6. The Cell membrane
Describe the structure and parts of
the cell membrane and explain
details of its role in the cell.
Starter.
• Name one type of lipid
• What is the name given to bonds between amino
acids
• What main elements make up carbohydrates?
• What is the difference between a monomer and a
polymer
• What is an essential amino acid?
• What has to happen to lipids, carbohydrates and
proteins once they are eaten by us?
The Cell Membrane
• Is the barrier between a living cell and the outside
world.
• The structure is often called the fluid mosaic model
discovered 1972
• Fluid because it is made of two layers (a bilayer)
of phospholipids molecules and other components
which can move sideways throughout the layer.
• Mosaic because the proteins, carbohydrates and
cholesterol dotted throughout the membrane look like
a mosaic pattern
• http://www.susanahalpine.com/anim/Life/memb.htm
Key components - Lipids
• Phospholipids – have two ends. The hydrophilic
(water soluble) phosphate end and the
hydrophobic (insoluble in w_______) fatty acid
end. Form a bilayer with the f______ acids tails
on the inside and the hydrop______ groups on
the outside in the watery environment. The two
layers stop m____________ of large molecules
into the cell. The fluid environment allows small
molecules such as o______ and water to diffuse
through.
• Cholesterol helps stiffen the membrane. Not
found in p________ cells.
• S_________ proteins help to give the cell
support and shape.
• Cell membrane r________ proteins help cells
communicate with their external environment
• T_______________ proteins, such as globular
proteins, transport molecules across cell
membranes.
• C_____________ are involved in cell
recognition.
Structure – add labels
• Add the missing labels to the diagram
A Carbohydrate
chains
B Phospholipid
bilayer
C Transport
protein
D Hydrophobic
tails
Lipid bilayer animation
• http://www.youtube.com/watch?v=Qqsf_UJcf
Bc
Group task – cell membrane model
• Use half toothpicks and plasticene to create
phospholipids.
• Make proteins, carbohydrates and cholesterol
from 3 other colours and create a cell
membrane model with toothpick tails turned
inwards.
Role of Membrane in Cells
• Isolate enzymes from rest of cell.
• Smooth ER is a network of membranes involved in lipid
synthesis
• Surround nucleus and contain DNA
• Rough ER – protein synthesis
• Entry and Export of substances from cell by vesicles
• Cell communication and recognition
• Packaging and secretion in the Golgi Apparatus
• Selective transport by channel proteins.
• Energy Transfer in mitochondria and choroplasts