Terms Flashcards
erythrocytes
red blood cells
simplest type of blood cell
holds hemoglobin which transports O2 and CO2
lymphocytes
white blood cells
electron microscopy
uses electrons as source of illuminating radiation
wavelength of electrons goes down as velocity goes up
electrophoresis
SDS-polyacrylamide gel electrophoresis
gel is stained with dye that reacts w/ proteins
each band represents a protein w/ a different molecular weight
- higher MW = slower
- lower MW = faster
differential centrifugation
separated by size/density used when purity not important low speed centrifuge - nuclei/whole cells/cytoskeleton at bottom mid speed centrifuge - mitochondria/lysosomes/perioxisomes high speed - microsomes and small vesicles
gradient centrifugation-
slow heavy dense stuff at bottom. poke hole in bottom and collect
B cells
in bone marrow
produce antibodies
humoral immune response
T cells
thymus
cell immunity
antigens
invaders – recognized BY antibodies
antibodies
recognize antigens
epitopes
site where antibodies bind to antigens
many on a single molecule
complementarity
ability of molecules to combine w/ one another
like a lock and key
Immunoglobins (ig)
among most abundant protein components in blood
recognize foreign molecules and initiate events leading to their destruction
fluorescence microscopy
fluorescently label antibodies to detect binding and localizations of these antibodies w/ antigens
antibody - antigen bonding
NONCOVALENT
ionic, hydrogen, van der waals
association constant can range from 10^4 - 10^6 L/mol
extreme specificity
- complementarity. only works with each other
multivalence
- multiple sites for bonding
- (Ig has 2)
- leads to increase in binding strength (avidity)
- allows formation of lattices = precipitate in solution
papain
cuts Ig in 2, creates monovalent fragments w/ ONE binding site
Fab vs Fc fragments
membrane function
- forms boundaries to separate environments from one another
- helps maintain differences in compartments by selectivley allowing things to enter/exit
- receives signals from environment and transduces them to inside
- plays a major role in establishing cell migration and association
- hydrophobic interior is exclusive site for some reactions
- gives identity to cell
Fluid Mosaic Model
lipid bilayer w/ proteins sticking out
proteins floating like icebergs in sea of lipids
membrane fluidity
- diffusion of protein only within the plane of the membrane
- fatty tails can flex, rotate or move laterally BUT CANNOT FLIP FLOP
- fluidity depends on temp, composition (shorter tails = more fluid)
integral membrane proteins
proteins that require detergent to release them from the membrane
either SPAN the membrane or are HYDROPHOBICALLY embedded in a portion of the membrane
- transmembrane proteins extended across membrane as alpha helix of 20-30 AAs
- or extend across membrane as rolled up beta sheet. each strand in barrel = 10 AAs
peripheral membrane protesn
attached to the membrane by noncovalent interactions with other proteins
can be removed from the membrane by treatment w/ high or low ionic strength OR extreme pH
synthetic bilayers
can form lipid bilayer by dropping phospholipids into water
energetically favorable
asymmetry of membranes
membranes are composed equally of proteins and lipids (30-50% each) and 1-10% carbohydrates
electron spin resonance (ESR)
introduce nitroxide radical into head group of lipid
contains an unpaired electron which emits a paramagnetic signal that can be detected by ESR
use this to determine whether lipid is on inside or outside of bilayer
lipid vs diffusion coefficient
LIPIDS ARE FASTER THAN PROTEINS
FRAP
fluorescence revory after photobleaching
tight junctions
help confine membrane proteins to apical or basal side of cell (often in epithelial)
black membrane
artificial lipid bilayer usually in water
semipermeable
ion channels
formed by integral membrane proteins
selectivity for certain ions
Bacterial K+ channel
K+ must lose its bound water molecules to enter the filter and interact w/ carbonyl groups lining the filter that are rigidly spaced at the exact distance to interact with K+
Na+ is smaller and these carbonyl groups won’t interact with it
patch clamp method
current through individual channels can be measured
detach patch of membrane with a micropipette
electronic device called the clamp maintains the membrane potential at a set value while recording the ionic current through individual channels
ionophores
tools cell biologists use to increase the permeability of membranes to specific ions
mobile ion carriers
carry an ion across the lipid bilyaer
channel forming ionophores
forms a channel in which other ions can get across lipid bilayer
passive transport
molecules flow in energetically favorable fashion down energy gradient
active transport
goes against concentration gradient and thus requires energy
- energy can be ATP driven, light driven, or a coupled carrier
primary active transport
dependent on direct hydrolysis of ATP
ATPases directly couple ATP hydrolysis to ion transport
P-type transport proteins
Na+ K+ ATPase is an example of this
maintains difference in sodium and potassium in cells
secondary active transport
energy stored in ion gradients can drive transport system
ex: Na+ - glucose transport
goes back and forth switching b/t Na+ gradient and glucose gradient. each facilitating the transfer of the other
uniport
just one molecule goes through carrier mediated transport
symport
transported molecule + co-transported ion
antiport
transported molecule + other molecule coming in from other side
hypothesis for evolutionary origin of nucleus
ancient procaryotic cell took up membrane which surrounded DNA. also took up ribosomes – formed ER
origin of mitochondria and plastids
pre-eukaryotic cell engulfed an prokaryotic cell which gained membranes and became mitochondria – have their own set of DNA
cytosol + nucleus + intermitochondrial matrices
REDUCING AGENTS
rest of cell + lumen
OXYDIZING ENVIRONMENT
microsome
lumen = inside = oxidizing environment
signal sequence
at amino-terminus of protein (side with N)
Signal Recognition Particle (SRP)
extracted from ER with salt
composed of 6 protein subunits and 1 RNA molecule
recognizes signal
arrests translation
binds to the signal and the ribosome and stops translation
SRP receptor is integral membrane protein
translocator
sec61 complex consists of 3-4 protein complexes, each composed of transmembrane proteins that can assemble into a donut like structure
transmembrane proteins
contain stop-transfer signals that anchor that portion of the protein in the membrane
can have signal sequences that are located a distance away from the amino terminus
can have several stop-start sequences
signals
ER: simple H2N —— COOH. signal at H2N side
Mitochondria: an amino-terminal amphipahtic alpha helix with positively charged residues on one face and hydrophobic residues on the other face
Peroxisomes: signal is at the carboxyl-terminus of protein - SKL
Nucleus: all contain 4-8 positively charged AAs. example = PPKKKRKV - can be anywhere in protein. not cleaved off after transport
chaperones
family of proteins that bind to protein in unfolded or denatured state
recognize hydrophobic patches on the protein
help proteins stay in unfolded state to promote correct folding of proteins that will remain in cytosol
need ATP hyrdolysis to relase chaperone from protein – can be bypassed with urea or denaturing agent that artificially unfolds protein
Hsp 70
family of molecular chaperones some of which are found in cytosol
gated transport
found in regulating traffic b/t nucleus and cytosol