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Chapter 7: Membrane Structure and Function - Coggle Diagram
Chapter 7: Membrane Structure and Function
Plasma Membrane
Main function
Controls what enters and leaves the cell
Selective permeability
Main Model
Fluid: Phospholipids move laterally
Mosaic: Embedded proteins, cholesterol, carbohydrates
Structure of Membranes
Cholesterol
At body temperature: reduces fluidity (stabilizes)
At low temperatrue: prevents tight packing (increases fluidity)
Membrane Proteins
Peripheral proteins
attached to surface
Functions
Enzymatic activity
Signal transduction
Transport
Cell to cell recognition
Intercellular joining
Attachment to cytoskeleton
Integral proteins
span at bilayer (amphipathic)
Phospholipid Bilayer
Hydrophobic tails
Forms semi-permeable barrier
Hydrophilic heads
Carbohydrates
Attaches to glycolipids or glycoproteins
Cell recognition
Found on extracellular side
Permeability
Not Permeable
Ions, polar molecules
glucose, Na+, Cl-
Requires Transport
Carrier proteins
Can transport glucose, amino acids, nucleosides, and ions into the cell
Permeable
Small, nonpolar molecules
O₂, CO₂
Types of Membrane Transport
Active Transport
Ex: Sodium-Potassium Pump
Pumps 3 Na+ out, 2 K+ in
Maintains membrane potential
Moves substances against concentration gradient
Requires energy (ATP)
Bulk Transport
Exocytosis
Vesicles fuse with membrane to release materials
Endocytosis
Pinocytosis: cell drinking (fluids)
Receptor-mediated endocytosis: Specific molecule uptake
Phagocytosis: cell eating (solids)
Mediated by vesicles
Passive Transport
Osmosis
Movement of water across semipermeable membrane from area of low solute concentration to high solute concentration
Facilitated Diffusion
Uses channel and carrier proteins
Moves down concentration gradient
Diffusion
Movement down concentration gradient