CTCS Quiz 2 Flashcards
How long does it take between successive mitoses?
~24 hours, but this can be variable.
How long does mitosis las for a cell in culture?
1 hour.
In which phase dose repair of the genome occur?
S phase.
Early Prophase
Chromatin make chromosomes, spindle fibers begin to form.
Late Prophase
Nuclear envelope goes away, chromosomes attach to spindles.
Metaphase
Chromosomes align at metaphase plate, held in tension by the opposing spindle fibers.
Anaphase
Sister chromatids are pulled apart, spindle poles start to move apart from each other.
Telophase
Chromatids arrive at poles, nuclear envelopes reform around decondensing chromsomes, cleavage furrow begins begins and causes cytokinesis.
Are the key mechanisms governing M phase conserved?
Yes. They are conserved in all species (yeast to man).
What can cause a cell cycle to stop in M phase?
unattached chromosomes or incorrect spindle assembly.
What can cause the cell cycle to arrest in G1?
Damaged DNA.
What can cause the cell cycle to arrest in G1 or G2?
DNA damage or unreplicated DNA.
What regulates the main events of the cell cycle?
Cdk-Cyclin complexes.
How does the cell make sure not to go backwards?
It destroys certain proteins after they are used,- ie destruction of M-cyclin
What does MPF stand for and what makes it?
M-phase Promoting Factor.
It is made by: 1) a Cdk catalytic subunit (Cyclin Dependent Kinase), 2) M-cyclin (or cyclin B sometimes)
What is M-Cdk?
Mitosis- Cyclin-Dependent Kinase
How quickly are MTs renewed during mitosis?
All are renewed with a half life of 15 secs.
How many directions can an individual motor protein travel on a spindle?
One. Some MPs can go towards the plus end, some towards minus end.
What actions can motor proteins have on spindles?
Slide, push, pull
What happens with M-Cdk is destroyed?
Mitosis ends.
What are some key structural features of cytokinesis?
- Actin and myosin filaments make contractile ring.
- Nuclear envelopes and membrane-bound organelles reformed.
- Golgi and other organelles send membrane to site of fission to help heal.
What are the three major filaments found in a cell?
Intermediate Filaments, MTs, and Actin Filaments
Which filaments are polar?
MTs and Actin
Which two filaments are important for cell motility?
Actin and MTs
What makes up MTs, Microfilaments and IFs?
MTs: Tubulin
MFs: Actin
IFs: Nestin, Vimentin, Keratins, Desmins, etc. (not important to memorize)
How is MT made?
- Heterodimers with alpha and beta tubulin
2. GTP must be bound to both alpha and beta subunits
What is the inner and outter diameter of MTs? How wide is an alpha or beta unit?
Inner: 14 nm
Outter: 25 nm
Alpha/Beta: 4-5 nm
How is Actin polymerized?
G actin makes dimers, then trimers, then they elongate at the barbed end (+ end). It now becomes known as F actin.
What is required for polymerization of actin?
- G-acting has to be above critical concentration.
2. ATP-Mg bound to actin
Are IFs polarized?
No
Where are IFs found in the cell?
Everywhere.
What property does IF have?
Rope-like properties, high tensile strength.
How are actin filaments regulated?
G and F-Actin binding proteins.
How do G-actin binding proteins work?
They bind to the monomers and either add them to the actin, or they prevent them from going to the actin. These different proteins compete for the actin substrates.
What are Actin Related Proteins (ARP)?
ARP2/3 induces nucleation at branched junction at 70 degrees animals.
What do formins do?
They elongate actin filaments.
What do Rho proteins do?
They determine the structure of the actins. Other proteins do this, too, but they determine whether the actin makes stress fibers, lamellipodia, filopodia, etc.
Is MT growth symmetric?
No, it is assymetric.
What are the 2 mechanisms that regulate MT dynamics?
- Inherent properties of tubulin assembly.
2. MT associated proteins.
What does a GTP cap do to MTs?
It can prevent depolymerization. But if hydrolysis catches up to the tip, as soon as the tip is mostly GDP, then rapid depolymerization occurs.
What is one function of a microtubule associated protein (MAP)?
The can act as spacers in neuronal cells.
What can happen to MTs when they are stabilized?
They can be modified. They are always modified with the plus end in the direction of the moving cell.
Can protein cap MTs to stabilize them?
Yes.
Are stabilized MTs affected by drugs?
No.
What fills most of the extracellular space in connective tissue?
Glycosaminoglycans (GAGs). They are unbranched polysaccharide chains, repeating units, and one sugar is always an amino sugar.
What is one of the simplest GAGs?
Hyaluronic acid. It can be made up of 25,000 repeating units.
What is a proteoglycan?
An ECM protein, heavily glycosylated, and one chain must be a GAG.
How does the Na/K pump work?
- 3 Na out, 2 K in
- requires ATP
What is one of the reasons why a high extracellular Na+ concentration is important?
Na+ is used to help bring other molecules back into the cell with cotransport (symport). It has to be flowing along its gradient in order to do this.
How does Na+ help to regulate acidity inside the cell?
Antiport. For every Na+ that enters cell, one H+ leaves the cell.
What is the difference between GAGs and Proteoglycans?
GAGs: occupies lots of space and make gels.
Proteoglycans: composed of GAGs bonded to a core protein.
