Page 70 - Biology Form Two

Ways of transport of materials Diffusion

This is a passive movement of particles
Task 3.2 from an area of high concentration
Search the library and internet sources to an area of low concentration, as
for the simulations or videos showing shown in Figure 3.1. The difference
FOR ONLINE READING ONLY
ways of transporting of materials. in the concentration of a substance
between the two areas is known as
Life processes in organisms take place a concentration gradient. When the
in the cell. Therefore, it is necessary difference in concentration between

for materials to move in and out of the the two areas is great, the concentration
cells. Movement of materials is through gradient becomes steep, and the rate of
the cell membrane. There are two ways diffusion increases. As the difference
through which materials can move in concentration between the two areas
across the cell membrane, which are decreases, the rate of diffusion slows
active transport and passive transport. down. This process continues until
Active transport occurs in the presence the substances are distributed evenly

of energy in the form of ATP. It enables throughout the two areas. When the
the movement of materials across particles are evenly distributed, they
the cell membrane. During active move at the same rate in either direction.
transport, substances move against Potassium direction
concentration gradient from an area of permanganate of diffusion
low concentration to an area of high
concentration. An example is the uptake
of glucose in the small intestine of a water
human being when the concentration

of glucose in the blood becomes higher
than that of the small intestine. Another
example is the uptake of mineral salts Figure 3.1: Experimental set-up to
into root hair cells of plants. demonstrate the diffusion process

Passive transport occurs spontaneously Roles of diffusion in living things
without the need for energy to transport Diffusion is important in living things.
materials through the cell membrane. It helps in the movement of substances
An example is the transport of materials in the body, including
in the cells through diffusion, osmosis, (i) movement of oxygen gas from the
and mass flow. alveoli to the blood capillaries;

Student’s Book - Form Two
64

05/10/2024 15:36:24
BIOLOGY FORM 2 NEW.indd 64
BIOLOGY FORM 2 NEW.indd 64 05/10/2024 15:36:24