Ch 12
Resting membrane potential in animal cells can be anywhere between ____ and ____ mV.
-20, -200
3 types of active transport via transmembrane pumps
1. ATP-driven 2. Coupled 3. Light-driven
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called ____. A. Active transport B. Free diffusion C. Facilitated diffusion D. Passive transport
A
Transporters, in contrast to channels, work by ____. A. Specific binding to solute B. A gating mechanism C. Filtering solutes by charge D. Filtering solutes by size
A
T or F: a transporter can only mediate passive/facilitated diffusion.
F
T or F: K+ concentrations are highest outside of the cell.
F, inside
Less polar molecules have ____ favorable interactions with water
Fewer
Channels
Form hydrophilic pores across the membrane thru which substances can pass by diffusion
Hypotonic means ____ salt outside the cell.
Low
Example of ligand-gated ion channel:
Acetylcholine receptor, neurotransmitter receptor
Which of the following ions would you expect to be able to freely diffuse through a Na+ channel? A. Mg2+ B. H+ C. K+ D. Cl-
B, H+ bc it is positively charged and small enough to fit through the channel
Neurotransmitter release is stimulated by the opening of voltage-gated ____ channels in the nerve terminal membrane.
Ca2+
The influx of ___ ions through ____ channels would trigger the release of neurotransmitters into the synaptic cleft.
Calcium, voltage-gated calcium
Lipid bilayers are highly impermeable to ALL ____ molecules.
Charged
Ligand gated ion channels in nerve membranes convert ____ signals into ____ ones.
Chemical, electrical
Active transport
Movement of solute against its concentration gradient
Transporters
Shift small organic molecules or ions from one side of membrane to other by changing shape
Example of a voltage-gated ion channel:
Sodium, potassium and Ca channels
Example of a stress-gated ion channel:
Stereocilia
What type of transporter is the Na+-glucose pump?
Symport
Neurons communicate with each other through specialized sited called ____.
Synapses
T or F: Na+ concentrations are highest outside of the cell.
T
T or F: a channel can only mediate passive/facilitated diffusion.
T
T or F: the K+ leak channel allows potassium to flow down its concentration gradient.
T
T or F: transporters can mediate active transporr
T
3 major differences between transporter and a channel?
Transporter specifically binds solute, undergoes conformational change, can mediate active transport
What type of transporter is bacteriorhodopsin?
Uniport
What type of transporter is the Ca2+ pump?
Uniport
What would happen to a cell if you placed it in a hypotonic solution?
Water would rush into the cell and it would swell
What would happen to a cell if you placed it in hypertonic solution?
Water would rush out of the cell and it would shrivel
What type of transporter is the Na+-K+ pump?
Antiport
The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens after the pump hydrolyzes ATP? A. NA+ is bound B. ADP is bound C. The pump is phosphorylated D. The pump changes conformation
C
Hypertonic means ____ salt outside the cell.
High
Lipid bilayers are impermeable to ____ and most uncharged ____ molecules.
Ions, polar
What would happen to the resting membrane potential if the inner channel of the K+ leak channel decreased in size by half?
No K+ would be able to leak out and resting membrane potential would become more positive
Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ____ cell membrane in response to neurotransmitters released by the ____ cell.
Postsynaptic, presynaptic
