Transcript Plasma Membrane

Plasma Membrane
Structure and Function
Plasma Membrane
• Made of a Lipid Bi-layer (two parts)
• Phospholipid heads are hydrophilic
(water loving)
• Phospholipid tails are hydrophobic
(water fearing)
• Described as a Fluid-mosaic.
• Proteins, glycolipids, carbohydrates,
and cholesterol are embedded in the bilayer.
Fluid Mosiac Model?
• This refers to the property of the bi-layer
which can move sideways in relation to
each other.
• Cells are flexible/pliable due to this
property.
• Also, the bi-layer is studded with several
different types of proteins.
• Each protein has a different function.
Proteins found in bi-layer
• Channel Proteins: substance can
move freely through.
• Carrier Proteins: using a substrate to
help move substances across the
membrane.
• Receptor protein: has a shape that
allows a specific molecule to bind to it,
causing protein to react.
• Enzymatic protein: carry out metabolic
reactions.
Passive Transport
• Diffusion: movement of molecules from
an area of high concentration to an
area of low concentration.
• Osmosis: the movement of WATER
molecules from an area of high
concentration to an area of low
concentration.
• Facilitated transport: movement of
molecules (like diffusion) using a
transport proteins.
• NONE OF THESE MECHANISMS USE
ENERGY.
Facilitated Diffusion of glucose
from liver cells.
Active Transport
These mechanisms require energy to move molecules.
• Ion pumps
– Molecules can be positively or negatively
charged.
– Must use ATP to move ions against a
concentration & electrical gradient.
• Cotransport
– Uses the element Hydrogen to assist in the
uptake of molecules.
• Endocytosis/Exocytosis
– The cell literally taking something inside/outside
by engulfing or receptor mediation/expulsion.
Ion Pump
Active Transport (cont.)
• Exocytosis: the expulsion of materials from a
cell by the fusion of a vesicle with the plasma
membrane.
• http://www.linkpublishing.com/Videos/transpo
rt/para_exo.wmv
Tonicity?
• Cells are continually adjusting the
composition of liquids inside and outside of
the cells.
• The different mixtures are categorized due to
their effects on a cell.
– Hypertonic solutions
– Hypotonic solutions
– Isotonic solutions
http://www.linkpublishing.com/Videos/transport/elod
ea_hyper.wmv
Hypotonic Solution
• http://www.linkpublishing.com/Videos/tr
ansport/elodea_hypo.wmv
• “A” is a cell in a hypertonic solution
while “B” is a cell in a hypotonic
solution.
Isotonic Solution
• http://www.linkpublishing.com/Videos/tr
ansport/blood_isotonic.wmv
What does Tonicity do?
• Cells can regulate the amount of specific
dissolved substances within them, thereby
regulating the amount of water entering or
leaving the cell through osmosis.
• Plant cells use the principle of tonicity to draw
water from the soil to the leaves. The series
of cells along the chosen path of water adjust
their tonicity to “move” water throughout the
entire plant.
Tonicity cont.
• Medical use in I.V. fluids.
• I.V. fluids are usually hypotonic. Why?
• What advantage would there be for an
isotonic I.V. solution?
• What is the make up of a sport’s drink?