The document discusses the movement of substances across the plasma membrane of cells. It explains that this movement is necessary and occurs in a continuous and controlled manner to ensure cell survival. The fluidity of the plasma membrane, which depends on its fatty acid and cholesterol composition as well as temperature, allows for this movement through the membrane bilayer. Maintaining the fluid nature of the membrane is important for substances to pass through it.

1. The Movement
of Substances
Across the
Plasma
Membrane
3 . 3 - A p p r e c ia t in g
The M o ve m e nt o f
S u b s ta nc e s A c ro s s
t h e P la s m a
Me mbra ne

2. LEARNING
OUTCOMES
• Explain the necessity of
movement of substances across
the plasma membrane which
occurs in a continuous &
controlled manner for survival
of a cell

3. • Occurs in a continuous & controlled
manner for the survival of a cell.
• The fluidity of the plasma membrane
depends on the specific fatty acid &
cholesterol present and the temperature.
• Unsaturated fatty acids with bend tails
break up the dense fatty acid packing &
cause the phospholipids bilayer to be
more fluid.