11-15 Test Flashcards
Receptor tyrosine kinase
This has two ligand binding sites, which contrasts the other two, that only have one. The binding of the signaling molecule causes the receptor monomers to connect. Dimerization (connectedness/process) activates the tyrosine kinase region of each monomer, each TK adds a phosphate from an ATP to a tyrosine on the tail of the other monomer. Now that it’s activated, it’s recognized by proteins. Each protein binds to a specific phosphorylated tyrosine, causing structural change. Each protein triggers a transduction pathway, leading to a cellular response. Contrast: two receptor sites and multiple cellular responses
G protein coupled receptors
G protein is a molecular switch either on or off. It’s off when Gdp binds to it, and on with Gtp. When Gtp binds, (on inside of cell) the G protein changes shape and then it binds to the Gdp, causing Gtp to displace gdp, activating the G protein. Then the G protein gets off the receptor and binds to the enzyme, changing its shape. This activates the next step in the cellular response. The Gtp changes to P and Gdp, making the enzyme inactive, returns to original state. Contrats: activates single response and uses an enzyme not a protein.
Cell cycle
an ordered sequence of events in the life of a cell, form its origin in the division of a parent cell until its own division into 2.Interphase (G1, S, and G2 subphases) & M phase (mitosis and cytokinesis)
G2 of interphase
The nucleus is contained by a nuclear envelope, and there is one or more nucleolus. The cent roscoes are formed, but are still tight next to each other, not at opposite ends yet. The chromosomes are all tangled together and haven’t been condensed yet
Prophase
The nucleoli dissapear and the chromatin fibers condense into chromosomes. The duplicated chromosomes appear as sister chromatids joined by the centromeres and the mitosis spindle begins to form. At the same time, centrosomes begin to move in opposite directions.
Prometaphase
As the nuclear envelope dissapears, the microtubules can now go in the nuclear area where it just was. The chromatids have become much more condensed, and now they each have a kinetichore. Some microtubules connect to the kinetichore, becoming kinetichore microtubules. At these move the chromosomes back and forth, the nonkinetichore microtubules connect with those of the opposite side.
Metaphase
The centrosomes are at opposite sides of the cell and the chromosomes all line up at the metaphase plate.
Anaphase
Starts when the cohesion proteins are cleaved. This causes the sister chromatids to separate and each chromatid becomes a chromosome. The chromosomes then begin to move to opposite ends of the cell. The cell elongates, and now each end of the cell has a complete collection of chromosomes.
Telophase
2 daughter nuclei and nuclear envelopes are formed. As the nucleoli reappear, the chromosomes become less condensed and extra spindles are depolymerized. Mitosis is now technically finished.
Cytokinesis
formation of the cleavage furrow, pinching cell into two.
What is the mechanism used by kinetichore microtubules to move chromosomes during anaphase?
The kinetichore microtubules have motor proteins that “walk” the chromosomes along the microtubules. These depolymerized once they’ve passed. Other people think that the chromosomes are “reeled in” by motor proteins at the spindle poles, and after they pass by the motor proteins the microtubules are depolymerized. (Both mechanisms are used)
How is the cell cycle controlled by checkpoints?
Checkpoints submit signals that report if cell cycle should proceed. They ensure that all the necessary processes have been been completed before sending the signal. In many cells the G1 checkpoint is very important because if the cell is allowed to pass this checkpoint, they’ll probably also got through G1, S, G2, M phase and then divide. If it’s not allowed to pass, it will go to the G0 phase which is the nondividing state that most cells are in. The cell will then most likely pass the G2 phase if it passed the G1, and then it will go into the M phase. This ensures that the kinetichore a of all the chromosomes are properly attached to the spindle.
Cancer
Cancer cells ignore signals that regulate the cell cycle. They don’t stop dividing even when the growth factors are completed. They also evade the cont This is likely caused by a mutation that changes the function of the cell’s protein products.
Benign tumor
cells remain at the original site, easily removed by surgery
Malignant tumor
genetic and cellular changes allow the cancer to spread to new tissues
