LESSON 1
THE CELL AND ITS ENVIRONMENT
DIFFUSION
This is the process by which molecules of substances, such as liquid or gases move
randomly from a region of higher concentration to a region of lower concentration
until the particles are evenly distributed. Diffusion can occur in air, liquid and
solid.
Biological significance: It is a process by which fine particles or molecules flow in
and out of cells; living things and it can occur in non-living material.
By diffusion, molecules of substance evenly spread in any available space.
FACTORS AFFECTING RATE OF DIFFUSION
(i)State of matter of diffusing molecules
(ii)Molecular size of the diffusing molecules
(iii)Differences in concentration of diffusing molecules and the medium
(iv)Temperature: High temperature increases the speed at which molecules move
thus, the higher the temperature, the faster the rate of diffusion.
DEMONSTRATION OF DIFFUSION IN LIQUID
Fill a beaker with distilled water use pipette to deliver small quantity of potassium
permanganate solution gently at the bottom of the beaker and leave it to stand for
few minutes. The purple colour of the potassium permanganate solution starts to
spread outside.
Gradually, the colour spreads evenly throughout the water medium so that the
water have the same shade of purple colour.
DEMONSTRATION OF DIFFUSION IN GASES
Take a bottle of ammonia solution, open the bottle and move some distance away
from the bottle and wait for some time. The smell of the ammonia gas shows that
diffuse ion of ammonia gas has taken place.
IMPORTANCE OF DIFFUSION IN PLANT
(i)Diffusion aids movement of oxygen produced during photosynthesis into the
atmosphere
(ii)Diffusion assists easy movement of carbon (iv) oxide from the atmosphere into
the leaves through the stomata cell
(iii)Diffusion promotes free movement of oxygen needed for respiration from the
atmosphere into the plant through stomata cell
, (iv)Movement of water vapour from the leaves of plant to outside in a process
called transpiration is possible because of diffusion
IMPORTANCE OF DIFFUSION IN ANIMAL
(i) Absorption of glucose and other food material through the villi in the
small intestine through diffusion
(ii) Diffusion aids the exchange of body nutrients in the placenta from the
mother to a developing foetus
(iii) Diffusion aids gaseous exchange in many cells and organisms for
instance amoeba takes in oxygen and get rid of carbon (iv) oxide by
diffusion
(iv) Diffusion aids the movement of carbon (iv) oxide from the lungs
capillaries into the air sac and vice- versa.
OSMOSIS
Osmosis is defined as the movement of water molecules from a region of low
concentration of solute to a region of high concentration of solute through a semi-
permeable membrane separating the two solution until equilibrium is attained.
A solution with higher solute concentration has a smaller amount of water left for
dissolution of more solute, while a solution with lower concentration of solute has
more water available.
CONDITION NECESSARY FOR OSMOSIS TO TAKE PLACE
(i)Presence of a stronger solution e.g. sugar or salt solution
(ii)Presence of weaker solution e.g. distilled water
(iii)Presence of a selective or differentially permeable membrane/pig bladder
TYPES OF SOLUTION
(i)Hypertonic Solution is a solution which gains water in osmosis or that is higher
in concentration
(ii)Hypotonic Solution is a solution that lose water in osmosis or a solution that is
weak-distilled water
(iii)Isotonic solution: when a state of equillibrum is established between two
solution, that is neither solutions gains nor loses water.
Osmosis is a special form of diffusion
DIFFERENCES BETWEEN DIFFUSION AND OSMOSIS
THE CELL AND ITS ENVIRONMENT
DIFFUSION
This is the process by which molecules of substances, such as liquid or gases move
randomly from a region of higher concentration to a region of lower concentration
until the particles are evenly distributed. Diffusion can occur in air, liquid and
solid.
Biological significance: It is a process by which fine particles or molecules flow in
and out of cells; living things and it can occur in non-living material.
By diffusion, molecules of substance evenly spread in any available space.
FACTORS AFFECTING RATE OF DIFFUSION
(i)State of matter of diffusing molecules
(ii)Molecular size of the diffusing molecules
(iii)Differences in concentration of diffusing molecules and the medium
(iv)Temperature: High temperature increases the speed at which molecules move
thus, the higher the temperature, the faster the rate of diffusion.
DEMONSTRATION OF DIFFUSION IN LIQUID
Fill a beaker with distilled water use pipette to deliver small quantity of potassium
permanganate solution gently at the bottom of the beaker and leave it to stand for
few minutes. The purple colour of the potassium permanganate solution starts to
spread outside.
Gradually, the colour spreads evenly throughout the water medium so that the
water have the same shade of purple colour.
DEMONSTRATION OF DIFFUSION IN GASES
Take a bottle of ammonia solution, open the bottle and move some distance away
from the bottle and wait for some time. The smell of the ammonia gas shows that
diffuse ion of ammonia gas has taken place.
IMPORTANCE OF DIFFUSION IN PLANT
(i)Diffusion aids movement of oxygen produced during photosynthesis into the
atmosphere
(ii)Diffusion assists easy movement of carbon (iv) oxide from the atmosphere into
the leaves through the stomata cell
(iii)Diffusion promotes free movement of oxygen needed for respiration from the
atmosphere into the plant through stomata cell
, (iv)Movement of water vapour from the leaves of plant to outside in a process
called transpiration is possible because of diffusion
IMPORTANCE OF DIFFUSION IN ANIMAL
(i) Absorption of glucose and other food material through the villi in the
small intestine through diffusion
(ii) Diffusion aids the exchange of body nutrients in the placenta from the
mother to a developing foetus
(iii) Diffusion aids gaseous exchange in many cells and organisms for
instance amoeba takes in oxygen and get rid of carbon (iv) oxide by
diffusion
(iv) Diffusion aids the movement of carbon (iv) oxide from the lungs
capillaries into the air sac and vice- versa.
OSMOSIS
Osmosis is defined as the movement of water molecules from a region of low
concentration of solute to a region of high concentration of solute through a semi-
permeable membrane separating the two solution until equilibrium is attained.
A solution with higher solute concentration has a smaller amount of water left for
dissolution of more solute, while a solution with lower concentration of solute has
more water available.
CONDITION NECESSARY FOR OSMOSIS TO TAKE PLACE
(i)Presence of a stronger solution e.g. sugar or salt solution
(ii)Presence of weaker solution e.g. distilled water
(iii)Presence of a selective or differentially permeable membrane/pig bladder
TYPES OF SOLUTION
(i)Hypertonic Solution is a solution which gains water in osmosis or that is higher
in concentration
(ii)Hypotonic Solution is a solution that lose water in osmosis or a solution that is
weak-distilled water
(iii)Isotonic solution: when a state of equillibrum is established between two
solution, that is neither solutions gains nor loses water.
Osmosis is a special form of diffusion
DIFFERENCES BETWEEN DIFFUSION AND OSMOSIS
