Download cell membrane

Cellular Transport:
Cell Membrane
How Molecules Are Transported
Across The Cell Membrane.
Essential Questions
• How do cells maintain homeostasis?
• How are cell membranes (plasma membranes)
selectively permeable (semi-permeable)?
• Why is it important that cells are able to
transport molecules with (active transport) and
without (passive transport) energy?
Cell Membranes
• Functions:
a. Controls what enters and
exits the cell to maintain
homeostasis
b. Provides protection and
support for the cell
TEM picture of a real
cell membrane.
What is the purpose of cellular transport?
• Homeostasis depends upon
appropriate movement of
materials across the cell
membrane.
• The cell membrane regulates
the passage of materials into
and out of the cell.
– Needed (required) materials
move in
• Ex. Oxygen and glucose
– Excess materials or wastes move
out
• Ex. The CO2 produced as waste
product of cellular respiration
How?
• A cell membrane is semi-permeable
(selectively permeable)
– means some substances can pass directly through
cell membrane while other substances can not.
• Materials enter or exit through the cell
membrane either passive transport or
active transport.
What is a membrane made of?
• Phospholipid – lipid
made of a phosphate
group and 2 fatty acids.
– 1 polar head –
phosphate group
• Hydrophilic -loves
water
– 2 non-polar tails fatty acids
• Hydrophobic -hates
water
Draw in Journal
• Lipid bilayer – double
layer of phospholipids
– polar head of one
faces outside and
other faces inside of
cell
– Non-polar tails face
towards each other
inside bilayer
Draw in Journal
• Membrane Proteins – allows large substances in cell
– located in lipid bilayer
– made of amino acids which contain polar and
non-polar sides
• Non-polar repelled by water on both sides of
bilayer, this holds proteins in place.
– proteins able to move along bilayer
Fluidity of Membranes
Membrane
movement
animation
• Phospholipids and proteins in plasma
membrane can move (drift lateally)
within bilayer
• This ability for the cell membrane to be
fluid is called the Fluid Mosaic Model