Chapter 4Membrane Structure

1

• Chapter 4 Membrane Structure Function

2
Membrane structure4.1.1 The Plasma Membrane
Isolates the Cell While Allowing Communication
with Its Surroundings

• Selective permeability-
• (1) selectively isolates the cells contents
  from its external environment
• (2) regulates essential substances between
  cell contents and surroundings
• (3) communicates with other cells
• (4) identify the cell as a particular type
  in a particular species

3
Membrane Structure

• Amphipathic hydrophobic hydrophilic regions
  

4
Membrane structure, II

• Phospholipids membrane fluidity
• Cholesterol membrane stabilization
• Mosaic Structure
• Integral proteins transmembrane
• proteins
• Peripheral proteins surface of
• membrane
• Membrane carbohydrates
• cell to cell recognition
• oligosaccharides (cell markers)
• glycolipids glycoproteins

5
extracellular fluid (outside)
glycoprotein
binding site
phospholipid bilayer
cholesterol
carbohydrate
phospholipid
receptor protein
transport protein
protein filaments
cytoplasm (inside)
recognition protein
6
Membrane structure, III

• Membrane protein function transport enzymati
  c activity signal transduction intercellular
  joining cell-cell recognition

7
Membrane traffic

• Diffusion tendency of any molecule to spread out
  into available space
• Movement with the Concentration gradient
• Passive transport diffusion of a substance
  across a biological membrane
• Osmosis the diffusion of water across a
  selectively permeable membrane

8
Diffusion

• The Diffusion Applet

9
Osmosis
Osmosis Demo
Demo 2
10
Water balance

• Osmoregulation 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

11
Hypotonic solution
Isotonic solution
10 micrometers
Hypertonic solution
12
selectively permeable membrane
H2O
sugar
pore
selectively permeable membrane
sugar molecule
water molecule
13
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

14
Facilitated diffusion

• Animation

15
Types of Active Transport

• Sodium-potassium pump
• Exocytosis secretion of
• macromolecules by the fusion of
• vesicles with the plasma membran
• Endocytosis import of
• macromolecules by forming new
• vesicles with the plasma membrane
• phagocytosis
• pinocytosis
• receptor-mediated endocytosis

16
Sodium potassium pump

• Animation

17
Exocytosis
18
Endocytosis - Phagocytosis

• Phagocytosis Animation

19
Endocytosis Pinocytosis

• Animation

20
Receptor-mediated endocytosis
21
Receptor-mediated endocytosis

• Animation

22
Cell Membrane Review

• Cool Review of the Cell

23
Tight junction
Desmosome
urinary bladder
small intestine
cells lining small intestine
cells lining bladder
plasma membranes (edge view)
desmosome
Tight Junctions Make the Cell Leakproof
DesmosomeStrengthen the connecton between cells
Protein filaments in cytoplasm
24
Gap junctions
Plasmodesmata
liver
root
root cells
liver cells
plasma membrane
cell wall
Gap Junctions and Plasmodesmata allow
communication between cells