A Closer Look at Membranes - PowerPoint PPT Presentation

Loading...

PPT – A Closer Look at Membranes PowerPoint presentation | free to download - id: 511982-ZTJmO



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

A Closer Look at Membranes

Description:

A Closer Look at Membranes Chapter 5 Cystic Fibrosis Caused by defective protein channel (CFTR) in epithelial cells Not enough Cl- and water cross membranes Thick ... – PowerPoint PPT presentation

Number of Views:29
Avg rating:3.0/5.0
Slides: 24
Provided by: christin48
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: A Closer Look at Membranes


1
A Closer Look at Membranes
  • Chapter 5

2
Cystic Fibrosis
  • Caused by defective protein channel (CFTR) in
    epithelial cells
  • Not enough Cl- and water cross membranes
  • Thick mucus clogs airways and ducts throughout
    body
  • Usually fatal by age 30

3
Lipid Bilayer
  • Main component of cell membranes
  • Gives membrane its fluid properties
  • Fatty acid tails sandwiched between hydrophilic
    heads

lipid bilayer
fluid
fluid
Figure 5.2c Page 82
4
Fluid Mosaic Model
  • Membrane is a mosaic of
  • Phospholipids
  • Glycolipids
  • Sterols
  • Proteins
  • Most phospholipids and some proteins can drift
    through membrane

5
Membrane Proteins
receptor protein
adhesion protein
recognition protein
communication protein
passive transporter
active transporters
Figure 5.5 Page 85
6
Membrane Experiments
  • Split membranes reveal embedded proteins

In-text figure Page 86
7
Membrane Experiments
  • Hybrid human-mouse cell shows some proteins drift
    within membrane

human cell
mouse cell
hybrid cell
Figure 5.6 Page 86
8
Selective Permeability
O2, CO2, and other small, nonpolar molecules
some water molecules
glucose and other large, polar, water-soluable
molecules ions, water molecules
9
Membrane Crossing Mechanisms
  • Diffusion across lipid bilayer
  • Passive transport
  • Active transport
  • Endocytosis
  • Exocytosis

10
Concentration Gradient
  • Means the number of molecules or ions in one
    region is different than the number in another
    region
  • In the absence of other forces, a substance moves
    from a region where it is more concentrated to
    one where its less concentrated - down gradient

11
Diffusion
  • The net movement of like molecules or ions down a
    concentration gradient
  • Although molecules collide randomly, the net
    movement is away from the place with the most
    collisions (down gradient)

12
Factors Affecting Diffusion Rate
  • Steepness of concentration gradient
  • Steeper gradient, faster diffusion
  • Molecular size
  • Smaller molecules, faster diffusion
  • Temperature
  • Higher temperature, faster diffusion
  • Electrical or pressure gradients

13
Example of Diffusion
14
Transport Proteins
  • Span the lipid bilayer
  • Interior is able to open to both sides
  • Change shape when they interact with solute
  • Move water-soluble substances across a membrane

15
Passive and Active Transport
Passive Transport
Active Transport
  • Doesnt require energy inputs
  • Solutes diffuse through a channel inside the
    proteins interior
  • Net movement is down concentration gradient
  • Requires ATP
  • Protein is an ATPase pump
  • Pumps solute against its concentration gradient

16
Figure 5.10 Page 88
Passive Transport
glucose transporter
solute (glucose)
high
low
Stepped Art
17
Figure 5.11 Page 89
Active Transport
Stepped Art
18
Osmosis
  • Water molecules tend to diffuse down water
    concentration gradient
  • Total number of molecules or ions dictates
    concentration of water
  • Tonicity - relative solute concentrations

19
Tonicity
2 sucrose solution
2 sucrose solution
10 sucrose solution
distilled water
Hypotonic Conditions
Hypertonic Conditions
Isotonic Conditions
Figure 5.13 Page 90
20
Fluid Pressure
  • Hydrostatic pressure
  • Turgor pressure
  • Osmotic pressure

normal plant cells
after plasmolysis
21
Exocytosis
Endocytosis and Exocytosis
plasma membrane
cytoplasm
Endocytosis
cytoplasm
22
Endocytosis Pathways
  • Bulk phase
  • Receptor-mediated
  • Phagocytosis

clathrin
Figures 5.17, 5.18 Pages 92, 93
23
Membrane Cycling
clathrin
  • Exocytosis and endocytosis continually replace
    and withdraw patches of plasma membrane

Golgi body
Figure 5.19 Page 93
lysosome
About PowerShow.com