Transcript Biology Monday, October 16

Cell Membrane Notes
Movement Across the Membrane
• Diffusion – particles move from an area of
high concentration to low concentration
in other words: particles spread out
http://www.biologycorner.com/bio1/diffusion.html
Selective Permeability
• Permeable – allows things to pass through
• Selectively Permeable – only certain things
can pass through
• Only small molecules can fit between the
phospholipids.
• The nonpolar tails of the phospholipids
prevent charged molecules from passing
between them.
• Proteins help certain larger molecules to
enter
Make up of the Cell Membrane
• Phospholipid bilayer - Two layers of charged
lipids face each other,
Only small particles with no charge can
pass through
• Proteins - Move material through the
membrane that can’t pass between lipids
• Carbohydrates - Identify the cell
Make up of the Cell Membrane
(cont)
• Cholesterol - Holds phospholipids together
Solutions
Concentration – the ratio of the amount of a substance in a
solution to the amount of water
Isotonic –
iso = same,
tonic = strength,
concentration
A solution in which the
concentration is the same
outside the cell as inside
Water will flow into and out of the cell equally.
The cell will stay the same.
Hypotonic –
hypo = below
A solution in which the concentration is lower
outside the cell than inside
Water will flow into the
cell to even out the
concentration.
The cell will expand.
Hypertonic –
hyper = above
A solution in which the concentration is
higher outside the cell than inside.
Water will flow out of the
cell to even out the
concentration.
The cell will shrink.
http://www.northland.cc.mn.us/biology/Biology1111/animations/passive1.html
Methods of transport
• Osmosis –
– Water flows between the lipids from an area of
high concentration to low concentration
– Through a membrane
– No energy is required
• Diffusion –
– Small, uncharged particles move between the
lipids
– from an area of high concentration to low
concentration
– this does not require energy
– Particles such as CO2, and O2
• Facilitated Diffusion / Passive Transport –
– Transport (carrier) proteins allow large particles
to flow through the membrane
– with the concentration gradient (from high
concentration to low concentration)
– This does not require energy
– Particles that are too
large to fit between
lipids: such as glucose
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_di
ffusion_works.html
• Active Transport –
– Transport proteins (ion pumps) pump ions and
other particles
– against the concentration gradient (from low
concentration to high concentration)
– This requires energy
– Particles such as Na + (sodium ion) and K+
(potassium ion)
– http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_the
_sodium_potassium_pump_works.html
Endocytosis (pinocytosis or phagocytosis)
• The cell membrane surrounds and engulfs a
large particle from outside the cell.
• The particle is then enclosed in a membrane
• Requires energy
• Particles such as food, proteins, or large
amounts of
water.
Exocytosis
• The opposite of endocytosis
• A membrane filled with particles fuses with
the cell membrane to release particles from
the cell
• Cell removes
waste or
sends out
proteins
• Requires
energy
• http://highered.mcgrawhill.com/sites/0072437316/student_view0/
chapter6/animations.html#