Lecture 2 Flashcards
2 sides of an epithelial cell
- Apical side : exposed to outside or lumen
- Basolateral side : exposed to blood vessels, faces the ECF
What is a tumor ?
Abnormal growth of tissue, serves no specific purpose. Develop when cells divide too quickly. Benign or Malignant.
What is a benign tumor ? Can it be harmful ?
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.
What is a malignant tumor?
Cells grow uncontrollably and invade nearby tissues (daughter cells go in the bloodstream) -> metastases
What are the 5 steps of tumor developement ? How could we avoid it ?
- 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.
Why are micelles useful ?
Transport of non-polar molecules in the digestive tract
4 general functions of the cell membrane
1) physical isolation (barrier)
2) regulation of exchange with the environment
3) communication between cell and environment
4) Structural support
What determines a substances’ permeability through cell membrane ?
Chemical nature : apolar can pass by free diffusion
List the types of membrane transport
Active : vesicular, primary (ATP) and secondary (no ATP) active transport
Passive : facilitated diffusion, ion channel, aquaporin channel, simple diffusion
What drives free diffusion ?
the concentration gradient
Explain two classes of membrane transporters
1) channel proteins -> water filled pore : gated or open
2) carrier proteins : uniport, symport, antiport (active)
free vs facilitated diffusion : what happens when concentration of transported substance increases ?
free : linear relationship, not saturable, fick’s law
facilitated : saturable, limited by numbers of transporters in membrane, can increase nb of transporters
in what direction do we move molecules in active transport ?
against the concentration gradient -> makes concentration differences more pronounced
main example for primary active transport, when does activity increase ?
Na+/K+: uses ATP, 3 Na+ outside - 2 K+ inside. Activity increases when [Na+] increases
secondary active transport, key characteristics
no need for metabolic energy, driven by primary active transport.
What are the body fluid compartments ?
ICF : intracellular fluid
ECF : extracellular fluid -> interstitial fluid and blood plasma
Are the K+ and Na+ channels always open ?
No
K+ : (mostly) always open
Na+ : (mostly) always closed
What is the distribution of the important ions in intra- and extracellular space
Extra : more Na+, Ca2+, Cl-
Intra : more K+, proteinate anions A- (can’t leave)
What is the approximate value of resting membrane potential ?
-70 mV
What kind of equilibrium is reached ? Why is K+ dominant ?
Flow equilibrium.
K+ is dominant because it has the largest ionic currents across the membrane.
What is decisive for the formation of the membrane potential ?
The membrane ! It separates the A- and Na+ -> electrostatic coulomb forces
What happens when low glucose levels (topic: insulin secretion)
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
What happens when the glucose levels are high ?
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.
