AQA A LEVEL BIOLOGY - DIFFUSION
REVISION PAPERS 2023 WITH CORRECT
QUESTIONS AND ANSWERS
Definition of diffusion (Correct Answers) 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/until they reach equilibrium.
Diffusion (Correct Answers) example of passive transport and does not use ATP; only
uses kinetic energy. Passive transport (no energy required) (does not require carrier
proteins)
Passive Transport (Diffusion) (Correct Answers) - all particles are constantly moving
due to the kinetic energy that they possess.
- the motion is random
- particles are bouncing off one another as well as other objects.
Molecules that can easily diffuse directly through the phospholipid bilayer (Correct
Answers) - small
- non polar e.g. oxygen and carbon dioxide
- lipid soluble e.g steroids
Molecules that can NOT easily diffuse directly through the phospholipid bilayer (Correct
Answers) - charged ions
- polar molecules
- large
- non soluble in lipids
Facilitated diffusion (Correct Answers) a passive process which relies on kinetic energy
of the molecules that are diffusing.
Carrier proteins or channel proteins speed up the rate of diffusion for large molecules
like ions and polar molecules. No ATP is involved.
Channels protein (Correct Answers) - they form water filled hydrophilic channels across
the membrane.
- they allow specific water soluble ions to pass through
- they are selective; they only open for specific ions, if the particular ion is not present,
they will not open; this allows selective control over the entry and exit of ions.
REVISION PAPERS 2023 WITH CORRECT
QUESTIONS AND ANSWERS
Definition of diffusion (Correct Answers) 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/until they reach equilibrium.
Diffusion (Correct Answers) example of passive transport and does not use ATP; only
uses kinetic energy. Passive transport (no energy required) (does not require carrier
proteins)
Passive Transport (Diffusion) (Correct Answers) - all particles are constantly moving
due to the kinetic energy that they possess.
- the motion is random
- particles are bouncing off one another as well as other objects.
Molecules that can easily diffuse directly through the phospholipid bilayer (Correct
Answers) - small
- non polar e.g. oxygen and carbon dioxide
- lipid soluble e.g steroids
Molecules that can NOT easily diffuse directly through the phospholipid bilayer (Correct
Answers) - charged ions
- polar molecules
- large
- non soluble in lipids
Facilitated diffusion (Correct Answers) a passive process which relies on kinetic energy
of the molecules that are diffusing.
Carrier proteins or channel proteins speed up the rate of diffusion for large molecules
like ions and polar molecules. No ATP is involved.
Channels protein (Correct Answers) - they form water filled hydrophilic channels across
the membrane.
- they allow specific water soluble ions to pass through
- they are selective; they only open for specific ions, if the particular ion is not present,
they will not open; this allows selective control over the entry and exit of ions.
