Membrane Protein : Integral/Peripheral Integral Membrane Proteins (transmembrane) – Exposed to...
-
Upload
virgil-hines -
Category
Documents
-
view
221 -
download
0
Transcript of Membrane Protein : Integral/Peripheral Integral Membrane Proteins (transmembrane) – Exposed to...
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 unassisted
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 (Integtral) Proteins – Channel proteins– Carrier proteins
Facilitated Diffusion • Channel Proteins– Form hydrophilic pathways in the membrane – Water and certain ions can pass
Facilitated Diffusion • Carrier Proteins – 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
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 Solutions (Cell) • Hypotonic
– Solute concentration is high in cell (swells)• Hypertonic
– Solute concentration is low in cell (shrinks)• Isotonic
– Solute and water concentration is equal both in and outside cell
Active Membrane Transport• Substance carried
across a membrane from an area of low concentration to an area of high concentration
• Use of pump• ATP used as energy
source
Exocytosis and Endocytosis • Vesicles are used to
transport• ATP is required• Exocytosis– Transport of proteins and
waste material from cytosol to exterior of cell
• Endocytosis– Transport proteins and
large molecules into cytosol of the cell.