on the extracellular side?

Answer 26

the cytosolic half of the plasma membrane is negative with respect to the outside which is positive

Question 27

Is the extracellular fluid and the intracellular cytosol electrically neutral?

Answer 27

The solution in the cytosol and the extracellular fluid are both neutral so the cell isn’t ripped apart by electrical forces. The high concentration of Na+ outside the cell is balanced by extracellular Cl- (chloride ions).

Question 28

What inhibits these ions from passing through the lipid bilayer freely?

Answer 28

The hydrophobic fatty acid tails make it hard for the ions to pass through the lipid bilayer, so they need the ion channel to pass through freely.