Lecture 2

Question 1

2 sides of an epithelial cell

Answer 1

• Apical side : exposed to outside or lumen
• Basolateral side : exposed to blood vessels, faces the ECF

Question 2

What is a tumor ?

Answer 2

Abnormal growth of tissue, serves no specific purpose. Develop when cells divide too quickly. Benign or Malignant.

Question 3

What is a benign tumor ? Can it be harmful ?

Answer 3

Cells don’t invade other tissues. They can be harmful if they take up space in the brain for example, or cause excess hormone production.

Question 4

What is a malignant tumor?

Answer 4

Cells grow uncontrollably and invade nearby tissues (daughter cells go in the bloodstream) -> metastases

Question 5

What are the 5 steps of tumor developement ? How could we avoid it ?

Answer 5

• hyperplasia : cells divide rapidly
• dysplasia : cells change form
• in situ cancer : cells stay in one place
• malignant tumor : cancer cells invade normal tissue and bloodstream
• metastases
  Avoid generation of blood cells in cancer tissue with medication to block oxygen and nutrients.

Question 6

Why are micelles useful ?

Answer 6

Transport of non-polar molecules in the digestive tract

Question 7

4 general functions of the cell membrane

Answer 7

1) physical isolation (barrier)
2) regulation of exchange with the environment
3) communication between cell and environment
4) Structural support

Question 8

What determines a substances’ permeability through cell membrane ?

Answer 8

Chemical nature : apolar can pass by free diffusion

Question 9

List the types of membrane transport

Answer 9

Active : vesicular, primary (ATP) and secondary (no ATP) active transport
Passive : facilitated diffusion, ion channel, aquaporin channel, simple diffusion

Question 10

What drives free diffusion ?

Answer 10

the concentration gradient

Question 11

Explain two classes of membrane transporters

Answer 11

1) channel proteins -> water filled pore : gated or open
2) carrier proteins : uniport, symport, antiport (active)

Question 12

free vs facilitated diffusion : what happens when concentration of transported substance increases ?

Answer 12

free : linear relationship, not saturable, fick’s law
facilitated : saturable, limited by numbers of transporters in membrane, can increase nb of transporters

Question 13

in what direction do we move molecules in active transport ?

Answer 13

against the concentration gradient -> makes concentration differences more pronounced

Question 14

main example for primary active transport, when does activity increase ?

Answer 14

Na+/K+: uses ATP, 3 Na+ outside - 2 K+ inside. Activity increases when [Na+] increases

Question 15

secondary active transport, key characteristics

Answer 15

no need for metabolic energy, driven by primary active transport.

Question 16

What are the body fluid compartments ?

Answer 16

ICF : intracellular fluid
ECF : extracellular fluid -> interstitial fluid and blood plasma

Question 17

Are the K+ and Na+ channels always open ?

Answer 17

No
K+ : (mostly) always open
Na+ : (mostly) always closed

Question 18

What is the distribution of the important ions in intra- and extracellular space

Answer 18

Extra : more Na+, Ca2+, Cl-
Intra : more K+, proteinate anions A- (can’t leave)

Question 19

What is the approximate value of resting membrane potential ?

Answer 19

-70 mV

Question 20

What kind of equilibrium is reached ? Why is K+ dominant ?

Answer 20

Flow equilibrium.
K+ is dominant because it has the largest ionic currents across the membrane.

Question 21

What is decisive for the formation of the membrane potential ?

Answer 21

The membrane ! It separates the A- and Na+ -> electrostatic coulomb forces

Question 22

What happens when low glucose levels (topic: insulin secretion)

Answer 22

Metabolism slows. ATP decreases. K_ATP channels are open, so K+ can cross the membrane normally and the potential is normal. Ca2+ channel remains closed, no insulin secretion

Question 23

What happens when the glucose levels are high ?

Answer 23

Metabolism increases. ATP increases. K_ATP channels close, thus K+ stay inside and potential increases. Ca2+ enters the cell because channels open, and triggers exocytosis of vesicles containing insulin.