What are the 3 classes of membrane transport proteins?
- Diffusion-mediated channels and facilitated transporters
- ATP pumps
- Co-transporters
How is intracellular osmolarity controlled in animal cells?
- Negatively charged small organics inside cell attract Na+ ions
- If left unregulated, water flows into cell –> cell swells
- Pump Na+ ions out of cell until water is balanced
How do facilitated transporters work? In what direction does it favor flow?
- Binding of solute changes conformation of protein to transport substance into cell
- Flow down diffusion gradient
Uniporter vs. Symporter vs. Antiporter?
- Uniporter: down conc gradient in one direction
- Symporter: transports one substance against and another substance down their respective conc gradients, but in the same direction
- Antiporter: transports one substance against and another substance down their respective conc gradients, but in diff directions
Is the conc of glucose higher inside or outside the cells?
Inside
What are Na+/K+ ATPase pumps? Function?
- Na+ from cytosol side binds to pump
- Phosphorylation of pump releases Na+ to extracellular space
- Dephosphorylated pump binds K+ from extracellular space and transports it into the cytosol
What are the 3 major ways of treating acid reflux and heartburn? How does each work?
- Zantac, Papcid, Tagamet: binds to receptor and blocks histamine itself –> no activation of H+/K+ pump
- Prilosec: inactivates the pump to reduce production of acid
- Antacids/tums: neutralizes acid
Describe the mechanism by which acid reflux and heartburn occur.
Histamine binds to a receptor on the lining of the stomach –> activates H+/K+-ATPase pump –> pumps K_ out and brings H in to generate acid for digestion
**production of too much acid –> acid reflux, heartburn
Which proteins go to the ER to complete their synthesis?
- ER
- Plasma membrane
- Lysosomes
- Golgi
Where do proteins go after synthesis is complete?
- Nucleus
- Peroxisomes
- Mitochondrion
- Chloroplasts
NLS vs. NES?
- NLS (nuclear localization sequence): code that determines if the protein goes in the nucleus
- NES (nuclear export sequence): code that determines if the protein goes out of the nucleus
What sequence characterizes a NLS?
KKK = lysine sequence
You are working with a protein ZZ that is normally localized to the cytoplasm. If you add PKKKRV sequence to the middle of ZZ protein, where would you expect to find ZZ?
Nucleus
Is K+ more concentrated inside or outside the cell?
Inside
Is Na+ more concentrated inside or outside the cell?
Outside
Is Ca2+ more concentrated inside or outside the cell?
Outside
Is Cl- more concentrated inside or outside the cell?
Outside (to balance Na+)
