Cell Membrane Flashcards
Common hereditary diseases
Familiar hypercholesterolemia
Hereditary spherocytosis
Acute pancreatitis
Cancer metastasis
Cystic Fibrosis
It can cause or lead to several DISEASES
Disruption of membranes
Properties of membranes
• Asymmetric
• Viscous and Plastic
• Dynamic
• Thermodynamically stable and metabolically active
• Noncovalent Assembly
_____________:
• Irregular distribution of proteins
•
External location of carbohydrates
• Specific enzymes exhibit specificity of location
• Phospholipids (_______ containing are external while _______ containing are in the inner
leaflet)*
Inside-outside asymmetry
choline
amino acid
Functions of cell membrane
• Permit cell individuality
• Has selective permeability
• Important for cell to cell interaction and adhesion
• Important for transmembrane signaling
• Forms specialized compartments for organelles
• Localize enzymes
• Integral elements in excitation-response coupling
Describe INTRACELLULAR FLUID COMPARTMENT (ICF)
− Contains 2/3 of body water
− Provides environment for the cell to :
● Synthesize, store and utilize energy
● Repair itself
● Replicate
● Perform special functions
Describe EXTRACELLULAR FLUID COMPARTMENT (ECF)
− Contains 1/3 of total body water distributed between PLASMA and INTERSTITIAL FLUID compartments
− Is a delivery system of nutrients, ions, oxygen and hormones to cells
− Removes waste products from the cells
Composition of cell membrane
Lipid
Protein
Carbohydrates
provides the basic structures of
biological membranes
Lipids
perform most of the membrane’s specific tasks
Proteins
Major Membrane Lipids
- PHOSPHOLIPIDS
1.1. phosphoglycerides - most abundant
1.2. sphingomyelin - GLYCOSPHINGLOLIPIDS
2.1. cerebrosides
2.2. gangliosides - STEROLS
3.1. cholesterol
MEMBRANE LIPIDS
• All major membrane lipids are _______
• forms _______
• Fatty acids may be ______ or ______
• AMPHIPATHIC
• BILAYERS
• saturated or unsaturated
Lipid bilayers are formed by
______ driven by ___________
SELF-ASSEMBLY
HYDROPHOBIC EFFECT
________ are the more common membrane phospholipid
The most common phosphoglycerides is ________
PHOSPHOGLYCERIDES
Phosphatidic acid
Sugar-containing lipids built on a backbone of ceramide
Include the cerebrosides (galactosyl- and glucosylceramide) and the gangliosides
Glycosphingolipids
Most common sterol in membranes
Intercalates among phospholipids in the cell membrane
Is also amphipathic with its hydroxyl group lying at the aqueous surface
“moderator molecule”
Cholesterol
ROLE OF CHOLESTEROL
Modifies membrane fluidity
At high temperatures (above T), its rigid structure LIMITS DISORDER AND FLUIDITY (condensing effect)
At low temperatures (below Tm), it INCREASES FLUIDITY by interfering with the interactions of hydrocarbon tails of fatty acids
Functions of membrane protein
• Enzymes
• Pumps, channel, carriers
• Antigens
• Receptors
• Structural Proteins
• occur in association with lipids or proteins : glycolipids or glycoproteins
• mostly found on the external membrane surface
FUNCTIONS:
✔ receptors
✔ antigens
✔ confers recognition, negative charge and protection to cell (as glycocalyx)
Carbohydrates
THE FLUID MOSAIC MODEL BY
SINGER AND NICOLSON (1972)
■ universally accepted description of membrane structure
■ “icebergs” (proteins) floating in a “sea” of phospholipids
■ membranes undergo phasic changes from stiff (gel or crystalline) to fluid state
both lipids and proteins undergo “rapid redistribution” in the plane of the membrane (“lateral diffusion”)
Factors affecting membrane fluidity
Lipid composite
Temperature
temperature at
which structure undergoes transition from ordered to disordered state
Temperature transition
Importance of membrane fluidity
• Permeability to water and hydrophobic molecules
• lateral mobility of integral proteins
– are formed when bile acids (which are amphipathic)
associate with products of lipid digestion
– bile acids-formed micelles assist in the digestion
and absorption of fat plus ADEK
Micelles
- are vesicles surrounded by a lipid bilayer
- consists of phospholipids that are of natural or
synthetic origin
Lyposome
• biochemical signals from hormones, neurotransmitters bind to receptors in the cell membrane
• transmits information to the cytoplasm via these membranes through the generation of signaling molecules : cyclic nucleotides, calcium, diacylglycerol and phosphoinositides
Signal Transduction
It is comprised of both peripheral and integral proteins
G-Protein Coupled Receptor (GPCR)
It is composed of 2 confirmation of proteins
Tyrosine kinase receptor
Cell membrane transport systems are very important because :
- The cell membrane is SELECTIVE
- Cell membrane RECEIVES AND
TRANSMITS SIGNALS from other cells
moves ONE TYPE of substance
bidirectionally
Ex:_______
Uniport
Glucose transporters (GLUT)
Two types of cotransport
Symport
Antiport
moves TWO solutes in the SAME
DIRECTION
Ex: ______, _____
Symport
SGLT1 and SGLT2
moves TWO solutes in OPPOSITE directions
Antiport
- transport across the membrane DOWN AN
ELECTROCHEMICAL GRADIENT - no energy involved
SIMPLE DIFFUSION
FACTORS AFFECTING SIMPLE DIFFUSION:
- concentration gradient across membrane
- electrical potential across membrane
- permeability coefficient of the substance to the
membrane,, lipid solubility - pressure difference across membrane
- thickness of membrane
- temperature
- distance
- number of channels
- are for water soluble substances /ions
- permeability depends upon size, extent of hydration and charge density of the ion
- specific channels for each ion
- activity of some channels are regulated by neurotransmitters or can be..
- “gated”
ION CHANNELS
