8-membrane transport ii
DESCRIPTION
TRANSCRIPT
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Membrane Transport and Permeability II
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Outline for Today
I. IntroductionII. Passive Processes
A. Simple diffusionB. OsmosisC. FiltrationD. Facilitated diffusion
III. Active TransportA. IntroductionB. Solute pumping
1. Na+/K+ ATPase pump
C. Bulk transport1. Endocytosis2. Exocytosis
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Active Transport
• Cells must use energy since the movement is non-favorable– ATP ADP + Pi
• Non-favorable means it goes against the concentration gradient
ATP
ADP
Pi
EnergyPi
Energy
Introduction
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Na+/K+ ATPase
K+
K+
K+K+
K+K+
K+
Na+
Na+
Na+
Na+ Na+
Na+
Na+
Na+
ATP
ADP + Pi
K+
Cytoplasm
Extracellular fluid
Gradient for Na+
Gradient for K+
Na+Na+Na+
Electrogenic Pump!!!
Na+Solute Pumping
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Na+/K+ ATPase pump
• Movement of materials against the gradient
Solute Pumping
Fig. 3.19
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Na+/K+ ATPase pump
• Transmembrane• Pump moves both
Na+ and K+
• Antiport• Enzyme catalyzes the
degradation of ATP• This pump never
stops– Can burn energy while
asleep
Solute Pumping
Fig. 3.19
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Na+/K+ ATPase pump
• It maintains a high extracellur and low intracellular [Na+] by moving Na+ (blue) outside
• It maintains a low extracellur and high intracellular [K+] by moving K+ (yellow) inside
• Mnemonic
Solute Pumping
Fig. 3.19
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Mnemonic
Potassium -does it go in or out?
Sodium -does it go in or out?
Kin Kout Nain Naout
K goes in so Na must go out of the cell
Solute Pumping
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Another way to think of it
• Life began in the sea• The sea is very salty
– Salt has a tendency to enter the organisms/cells so we tend to be bathed in it
• Na tends to enter the cells so we must find a way to get rid of it
• Pump Na+ out of cell
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Na+/K+ ATPase pump
• Notice #’s– Moves 3 Na+ outside– Moves 2 K+ inside– mnemonic- 2 letters in “in”
and 3 letters in “out”• Creates a charge
difference– Inside becomes negative– Cell becomes polarized– Can conduct electricity– Called electrogenic pump
Solute Pumping
Fig. 3.19
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Na+/K+ ATPase
K+
K+
K+K+
K+K+
K+
Na+
Na+
Na+
Na+ Na+
Na+
Na+
Na+
ATP
ADP + Pi
K+
Cytoplasm
Extracellular fluid
Gradient for Na+
Gradient for K+
Na+Na+Na+
Electrogenic Pump!!!
Na+Solute Pumping
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Na+/K+ ATPase pump
• Regulation of cell volume– Where Na+ goes water
follows– Prevents the cell from
swelling
Solute Pumping
Fig. 3.19
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Na+/K+ ATPase pump• Secondary Active
Transport– e.g. sodium glucose
transport protein (SGLT)– Pump maintains low
intercelluar Na+ levels• Pump on basal end
– SGLT, in bringing Na back into the cell (down concentration gradient) , carries glucose with it
• SGLT on apical end– Saves glucose from being
dumped out of the body with urine
Solute Pumping
Fig. 3.20
Na levels low
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Na+/K+ ATPase pump
• Heat Production– Thyroid hormone
stimulates cells to make more Na+/K+ ATPase pumps
– As they use ATP they release heat
Solute Pumping
Fig. 3.19
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Na+/K+ ATPase pump
• Maintain Membrane Potential– Established concentration
gradients for Na+ and K+ across the membrane
• Also, 3 Na+ out and only 2 K+ in
• Charges of cell– Crucial for excitable cells– Like two poles of a battery
Solute Pumping
Nerve Cell
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Introduction
• Energy is required for this process
• Movement of large macromolecules
• Types defined by the direction of movement– Endocytosis
• Intake– Exocytosis
• Output (e.g. secretion or excretion)
Fig. 3.21
Bulk Transport
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Endocytosis
• Three different types– Phagocytosis– Pinocytosis– Receptor mediated
endocytosis
Bulk Transport
Fig. 3.21
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Phagocytosis
• Literally means cell eating
• Usually a protective function
• Not all cells are phagocytic
• May bring in cell debris for clean up
Bulk Transport
Fig. 3.21
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fusion
excretion
Bulk Transport
Fig. 3.21
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Phagocytosis• Extends pseudopods
around the particle• Pseudopods meet and
package the material into a vessel (phagosome)
• Processes ingested material by fusion of phagosome with lysosome (phagolysosome)
• Residue is released by excretion (via exocytosis)– Can go into blood and be
filtered by the kidney
Bulk Transport
Fig. 3.21
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Phagocytosis
• Phagocytes– Cells’ function is
phagocytosis– Found in almost every
tissue compartment but only in specialized cells
• Lungs, for example, are rich in macrophages which are phagocytes
Bulk Transport
Fig. 3.21
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Pinocytosis
• Pino = tiny• “cell drinking”• Little pockets or divots
form invaginations in the membrane
• Typically get this occurring in all human cells
• Extracellular fluid with whatever molecules were there at the time
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/endocytb.htm
Bulk Transport
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Receptor Mediated Endocytosis
• More selective than the other types– Specific molecules without a lot of fluid
• Particles bind to specific receptors
• Membrane protein called clatharin• When the clatharin and LDL’s (for example) are taken inside there is
a clatharin coated vesicle• Can serve as an address label to tell it where to go in the cell
Bulk Transport
Fig. 3.22
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Receptor Mediated Endocytosis
• Example is LDL (low density lipoproteins) and insulin• Familial hypercholesterolemia
– Low number of LDL receptors so the cholesterol stays in the blood
– 1200 mg/dL – Can have heart attacks before age 20 and usually die before
age 30
Bulk Transport
Fig. 3.22
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Exocytosis
• Secreting or excreting materials from the cell– e.g. release of insulin, milk release from breast tissue, hormone
release • Like endocytosis in reverse• Both endocytosis and exocytosis subtract from and add
to the cell membrane so the amount is relatively constant
Bulk Transport
Fig. 3.24
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ID 12051--- where the last three is your test number
Your lab section you attend: A=001, B=002, etc. A list will be on the exam.