Week 7 - Cytoskeleton. Cell division of eukaryotic cells - mitosis and meiosis Flashcards
3 filamentous structures of the cytoskeleton of a cell
Microtubuli
Microfilaments = actin filaments
Intermediate filament
Functions of cytoskeleton
Shape of cell;
Maintains cells shape. Changes shape of cell during movement (e.g. organelle migration or cell division)
Positions organells
Resist deformation
Transports material from cell (e.g. vesicles), helps in transporting communication signals between cells.
Tell me more about the largest type of filament;
- What does it consist of?
- They can do 2 things, what and how?
Microtubules
- Protein tubulin (25 nm)
Tubulin consists of α- and β-tubulins assembled into linear protofilaments
- SPECIAL ATTACKS
Can rapidly grow: Polymerization
Or rapidly shrink : Depolymerization
Depending on how many tubulin molecules they have
A single microtubule contains about how many protofilaments
… that wind together and forms what?
10 - 15
We humans have 13
Forms a hollow cylinder
OBS FRÅGA
om man ska kunna förklara de hon säger i videolecture
- pt1
7.58
What is MTOCs
Centrosomes consists of 2 what?
What role do they play in?
Microtubule organizing centers
Minus ends of microtubule are anchored in MTOC
Primary MTOC = centrosome
2 centrioles build up centrosomes
Centrosomes and both centrioles play important role during cell division. Origin where mytotic spindle is growing.
Duplicated during S phase of the cell cycle.
Centrioles
Paired cylindrical organells
together with periocentriolar material (PCM, 100+ different proteins)
Built up by microtubules
Cylindrical formation + PCM = produce microtubules e.g. miotic spindle fibers
Intermediate filaments
- Size? Composed of?
- What are they associated with?
Intermediate meaning size is between actin and microtubules!
Composed from many different protein subunits (70 in humans)
Associated with specific cell types:
- Neurofilaments in neurons
- Desmin filaments in muscle cells
- Keratins in epithelial cells
Microfilaments
- Size?
- Consists of?
- Prevalent where?
- Similar to microtubules how?
- Smallest of all filaments
- Consists of actin (contracile)
- Prevalent especially in muscle cells, takes part in muscle contraction
- Similar to microtubules in having a (+) and (-) end which allows them to extend.
Motor proteins
What do they do?
3 motor proteins that are involved in cell movement?
They use energy from ATP hydrolysis to generate movement and force
**Kinesin** ; Moves along microtubules, pulls organells toward the cell membrane
**Dynein** ; Pulls cellular components inwards towards nucleus. Work to slide microtubules?
**Myosin**; NPC interaction with actin → muscle contractions
Also involved in cytokinesis, endocytosis and exocytosis
Somatic cell division in eukaryotes (simple)
Result?
Function?
Result: 2 genetically identical daughter cells
Needed for
Tissue growth, regeneration or vegetative reproduction
M-phase in eukaryotic cell cycle
Consists of what 2 parts?
In what order?
Mitosis and Cytokinesis
1st phase in M-phase
Mitosis: All five phases are called karyokinesis – division of the
nucleus
2nd phase in M-phase
Cytokinesis: - the two daughter cells become independent by
division of cytoplasm and the rest of organoids
OBS both parts partly overlapping!!
5 phases of mitosis
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Struggling to remember? Remember following
pro = before
pro meta = before mid
meta = mid
ana = upper
telos = end.
Key cell cycle regulation proteins are …?
- What is their main thing?
- What is Kinase and what does it do?
cyclin-dependent kinases; CDK
Ensures accurate cell cycle progression
CDK does not have kinase activity unless bound with cyclin.
Kinase: an enzyme, adds phosphate groups (PO4 3−) to other
molecules. Kinases can phosphorylate the amino acids serine,
threonine, and tyrosine.
Concentration of cyclins in the cell fluctuate, CDKs
concentration is stable.
What are PLKs and Aurora kinases
Another type of kinases
Plks (Polo-like kinases) and Aurora kinases control phosphorylation
Major regulators of
- centrosome function
- spindle assembly
- chromosome segregation
- cytokinesis
What does this picture show?
OBS ask if we should know what is activated during different phases
Picture shows different kinases being active during different phases. Through changing different kinases activity by phosforylating different proteins → physical seperations of the nucleus takes place
Picture showing before m-phase starts and start of prophase
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Gå t lecture 7 pt 2; 10.18
Prophase
chromosomes condense into compact structures, condensins attach to chromosomes that coil chromosomes into highly compact forms
- H1 histone phosphorylation and attachment of condensins are mediated by Cdk1
- H3 phosphorylation is mediated by Aurora B kinase
Cohesin
holy fuck så mkt hon yappa (innan) lecture 7 pt2 13.00
cohesin forms rings that hold the sister chromatids together
Sister chromatides arises during replication where duplication of DNA takes place. Proteins that help with this process are already created before this phase.
Since condensine helps to condense chromosomes → cohesin helps to hold something together
nuclear membrane breaks down to form a number of small vesicles, nucleolus disintegrates (nuclear membrane),
transcription and synthesis stop
- beginning of formation of the mitotic spindle
- centrosomes gradually move to take up positions at the poles
of the cell - process is mediated by Plks and Aurora A kinases
Prometaphase
chromosomes are completely attached to the mitotic spindle, spindle fibers bind to kinetochore
chromosomes, led by their centromeres, start migrate to equatorial plane in the mid-line of the cell, this region of mitotic spindle is known as
the metaphase plate