4.3a Passive Processes: Diffusion
Terms in this set (41)
What are 3 substances needed from interstitial fluid?
Nutrients, oxygen, ions
What are 2 wastes to be eliminated from cells?
Carbon dioxide, ions
Obtaining and eliminating substances across the plasma membrane
Membrane transport (subcategories)
Passive processes, active processes
Passive Processes (membrane transport)
Processes that do not require energy expenditure.
What type of energy do passive processes rely on?
What can provide kinetic energy on a cellular level?
Movement of substances in a concentration gradient.
Passive processes (examples)
Active processes (membrane transport)
Processes that require cells to expend energy.
What type of energy to active processes rely on?
What can provide potential energy on a cellular level?
Cells, ATP, ions can provide energy through chemical bonds for transport.
Define an active process.
A process that moves cells up a concentration gradient, expending energy.
Random movement of molecules or particles down their concentration gradient.
A state where molecules become evenly distributed througout a given area.
Steepness of concentration gradient, temperature
Steepness of concentration gradient (diffusion)
Steepness is the difference in concentration of a substance between two areas.
Steepness of concentration gradient (relationship to rate of diffusion)
A steeper concentration gradient causes a faster rate of diffusion
Reflection of kinetic energy of a substance
Temperature (relationship to rate of diffusion)
Higher temperatures mean greater kinetic energy, resulting in faster rates of diffuion.
Cellular Diffusion (subcategories)
Simple diffusion (definition)
Passive transport process used when a chemical slips between plasma membrane phospholipids to enter or leave a cell down a concentration gradient.
Simple diffusion (examples)
O2, CO2, small nonpolar fatty acids, ethanol, urea that move easily through membranes.
Simple diffusion (regulation)
Plasma membrane cannot regulate simple diffusion
Facilitated Diffusion (definition)
Passive transport process using carrier proteins or channel proteins to move a chemical across the plasma membrane.
Facilitated Diffusion (subcategories)
Channel-mediated diffusion (definition)
Movement of small ions across the plasma membrane through water-filled protein channels.
Leak Channel (2 words)
Gated Channel (2 words)
Leak channel (example)
Na+ leak channels allow Na+ to pass through continuously.
Gated Channel (example)
Na+ gated channels open only to allow Na+ to moev through the channel in response to the presence of a particular chemical.
What allows substances to pass through leak channels?
What allows substances to pass through gated channels?
Stimuli that open the channel; concentration gradients
Carrier-mediated diffusion (definition)
Movement of small, polar molecules, such as simple sugars or amino acids assisted across the plasma membrane by a carrier protein.
Carrier protein (definition)
Proteins that transport substances such as glucose by allowing it to bind, changing the shape and moving it to the other side of the membrane.
Carrier protein (direction of movement)
Down a concentration gradient.
A carrier protein that only moves one substance
Glucose carriers to prevent the loss of glucose in the urine.
What determines the maximum rate at which a substance can be transported?
The number of channels and carriers in a plasma membrane.
How does O2 diffuse into a cell and CO2 diffuse out of a cell?
Through the process of simple diffusion.
Compare and contrast how an ion is transported across the plasma membrane versus how a small, polar molecule is transported.
Ions are transported through channels (leak or gate), by means of simple or facilitated diffusion down a concentration gradient. A small, polar molecule is transferred through carrier-mediate diffusion by carrier proteins, which change shape to move the molecule through the plasma membrane.
Does carrier-mediated diffusion proceed based on concentration gradient?
Yes. Although carrier proteins transport the substance across the membrane, the movement is energized by the concentration gradient and will always move DOWN the concentration gradient.
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