Lecture 3: Transport of solutes and water Flashcards
What is the difference between Active and Passive Transport?
Active: Transport of molecules from low to high concentration (against the conc. gradient) with energy.
Passive: Transport of molecules from high to low concentration (down the conc. gradient) without energy.
Isotonic
Equal amounts of solute concentration in the outside and inside of the cell.
Hypotonic
Solute concentration is smaller on the outside of the cell relative to the inside.
Water concentration is larger on the outside of the cell relative to the inside.
Hypertonic
Solute concentration is greater on the outside of the cell relative to the inside.
Water concentration is smaller on the outside of the cell relative to the inside.
Describe the Sodium/Potassium Pump:
- What gets transported in?
- What powers this active transport?
- What is the net charge on the outside of the cell?
3 Sodium gets transported out, and 2 Potassium gets transported in.
This process is powered by energy from ATP hydrolysis.
There will be a net positive charge on the outside of the cell.
- Sodium binds to the pump
- ATP hydrolysis occurs and the pi group binds to the pump
- Conformational change in the pump, and sodium gets released out of the cell
- The Pi group on the pump gets released when Potassium binds.
- Conformational change occurs, and Potassium gets released into the cell
Why do Plant cells not rupture or undergo lysis in a hypotonic environment?
They have cell walls that are swollen. The hypotonic environment creates this “turgor pressure”. The cell walls prevent the plant cell from rupturing.
What are the names of hypotonic, isotonic, and hypertonic plant cells?
Hypo: Turgid
Iso: Flaccid
Hyper: Plasmolyed
Membrane potential vs Chemical potential
Membrane potential: voltage difference across a membrane created by concentrations of (+) or (-) charged ions across the membrane
Chemical potential: concentration difference of any molecule across the membrane
Do ion channels mediate active transport?
No- just passive transport.
What is Net flow?
The number of molecules that pass through a given area membrane in a given amount of time.
What is facilitated diffusion of water is facilitated by?
Aquaporins
What can change whether a channel that facilitates diffusion is open?
pH and Voltage
What is the alternating-access model? Which one of the transports mostly uses this model? Which one only sometimes uses it? What changes the model from a closed to open state?
The conformational changes of a pump controls substrate entry.
Active transport mostly uses the model.
Passive transport sometimes uses the model.
ATP binding and hydrolysis toggles protein from an open and closed state.
Describe Exocytosis vs. Endocytosis.
Is it passive or active transport?
Endocytosis: Bulk transport of solutes/water in the cell when the membrane pinches inward, forming a vesicle.
Exocyotosis: Bulk transport of solutes/water out of the cell through the fusion of intracellular vesicles with the cell membrane
Active transport.
What are the 3 types of Endocytosis?
Pinocytosis - liquid uptake
Phagocytosis- solute uptake
Receptor-mediated Endocytosis- Endocytosis is triggered when a ligand binds to a receptor.
What is an example of the specificity of transport channels for their transported materials? (Probably low yield)
Sodium and Potassium are both positive ions that can bind to the ion binding site, but only potassium can open the channel gate.
