Chapter 12 Flashcards
Why do we need to be able to transport molecules and ions?
Transport nutrients and waste, maintain concentrations of ions, create gradients, control osmosis, electrical signaling of neurons
What are the factors that control rate of diffusion?
Size, solubility, and charge
Which molecules flow through membranes the easiest? Which molecules flow through membranes the slowest?
(size, polarity, charge)
1 Small hydrophobic (nonpolar)
2 Small charged
3 Large uncharged polar
4 Ions
How do transport proteins effect Ea?
Lower it by creating a hydrophilic environment
Differentiate between transporters and channels
Transporters undergo a conformational change that allows transport across membranes, they have binding sites similar to enzymes (non-covalent interactions). Transporters are also subject to competitive inhibition
Channels are tiny hydrophilic pores that can be opened or closed, they discriminate between ions based on size and charge.
Describe Simple Diffusion. Are specific proteins needed? What type of kinetics would you see in a graph of concentration vs rate of diffusion?
Certain molecules like H2O and CO2, pass directly through the membrane, no proteins needed. Linear kinetics
Describe Passive Transport/Facilitated Diffusion. Are specific proteins needed? What type of kinetics would you see in a graph of concentration vs rate of diffusion?
No energy required, molecules move through channels or transporters. Molecules follow their concentration gradients. Hyperbolic kinetics, has Vmax where the rate is limited by the number of transport proteins.
Describe Active Transport. Are specific proteins needed?
Requires energy, uses transporters but not channels.
Where could the energy used for active transport come from?
Light (bacteria), ATP hydrolysis, Coupled against another molecule that is transported across its gradient (that molecule has a negative deltaG)
Differentiate between Uniporters, Symporters, Antiporters
Uniporters = 1 solute, Symporters = 2 solutes, same direction, Antiporters = 2 solutes, different direction
They could all be passive or active
Describe the sodium potassium pump. Describe its purpose, the electrochemical gradient of each ion, which is on each side of the membrane, how it works and what it does.
Higher solute concentration inside the cell vs outside means water will move in by osmosis
Plant cells deal with this by tough cell walls, protozoans by contractile vacuole
Na+ has an electrochemical gradient heading inside the cell and K+ has an electrochemical gradient heading outside of the cell. This is because the inside of the cell has a negative charge, Na+ is more concentrated outside the cell, and K+ is more concentrated inside the cell.
The pump moves both Na+ and K+ against their concentration gradient by using ATP. The pump goes through a cycle of Na+ binding, ATP adding P, Na+ ejected outside of the cell, K+ binds, pump loses P, K+ ejected.
Na+’s electrochemical gradient can be used to do work.
Describe what the Glucose/Na+ Symporter does. Active or passive?
Active. Uses the Na+ gradient to move glucose against its concentration gradient, into the cell
Describe the Uniporter of Glucose. Active or passive?
“GLUT1”. Passive. Moves glucose along its concentration gradient (bidirectional). Has a Vmax, hyperbolic type curve. Similar to Michaelis-Menton enzyme kinetics.
Describe the Ca+2 pumps. What is its purpose? What is the purpose of Ca? Where are these pumps located?
Ca+2 can bind tightly to a variety of proteins and alter their activities.
An influx of that ion is used as an intracellular signal to trigger various cell processes
Lower concentration = more sensitive -> want to keep low
Pumps are in the plasma membrane and the endoplasmic reticulum membrane.
If only the ER pumps are working, they can keep calcium low by themselves
Describe aquaporins. What type of protein are they?
Helps to move H2O across the membrane, type of transporter protein
