Mitosis + Protein Traffacking+cell Communication Flashcards
1
Q
Components of interphase
A
- G1
- G2
- S
2
Q
When is DNA synthesized in mitosis
A
- S phase
3
Q
G1
A
Growth and going about its business.
4
Q
G2
A
- preparing materials to go through M phase
- eg making proteins, re checking
5
Q
Cultured human cells time spent in each phase.
A
11 hours in G1, 8 hours in S, 4 hours in G2, 1 hour in M.
6
Q
Budding yeast cells time spent in each phase
A
- all 4 phase in 90 mins
- same ish distribution of time spent in each phase, just accelerated
7
Q
Early embryonic cells
A
- divide without growing.
- so only M and S phase, no Gs
8
Q
G0
A
- when some adults cease dividing, but are still metabolically active
- so G0 is when it is NOT growing - just chillin doing its function.
9
Q
M phase components
A
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
10
Q
Prophase
A
Disassemble interphase MT array, form mitotic spindle
• Centrosomes move to opposite poles
• Chromatin condenses
• Nuclear envelope dissociates
11
Q
Prometaphase
A
Kinetochore MTs move pairs of sister chromatids back and forth until they reach
the metaphase plate
12
Q
Metaphase
A
All pairs of sister chromatids are lined up on metaphase plate; connection between
chromatids broken (centromere)
13
Q
Anaphase
A
Anaphase A: kinetochore MTs separate sister chromatids
• Anaphase B: polar MTs “push” and astral MTs “pull” poles
14
Q
Telophase
A
Undo what was done during prophase - nuclear envelope re-forms, chromosomes de-condense to chromatin etc.
15
Q
Cytokinesis
A
Cytoplasmic division using contractile ring of actin and myosin
16
Q
How to disassemble nuclear envelope
A
Phosphorylating lamin proteins
A and C free floating
B attached to vesicles.
17
Q
Kinetochores
A
- aggregation of different types of proteins attached to the centromere of a chromatid.
18
Q
Anaphase A
A
- Movement of sister chromatids to opposite poles via kinetochore microtubules.
19
Q
Anaphase B
A
- spindles distance themselves from each other, further separating sister chromatids. (So moving the poles), stretching boundary of the cell.
20
Q
What happens to a protein that is made on a cytostolic ribosome?
A
Remains in cytoskeleton
Imported into an organelle.
21
Q
Path of protein made on ReR ribosome (co-translational sorting)
A
- Ribosome
- RER
- Golgi
- secretory vesicle, lysosome or plasma membrane
22
Q
Active transport for transport through the nuclear pore complex
A
- uses GTP as energy stores
- form molecules more that 60kDa in width
23
Q
What keeps cytoplasmic proteins out of the nucleus
A
- rich in basic amino acids sequence called a nuclear localisation site.
- only the appropriate proteins have that right signal.
- exists as a bipartite signal -
24
Q
What keeps nuclear proteins out of the cytoplasm
A
- only the appropriate proteins have the right signal
- called a nuclear import signal
- rich in Lyceins, nessasary and sufficient to allow this or other proteins to leave the nucleus.
25
Nuclear protein import
- NLS recognized by importin
- both encounter a nuclear protein complex,
- conformational change happens when Ran GTP binds to the importin, making it let go of the NLS.
26
Nuclear export
- NES recognized by exportin, and binds to NES
- RanGTP also binds to this complex
- these 3 can go out of the nucleus
- GTP hydrolysed, s changes conformation of exportin, NES is let go, mission accomplished
27
Human mitochondrial genome
- 16.5K base pairs of DNA
- 13 protein coding genes
- 22 tRNA genes
- 2 rRNA genes - 2 subunits in mitochondrial ribosome
- ori
28
Where does
Transcription
Translation
Transport
Happen for most mitochondrial proteins on doses from by genes on the mitochondrial genome
- nucleus
- cytoplasm
- present signal, signal recognized, action taken
29
Mitochondrial protein import
- hsp70 chaperone (a type of chaperonin) binds to polypeptide - prevents folding
- transit sequence binds to TOM receptor (located on the N terminus)
- hsp70 molecules detach as polypeptide passes through membranes
- transit sequence cleaved by signal peptidase
- mitochondrial hsp70 molecules bind and release polypeptide as it enters matrix (driven by ATP hydrolysis)
- polypeptide folds aided by hsp60
30
Types of cell-cell communication
- direct intercellular signaling
- contact-depending signaling
- Autocrine signaling
- Paracrine signaling
- endocrine signaling
31
Direct intercellular
- signals pass through a cell junction from the cytoskeleton of one cell to adjacent cells
32
Contact dépendant
Membrane bound signals bind to receptors on adjacent cells
33
Autocrine signaling
- cells release signals that affect themselves and nearby target cells
34
Paracrine signaling
- cells release signals that affect nearby target cells
35
Endocrine signaling
- cells release signals that travel long distances to affect target cells
36
3 stages of a response to a signal
1. Receptor activation: Binding of a signaling molecule causes a conformational change in a receptor that activates its function
2. Signal transduction: the activated receptor stimulates a series of proteins that forms a signal transduction pathway
3. Cellular response: the signal transduction pathway affects the functions and or amounts of cellular proteins, thereby producing a cellular response
37
Kd and its indication on receptor-ligand interaction
- the higher the Kd, the lower the affinity
38
Kd
- the concentration at which 50% of the cell’s receptors for that ligand are bound
39
Above the Kd is likely to lead to what?
- greater cellular response than a lower Kd
40
Receptor-ligand interaction
- binding of a ligand to a receptor cause a change in conformation of the receptor, triggering an effect
41
Why are intracellular receptors localized to the cytoplasm
- because the ligand binding causes a change in conformation, thus allowing it to act as an NLS, thus allowing it to act as a transcription factor.
42
Extracellular binding domains
- Channel
- GPCR (G protein coupled receptor)
- Enzyme linked
43
Best way to get rid of the signaling molecule
- get it into the cell and let a lysosome degrade it.
44
Adenylyl cyclase
-makes cAMP by hydrolysis of ATP (producing a pyrophosphate)
- when a subunit bound to GTP binds to it.
45
GPCR, second messengers and epinephrine pathway
- binding of épi activates GPCR, causes G protein to bind to GTP, which triggers the dissociation of the a subunit from the b/y dîmer
- binding of a subunit ot adenylyl cyclase promotes synthesis of cAMP from ATP.
CAMP binds to the regulatory subunits of PKA which releases the catalytic subunits of PKA
- catalytic subunits of PKA use ATP to phosphorylate specific cellular proteins and thereby cause a cellular response.
46
Outcomes of the épi pathway
- activation of catalytic subunits of PKA means that GPK is phosphorylated, activating GPK. (Glycogen phosphorylation kinase)
- GPK phosphorylates GP (Glycogen phosphorylase)
- This activates GP
- glycogen is broken down into glucose 1 phosphate.
- glucose is then used in other metabolic pathways
47
Amplification
48
Cross talk
When one part of a signaling pathway produces/activates molecules that can activate/deactivate molecules that are involved in other adjacent pathways.
49
Why does apoptosis happen
- sculpting tissues
- maintenance of organ size and shape
- removal of damaged/infected/worn out cells.
50
2 paths of apoptosis
- extrinsic
- intrinsic (mitochondrial)
51
Extrinsic apoptosis
- signaling molecule, a trimer, binds to 3 death receptors, causing them to aggregate and exposing the death domain
- adaptor proteins and initiator procaspase bind to the death domain, forming a death inducing signaling complex (DISC) - intiator procaspase is bound to the death domain via an adaptor.
- initiator procaspase is cleaved, and a smaller active active inhibitor caspase is released
- initiator caspase cleaves the executioner procaspase, making it active
- the executioner caspase cleaves cellular proteins causing the cell to shrink
52
Intrinsic apoptosis
- cytochrome C leaks out of mitochondria (the pores are made by activating BAX proteins)
- cytochrome C then binds to APAF proteins - which forms a complex of 7 APAF proteins and exposes CARD domains, which allows initiator procaspase to bind (forms an apoptosome)
- This then allows for the initiator procaspase to be cleaved into initiator caspase, which then cleaves the executioner procaspase to activate executioner caspase.
- this then cleaves cellular proteins, resulting in apoptosis.
53
Non coding RNA molecules
- ncRNA
- any type of RNA other than mRNA
- if found within a protein, called ribonucleoprotein complex
- interact with a variety of other things in a cell.
54
Function of ncRNAs
- scaffolding - framework for formation of a complex
- guide - targeting specific nucleic acid sequences
- alteration of protein function or stability
- ribozyme
- blocker - prevent another molecule from binding
- decoy - prevent other ncRNA from functioning (trickster)
55
Telomerase ncRNA component
TERC - is a guide and template - guides it to a specific DNA sequences, and then uses its template molecule to extend the DNA sequence
56
SRPs (add more later)
- Rico-nucleoprotein complex involved in pushing synthesized polypeptide into RER
- scaffold and alteration of function (SRP protein and receptor to hydrolyse GTP to let go of ribosome)
57
Sense and antisense mRNA
- sense: mRNA synthesized from template DNA strand
- anti-sense: RNA synthesized from coding strand (anti-parallel to the sense mRNA.
Anti sense RNA is NOT mRNA.
Can make double stranded RNA with one mRNA (sense) and antisense RNA.
58
HOTAIR ncRNA
HOx transcript antisense intergenic RNA
2 different histone-modifying complexes bind to HOTAIR
- HOTAIR binds to a GA rich region next to a target gene
- histone modifying complexes covalently modify histones within the target gene - stopping expression of that gene.
- so acts as a scaffold and guide.
59
Fire and Mello Experiment method
- make sense and antisense mex-3 RNA in vitro using cloned genes for mex-3 with promoters on either side of the gene. RNA polymerase and nucleotides are added to synthesize the RNAs.
- inject either mex-3 antisense RNA or a mixture of mex-3 sense and antisense RNA into the gonads of the worm. This RNA is taken up by the effs and early embryos. In the control, do not inject any RNA.
- incubate and then subject early embryos to in situ hybridization. In this method, a labelled robe is added hat is complementary to mex-3 mRNA in the cells will bind to the probe and become labelled. After incubation with a labelled probe, the cells are washed to remove unbound probe.
- observe embryos under microscope
60
Fire and Mellow results
- control showed dark green
- the thing injected with mex-3 anti-sense RNA showed light green
- the thing injected with double stranded RNA (sense and antisense RNA) showed no color
- showed that double stranded RNA is more potent at inhibiting mex-3 mRNA than antisense RNA alone.
61
SiRNA
Small interfering RNA - come from outside of the cell.
62
MiRNA
- micro RNAs - regulatory purpose, made by the cell itself.
- acts as a guide and blocker
63
RNA interference
- either miRNA or siRNA will be recognized by the dicer
- will be cut up into segments that are about 20-25 bps long that is double stranded
- this is then recognised by a protein that associates with other proteins to form an RNA induced silencing complex (RISC) - one of these strands is degraded
- RISC recognizes specific cellular mRNAs due to complementary sequences.
- if a perfect match, mRNA is degraded
- if partially complimentary, mRNA is inhibited.
