13.1 Flashcards
Organelle summary - DRAW (p. 283)
RER - synthesis and modification of secretory, membrane-bound and organelle proteins
SER - DETOX, glycogen breakdown in liver, steroid synthesis in gonads (“the detox was smooth”), lipid manufacture/metabolism
Golgi - modification and sorting of proteins, some synthesis - the PACKAGER, also adds sugars to proteins (GLYCOSYLATION)
Peroxisome - metabolize lipids and toxins with hydrogen peroxide; contains enzyme called CATALASE which converts h2o2 to H2O + O2
Lysosomes - contains acid hydrolase (“lysing”) for digestion
euchromatin
less dense than heterochromatin
nucleolus
the ribosome factory
NO membrane surrounding it
consists of DNA, RNA pol, rRNA, protein components of ribosome
site of transcription of rRNA by RNA pol I
protein ribosome is transported into the nucleus
nuclear localization sequence
larger proteins (>60 kDaltons) cannot freely enter the nucleus, they need a sequence of basic amino acids called a NLS - transported inside by specific transport mechanism
mitochondria
single circular DNA molecule -> encodes rRNA, tRNA, and several proteins of the ETC
all proteins start translation in the…? what is the signal sequence…?
ALL PROTEINS START translation in the cytoplasm
some proteins (secreted proteins, lysosomal proteins) have an amino acid sequence at their N-terminus called a SIGNAL SEQUENCE
the SS recognized by the signal recognition particle (SRP), which binds to the ribosome, forms a ribosome-SRP complex
ER has SRP receptors, the peptide is “pushed” into the ER lumen
after translation, the signal peptide is removed from the polypeptide by SIGNAL PEPTIDASE
for secreted proteins, the signal sequence is REMOVED
two sites of protein synthesis
- free ribosomes in cytoplasm
- ribosomes bound to rough ER
free ribosomes -> head to peroxisome, mitochondria, nucleus, or cytoplasm
rough ER -> secreted to extracellular environment, or plasma membrane, or membrane or interior of ER, GA, Lysosome (traffic’ed through VESICLES) => interior of ER, Golgi, lysosome, and extracellular environments are in a sense CONTIGUOUS
integral membrane proteins have… TD
have hydrophobic amino acid residues called transmembrane domains – these DOMAINS are essentially signal sequences found in the interior of protein (NOT AT N-TERMINUS)
TDs are NOT REMOVED
TDs are threaded through the ER membrane during translation
portion of protein in the ER lumen faces the EXTERIOR
ER additional functions
- post-translational modification of proteins (sometimes glycosylates)
- disulfide bond formation occurs in ER lumen
default target for proteins of secretory path
PLASMA MEMBRANE
targeting signals are needed if a protein ends up elsewhere (GA, ER, lysosomes)
disulfide bonds occur in…
oxidative conditions
Golgi, ER, and extracellular are OXIDATIVE
a protein produced in secretory pathway that needs to be sent to an organelle outside of the S-pathway needs…
…localization signals
Cellular Protein Traffic - DRAW (p. 290)
p. 290
GA - 3 purposes
- modification of proteins made in RER (especially oligosaccharide chains)
- Sorting and sending proteins (MAIL FACILITY)
- synthesis of macromolecules to be secreted
acid hydrolase
they only function in acidic environments - safety mechanism
a phagocytic vesicle fuses with lysosome
cell wall of bacteria, plants, and fungi
- bacteria -> peptidoglycan
- plants -> celluose
- fungi -> chitin
colligative property
identity of particle is not important
- vapor-pressure depression
- boiling point elevation
- freezing-point depression - solute causes melting point to decrease
- osmotic pressure
vapor pressure
adding more solute decreases vapor pressure (salt water)
boiling - atmospheric pressure = vapor pressure
ion channels
involved in facilitated diffusion, down a EC gradient
pores are found
- double nuclear membrane
- outer mitochondrial membrane
- Gram-(-) bacterial outer membrane
Na/K ATPase
the driving force behind secondary active transport
- maintains osmotic balance between interior/exterior
- establish resting potential
- provide sodium concentration gradient used to drive secondary active transport
secondary active transport
the transport process is not coupled directly to ATP hydrolysis; ATP is used to create a gradient, which is used to drive the transport of another molecule (coupling)
chloride and calcium are…
preferentially extracellular
clathrin
inside the cell involved in receptor-mediated endocytosis
ligand and 3 types of signal transduction
ligand = key (“ligkey”), usually a hormone or neurotransmitter
the response = signal-transduction
- ligated-gated ion channels - an ion channel opens when binding a neurotransmitter
- catalytic receptors - enzymatic active site on the cytoplasmic side; enzyme activity initiated by ligand binding at the extracellular surface
- G-protein linked receptor - uses a secondary messenger to communicate with enzymes in the cytoplasm (cAMP is important, which AMPLIFIES the signal)
G-protein epinephrine pathway (DRAW - p. 309)
…
cytoskeleton (3 components)
- microtubules - thickest (25 nm)
- intermediate filaments (10 nm)
- microfilaments - thinnest (7 nm)
made of noncovalently polymerized proteins
example of QUATERNARY structure
microtubule
hollow rod, alpha and beta-tubulin
ONLY 1 end can elongate
the other end is anchored to MICROTUBULE ORGANIZING CENTER (MTOC) – within MTOC is a pair of centrioles, which are organized into 9 microtubule triplets
aster - star-shaped, radiate out from the centrioles (Aster = MTOC). Fungi/plants do NOT have MTOC
polar fibers - connect chromosome to the aster
mitotic spindle - whole thing
Also: transport substances within the cell (railroad analogy) - driven by proteins that hydrolyze ATP and act as molecular motors
9+2 arrangement found in flagellum and cilia (9 pairs of MTs form a ring around two lone microtubules in the center). Prokaryotes have different structure.
what connects microtubules?
each microtubule is bound to its neighbor by contractile protein called DYNEIN causes the movement of filaments past one another
what attaches MTs to plasma membrane?
basal body (same structure as centriole)
microfilaments
rods formed in cytoplasm from polymerization of globular protein ACTIN, which form a chain and wrap each other to form ACTIN FILAMENT
PINCHES the parent cell
AMOEBOID movement
intermediate filaments
heterogenous, wide range of polypeptides
more permanent
provides strong cell structure
tight junctions and desmosomes
epithelial cells in the gut
the seal is completed by desmosomes
desmosome -> hold cells together at concise points, not bands, composed of fibers that span the plasma membranes of two cells (anchored to plasma membrane by a plaque formed by protein keratin) - found at mechanically-stressed locations (bladder, cardiac)
gap junctions
heart muscle cells
holes called gap junctions that allow ions to flow back and forth
apical and basolateral
apical - facing the intestinal lumen
basolateral - facing the tissues
gap junctions
pore-like connections between adjacent cells (cytoplasms can MIX ions, AAs, carbs, but not polypeptides or organelles)
allow membrane depolarization of action potential to pass from cell to cell
prophase
- nucleolus disappears
- spindle and kinetochore fibers appear
- centriole pairs move to opposite ends
- nuclear envelope converts into tiny vesicles
cleavage furrow
ring of actin filament that contracts
Benzene
a mutagen, as is UV
what kills a cell?
stressors include 1. nitric oxide, 2. toxin 3. cytokines
also, p53 -> apoptosis
caspases
a type of protease, carries out apoptosis
cysteine in active site
cleave target proteins at aspartic acid sites (cleave-asp)
grouped into initiators and effectors
initiators - respond to extra- or intracellular death signals by clustering together and activating each other
activation of initiators leads to activation of effector caspase to trigger APOPTOSIS (see illustration p. 318)
