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Membrane Transport How stuff gets in or out
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Membrane Transport
How stuff gets in or out
Membrane Transport
Objectives:Relate membrane structures to transport processes
Membrane Transport
Objectives:Relate membrane structures to transport processesCompare and contrast types of transport processes
Membrane Transport
The cell membrane’s most important function is to select what goes in and out of the cell.
Membrane Transport
The cell membrane’s most important function is to select what goes in and out of the cell.
This property is known as selective permeability.
Membrane Transport
Two processes allow materials to move in and out of the cell:
1) passive transport
Membrane Transport
Two processes allow materials to move in and out of the cell:
1) passive transport
2) active transport
Passive Transport
Passive transport requires No Energy (ATP).
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Passive Transport
There are three types:Simple diffusion
Passive Transport
There are three types:Simple diffusionFacilitated diffusion
Passive Transport
There are three types:Simple diffusionFacilitated diffusion &Osmosis
Passive Transport
Simple DiffusionSubstances move from a high concentration to a low concentration.This influenced by: Temperature
Passive Transport
Simple DiffusionSubstances move from a high concentration to a low concentration.This influenced by: Temperature Concentration
Passive Transport
Simple DiffusionSubstances move from a high concentration to a low concentration.This influenced by: Temperature Concentration Distance
Passive Transport
Simple DiffusionIn the cell, only nonpolar and lipid soluble substances diffuse directly through the bilayer.
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Extracellular fluid
Lipid-solublesolutes
Cytoplasm
Passive Transport
Simple DiffusionCommon substances that diffuse in this manner include Oxygen and Carbon Dioxide
Passive Transport
Facilitated Diffusion
Molecules which can not pass through the lipid bilayer because of size or polarity pass through using protein carriers or channels.
Passive Transport
Carriers are integral proteins and are typically designed for a specific type of molecule, for example, glucose.
Passive Transport
Carriers are integral proteins and are typically designed for a specific type of molecule, for example, glucose.
What is meant by an integral protein?
Passive Transport
What is meant by an integral protein?This is a protein that transverses the entire membrane.
Passive Transport
Carriers are integral proteins and are typically designed for a specific type of molecule, for example, glucose.
Rate is only limited by the number of carriers on the membrane.
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Passive Transport
Channels are integral proteins that allow smaller molecules (ions and water) to pass through.
Passive Transport
Channels are integral proteins that allow smaller molecules (ions and water) to pass through.They can be specific for certain types of ions (Na+ or K+ )
Passive Transport
Channels are integral proteins that allow smaller molecules (ions and water) to pass through.They can be specific for certain types of ions (Na+ or K+ )Some are always open while others are gated and open only when stimulated.
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Passive Transport
Passive Transport
Osmosis is the diffusion of water across a semi permeable membrane.
Passive Transport
Osmosis is the diffusion of water across a semi permeable membrane.
Water moves depending on its concentration through channels lined with proteins called aquaporins.
Passive Transport
Osmosis is the diffusion of water across a semi permeable membrane.
Water moves depending on its concentration through channels lined with proteins called aquaporins.It can also pass through the lipid bilayer!
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Passive Transport
The rate of osmosis is dependent on the concentration of impermeable molecules andpermeable molecules.
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Passive Transport
In biological systems, the ability of a solution to change the shape of a cell by osmosis is called tonicity.
Passive Transport
Isotonic solutions do not change the shape of the cells. In the hospital these are iv solutions of 0.9% NaCl or 5% dextrose (D5W).
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Passive Transport
Hypertonic solutions do change the shape of the cells because the concentration of impermeable solutes is greater than the cell. In the hospital these are used in cases of cerebral edema.Pulls water out of the cell.
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Passive Transport
Hypotonic solutions do change the shape of the cells because the concentration of impermeable solutes is less than the cell. In the hospital these are used in cases of dehydration
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Active Transport
Active transport requires Energy (ATP).
Active Transport
Active transport requires Energy (ATP).
Substances move from a LOW to a HIGH concentration.
Active Transport
Active Transport
Active transport requires membrane proteins that are specific for a particular substance.
There are two types: Primary Active Transport
Active Transport
Active transport requires membrane proteins that are specific for a particular substance.
There are two types: Primary Active Transport & Secondary Active Transport
Active Transport
Primary Active Transport uses ATP directly to move a solute across the plasma membrane, against the gradient.
Active Transport
Primary Active Transport uses ATP directly to move a solute across the plasma membrane, against the gradient.The best example is the sodium-potassium pump.
Active Transport
Active Transport
Secondary Active Transport uses a single ATP to indirectly move more than one substance across the cell membrane.
Active Transport
Secondary Active Transport uses a single ATP to indirectly move more than one substance across the cell membrane.
The ATP creates a gradient for one substance and as it flows back with the gradient it carries another substance with it.
Active Transport
There are two types of secondary active transport: Symport which moves two transported substances
in the same direction
Active Transport
There are two types of secondary active transport: Symport which moves two transported substances
in the same direction & Antiport which moves them in opposite
directions.
Active Transport
Active Transport
Example, Na+ is pumped out of the cell by primary active transport.
Active Transport
Example, Na+ is pumped out of the cell by primary active transport.
It then flows passively back into the cell and uses that energy to move other substances through.
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1 2 The ATP-driven Na+-K+ pump stores energy by creating a steep concentration gradient for Na+ entry into the cell.
As Na+ diffuses back across the membrane through a membrane cotransporter protein, it drives glucose against its concentration gradientinto the cell. (ECF = extracellular fluid)
Na+-glucosesymporttransporterloadingglucose fromECF
Na+-glucosesymport transporterreleasing glucoseinto the cytoplasm
Glucose
Na+-K+
pump
Cytoplasm
Extracellular fluid
Active Transport
Vesicular Transport is another type of active transport where large macromolecules and fluid are transported.
Active Transport
Vesicular Transport is another type of active transport where large macromolecules and fluid are transported.
There are two types: Exocytosis
Active Transport
Vesicular Transport is another type of active transport where large macromolecules and fluid are transported.
There are two types: Exocytosis
Active Transport
Vesicular Transport is another type of active transport where large macromolecules and fluid are transported.There are two types: Exocytosis & Endocytosis
Active Transport
Endocytosis is the process where materials are taken into the cell using a membranes with a protein coated vesicle.
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Coated pit ingestssubstance.
Protein-coated vesicle detaches.
Coat proteins detachand are recycled to plasma membrane.
Uncoated vesicle fuseswith a sorting vesicle called an endosome.
Transport vesicle containing
membrane components moves to the plasma
membrane for recycling.Fused vesicle may (a) fusewith lysosome for digestion of its contents, or (b) deliver its contents to the plasmamembrane on the opposite side of the cell (transcytosis).
Protein coat(typically clathrin)
Extracellular fluid Plasmamembrane
Endosome
Lysosome
Transportvesicle
(b)(a)
Uncoatedendocytic vesicle
Cytoplasm
1
2
3
4
5
6
Active Transport
Exocytosis is the process where materials are removed from the cell using a membranes with a protein coated vesicle.
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1 The membrane-bound vesicle migrates to the plasma membrane.
2 There, proteinsat the vesicle surface (v-SNAREs) bind with t-SNAREs (plasma membrane proteins).
(a) The process of exocytosisExtracellular
fluid
Plasma membraneSNARE (t-SNARE)
Secretoryvesicle Vesicle
SNARE(v-SNARE)
Molecule tobe secreted
Cytoplasm
Fusedv- and
t-SNAREs
3 The vesicleand plasma membrane fuse and a pore opens up.
4 Vesiclecontents are released to the cell exterior.
Fusion pore formed
Resting Membrane Potential
The transport processes discussed are responsible for the generation of a membrane potential or voltage.
Resting Membrane Potential
The transport processes discussed are responsible for the generation of a membrane potential or voltage.
The result is that at rest, cells exhibit a resting membrane potential between -50 to -100 millivolts.
Resting Membrane Potential
This is achieved by a process of active transport and movement of ions to either the exterior or interior of the cell.
Resting Membrane Potential
Inside the cell, potassium ions are in large concentration while outside sodium ions are in large concentration.
Inside the cell are large negatively charged proteins.
Resting Membrane Potential
Resting Membrane Potential
Due to the preferential “leaking” of potassium ions to the outside, there is a net NEGATIVE voltage relative to the outside.
Resting Membrane Potential
Resting Membrane Potential
Resting Membrane Potential
– Stimulation of the membrane results in a sudden change in polarity called an action potential. This can lead to:• Muscle Contraction• Gland Secretion• Nerve Impulse
