Hosam Mohamed-
Diffusion
-the movement of molecules from one location to another across a membrane
-always proceeds from higher to lower concentrations
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Magnitude
The _______ of diffusion is the same as direction
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Temperate, mass, surface area, medium
What are some factors that influence the magnitude of diffusion?
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higher temperatures will increase speed of molecules; increasing net flux
How does temperature affect diffusion & net flux?
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slows the speed of molecules; slows net flux
How does the mass of the molecules affect diffusion & net flux?
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greater surface area leads to greater diffusion; greater net flux
How does the surface area of the container affect diffusion & net flux?
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denser the medium; slower net flux
How does the medium affect diffusion & net flux?
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size of concentration gradient/ how dense molecules are
What does dC/dX represent?
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size
What does Ds represent?
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impacts diffusion rate
What happens when a membrane is present?
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hydrophilic
Diffusion through membranes will cause diffusion rates for what types of molecules to decrease?
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oxygen, carbon dioxide, fatty acids, steroid hormones, nonpolar molecules
Which substances diffuse rapidly through lipid portions of membranes?
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Na, K, Cl, and Ca
Which substances must form water channels to enter or exit the cell?
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Channels
-this machinery regulates the control and movement of ions into and out of a cell
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channel gating; conformational change
The process of opening or closing is called _______; results from ____________
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how often the channel opens, how long it stays open
What factors determine an ion passing through the channels?
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ligand, voltage, mechanical
What are your types of Gated channels?
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Ligand gated
-opens when ligands bind to it
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Voltage gated
-opens when changes in membrane potential occur
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Mechanically gated
-opens due to mechanical stress
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transporter moves molecules down concentration gradient and across cell membrane; continues until concentrations are equal on both sides of membranes
How does facilitated diffusion work?
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atp
Facilitated diffusion does not utilize ______ to move molecules
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active transport
-this form of transport uses ATP to move molecules against the concentration gradient
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pumps
Transporters that utilize ATP are called ?
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Primary active transport
-this form of active transport utilizes a direct source of ATP
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Secondary active transport
-uses an electrochemical gradient found across the plasma membrane to drive the transport process
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Na+
-a major EXTRACELLULAR ion
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K+
-a major INTRACELLULAR ion
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3 Na+ out; 2 K+ in
How does the Na+/K+ ATPase pump work?
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Cotransporters (symporters)
move molecules in the same direction
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Countertransporters (antiporters)
move molecules in opposite directions
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Osmosis
-the net diffusion of water across a membrane
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aquaporins
What type of channel proteins diffuse water across a membrane?
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Kidney
Which organ contains a high number of aquaporins inside of its cells?
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increase in permeability
Increasing the number of aquaporins=?
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Isotonic
-have the same concentration of solutes inside the cell as extracellular fluid
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Hypotonic
-have lower concentration of solutes inside the cell compared to extracellular fluid
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Hypertonic
-have higher concentration of solutes inside the cell compared to extracellular fluid
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shrink
Hypertonic solution causes the cell to _____
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swell
Hypotonic solution causes the cell to _____
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transcellular transport
-movement that occurs through cells
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paracellular transport
-movement that occurs around cells
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tight junctions
Paracellular transport is minimized by ________ of epithelium
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Claudins
How does our body regulate tight junctions? (i.e. make them less tight)
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Epithelial transport
- molecules entering or leaving the body
-molecules moving between compartments
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cross layers of polarized epithelial cells
In order for epithelial transport to occur, what must the molecule do?
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2 step
Transcellular transport is a ________ process
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3
Glucose transport from intestinal lumen or kidney tubule to ecf requires how many transport systems?
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Sodium-glucose cotransporter
-brings glucose into cell against its gradient using sodium concentration gradient and kinetic energy
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GLUT transporter
-transfers glucose to ECF by facilitated diffusion
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Sodium-Potassium ATPase pump
-pumps sodium out of the cell to keep intracelluar sodium concentrations low
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concentration differences, electrical differences
The direction and magnitude of ion fluxes depend on what ?
