4.2: Diffusion

Question 1

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?

Answer 1

Diffusion is an example of passive transport

Question 2

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?

Answer 2

In this sense, ‘passive’ means that the energy comes from the natural, inbuilt motion of particles

Question 3

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?

Answer 3

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

Question 4

To help understand diffusion and other passive forms of transport, it is necessary to understand that:
1. All particles are constantly what?

Answer 4

All particles are constantly in motion

Question 5

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?

Answer 5

All particles are constantly in motion, due to the kinetic energy that they possess

Question 6

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 what?

Answer 6

This motion is random

Question 7

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 what?

Answer 7

This motion is random, with no set pattern to the way the particles move around

Question 8

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 doing what as well as off other objects?

Answer 8

Particles are constantly bouncing off one another as well as off other objects

Question 9

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 what?

Answer 9

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

Question 10

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?

Answer 10

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

Question 11

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?

Answer 11

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

Question 12

Most molecules do not easily pass across the cell-surface membrane.
Amongst the few molecules that can diffuse across membranes are what molecules?

Answer 12

Amongst the few molecules that can diffuse across membranes are:
1. Small
2. Non-polar
molecules

Question 13

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?

Answer 13

Amongst the few molecules that can diffuse across membranes are small, non-polar molecules such as:

1. Oxygen
2. Carbon dioxide

Question 14

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?

Answer 14

1. Charged ions
2. Polar molecules
   do not diffuse easily

Question 15

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?

Answer 15

1. Charged ions
2. Polar molecules
   do not diffuse easily, because of the hydrophobic nature of the fatty acid tails of the phospholipids in the membrane

Question 16

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?

Answer 16

The movement of these molecules is made easier (facilitated)

Question 17

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?

Answer 17

The movement of these molecules is made easier (facilitated) by transmembrane:

1. Channels
2. Carriers

Question 18

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?

Answer 18

The movement of these molecules is made easier (facilitated) by transmembrane:
1. Channels
2. Carriers
that span the membrane

Question 19

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?

Answer 19

The process is therefore called facilitated diffusion

Question 20

Facilitated diffusion is a what process?

Answer 20

Facilitated diffusion is a passive process

Question 21

Facilitated diffusion is a passive process.

It relies only on what?

Answer 21

Facilitated diffusion relies only on the inbuilt motion (kinetic energy) of the diffusing molecules

Question 22

Diffusion is the net movement of particles.
All particles move at random in diffusion.
It is just that more do what?

Answer 22

It is just that more move in one direction than in the other

Question 23

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?

Answer 23

This is due to concentration differences

Question 24

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?

Answer 24

Like diffusion, facilitated diffusion occurs down a concentration gradient

Question 25

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?

Answer 25

Like diffusion, facilitated diffusion occurs down a concentration gradient, but it differs in that it occurs at specific points on the plasma membrane

Question 26

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?

Answer 26

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

Question 27

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?

Answer 27

2 types of protein are involved:

1. Protein channels
2. Carrier proteins

Question 28

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?

Answer 28

Each has a different mechanism

Question 29

Diffusion only occurs between what?

Answer 29

Diffusion only occurs between different concentrations of the same substance

Question 30

Diffusion only occurs between different concentrations of the same substance.
Example

Answer 30

For example, diffusion may occur between different concentrations of oxygen or between different concentrations of carbon dioxide

Question 31

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?

Answer 31

Diffusion never occurs between different concentrations of:

1. Oxygen
2. Carbon dioxide

Question 32

Diffusion is proportional to what?

Answer 32

Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient)

Question 33

Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient), not what?

Answer 33

Diffusion is proportional to the difference in concentration between 2 regions (the concentration gradient), not concentration

Question 34

Protein channels and carrier proteins have what?

Answer 34

1. Protein channels
2. Carrier proteins
   have binding sites

Question 35

Protein channels and carrier proteins have binding sites, but these are different to what?

Answer 35

1. Protein channels
2. Carrier proteins
   have binding sites, but these are different to active sites

Question 36

Protein channels:

These proteins form what?

Answer 36

Protein channels form water-filled hydrophilic channels

Question 37

Protein channels:

Protein channels form water-filled hydrophilic channels where?

Answer 37

Protein channels form water-filled hydrophilic channels across the membrane

Question 38

Protein channels:
Protein channels form water-filled hydrophilic channels across the membrane.
They allow what to pass through?

Answer 38

The water-filled hydrophilic channels allow specific water-soluble ions to pass through

Question 39

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?

Answer 39

The water-filled hydrophilic channels are selective

Question 40

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?

Answer 40

The water-filled hydrophilic channels are selective, each opening in the presence of a specific ion

Question 41

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?

Answer 41

If the particular ion is not present, the channel remains closed

Question 42

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?

Answer 42

In this way, there is control over the:
1. Entry
2. Exit
of ions

Question 43

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?

Answer 43

The ions bind with the protein

Question 44

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?

Answer 44

The ions bind with the protein, causing it to change shape in a way that:

1. Closes it to one side of the membrane
2. Opens it to the other side

Question 45

Carrier proteins:

An alternative form of facilitated diffusion involves carrier proteins that span what?

Answer 45

An alternative form of facilitated diffusion involves carrier proteins that span the plasma membrane

Question 46

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?

Answer 46

When a molecule such as glucose that is specific to the protein is present, it binds with the protein

Question 47

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?

Answer 47

This causes it to change shape

Question 48

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?

Answer 48

This causes it to change shape in such a way that the molecule is released to the inside of the membrane

Question 49

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?

Answer 49

No external evidence is needed for this

Question 50

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?

Answer 50

The molecules move from a region where they are highly concentrated to one of lower concentration

Question 51

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?

Answer 51

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

Question 52

Diffusion

Answer 52

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

Question 53

Factors affecting the rate of diffusion

Answer 53

Factors affecting the rate of diffusion are:

1. Concentration gradient
2. Surface area
3. Thickness of exchange surface

Question 54

Diffusion happens down a concentration gradient, until they are what?

Answer 54

Diffusion happens down a concentration gradient, until they are evenly spread

Question 55

Diffusion happens down a concentration gradient, until they are evenly spread.
What continue to move?

Answer 55

Individual particles continue to move

Question 56

Diffusion happens down a concentration gradient, until they are evenly spread.
Individual particles continue to move, but there is no what?

Answer 56

Individual particles continue to move, but there is no overall net movement

Question 57

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?

Answer 57

This is dynamic equilibrium

Question 58

The structure of the plasma membrane affects the rate of diffusion, because of what?

Answer 58

The structure of the plasma membrane affects the rate of diffusion, because of the:
1. Composition
2. Number
of the pores

Question 59

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?

Answer 59

Small molecules diffuse faster than large molecules

Question 60

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?

Answer 60

Fat-soluble molecules diffuse faster than water-soluble molecules

Question 61

With facilitated diffusion, the rate of diffusion depends on what?

Answer 61

With facilitated diffusion, the rate of diffusion depends on:

1. The number of channels
2. If they are open or not

Question 62

Fick’s law of diffusion

Answer 62

Fick’s law of diffusion is that diffusion is:

(SA x The difference in concentration) ÷ The length of diffusion pathway