Download Membrane Protein : Integral/Peripheral

Membrane Protein : Integral/Peripheral
• Integral Membrane
Proteins (transmembrane)
– Exposed to aqueous
environment on both sides
of the membrane
– Used to transport molecules
across membrane
• Peripheral Membrane
Proteins
– Located on surface of a
membrane
– Eg. Cytoskeleton
Passive Membrane Transport
• No chemical energy required
• Diffusion
– Net movement of a substance from a region of high
concentration to a region of low concentration until
dynamic equilibrium between cells is met
Simple Diffusion (Passive Transport)
• Diffusion of
small/non-polar
molecules across
plasma
membrane
without the help
of an integral
protein
Facilitated Diffusion
• Diffusion of large/polar molecules with the help of a
transport protein (integral membrane protein)
• Stops when equilibrium is reached
• Two types of Transport (Integral) Proteins
– Channel proteins
– Carrier proteins
• Channel Proteins
Facilitated Diffusion
– Form hydrophilic pathways in the membrane
– Water and certain ions can pass
– Voltage-gated channels
• Open or closed by changes in voltage across the membrane or
by binding molecules
• Eg. Muscle contractions
• Carrier Proteins
Facilitated Diffusion
– Form pathways through the membrane
– Bind to a specific solute (glucose, amino acid)
– Carrier protein changes shape allowing solute to move
from one side of the membrane to the other
Simple vs Facilitated
• Simple Diffusion
– Rate of diffusion
increases as
difference in
concentration
gradient increases
• Facilitated Diffusion
– Maximum rate is
reached but limited
by number of
transport protein in
membrane
Osmosis
• Passive diffusion of water across a membrane via
aquaporins
• Water always diffuses from an area of low solute
concentration (high water concentration) to an area of
greater solute concentration (low water concentration)
• Three Types of Solutions
– Hypotonic
– Hypertonic
– Isotonic
Hypertonic Solutions
• Solution that has a greater concentration of solute (dissolved
substance) than what is being compared
• Dehydration occurs because body fluids contain too much
solute (salt)
• Lead to liver/kidney failure
• Hypertonic IV fluids are used to restore electrolyte balance
Hypotonic Solutions
• Solution that has a
lesser concentration
of solute (dissolved
substance) than what
is being compared
• Hypotonic IV’s are
used to treat true
dehydration (water
loss)
• Water will move into
our cells
Isotonic Solutions
• Solution that has an equal concentration of solute
(dissolved substance) than what is being compared
• Isotonic IV’s are used to increase fluid in blood
• Maintain homeostasis (equilibrium)
Exocytosis
• Vesicles are used to
transport
• ATP is required
• Transport of soluble
proteins, membrane
proteins and lipids
• Degranulation
– Cells release
antimocrobial
cytotoxic molecules
– Immune response
– Histamine (allergic
reaction)
Endocytosis
• Transport of
molecules inside cell
– Large polar molecules
• Pinocytosis
– ECF and molecules
• Phagocytosis
– Immune response
– Macrophage
• Receptor-mediated
– Clathrin (protein)
assists in ingestion of
specific molecules
inside cell