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MCB 150 > Mitosis + Protein Traffacking+cell Communication > Flashcards

Mitosis + Protein Traffacking+cell Communication Flashcards

1
Q

Components of interphase

A
  • G1
  • G2
  • S
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2
Q

When is DNA synthesized in mitosis

A
  • S phase
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3
Q

G1

A

Growth and going about its business.

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4
Q

G2

A
  • preparing materials to go through M phase
  • eg making proteins, re checking
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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.

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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
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7
Q

Early embryonic cells

A
  • divide without growing.
  • so only M and S phase, no Gs
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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.
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9
Q

M phase components

A
  • prophase
  • prometaphase
  • metaphase
  • anaphase
  • telophase
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10
Q

Prophase

A

Disassemble interphase MT array, form mitotic spindle
• Centrosomes move to opposite poles
• Chromatin condenses
• Nuclear envelope dissociates

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11
Q

Prometaphase

A

Kinetochore MTs move pairs of sister chromatids back and forth until they reach
the metaphase plate

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12
Q

Metaphase

A

All pairs of sister chromatids are lined up on metaphase plate; connection between
chromatids broken (centromere)

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13
Q

Anaphase

A

Anaphase A: kinetochore MTs separate sister chromatids
• Anaphase B: polar MTs “push” and astral MTs “pull” poles

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14
Q

Telophase

A

Undo what was done during prophase - nuclear envelope re-forms, chromosomes de-condense to chromatin etc.

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15
Q

Cytokinesis

A

Cytoplasmic division using contractile ring of actin and myosin

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16
Q

How to disassemble nuclear envelope

A

Phosphorylating lamin proteins
A and C free floating
B attached to vesicles.

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17
Q

Kinetochores

A
  • aggregation of different types of proteins attached to the centromere of a chromatid.
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18
Q

Anaphase A

A
  • Movement of sister chromatids to opposite poles via kinetochore microtubules.
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19
Q

Anaphase B

A
  • spindles distance themselves from each other, further separating sister chromatids. (So moving the poles), stretching boundary of the cell.
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20
Q

What happens to a protein that is made on a cytostolic ribosome?

A

Remains in cytoskeleton
Imported into an organelle.

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21
Q

Path of protein made on ReR ribosome (co-translational sorting)

A
  • Ribosome
  • RER
  • Golgi
  • secretory vesicle, lysosome or plasma membrane
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22
Q

Active transport for transport through the nuclear pore complex

A
  • uses GTP as energy stores
  • form molecules more that 60kDa in width
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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 -
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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.
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25
Q

Nuclear protein import

A
  • 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.
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26
Q

Nuclear export

A
  • 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
Q

Human mitochondrial genome

A
  • 16.5K base pairs of DNA
  • 13 protein coding genes
  • 22 tRNA genes
  • 2 rRNA genes - 2 subunits in mitochondrial ribosome
  • ori
28
Q

Where does
Transcription
Translation
Transport
Happen for most mitochondrial proteins on doses from by genes on the mitochondrial genome

A
  • nucleus
  • cytoplasm
  • present signal, signal recognized, action taken
29
Q

Mitochondrial protein import

A
  • 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
Q

Types of cell-cell communication

A
  • direct intercellular signaling
  • contact-depending signaling
  • Autocrine signaling
  • Paracrine signaling
  • endocrine signaling
31
Q

Direct intercellular

A
  • signals pass through a cell junction from the cytoskeleton of one cell to adjacent cells
32
Q

Contact dépendant

A

Membrane bound signals bind to receptors on adjacent cells

33
Q

Autocrine signaling

A
  • cells release signals that affect themselves and nearby target cells
34
Q

Paracrine signaling

A
  • cells release signals that affect nearby target cells
35
Q

Endocrine signaling

A
  • cells release signals that travel long distances to affect target cells
36
Q

3 stages of a response to a signal

A
  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
Q

Kd and its indication on receptor-ligand interaction

A
  • the higher the Kd, the lower the affinity
38
Q

Kd

A
  • the concentration at which 50% of the cell’s receptors for that ligand are bound
39
Q

Above the Kd is likely to lead to what?

A
  • greater cellular response than a lower Kd
40
Q

Receptor-ligand interaction

A
  • binding of a ligand to a receptor cause a change in conformation of the receptor, triggering an effect
41
Q

Why are intracellular receptors localized to the cytoplasm

A
  • 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
Q

Extracellular binding domains

A
  • Channel
  • GPCR (G protein coupled receptor)
  • Enzyme linked
43
Q

Best way to get rid of the signaling molecule

A
  • get it into the cell and let a lysosome degrade it.
44
Q

Adenylyl cyclase

A

-makes cAMP by hydrolysis of ATP (producing a pyrophosphate)
- when a subunit bound to GTP binds to it.

45
Q

GPCR, second messengers and epinephrine pathway

A
  • 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
Q

Outcomes of the épi pathway

A
  • 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
Q

Amplification

A
48
Q

Cross talk

A

When one part of a signaling pathway produces/activates molecules that can activate/deactivate molecules that are involved in other adjacent pathways.

49
Q

Why does apoptosis happen

A
  • sculpting tissues
  • maintenance of organ size and shape
  • removal of damaged/infected/worn out cells.
50
Q

2 paths of apoptosis

A
  • extrinsic
  • intrinsic (mitochondrial)
51
Q

Extrinsic apoptosis

A
  • 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
Q

Intrinsic apoptosis

A
  • 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
Q

Non coding RNA molecules

A
  • 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
Q

Function of ncRNAs

A
  • 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
Q

Telomerase ncRNA component

A

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
Q

SRPs (add more later)

A
  • 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
Q

Sense and antisense mRNA

A
  • 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
Q

HOTAIR ncRNA

A

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
Q

Fire and Mello Experiment method

A
  • 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
Q

Fire and Mellow results

A
  • 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
Q

SiRNA

A

Small interfering RNA - come from outside of the cell.

62
Q

MiRNA

A
  • micro RNAs - regulatory purpose, made by the cell itself.
  • acts as a guide and blocker
63
Q

RNA interference

A
  • 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.

MCB 150 (8 decks)

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