4.2: Diffusion Flashcards
The exchange of substances between cells and the environment occurs in ways that require metabolic energy (active transport) and in ways that do not require metabolic energy (passive transport).
What is diffusion an example of?
Diffusion is an example of passive transport
The exchange of substances between cells and the environment occurs in ways that require metabolic energy (active transport) and in ways that do not require metabolic energy (passive transport).
Diffusion is an example of passive transport.
As all movement involves energy, it is possibly confusing to describe diffusion as passive transport.
In this sense, ‘passive’ means what?
In this sense, ‘passive’ means that the energy comes from the natural, inbuilt motion of particles
The exchange of substances between cells and the environment occurs in ways that require metabolic energy (active transport) and in ways that do not require metabolic energy (passive transport).
Diffusion is an example of passive transport.
As all movement involves energy, it is possibly confusing to describe diffusion as passive transport.
In this sense, ‘passive’ means that the energy comes from the natural, inbuilt motion of particles, rather than from what?
In this sense, ‘passive’ means that the energy comes from the natural, inbuilt motion of particles, rather than from some external source such as ATP
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
1. All particles are constantly what?
All particles are constantly in motion
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
1. All particles are constantly in motion, due to what?
All particles are constantly in motion, due to the kinetic energy that they possess
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
- All particles are constantly in motion, due to the kinetic energy that they possess.
- This motion is what?
This motion is random
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
- All particles are constantly in motion, due to the kinetic energy that they possess.
- This motion is random, with no set pattern to what?
This motion is random, with no set pattern to the way the particles move around
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
- All particles are constantly in motion, due to the kinetic energy that they possess.
- This motion is random, with no set pattern to the way the particles move around.
- Particles are constantly doing what as well as off other objects?
Particles are constantly bouncing off one another as well as off other objects
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
- All particles are constantly in motion, due to the kinetic energy that they possess.
- This motion is random, with no set pattern to the way the particles move around.
- Particles are constantly bouncing off one another as well as off other objects, for example what?
Particles are constantly bouncing off one another as well as off other objects, for example the sides of the vessel in which they are contained
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
1. All particles are constantly in motion, due to the kinetic energy that they possess.
2. This motion is random, with no set pattern to the way the particles move around.
3. Particles are constantly bouncing off one another as well as off other objects, for example the sides of the vessel in which they are contained.
Given these facts, particles that are concentrated together in part of a closed vessel, will, of their own what, do what?
Given these facts, particles that are concentrated together in part of a closed vessel, will, of their own accord, distribute themselves evenly throughout the vessel as a result of diffusion
To help understand diffusion and other passive forms of transport, it is necessary to understand that:
1. All particles are constantly in motion, due to the kinetic energy that they possess.
2. This motion is random, with no set pattern to the way the particles move around.
3. Particles are constantly bouncing off one another as well as off other objects, for example the sides of the vessel in which they are contained.
Given these facts, particles that are concentrated together in part of a closed vessel, will, of their own accord, distribute themselves evenly throughout the vessel as a result of diffusion.
Diffusion is therefore defined as what?
Diffusion is therefore defined as the net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower until evenly distributed
Most molecules do not easily pass across the cell-surface membrane.
Amongst the few molecules that can diffuse across membranes are what molecules?
Amongst the few molecules that can diffuse across membranes are:
1. Small
2. Non-polar
molecules
Most molecules do not easily pass across the cell-surface membrane.
Amongst the few molecules that can diffuse across membranes are small, non-polar molecules such as what?
Amongst the few molecules that can diffuse across membranes are small, non-polar molecules such as:
- Oxygen
- Carbon dioxide
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
What ions and what molecules do not diffuse easily?
- Charged ions
- Polar molecules
do not diffuse easily
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
Charged ions and polar molecules do not diffuse easily, because of what?
- Charged ions
- Polar molecules
do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
Charged ions and polar molecules do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane.
The movement of these molecules is what?
The movement of these molecules is made easier (facilitated)
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
Charged ions and polar molecules do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane.
The movement of these molecules is made easier (facilitated) by what?
The movement of these molecules is made easier (facilitated) by transmembrane:
- Channels
- Carriers
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
Charged ions and polar molecules do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane.
The movement of these molecules is made easier (facilitated) by transmembrane channels and carriers that do what?
The movement of these molecules is made easier (facilitated) by transmembrane:
1. Channels
2. Carriers
that span the membrane
Plasma membranes are not readily permeable to molecules.
Only small, non-polar molecules like oxygen can diffuse across them easily.
Charged ions and polar molecules do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane.
The movement of these molecules is made easier (facilitated) by transmembrane channels and carriers that span the membrane.
The process is therefore called what?
The process is therefore called facilitated diffusion
Facilitated diffusion is a what process?
Facilitated diffusion is a passive process
Facilitated diffusion is a passive process.
It relies only on what?
Facilitated diffusion relies only on the inbuilt motion (kinetic energy) of the diffusing molecules
Diffusion is the net movement of particles.
All particles move at random in diffusion.
It is just that more do what?
It is just that more move in one direction than in the other
Diffusion is the net movement of particles.
All particles move at random in diffusion.
It is just that more move in one direction than in the other.
This is due to what?
This is due to concentration differences
Facilitated diffusion is a passive process.
It relies only on the inbuilt motion (kinetic energy) of the diffusing molecules.
Like diffusion, facilitated diffusion occurs down what?
Like diffusion, facilitated diffusion occurs down a concentration gradient
Facilitated diffusion is a passive process.
It relies only on the inbuilt motion (kinetic energy) of the diffusing molecules.
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs where?
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane
Facilitated diffusion is a passive process.
It relies only on the inbuilt motion (kinetic energy) of the diffusing molecules.
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane where there are what?
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane where there are special protein molecules
Facilitated diffusion is a passive process.
It relies only on the inbuilt motion (kinetic energy) of the diffusing molecules.
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane where there are special protein molecules.
How many types of protein are involved?
2 types of protein are involved:
- Protein channels
- Carrier proteins
Facilitated diffusion is a passive process.
It relies only on the inbuilt motion (kinetic energy) of the diffusing molecules.
Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane where there are special protein molecules.
2 types of protein are involved - Protein channels and carrier proteins.
Each has a different what?
Each has a different mechanism
Diffusion only occurs between what?
Diffusion only occurs between different concentrations of the same substance
Diffusion only occurs between different concentrations of the same substance.
Example
For example, diffusion may occur between different concentrations of oxygen or between different concentrations of carbon dioxide
Diffusion only occurs between different concentrations of the same substance.
For example, diffusion may occur between different concentrations of oxygen or between different concentrations of carbon dioxide.
Diffusion never occurs between what?
Diffusion never occurs between different concentrations of:
- Oxygen
- Carbon dioxide
Diffusion is proportional to what?
Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient)
Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient), not what?
Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient), not concentration
Protein channels and carrier proteins have what?
- Protein channels
- Carrier proteins
have binding sites
Protein channels and carrier proteins have binding sites, but these are different to what?
- Protein channels
- Carrier proteins
have binding sites, but these are different to active sites
Protein channels:
These proteins form what?
Protein channels form water-filled hydrophilic channels
Protein channels:
Protein channels form water-filled hydrophilic channels where?
Protein channels form water-filled hydrophilic channels across the membrane
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow what to pass through?
The water-filled hydrophilic channels allow specific water-soluble ions to pass through
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are what?
The water-filled hydrophilic channels are selective
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are selective, each doing what?
The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion.
If the particular ion is not present, what does the channel do?
If the particular ion is not present, the channel remains closed
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion.
If the particular ion is not present, the channel remains closed.
In this way, there is what over what?
In this way, there is control over the:
1. Entry
2. Exit
of ions
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion.
If the particular ion is not present, the channel remains closed.
In this way, there is control over the entry and exit of ions.
What do the ions do?
The ions bind with the protein
Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow specific water-soluble ions to pass through.
The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion.
If the particular ion is not present, the channel remains closed.
In this way, there is control over the entry and exit of ions.
The ions bind with the protein, causing it to do what?
The ions bind with the protein, causing it to change shape in a way that:
- Closes it to one side of the membrane
- Opens it to the other side
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span what?
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as what that is what to the protein is present, it does what?
When a molecule such as glucose that is specific to the protein is present, it binds with the protein
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as glucose that is specific to the protein is present, it binds with the protein.
This causes it to do what?
This causes it to change shape
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as glucose that is specific to the protein is present, it binds with the protein.
This causes it to change shape how?
This causes it to change shape in such a way that the molecule is released to the inside of the membrane
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as glucose that is specific to the protein is present, it binds with the protein.
This causes it to change shape in such a way that the molecule is released to the inside of the membrane.
What is needed for this?
No external evidence is needed for this
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as glucose that is specific to the protein is present, it binds with the protein.
This causes it to change shape in such a way that the molecule is released to the inside of the membrane.
No external evidence is needed for this.
The molecules move from a region where they are what to one of what?
The molecules move from a region where they are highly concentrated to one of lower concentration
Carrier proteins:
An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane.
When a molecule such as glucose that is specific to the protein is present, it binds with the protein.
This causes it to change shape in such a way that the molecule is released to the inside of the membrane.
No external evidence is needed for this.
The molecules move from a region where they are highly concentrated to one of lower concentration, using only what?
The molecules move from a region where they are highly concentrated to one of lower concentration, using only the kinetic energy of the molecules themselves
Diffusion
Diffusion is the net movement of: 1. Molecules Or, 2. Ions from a region of high concentration to a region of lower concentration until evenly distributed
Factors affecting the rate of diffusion
Factors affecting the rate of diffusion are:
- Concentration gradient
- Surface area
- Thickness of exchange surface
Diffusion happens down a concentration gradient, until they are what?
Diffusion happens down a concentration gradient, until they are evenly spread
Diffusion happens down a concentration gradient, until they are evenly spread.
What continue to move?
Individual particles continue to move
Diffusion happens down a concentration gradient, until they are evenly spread.
Individual particles continue to move, but there is no what?
Individual particles continue to move, but there is no overall net movement
Diffusion happens down a concentration gradient, until they are evenly spread.
Individual particles continue to move, but there is no overall net movement.
This is what?
This is dynamic equilibrium
The structure of the plasma membrane affects the rate of diffusion, because of what?
The structure of the plasma membrane affects the rate of diffusion, because of the:
1. Composition
2. Number
of the pores
The structure of the plasma membrane affects the rate of diffusion, because of the composition and number of the pores.
Small molecules diffuse faster than what?
Small molecules diffuse faster than large molecules
The structure of the plasma membrane affects the rate of diffusion, because of the composition and number of the pores.
Small molecules diffuse faster than large molecules.
Fat-soluble molecules diffuse faster than what?
Fat-soluble molecules diffuse faster than water-soluble molecules
With facilitated diffusion, the rate of diffusion depends on what?
With facilitated diffusion, the rate of diffusion depends on:
- The number of channels
- If they are open or not
Fick’s law of diffusion
Fick’s law of diffusion is that diffusion is:
(SA x The difference in concentration) ÷ The length of diffusion pathway
