Molecular Review (Zaidi) Flashcards
Gated, Transmembrane, and Vesicular Transport
Gated - between nucleus and cytosol (active transport and free diffusion)
Transmembrane - from cytosol across organelle membrane (protein translocators)
Vesicular - between various compartments via vesicles (membrane-enclosed transport)
Protein Sorting Signals
- on N or C terminus or within protein sequence
- signals both necessary and sufficient for protein targeting
- recognized by complimentary receptors
Nuclear Transport
- bidirectional, selective, gated
- sorting signals = nuclear localization sequence (lysine/arginine-rich)
Nuclear Import and Export
- Import - Ran-GDP dissociates from receptor; receptors binds with cargo, and passes through NPC
- Export - Ran-GTP binds to receptor; receptors bind cargo, pass through NPC, cargo and Ran-GDP dissociate
Outer Mitochondrial Membrane Translocators
- TOM complex
2. SAM complex
Inner Mitochondrial Membrane Translocators
- TIM22 complex
- TIM23 complex
- OXA
TOM Complex
- required for import of ALL nuclear encoded proteins
- inserts them in Outer Membrane
TIM 22 and 23
22 - mediates insertion of specific subclass of proteins
23 - transports soluble proteins into matrix and helps insert membrane proteins in inner membrane
SAM Complex
translocates and inserts/folds beta barrel proteins in OUTER membrane
OXA Complex
insertion of all proteins synthesized IN MITOCHONDRIA
- also some proteins already present in matrix brought from outside
Ribosomes to ER membrane
- SRP binds to signal sequence of growing peptide
- pauses translation and binds to SRP receptor
- protein translation continues into translocator
- SRP dissociates and recycles
Rab and SNARE in vesicle targeting
Rab proteins - direct vesicles to specific spots on target membrane
SNARE - mediate fusion of vesicle with membrane
MP6 and lysosomal hydrolases
- receptors in TGN recognize mannose-6-phosphate (attached to lysosomal hydrolases in CGN)
- packaged into clathrin-coated vesicles, which are delivered into endosomes and then to lysosomes
Pellets in Centrifugation
- low speed pellet = whole cells, nuclei, cytoskeletons
- medium speed pellet = mitochondria, lysosomes, peroxisomes
- high speed pellet = microsomes, small vesicles
- very high speed pellet = ribosomes, viruses, large macromolecules
Ion-Exchange, Gel-Filtration, and Affinity Chromotography
Ion - charged beads attract molecules of certain charge
Gel - small molecules trapped in porous beads
Affinity - beads with covalently attached substrate bind certain enzymes
3 Restriction Endonucleases (HaeIII, EcoRI, HindIII)
HaeIII - cuts between G and C
EcoRI - cuts between G and A
HindIII - cuts between A and A
Agarose Gel Electrophoresis
- different than SDS-PAGE (DNA is already CHARGED)
How can genes be cloned?
- by using bacteria
- insert clone segment into circular, DS plasmid vector
Homologous proteins are functionally what?
INTERCHANGEABLE
Ectoderm, Endoderm, Mesoderm
Ectoderm - precursor of nervous system and epidermis
Endoderm - precursor of gut, lung, liver
Mesoderm - precursor of muscles and CT
Gastrulation
transformation of blastula, a hollow sphere of cells, into a layered structure with a gut
What makes one organism different from another?
non-coding DNA sequences
- coding sequences in DNA similar in most organisms
Cell Fates (determined, completely undetermined, committed)
Determined - fated to develop into specialized cell type DESPITE changes in environment
Undetermined - cells that rapidly change due to alterations in environment
Committed - cells have some attributes of particular cell type but can change with environment
What are the most important environmental cues?
signals from neighboring cells
INDUCTIVE SIGNALING = induction of different developmental program in select cells in a homogonous group leading to altered character
morphogen
- long range inductive signal that imposes pattern on a field of cells
- exert graded effects by forming gradients of different concentrations (may direct target cells into different developmental pathway)
3 phases of neural development
Phase I - different cell types develop independently at widely separate locations
Phase II - axons/dendrites grow along routes, setting up provisional but orderly networks of connection
Phase III - connections adjusted and refined through interactions with distant regions
CNS and PNS development
CNS - from neural tube (brain, spinal cord, retina)
PNS - neural crest (nerves, sensory neurons)
Radial Glial Cells
what neurons travel on
- older neurons are closer to layers of cortical neurons (closer to origin)
Growth Cones
- behavior dictated by cytoskeletal machinery
- throw out filopodia and lamelopodia
- Rho/Rac (GTPases) control assembly/disassembly of actin filaments, controlling movement of growth cone
Growth Cone Migration
- travel towards targets along PREDICTABLE ROUTES
- sense extracellular matrix environment and chemotactic factors
Netrin, Slit, Semaphorin
Netrin - attractor
Slit/Semaphorin - repellants
Neurotrophic Factors
- axonal growth cone reaches target
- signals from target tissue regulate which growth cones synapse and where
- produce limited amount of specific neurotrophic factors needed for survival (those that do not get enough die)
Synaptic Remodeling rules that create spatial order
- axons from different regions compete for tectal neurons
2. axons from neighboring sites excited at the same time collaborate and strengthen synapses with tectal neurons
Characteristics of Stem Cells
- not terminally differentiated
- can divide without limit
- renew themselves
- slow division, ability to remain stem cell or become differentiated
Totipotency, Pluripotency, Multipotency
Totipotency - cell gives rise to all cells of organism (Zygote)
Pluripotency - cell gives rise to all cells of embryo and adult tissues (embryonic stem cell)
Multipotency - cell gives rise to different cells types of given lineage (adult stem cells)
Skin Layers (outer to inner)
- squame - flakes
- keratinized squames
- granular cell layer (waterproof barrier)
- prickle cell layer
- basal cell layer (only dividing cells in epidermis)
- basal lamina
Renewal of Epidermis
- self-renewing process
- stem cells provide indefinite supply of fresh differentiated cells
- basal layer has stem cells
Somatic Nuclear Transfer (SCeNT)
- nucleus taken from somatic cell of patient and injected into oocyte of donor replacing the oocyte nucleus
- blastocyst generated from this hybrid oocyte and ES cells isolated
