Cell Bio: Chapter 12 Flashcards
(30 cards)
Membranes are used for:
Keeping things separate in cells.
Which substances can cross a membrane via diffusion?
Anything nonpolar or small polar substances.
What do cells use to transport things across membranes?
Transporters, pumps and channels.
Living cells set up ion gradients across membranes. What are three important ions?
Na+, K+, and Cl-.
Where is Na+ high in concentration?
Outside the cell.
Where is K+ high in concentration?
Inside the cell.
What characterizes a transporter?
Solutes that specifically fit in an active (binding) site.
What happens when a solute binds to a transporter?
It undergoes a conformational change, trasporting one or a small number of substrates across.
How do channels discriminate between solutes?
By size and charge.
What is passive transport?
With or down a cell’s concentration gradient.
What is active transport?
Transporting substrates against or up the concentration gradient.
Regarding diffusion, are transporters and channels passive?
Some transporters are passive and some are active. CHannels are passive.
For the Glut1 passive transporter, is the solute transported across the membrane passively or actively?
Passively, the net movement of glucose is always down the gradient. But it can work both ways to transport glucose in and out of the cell.
What determines the direction of movement for glucose across a membrane?
The gradient.
How much ATP is used to power the Na+/K+ pump?
30% of cellular ATP; it actively sets up gradients so they can use it to do other work in the cell.
What ions does the Na+/K+ pump transport?
Three Na+ ions, and two K+ ions into the cell for each ATP used.
(Both go against the gradient).
What is couple transport?
The movement of one substrate down its gradient driving the movement of another substrate up its gradient.
What is a glucose-Na+ symport protein?
It transports an Na+ ion and glucose molecule into the cell together.
How do glucose and Na+ come into the cell?
Na+ comes into the cell with its gradient, and glucose comes into the cell against its gradient.
Where does glucose go after the intestine?
It moves against its gradient to the intestinal epithelial cells.
Where does glucose go from the intestinal epithelial cells?
It moves down its concentration gradient to the extracellular fluid on the basolateral side of the cells (it uses the Glut passive transporters).
Where does glucose go from the extracellular fluid on the basolateral side of the epitheila cells?
The bloodstream for transport to other tissues.
What are ion channels?
Pores that can be opened to permit a solute through.
Why are ion channels selective?
Because of the diameter and charges in the pore that make up the selectivity filter.
