chapter 5 membrane structure & function. membrane structure, i selective permeability...
TRANSCRIPT
![Page 1: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/1.jpg)
Chapter 5
Membrane Structure & Function
![Page 2: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/2.jpg)
Membrane structure, ISelective permeability
Amphipathic
polar & non-polar regions(ex. hydrophilic & hydrophobic)
Davson-Danielli (1935-1970)
protein “sandwich”
Singer-Nicolson:
“fluid mosaic” model
currently widely accepted
![Page 3: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/3.jpg)
Membrane structure, IIPhospholipids membrane fluidity
Cholesterol fluidity/stabilization
“Mosaic” Structure
Integral proteins
trans-membrane proteins
Peripheral proteins surface of membrane
Membrane carbohydrates
cell to cell recognition;
Oligosaccharides (cell markers);
glycolipids
glycoproteins
![Page 4: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/4.jpg)
Membrane structure, III
Membrane protein
function:
•transport
•enzymatic activity
•signal transduction
•intercellular joining
•cell-cell recognition
•ECM attachment
![Page 5: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/5.jpg)
Membrane trafficDiffusion movement of a substance from
an area of high concentration of that substance to an area of low concentration of that substance.
Concentration gradient imbalance in concentration
Passive transport diffusion of a substance across a biological membrane without the need for energy
Osmosis the diffusion of water from an are of high concentration of water to an are of low concentration of water across a selectively permeable membrane
![Page 6: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/6.jpg)
High Concentration
Low Concentration
Passive (with gradient)
Diffusion, Osmosis, Facilitated Diffusion
Active-Need ATP (against (or with) gradient)
Active Transport
![Page 7: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/7.jpg)
Water balanceOsmoregulation control of
water balance
Hypertonic higher concentration of solutes
Hypotonic lower concentration of solutes
Isotonic equal concentrations of solutes
Cells with Walls:Turgid (very firm)
Flaccid (limp)
Plasmolysis plasma membrane pulls away
from cell wall
![Page 8: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/8.jpg)
Specialized Transport
Transport proteins
Facilitated diffusion
passage of molecules and ions with transport proteins across a membrane down the concentration gradient
Active transport movement of a substance against its concentration gradient with the help of cellular energy
![Page 9: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/9.jpg)
Types of Active TransportSodium-potassium pumpExocytosis secretion of
macromolecules by the fusion of vesicles with the plasma membrane
Endocytosis import of macromolecules by forming new vesicles with the plasma membrane•phagocytosis•pinocytosis•receptor-mediated
endocytosis (ligands)
![Page 10: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/10.jpg)
A Closer Look at Cell Membranes
Aim: How do large particles enter and exit cells?
Do Now: Name some molecules/materials that enter and exit the cell.
How would you describe the cell membrane that allows passage of these materials?
![Page 11: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/11.jpg)
Exocytosis and Endocytosis
Exocytosis (out of the cell)• The fusion of a vesicle with the cell membrane,
releasing its contents to the surroundings
Endocytosis (into the cell)• The formation of a vesicle from cell membrane,
enclosing materials near the cell surface and bringing them into the cell
![Page 12: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/12.jpg)
Endocytosis and Exocytosis Examples
![Page 13: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/13.jpg)
Endocytosis and Exocytosis Examples
![Page 14: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/14.jpg)
Three Pathways of Endocytosis
Bulk-phase endocytosis• Extracellular fluid is captured in a vesicle and
brought into the cell; the reverse of exocytosis
Receptor-mediated endocytosis• Specific molecules bind to surface receptors,
which are then enclosed in an endocytic vesicle
Phagocytosis• Pseudopods engulf target particle and merge as
a vesicle, which fuses with a lysosome in the cell
![Page 15: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/15.jpg)
Phagocytosis (“engulfment”)
![Page 16: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/16.jpg)
Membrane Cycling
Exocytosis and endocytosis continually replace and withdraw patches of the plasma membrane
New membrane proteins and lipids are made in the ER, modified in Golgi bodies, and form vesicles that fuse with plasma membrane
![Page 17: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/17.jpg)
Exocytic Vesicle
![Page 18: Chapter 5 Membrane Structure & Function. Membrane structure, I Selective permeability Amphipathic polar & non-polar regions (ex. hydrophilic & hydrophobic)](https://reader035.vdocument.in/reader035/viewer/2022081504/5697c01d1a28abf838cd0a7e/html5/thumbnails/18.jpg)
5.5 Key Concepts: Membrane Trafficking
Large packets of substances and engulfed cells move across the plasma membrane by processes of endocytosis and exocytosis
Membrane lipids and proteins move to and from the plasma membrane during these processes