Exam 2 Flashcards
What is Tay Sach’s Disease?
Ganglioside accumulation inbrain caused by loss of hexosaminidase A resulting in impaired functions
What is hexosaminidase A?
Lysosomal enzyme that degrades gangliosides
What is cystic fibrosis?
Defective chloride ion transport due to loss of CFTR resulting in thick mucus in the lungs
What is I-cell disease?
Lysosome doesn’t receive lysosomal enzymes and they become engorged because a phosphotransferase enzyme that adds mannose-6-phosphate is defective
What are the 3 lysosomal storage diseases?
Type II glycogenosis
Hurler syndrome, Hunter syndrome
Tay-sachs disease
What is Type II glycogenosis?
accumulation of excessive glycogen
What is Hurler, Hunter syndrome?
accumulation of glycosaminogylcans
What are the 5 function of membranes?
- Define boundaries
- Site of biological function
- Regulate movement of substances
- Detect external signals
- Mechanisms for cell-to-cell communication
What comprises the “fluid” part of the fluid mosaic model?
Membrane lipids
What are the 3 main classes of membrane lipids?
Phospholipids
Glycolipids
Sterols
What are phospholipids?
- most abundant
- include phosphoglycerides and sphingolipids
What are glycolipids?
- formed by adding carb and lipids
- include cerebrosides and gangliosides, glycosphingolipids, and glycoglycerolipids
What are cerebrosides?
Neutral glycolipids
What are gangliosides?
oligosaccharide head with one or more negatively charged sialic acid residue
What types of lipids are prominent in brain and nerve cells?
Glycolipids (cerebrosides and gangliosides)
What are sterols?
-include cholesterol, phytosterols, ergosterol
What sterol is used in animal cell membranes?
Cholesterol
What type of sterol is used in plant cell membranes?
phytosterols
What type of sterol is used in fungal cell membranes?
ergosterol
What are the 2 common saturated fatty acids?
Palmitate (16)
Stearate (18)
What are the 2 common unsaturated fatty acids?
Oleate (1 double bond)
Linoleate (2 double bonds)
Polyunsaturated fatty acids
Have more than one double bond
What type of unsaturated fat occurs naturally?
Cis unsaturated fat
What is the FRAP technique?
laser uses fluorescent signal and watch live cells to see if they move to replenish the area damaged by the laser
What are lipid rafts?
Localized regions of membrane lipids in association with specific proteins, dynamic structures
How do lipid rafts form?
Actin-binding proteins present suggesting cytoskeleton may play a role in their formation
Depleting cholesterol from a membrane or disrupting the actin cytoskeleton can interfere with
targeting of proteins to rafts
What are the functions of lipid rafts?
- Transport nutrients and ions across membranes
- Bind immune cells to microbial targets
- Transport cholera toxin to intestinal cells
What is the “mosaic” part of the fluid-mosaic model?
membrane proteins
What are the 3 types of membrane proteins?
integral
peripheral
lipid anchored
What are integral membrane proteins?
embedded in lipid bilayer because of their hydrophobic regions
What are peripheral proteins?
hydrophilic located on surface of the bilayer
What are lipid-anchored proteins
hydrophilic and attached to the bilayer by covalent attachments to lipid molecules embedded in the bilayer
What is an integral monotropic protein?
integral membrane protein embedded in just one side of the bilayer
What is a singlepass protein and an example?
Transmembrane protein (spans both sides) that cross once ex. glycophorin
What is a multipass protein and an example?
Transmembrane protein that cross several times
ex. bacteriorhodopsin
What is glycosylation?
Addition of acarbohydrate side chain to a protein
Glycosylation begins in ___ and finishes in ____
ER
Golgi compartments
N-linked Glycosylation
addition of a carb to the nitrogen atom of an amino group
O-linked Glycosylation
addition of a carb to the oxygen atom of a hydroxyl group
What are the most common sugars attached to proteins?
Galactose
Mannose
N-acetylglucosamine (GlcNAc)
Sialic acid
Describe SDS PAGE Technique
Add SDS to protein to give it net negative charge and disrupt secondary structure of protein. Introduce electric current, proteins migrate in same direction. Negatively charged atoms move down gradient.
During SDS PAGE, charged proteins run
Cathode to anode
- to +
After SDS PAGE
transfer proteins from gel to membrane, introduce antibody, wash, introduce secondary blot, expose thin film
We use SDS PAGE and antibodies in a technique called
Western blot
Advantage of western blot
Shows us actual size
Describe polyclonal antibodies
mixture of antibodies, produced by clonally related B cells
nonrenewable
Describe monoclonal antibodies
Single antibody against single antigen
Grown from cultured cells
What three mechanisms are involved in moving solutes across membranes?
- simple diffusion
- facilitated diffusion
- active transport
Facilitated diffusion utilizes what types of channels to allow specific solutes to cross the membrane directly?
ion channels
porins
aquaporins
What are ion channels?
tiny pores lined with hydrophilic atoms
most allow passage of just oneion
What are the functions of ion channels?
- muscle contraction
- electrical signaling of nerve cells
- maintain salt balance in cells and airways
What ion channel maintains proper chloride concentration in cells
Cystic fibrosis transmembrane conductance regulator (CFTR)
What are porins
pores formed by multipass transmembrane proteins that allow rapid passage of various solutes
What is the structure of porins
The beta barrel has water-filled pore at its center. Polar side chains line inside of pore (tell hydrophilic solutes to pass). Outside of barrel contains nonpolar side chains interact with hydrophobic interior of membrane.
What are aquaporins?
Transmembrane channels that allow rapid passage of water
What is structure of aquaporins?
tetrameric integral membrane proteins. Central channels are lined with hydrophilic side chains
What is the E1 conformation of the Na+/K+ pump
open to inside of the cell and has high affinity for Na+ ions
What is the E2 conformation of the Na+/K+ pump
open to outside of the cell and has high affinity for K+ ions
Describe the mechanism of the Na+/K+ pump?
- 3 Na+ binds to E1 conformation
- Triggers phosphorylation of the alpha subunit by ATP
- Pump shifts to E2, causes release of Na+ ions outside the cell
- K+ ions bind to alpha subunit outside
- Dephosphorylation of alpha subunit occurs, E1 conformation restored
- K+ ions carried to inside of the cell and released
Name the 4 components of the endomembrane system
- ER
- Golgi Complex
- Endosomes
- Lysosomes
Function of the ER
synthesize proteins and lipids
Rough ER
- Form large flattened sheets
Functions of Rough ER
- synthesize proteins
- add carbs to glycoproteins
- fold polypeptides
- recognize remove misfolded proteins
- Assemble multimeric proteins
Smooth ER functions
- drug detox
- carb metabolism
- calcium storage
- steroid biosynthesis
- biosynthesis of membranes
What is an example of carb metabolism function of Smooth ER
glycogen breakdown (via phosphorolysis) in liver to provide energy source during fasting or exercise, producing glucose 6 phosphate
What is the CGN?
cis-Golgi Network
oriented toward ER
What is the TGN?
trans-Gogli Network
oriented away from ER
Describe the stationary cisternae model
cisterna is a stable structure
transport between cisterna mediated by shuttle vesicles
bud off from one cisterna and fuse with the next via cis-to-trans sequence
Describe the cisternal maturation model
Golgi cisternae are transient compartments
gradually change from CGN to TGN
Enzymes not needed later are returned (recycled)
What are the roles of ER and Golgi complex in protein trafficking?
- sorting proteins
- retention and retrieval tags
- fusion protein experiments
- protein sorting in TGN
What is the RXR tag
NMDA receptor has it
causes NMDA to be retained in ER till complex completely assembles
Retention tag
what is a retrieval tag
KDEL or KKXX
receptor ligand complex is packaged into a transport vesicle for return to the ER
