PASSIVE TRANSPORT QUESTIONS Flashcards
(25 cards)
What is diffusion?
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration.
This movement happens down their concentration gradient.
What causes molecules to move during diffusion?
The kinetic energy stored inside each molecule causes random movement and bouncing off each other.
This random movement is fundamental to the process of diffusion.
What is the result of random molecular movement over time?
An even dispersion of particles in an area.
This leads to a more uniform concentration of solutes and solvents.
In the context of diffusion, what are the solute and solvent?
The solute is the dissolved molecules, and the solvent is the liquid through which they diffuse, such as water.
In many biological and chemical processes, water is the most common solvent.
Fill in the blank: Diffusion occurs down the _______.
concentration gradient
What is facilitated diffusion?
The passive movement of molecules down their concentration gradient through a membrane-bound protein
Facilitated diffusion allows large and/or polar molecules like glucose and ions to move between intra- and extra-cellular environments.
What types of molecules typically use facilitated diffusion?
Large and/or polar molecules like glucose and ions
These molecules cannot freely cross the plasma membrane due to their size or charge.
What is a protein channel?
A transmembrane protein pore in a phospholipid bilayer that selectively enables transport of large or polar molecules
Protein channels are specific to the substances they allow to pass through.
What is a carrier protein?
A membrane protein that undergoes conformational change to transport molecules across a membrane
Carrier proteins bind to the substance being transported and push it down its concentration gradient.
How do carrier proteins transport substances?
By binding to the substance and undergoing a conformational change to push it across the membrane
Carrier proteins return to their original shape after the molecule has been transported.
What contributes to the selective permeability of the plasma membrane?
The specificity of channels and carrier proteins for the molecules they transport
This ensures that only certain substances can pass through the membrane.
True or False: Facilitated diffusion requires energy.
False
Facilitated diffusion is a passive transport process.
Fill in the blank: Facilitated diffusion is a type of _______ transport.
passive
It does not require energy to move molecules down their concentration gradient.
What is the main advantage of facilitated diffusion over simple diffusion?
Facilitated diffusion can be faster than simple diffusion
Some small and/or nonpolar molecules that can diffuse, like water, also have dedicated protein channels.
What is osmosis?
The diffusion of water from an area of low solute concentration to an area of high solute concentration.
Osmosis specifically refers to water movement across a selectively permeable membrane.
How does water move through the phospholipid bilayer?
Water molecules can move through due to their small size, despite being hydrophilic.
This movement can be facilitated by protein channels known as aquaporins.
Why is osmosis important?
It allows water to cross membranes while many solutes cannot, affecting cell concentration balance.
This balance can lead to dilution of solutes like sugar within the cell.
What happens when there is a high concentration of sugar in the cytosol?
Water moves into the cell to dilute the sugar molecules until concentrations equalize.
The alternative is facilitated diffusion of sugar molecules out of the cell.
What is tonicity?
The term used to describe differences in solute concentrations between two compartments.
Tonicity is crucial for understanding osmosis and water movement.
What characterizes hypertonic solutions?
They have higher solute concentrations, causing water to move into the hypertonic solution from adjacent areas.
This can lead to cell shrinkage if cells are placed in a hypertonic environment.
What are isotonic solutions?
Solutions with equal solute concentrations, resulting in no net movement of water.
Although there is water movement, the rate in equals the rate out.
What occurs in hypotonic solutions?
They have lower solute concentrations, causing water to move from the hypotonic solution into adjacent areas with higher solute concentration.
This can lead to cell swelling or lysis if cells are in a hypotonic environment.
Fill in the blank: Osmosis is the diffusion of water across a _______ membrane.
selectively permeable
True or False: In isotonic solutions, there is no movement of water.
False
Water still moves, but the rates are equal, resulting in no net movement.
