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Week 3
• State that plasma (cell surface) membranes are partially permeable barriers.
• Outline the roles of membranes within cells and at the surface of cells.
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What are the functions of cell
membranes?
What are the functions of cell
membranes?
• Separate cell contents from the external
environment
• Separating cell components from cytoplasm
• Cell recognition and signalling
• Holding the components of some metabolic
pathways in place
• Regulating the transport of materials in and out
of cells
Cell membranes are made of
phospholipids.
What is a phospholipid?!
• Phospholipids are made from triglycerides
or fats
• Remember back to GCSE:
• Fats are digested to fatty acids and
glycerol, therefore that is what they must
be made from.
Structure of Glycerol and Triglyceride
• Fatty acid chains are
joined to glycerol by
“Condensation
Reactions”
• These result in the
formation of “Ester
Bonds”
• We will cover this
later in the course!
• Don’t panic
Phospholipids
• In a
phospholipid
one of the three
fatty acids in a
triglyceride is
replaced by a
phosphate
group
• See page 16 in
your text book
In a phospholipid molecule the phosphate head is
attracted to water molecules (Hydrophilic)
The fatty acid tail is repelled by water molecules
(Hydrophobic)
• If phospholipid
molecules are put
into water they
interact with the
water molecules
to produce a
single layer
orientated as in
the diagram
Week 3
A phospholipid bilayer produced by mixing phospholipid into water
Hydrophilic Heads
attracted to the
water molecules
Hydrophobic Tails
repelled by water
molecules, so
tucked inside
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Week 3
• Describe the fluid mosaic model of membrane structure.
• Describe the roles of the components of the cell membrane, including
phospholipids, cholesterol, glycolipids, proteins and glycoproteins.
• Outline the effects of changing temperature on membrane structure and
permeability.
© Pearson Education Ltd 2008
This document may have been altered from the original
Week 3
The fluid mosaic model of cell membrane structure
You have 15 seconds to remember as much as possible!
© Pearson Education Ltd 2008
This document may have been altered from the original
Homework!
• Find animations of cell membrane
structure and function on the internet to
help you to understand and remember the
components of the cell membrane!
Week 3
• Explain the term ‘cell signalling’.
• Explain the role of membrane-bound receptors as sites where hormones
and drugs can bind.
© Pearson Education Ltd 2008
This document may have been altered from the original