Membrane Structure, Lipids and Function Flashcards
Two essential fatty acids
Linoleic acid and linolenic acid
Phospholipids are derivatives of
Phosphatidic acid
RDS
Respiratory distress syndrome is associated with insufficient lung surfactant leading to partial lung collapse
Lysosomal Storage Disease
Mostly autosomal recessive
Inborn error of metabolism which results in an enzyme absence or deficiency
Leads to innaproprite storage in the cells
Sphingosine is derived from
Serine
Palmitate (fatty acid)
Sphingophosholipids
Made up of a sphingosine back bone
Sphingomyelin
Abundant in nerve tissue
Has a phosphocholine attached to sphingosine back bone
Sphingolipids are a derivative of
ceramide
Cerebroside
Ceramide + 1 glucose or galactose
Found primarily in the myelin sheath
Gaucher disease
AR
Defects in glucocerebrosidase which breaks down glucocerebrosides
Results in hepatosplenomegaly
Globosides
Ceramide + > 1 sugar
Sugar is often galalctose, glucose, or N-acetyl galactosamine
Gangliosides
Globoside + acidic sugar
They also have a glucose or galalctose attachment
Found in myelin sheath
Tay Sachs disaease
AR
Defect in hexosaminidase A
Enzyme breaks down GM2 gangliosides
Diagnosed at 3-6 months
Development slows
Muscles weaken
Loss of motor skills
Cherry red spot (on eye exam)
Neimann-pick disease
AR
Deficiency in sphingomyelinase
Accumulation of sphingomyelin in lysosomes causes hepatosplenomegaly and neurological damage
Cherry red spot in eye is present
Sulfatides
Galactocebrosides + sulfuric acid
Major component of myelin
Integral proteins
Firmly embedded in the membrane
Stabilized through hydrophobic interactions
6 types of integral proteins
Transmembrane proteins
A type of integral protein which can interact with both external and internal envt
Peripheral proteins
loosely bound to the membrane surface through electrostatic interactions with other proteins or lipids
Removed through pH change or ionic concentration change
Lipid anchored proteins
Covalent interaction with lipid molecules
Functions of proteins on membrane
Recpetors
Channels, gates, pumps
Enzymes
ATP synthesis
Carbohydrates and the cell membrane
Covalently attached to membrane
Form glycocalyx which serves in protection, adhesion and identification (diseased/foreign cells vs healthy cells)
Membrane is selectively permeable to:
and impermeable to:
Small polar solutes and
non polar molecules
Large polar molecules and ions
Factors affecting membrane fluidity
Temperature
Cholesterol
Saturation
Temperatures affect on membrane fluidity
Temp»_space;» Tm (membranes transition temperature) - too fluid
Temp > Tm - optimal
Temp < Tm - too rigid
Lipid composition on membrane fluidity
Saturated - decreases fluidity
Unsaturated - increases fluiditiy
Cholesterol on membrane fluidity
Cholesterol in a fluid membrane - less fluidity
Cholesterol in a rigid membrane - more fluidity
Lateral diffusion
Fast
Not catalyzed
Transverse diffusion
Flipping form one side of the mebrane to the other
With out enzymes - very slow
With enzymes - fast
Enzymes that help with transverse diffusion
Floppase
Flippase
Scarmblase
Use ATP hydrolysis
Flippase
Outer to cytosolic
Floppase
Cytosolic to outer
Scramblase
Move in either direction toward equilibrium
Amphitropic
Having an affinity for both lipid and aqueous environments
Rate of passive transport depends on
Temperature Concentration Mass Thickness Solubility Density Surface area
Molecules that are transported via passive diffusion
N2 O2 CO2 lipids hormones
Facilliated diffusion 2 types
Channel mediated
Carrier mediated
Types of channel mediated diffusion
Leakage channels - periodically open
Gated channels - open in response to stimuli
3 types of gated channels
Ligand gated
Voltage gated
Mechanical gated
2 types of ligand gated channels
Ionotropic - ligand binds, channel opens
Metabotropic - G-coupled receptor bound which causes another channel to open
Carrier mediated transport
Transmembrane proteins bind to a specific substance causing a conformational change that allows for substance to be carried through
GLUT 4, aquaporins
Tonicity
Concentration of a solution
Physiological tonicity
0.9% saline
Cystinuria
The result of mutations in channels that reabsorb basic AAs
COLA Cysteine Ornithine Lysine Arginine
High levels of cysteine in urine, crystallization, stone formation
Antiport vs symport
Antiport- primary active transport, rely on ATP, pumped in opposite direction, Na+/K+ pumps
Symport- secondary active transport, use energy stored in chemical gradients, pumped in the same direction
Antiport pump types
V-type pumps
F-type pumps
P-type pumps
ATP binding cassette (ABC) pump
ATP binding cassette (ABC) pump
Transport outside of the cell (effluxors)
Substrate binds > conformational change > ATP binds > channel opens
ATP binding cassette (ABC) pump example
CFTR channels mediate active transport of Cl– ions from inside cells to outside in the airway, Na+ and H2O usually follow
Cystic fibrosis is a genetic disorder resulting in mutations to CFTR which don’t allow the transport of Cl- and therefore Na+ and H20 which leads to a build up of thick mucous (w/o water) outside of the cells
Multi Drug Resistance (MDR) in chemotherapy - pumps out medication too quickly
P-type pumps
Transport cations, autophosphorylation using ATP
F-type pumps
Transports H+
Catalyze ATP formation
ex: ETC
V-type pumps
Transport H+ to acidify compartments such as intracellular organelles or across the plasma membrane
Osteoclasts use V-pumps to absorb bone mineral. Defects in the pumps result in osteopetrosis
Renal tubules rely on V-pumps to secrete protons into the urine. Renal tubular acidosis results from a failure of these pumps, resulting in proton accumulation in the blood
Symport pumps
Potential energy stored in H+ or Na+ concentration gradient drives transport of a separate substances against their own concentration gradient
Ex of symport pumps
Absorption of glucose (Glc) and amino acids in renal tubule rely on Na+ concentration gradients
3 types of endocytosis
Phagocytosis - solid phase uptake (eating)
PInocytosis - liquid phase uptake (drinking)
Receptor mediated endocytosis - ligand binds to cell surface receptor which allows entry to cell (seen with viruses)
Transcytosis
Combination of endocytosis and exocytosis to move substances from one side of a cell, across it, and out the other side
(insulin transport across cell)
What allows the fusing of two membranes in vessicle formation
Fusogen
2 broad classes of viral fusogens
pH independent fusion proteins - function at neutral conditions
Acid-dependent fusion proteins
Syncytium
multinucleate cell which can result from multiple cells fusing together
Ex: sperm with oocyte fusion
Transport of vesicles between compartments involves _______
Budding and fusion
Premiscous/permissive carriers
ABC transporters
-MDRs
