41 Questions
What does the Na+/K+-ATPase pump do?
Pumps Na+ ions out and K+ ions in
Which molecule-specific transmembrane protein is usually called 'pumps'?
Na+/K+-ATPase
What is the purpose of the Na+/K+-ATPase pump?
To keep internal Na+ low
What is the net charge on each side of the membrane as the Na+/K+-ATPase pump operates?
The cell interior becomes more negative
What is the rate at which the Na+/K+-ATPase pump operates?
~100 cycles/sec
How much energy does the Na+/K+-ATPase pump use in most animal cells?
1/3
What does the Na+/glucose cotransporter use to drive the import of glucose?
The electrochemical Na+ gradient
How many Na+ ions bind to the Na+/glucose cotransporter on the outer apical surface?
2
How many moles of Na+ ions need to move into a cell to generate a glucose concentration that is 30,000 times higher inside than outside?
2
What is the movement of Na+ and glucose across the apical membrane an example of?
Secondary active transport
Which of the following is true about the lipid bilayer?
It prevents loss of charged and polar solutes
What determines the rate of simple diffusion across protein-free bilayer membranes?
Size and solubility
Which statement about the permeability of membranes to water and small ions is true?
Membranes are more permeable to water than to small ions
What is the main electrical effect of tiny excesses of charges near the plasma membrane?
They create an electrochemical gradient
What are the two components of an electrochemical gradient?
Chemical and electrical
Which process allows substances to move from a region of high concentration to a region of low concentration?
Facilitated diffusion
What is the main driving force for diffusion?
Random thermal motion
What are the two means for movement across a selectively permeable membrane?
Simple diffusion and active transport
What is the characteristic set of carrier proteins for each cell membrane?
Membrane transporters
What are the two types of transporters and channels involved in facilitated diffusion?
Carrier proteins and ion channels
Which process allows substances to move across membranes by directly passing through the lipid bilayer?
Simple diffusion through lipid bilayer
Which type of transport uses protein-lined channels to facilitate the movement of substances across membranes?
Facilitated transport through aqueous, protein-lined channel
Which type of transport involves membrane-spanning proteins that change shape to facilitate the movement of substances across membranes?
Facilitated transporters
Which type of transport requires energy to move molecules against their concentration gradient?
Active transport
Which category of ion channels opens due to a change in voltage difference across the membrane?
Voltage-gated channels
Which category of ion channels opens due to the binding of a specific ligand, usually not the transported species?
Ligand-gated channels
Which category of ion channels opens due to mechanical stimulation, such as pressure or stretch?
Stress-gated channels
Which type of transporter allows facilitated diffusion of glucose into muscle cells down its concentration gradient?
Glucose transporter
Which transporter is regulated by insulin and is responsible for glucose uptake into various cells?
Glucose transporter
Which type of transport uses energy to move molecules against their concentration gradient?
Active transport
Diffusion of ions through membrane channels transport is ______ and proceeds down the concentration gradient of the ion being transported
passive
Major categories of gated ion channels: 1. Voltage-gated channels -- opens due to change in ______ difference
voltage
Glucose transporter -- facilitated diffusion of ______ into muscle cell down concentration gradient (High --> Low)
glucose
Active transport uses ______ to move molecules 'up' conc. gradient (Low --> High)
energy
Na+/K+-ATPase pump changes shape when ________
autophosphorylated
The Na+/K+-ATPase pump pumps ________ ions out and ________ ions in
Na+, K+
The Na+/glucose cotransporter binds ________ Na+ ions and ________ glucose molecule(s) on the outer apical surface
2, 1
Movement of ________ moles of Na+ ions into a cell can generate a glucose concentration that is 30,000 times higher inside than out
2
Membranes are a billion times more permeable to water than to small ions Fig. 12-2 Inside Outside Approximately equal quantities of +/- charges inside and outside of cell Tiny excesses of + or - charges do occur near PM and have imp. electrical effects Table 12-1 Remember a salty banana Na+______ClK+
Each cell membrane has its own characteristic set of carrier proteins Figure 12-8 Transporters and channels move inorganic ions and small, polar molecules cross membrane — facilitated diffusion A — channels either open or close; faster transport rates than transporters B — transporters undergo a series of conformational changes (alternate access) Fig. 12-3 Membranes are a selectively permeable barrier - two means for movement both of which lead to net flux of ions/compounds (influx - into cell; efflux out of cell) 1. Passively by diffusion 2. Actively by energy-coupled transport process Diffusion substance moves from region of high conc. to region of low conc.; eventually eliminating conc. difference driven by random thermal motion leading to increase in entropy electrochemical gradient --chemical - compartment concentration difference -- electrical - compartment charge difference An electrochemical gradient has two components Width of green arrow -- magnitude of gradient Fig. 12-5 Different processes by which substances move across membranes 1. Simple diffusion through lipid bilayer 2.
Membranes are a billion times more permeable to water than to small ions Fig. 12-2 Inside Outside Approximately equal quantities of +/- charges inside and outside of cell Tiny excesses of + or - charges do occur near PM and have imp. electrical effects Table 12-1 Remember a salty banana Na+Cl______+
K+
Membranes are a billion times more permeable to water than to small ions Fig. 12-2 Inside Outside Approximately equal quantities of +/- charges inside and outside of cell Tiny excesses of + or - charges do occur near PM and have imp. electrical effects Table 12-1 Remember a salty banana ______ClK+
Na+
Test your knowledge on membrane transport and the properties of lipid bilayers in this quiz. Explore the concepts of simple diffusion, semipermeability, and the permeability of membranes to water and small ions.
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