Zaidi Flashcards
what is gated transport
between nucleus and cytosol through nuclear pore complexes (active transport and free diffusion)
what is transmembrane transport
membrane protein translators directly transport specific proteins from cytosol across an organelle membrane
what is vesicular transport
membrane enclosed transport intermediates move proteins between various compartments via vesicles
protein transfer/transport to various compartments guided by ______
sorting signals
describe sorting signals
stretch of amino acids, typically 15-60 residues long with localization on N or C terminus within protein sequence
multiple scattered sequences in protein may form ______
signal patch
what removes signal after protein reaches final destination?
signal peptidase
Signal sequences are both necessary and sufficient for what?
protein targeting
What are signal sequences recognized by?
complementary receptors
Describe nuclear transport
bidirectional, selective and gated
what are sorting signals called for nuclear?
nuclear localization sequence
nuclear localization sequences are rich in what amino acids?
lysine and arginine
what are nuclear pore complexes?
perforate nuclear envelope in eukaryotic cells which transports molecules in both directions, passive diffusion of small molecules and facilitated transport
transport of the nuclear pore complex is facilitated by the binding of particles to _____ extending from NPC
fibrils
what are nuclear localization signals (NLS)
sorting signals that direct molecules to nucleus, rich in lysine and arginine
look at nuclear import and export pictures
slide 9
the mitochondrial signal sequence is made up of _______ and _____ signal sequences
n terminal and internal
In the mitochondrial signal sequence specific receptor proteins recognize a configuration which is what?
positively charged residues cluster on one end and uncharged hydrophobic on the other end to form an amphiphilic alpha helix
review the translators in mitochondrial membrane slide
slide 12
Where is the tom complex located?
outer mitochondrial membrane
where is the Sam complex located
outer mitochondrial membrane
Where is the Tim22 and tim23 complexes located?
inner mitochondrial membrane
Where is the Oxa membrane complex located?
inner mitochondrial membrane
What does the TOM do?
import of all nuclear encoded proteins to insert them in the outer membrane
what does TIM 23 do?
transports soluble proteins into matrix and helps insert membrane proteins in inner membrane space
what does TIM 22 do?
mediates the insertion of a specific subclass of proteins
What are the two components of the tom and Tim complexes?
receptors for mitochondrial precursor proteins
translocation channels
What does the sam complex do?
translocates and inserts/folds beta barrel proteins in the outer membrane
What does the oxa complex do?
mediates insertion of all proteins synthesized in mitochondria. Also some proteins already present in matrix brought from outside
ER signal sequence guided to ER membrane by 2 components:
- signal recognition particle (SRP)
- SRP receptor
What is the SRP large hydrophobic pocket lined with?
methionine
review SRP role slide
slide 17
proteins and other biomolecules are transported via ______
transport vesicles
contents of vesicles are called
cargo
look at vesicular transport slides
slides 20-21
what do Rab proteins do?
direct vesicle to specific spots on target membrane
what do SNARE proteins do?
mediate fusion of vesicle with membrane
docking and fusion of vesicle slide
slide 23
what are the pathways in which materials are delivered to the lysosome
phagocytosis
endocytosis
autophagy
lysosomal hydrolyses have sorting signal _______ attached to them in the cis Golgi network
mannose-6-phosphate
the mannose 6 phosphate receptor in the trans golgi network recognize a sugar and then package them into _____
clathrin coated vesicles
where are clathrin coated contents delivered
endosomes then to lysosome
sorting of lysosomal protein slide
slide 28
describe sub cellular fractionation
tissue: mechanical blending
homogenate: suspension of different cell types
centrifugation to separate different cell types, based on size and density
lysis of cells: osmotic shock, ultrasonic vibration, mechanical blending, forcing through small orifice
ultracentrifugation: separates organelles
after low speed centrifugation, what is in the pellet?
whole cells
nuclei
cytoskeletons
after medium speed centrifugation, what is in the pellet?
mitochondria, lysosomes, peroxisomes
after high speed centrifugation, what is in the pellet?
microsomes, small vesicles
after very high speed centrifugation, what is in the pellet?
ribosomes, viruses, large macromolecules
describe ion exchange chromatography
positively charged bead attract negatively charged molecules, so positively charged molecules can travel freely
describe gel filtration chromatography
porous beads attract small molecules, and large molecules can get through
describe affinity chromatography
beads have covertly attached substate, so certain proteins bind while others can go through
where does HaeIII cut DNA
at G-C binding
Where does EcoRI cut DNA
at G-A binding
Where does HindIII cut DNA
at A-A binding
in agarose gel electrophoresis, DNA is already ____
charged
how is DNA ‘glued’ together?
ligase reaction (with help of ATP)
homologous proteins are functionally _______
interchangeable
what is a blastula? and what does it give rise to?
blastula consists of a sheet of epithelial cells facing the external medium, which gives rise to the ectoderm
what is the ectoderm?
precursors to nervous system and epidermis, gives rise to endoderm
what is the endoderm
precursor of gut, lung and liver
gives rise to mesoderm
what is the mesoderm
precursor of muscles and connective tissue
where are the instructions for producing a multicellular animal?
non-coding regulatory DNA
Cells make developmental decisions long before they show signs of ______
differentiation
what are determined cells
Cells that are fated to develop into a specialized cell type despite changes in the environment
What are completely undetermined cells
cells that can change rapidly due to alterations in the environment
What are committed cells
cells that have some attributes of a particular cell type but can change with environment
most important environmental cues are from where?
signals from neighboring cells
describe a short range signal
cell-cell contacts
describe a long range signal
substances that can diffuse through the extracellular medium
What is a morphogen
long range inductive signal that imposes a pattern on a filed fo cells, forms gradients of different concentrations
What is the morphogen gradient formed by?
localized production of an inducer that diffuses away from its source
localized production of an inhibitor that diffuse away from its source and block the action of a uniformly distributed inducer
describe phase 1 of neural development
different cell types develop independently at widely separate locations in embryo according to local program and are unconnected
describe phase 2 of neural development
axons and dendrites grow out along specific routes setting up a provisional but orderly network of connections between various parts of the system
describe phase 3 of neural development
continues into adult life, connections are adjusted and refined through interactions with distant regions via electric signals
neurons are produced in association with ______ cells
glial
CNS is derived from what?
neural tube
PNS is derived from what?
neural crest
tip of axon/dendrite has irregular, spiky enlargement called the ______
growth cone
what is growth cone behavior dictated by?
its cytoskeletal machinery
monomeric GTPases ____ and ____ control the assembly and disable of actin filaments, which control _____ of growth cone
Rho and Rac, movement
growth cones travel toward target cells along predictable routes by exploiting two major cues to find their way. What are these?
extracellular matrix environment: sensed by receptors present on membrane
chemotactic factors: related by neighboring cells, attractive or repulsive
what are chemotactic factors?
guidance factors at strategic points along path and are attractive or repulsive
What are examples of chemotactic factors?
netrin
slit
semaphorin
look at mechanism of commissural neuron guidance
slide 64
once axonal growth cone reach eventual target cells what does it do?
halt, communicate and make synapses with target cells
signal form target tissue regulate which growth cone synapses and where
synaptic remodeling is dependent upon 2 rules that create spatial order. What are these?
- axons from cells in different regions of retina compete for tectal neurons
- axons from neighboring sites which are excited at same time cooperate/collaborate to retain and strengthen synapses with tectal neurons
What does activity dependent synaptic remodeling depend on?
electrical activity and synaptic signaling
What are the characteristics of stem cells?
not terminally differentiated can divide without limit ability to renew themselves when divide each new cell has ability to remain a stem cell or become differentiated into a different cell type undergo slow division
totipotency
ability of a cell to give rise to all cells of an organism, including embryonic and extra embryonic tissues (zygote)
pluripotency
ability of cel to give rise to all cells of the embryo and subsequently adult tissues (embryonic stem cells)
multi potency
ability of a cell to give rise to different cell types of a given lineage (adult stem cells)
asymmetric division
creates 2 cells, one with stem cell characteristics and another with ability to differentiate
independent choice
division makes 2 identical cells but he outcome is stochastic and/or influenced by environment
describe epidermis
forms outer covering of skin
creates water barrier
made of epithelial cells
continuously repaired and renewed
describe dermis
second layer, rich in collagen, provides toughness
describe hypodermis
fatty subcutaneous layer
what is the only dividing cells in the epidermis
basal cell layer
look at epidermis layer picture
slide 77
renewal of epidermis slide
slide 78-79
describe the olfactory neuron
bipolar neurons with a dendrite facing extracellular environment and an axon that travels along the olfactory nerve. Hair like cilia protrude from dendrite.
describe the odorant receptors of the olfactory neurons
on the free surfaces of cilia, and are a type of G protein coupled receptors
describe the process of what happens when an olfactory receptors is activated
activates intracellular G protein (Golf)
activates adenylate cyclase which produces cyclic AMP
opening of ion channels in plasma membrane which results in influx of sodium and calcium
influx of positive ions cause neuron depolarization, generating action potential
individual olfactory neurons survive only for _____
a month
what do embryonic stem cells develop into?
different cell types with characteristics appropriate for that site
look at derivation of ES cell slide
slide 91
what is a different source of human embryonic stem cells?
somatic cell nuclear transfer (SCeNT)
strategies to induce ES cell like properties in adult somatic cells
induced pluripotent stem (iPS) cells
describe SCeNT
nucleus taken from somatic cell of patient and injected into oocyte of a donor, replaces oocyte nucleus. Blastocyst generated form hybrid oocyte and ES cells isolated
descrive iPS cells
somatic cells can be reprogramed to form iPSC by exposing them to defined, limited sets of transcription factors (genes for stem-ness)
