Transcript Membrane Transport

Essentials of Anatomy & Physiology, 4th Edition
Martini / Bartholomew
3
Cell Structure
and Function
PowerPoint® Lecture Outlines
prepared by Alan Magid, Duke University
Slides 1 to 102
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Key Note
Things tend to even out, unless
something—like a cell membrane—
prevents this from happening. Across a
freely permeable or water permeable
membrane, diffusion and osmosis will
quickly eliminate concentration
gradients.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Membrane Transport
• Permeability – property that determines
which substances can enter/leave the
cytoplasm
• Freely – any substance crosses
• Selective – certain substances cross
• Permeability factors
• Molecular size/shape
• Electrical charge
• Lipid solubility
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Membrane Transport Processes
• Passive Transport – no energy expended
• Diffusion (includes osmosis)
• Filtration
• Facilitated Transport (carrier-mediated)
• Active Transport – energy expended
• Carrier-Mediated
• Vesicular Transport
• Endocytosis
• Exocytosis
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Membrane Transport Definitions
• Diffusion
Random movement down a concentration
gradient (higher to lower [C])
• Osmosis
Movement of water across a membrane
down a gradient in osmotic pressure (lower
to higher osmotic pressure)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Diffusion
Figure 3-4
The Cell Membrane
Diffusion Across Cell Membranes
Figure 3-5
The Cell Membrane
Osmosis
Figure 3-6
The Cell Membrane
Osmotic Effects of Solutions on Cells
• Isotonic—Cells maintain normal size and
shape
• Hypertonic—Cells lose water osmotically
and shrink and shrivel
• Hypotonic—Cells gain water osmotically
and swell and may burst.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Osmotic
Flow across
a Cell
Membrane
Figure 3-7
The Cell Membrane
Passive Membrane Transport
• Filtration
• Hydrostatic pressure pushes on
water
• Water crosses membrane
• Small solutes follow water
through pores
• Examples: blood pressure and
urine formation
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Carrier-Mediated Transport - Passive
• Membrane proteins as carriers
• Facilitated Diffusion (no ATP required)
• Co-transport
• Counter-transport
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Facilitated Diffusion
Figure 3-8
Carrier-Mediated Transport – Active
• Active transport (ATP consumed)
• Independent of concentration gradients
• Ion pumps
- Na+/K+ Exchange Pump
The Cell Membrane
The SodiumPotassium
Exchange Pump
Figure 3-9
The Cell Membrane
Vesicular Transport
• Active Transport
• Membranous vesicles move material
into/out of cell
• Types:
• Endocytosis - movement into cell
• Receptor-Mediated
• Pinocytosis – cell drinking
• Phagocytosis – cell eating
• Exocytosis - Movement out of cell
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Exocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The membrane containing the
receptor molecules separates from
the lysosome.
The vesicle returns to the surface.
Figure 3-10
1 of 8
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Ligands
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Ligand
receptors
CYTOPLASM
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
2 of 8
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Ligands
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
CYTOPLASM
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
3 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
4 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Lysosome
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
5 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
6 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
The membrane containing the
receptor molecules separates from
the lysosome.
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
7 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Exocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The membrane containing the
receptor molecules separates from
the lysosome.
The vesicle returns to the surface.
Figure 3-10
8 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive
enzymes.
CYTOPLASM
EXTRACELLULAR FLUID
Undissolved
residue
The enzymes break down the
structure of the phagocytized
material.
Residue is then ejected from the
cell by exocytosis.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
1 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
2 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
3 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
4 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
5 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
This fusion activates digestive
enzymes.
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
6 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
This fusion activates digestive
enzymes.
The enzymes break down the
structure of the phagocytized
material.
Figure 3-11
7 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive
enzymes.
CYTOPLASM
EXTRACELLULAR FLUID
Undissolved
residue
The enzymes break down the
structure of the phagocytized
material.
Residue is then ejected from the
cell by exocytosis.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
8 of 8
Coloring Workbook
The packet will be due the day before the
test.
You can now complete numbers 8, 9,
10 and 11.