Caspaces
Proteolytic enzymes that mediate process
Already there but in safe form --> procaspaces
- no activity = safe form
Once activated
- activated more = initiator
- cascade of proteolysis = executioner
Singlas that induce process:
extracellular = extrinsic
- F
Signal that Aptosis is occurring
Fragmented DNA --> cut linker DNA between nucleosome
Phosphatidylserine (pt-SER) - on outer membrane
- "eat me" signal
- Inhibits inflammation - inducing signal in phagocyte
Lose Vm across inner mt membrane
Cytochrome C in cytosol
Extracellular survival factors (impacting cells to stay alive)
Binding suppresses apoptotic pathways
Most cells need continuous input, or aptosis occurs
Cells occurring only where needed (neurons)
Regulator Proteins (extracellular)
Mitogenes
- simulate mitosis
- overcome brakes
- most stimulate G1 and G1S-cdk's
- abnormally high activity --> cell cycle arrests
Growth factors
- stimulate cell growth
- promote protein synthesis
- activation often depends on signal from other cells
- s
Other regulatory factors (EC signaling)
Cell density
- too high limits access to mitogens or growth factors
Substrate requirements
- extracellular matrix proteins
- Bind to actin cytoskeleton
- Activate cell cycle protein
Inhibitor of growth and survival
- regulate cell / organize
- stimulate a
Cell Attachment Functions
Maintain cohesion of metazoans
Provide structure support
Facilitate communication
Allow for migration
Functional Classes of Junctions
Anchoring: tether; strength [200]
Cell-Cell
- adherens (AF) or desmosomes (IF)
Cell-Matrix
- adhesions (AF) or hemidesmosome (IF)
Occluding: seal gaps between cells
- tight junctions in vertebrae; separate junctions in vertebrae
Channel forming: connect c
Cell-Cell attachments mediated by cadherins
Ca 2+ dependent
-Extends dimer
- Allows for hemophilic binding (2 things have to match)
Tissue specific
In all animals, almost all cells
Critical role in development
- organize similar cells (when no Ca2+...)
- expression changes during development
Adheri
Cell-Cell attachments mediated by Cadherins - desmosomes
Cadherins linked to cytoskeletal IFs
Hold cells together
Mechanical Cells together
Examples
- epithelial cells = keratin
- heart muscle cells = desmin
Cell-Cell attachments not mediated by cadherins
immunoglobulin super family proteins (e.g. N-CAM)
- Ca2+ independant
- weaker than cadherins
- homo and heterophilic binding
Selectins: in blood; Ca2+ dependent
- has lectin domain = binds to carbs (GLs, PGs, GPs = glycocalyx)
Add integrins = superhold
-
Anchoring Junctions - Cell to Matrix
Focal adhesions
- Link extracellular matrix proteins to cytoskeletal actin filaments
- Bind cells to extracellular matrix
- Integrin family
Hemidesmosomes
- Link ECM protein to cytoskeleton intermediate filaments
- Attach epithelial cells to basal lamina
Occluding Junction - Functions
Barrier to interstitial fluid flow: compartmentalize - relatively impermeable
- requires transcellular transport
Limits diffusion of membrane components
Occluding Junction - Structure
Zipper Like
Membrane protein binding
Principle ones
- claudins: many types, variable permeability
- Occludins: much bigger and more likely + uncertain role
Channel Forming Junctions - Functions
Cystolic connection
- Limited by size
- ions and small molecules
Electrical and chemical coupling
- synchronize responses
Channel Forming Junctions - Structure
Channel composed by connexins
- 6 connexins = connexon (1/2 is gap/channel)
- 2 connexon's = channel/gap
Channel Forming Junctions - Permeability
Can vary - gated
Decreases when pH decreases
Decreases when cytosolic Ca2+ increases - leakage
Signal Relaying Junctions
Synapse
Many cell adhesions acting together
Scaffold protein
- proteins on post synaptic membrane that receive neurotransmitters
- Organize communication complexes
- connects two cells together
- IG superfamily
-Neurotransmitter receptor
ECM - Secretion by cell
Porteins (fibers), staying in linear form
Polysaccharides (ground substance)
ECM - Function
Structural support
- physical structure
- orienting cells
Fill space
- form gels
- regulate molecular traffic
Chemical signaling
- bind growth factor
- cross-link membrane proteins
Regulated secreted proteins
- immobilize, store, insulate, activate
- ex.
Cofilin destabilizes actin filaments by decreasing the protofilament twisting.
False, increases
The mitochondria requires a large surface area of its inner membrane to carry out the maximum amount of glycolysis
False, carries out oxidative phosphorylation
Compared to aerobic conditions, the net gain of ATP per one glucose is lower underanaerobic conditions.
True
The treadmilling process occurs in actin and microtubule filaments allowing for movement across a cell.
False, only occurs in actin filaments
Microtubules are formed by homodimers that are energized by GTP.
False, they are formed by heterodimers
Actin related proteins can't bind in the middle of an actin filament.
False, they can
More ATPs are typically able to be generated by an NADHthan an FADH2.
True
Which is a protein that increases the growth of actin filaments?
Formin and Profilin
Which is a correct ordering of components from highest to lowest affinity for electrons?
Cytochrome Oxidase, Cytochrome C, oxidase
Cytochrome b-c1, ubiquinone, NADH
Which statements are correct about the contraction of intermediate filaments
Base Unit is a non polarized helical monomer
Staggered tetramers are combined to create structures like Keratin
Gelsolin
Accessory Protein for actin filaments that is activated by by high levels of cytosolic Ca2+ and cuts the filaments
Compared to kinesins, dyneins move faster and always move in the opposite direction.
False, only sometimes
An organelle moving from the endoplasmic reticulum to Golgi apparatus will attach to Kinesin
True
During interphase, the DNA is replicated but not condensed into chromosomes
True
No motor proteins can move in both directions along filament
True
Actin filament will be linked into parallel arrays by fimbrin
True
Apoptosis is a cell death mechanism that leads to the cell exploding
False, Imploding
After being activated by high levels of calcium, gelsolin severs actin filaments
True
What are correct properties that allow animal embryos to be a a good study systems for the cell cycle
growth phase is absent
It begins as a very large cell
What are the correct order for a normal cell cycle
M-G1-S-G2
G0-G1-S-G2-M
Which is a correct occurrence in anaphase
Chromosones break at the centromeres
Microtubules are involved in the movement of chromatids
Conditional mutation
DNA changes the impact the cell's normal activities but only under certain environmental / external conditions