Membranes and Channels Flashcards
Importance of cell membrane
- proper nutrition
- maintenance of irritability
- homeostasis
cell membrane is a ___ ___ permeable barrier that surrounds all living cells
highly selective
properties of cell membrane
- define boundaries
- compartmentalization
- signal detection
- cell-to-cell communication
- surround all animal cells
- extraordinary thin
- lipid-based structure
Describes the organization of cell membranes. phospholipid drift and move like a fluid
fluid mosaic model
Composition of membrane
Phospholipids, proteins, and carbohydrates
Lipid and protein molecules kept together by ______
non-covalent interactions
impermeable to the passage of most water-soluble molecules
lipid bilayer
fundamental structure of the membrane
lipid molecules
Proteins embedded in the bilayer provide a mechanism for trans-membrane transport
integral proteins
Protein associated with the surface of the membrane via electrostatic interaction
peripheral proteins
Catalyzing reactions in the cytoplasm
enzymes
acts as ___ (specific binding site hormones or other chemicals can bind; used for ___ and ___)
receptors; cell signaling and cell recognition
Special functions of proteins
ARRET
- Adhesion
- Recognition
- Receptor
- Enzymes
- Transport
clumping of RBCs caused by the reaction between antibodies on the blood plasma and the antigen on the RBCs
agglutination
A condition where a pregnant women who is Rh positive becomes exposed to Rh negative blood from her baby
Rh sensitization
Found on the outer surface and attached to the proteins or sometimes to the phospholipids
carbohydrates
Carbohydrates on membranes
glycoproteins and glycolipids
Cell coat outside the cell membrane
glycocalyx
Glycoprotein bears oligosaccharide side chains and vital for ___ ___ and ___
cell recognition and communication
Primary types of lipids
- Phosphoglycerides
- Sphingolipids
- Sterols
Glycerol backbone
phosphoglycerides
Backbone made of sphingosine bases
Sphingolipids
Cholesterol, nonpolar and only slightly soluble in water
sterols
Lateral movement of lipids and proteins within a surface of the bilayer is very common
membrane fluidity
Splits a membrane along the middle of the phospholipid bilayer prior to electron microsope
freeze fracture
What is revealed in freeze fracture
protein particles insterspersed with a smooth matrix supporting the fluid mosaic model
It makes membranes highly impermeable to most polar molecules
hydrophobic interior
Regulates the passage of materials in and out of the cell
Selective permeability
The rate at which a substance can passively penetrate a cell membrane
membrane permeability
Transport systems
- Passive processes
- Active transport
Passive processes
- no energy expenditure and move down their normal gradient
- simple diffusion/ lipid diffusion
Active transport
requires metabolic energy and moves substance against their gradient
Depends on concentration and electrical gradients
passive transport
Three Basic Routes
- Dissolving in the lipid phase
- Diffusion through labile or fixed aqueous channels
- Carrier-mediated transport
Random thermal motion of suspended or dissolves molecules causes their dispersion from regions of higher concentration to regions of lower concentrations
diffusion
Fick’s Law
- proportional to the difference in partial pressure
- proportional to the area of the membrane
- inversely proportional to the thickness of the membrane
Rate at which substance passively penetrates the membrane under a specified set of conditions
Permeability
Intrinsic factors governing diffusion across membranes
- Size rule
- Polarity rule
- Ionic rule
Factors of rate of diffusion
- Size
- Temperature
- Steepness of the concentration gradient
- Charge
- Pressure
Factors that influence mobility of solute molecule
- Lipid solubility
- Hydrogen Bond with water
- Molecular weight
- Molecular shape
- Partition coefficient
ratio of distribution of a substance between two different liquid phases
partition coefficient
