CELL CYCLE REGULATION Flashcards

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1
Q

Cell cycle checkpoints are…

A

Internal cellular mechanisms that control progression through the cell cycle phases
They search for, detect, and repair biochemical errors

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2
Q

Each checkpoint sensor verifies the…

A

Accurate completion of essential cellular events

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3
Q

When the adult stem cell encounters the checkpoint the-

A

-Cell cycle pauses
-Checkpoint sensors search for biochemical errors
-Cell cycle continues if no errors are detected

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4
Q

Process of the checkpoint:

A
  1. the cell recognized the proper Go-Signal
  2. the “continue signal” was released
  3. the cell crossed the G1/S checkpoint
  4. the cell advanced to the S phase
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5
Q

Each checkpoint sensor recruits the proper repair enzymes when an error is…

A

Detected, corrects the error, and instructs the cell to advance to the next phase

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6
Q

Checkpoint sensor process

A
  1. sensor searches for errors
  2. activated checkpoint recruits repair enzymes
  3. after repairing the error, the “continue signal” is released
  4. cell passes the checkpoint and advances to next phase
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7
Q

The checkpoint sensory detects a critical biochemical error that cannot be repaired… =

A

The cell self destructs by apoptosis

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8
Q

Apoptosis eliminates cells that are…

A

-Precancerous
-Cancerous (some cancer cells are mutated and apoptosis cannot occur)
-No longer needed
-Infected
-Defective and need to be replaced

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9
Q

What is the first checkpoint?

A

The G1/S phase checkpoint

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10
Q

Cells in the G1 phase must recognize a…

A

“Go-signal” to pass the G1/S checkpoint and enter the S phase

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11
Q

Growth factors are

A

Protein Go-Signals

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12
Q

Example of Go-Signals

A

Steroid hormones (estrogen, testosterone)

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13
Q

Roughly how many human Go-Signals?

A

~50

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14
Q

Why are growth hormones prescribed?

A

To treat growth hormone deficiency, Turner Syndrome, and other conditions associated with short stature

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15
Q

At the G1 checkpoint, if the cell does not receive a go ahead signal where does the cell go?

A

G0

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16
Q

What is the second checkpoint?

A

G2/M phase

17
Q

G2/M phase

A

-Verifies the accuracy of DNA replication during the S phase
-Instructs the cell to advance to the G2 phase
-DNA damage checkpoint

18
Q

What is the third checkpoint?

A

M phase (spindle)

19
Q

M phase (spindle) checkpoint

A

-Controls the metaphase to anaphase transition during mitosis
-Ensures all chromosomes are attached to the spindle before the adult stem cell can complete mitotic cell division

20
Q

What does the M phase checkpoint prevent?

A

Prevents Aneuploidy in each daughter cell

21
Q

What are the regulatory molecules that control cell cycle progression?

A

-Cyclin proteins
-Cyclin dependent kinases (CDKs)

22
Q

After each checkpoint is crossed…

A

The cyclin proteins and CDKs enable the cell to advance to the next cell cycle phase

23
Q

How is CDK activated?

A

Cyclin binds to the CDK

24
Q

What enables the cell to pass the G1/S checkpoint and enter S phase?

A

Active CDK

25
Q

MPF

A

Mitosis promoting factor

26
Q

MPF enables…

A

Cell entry into the M phase by phosphorylation and other regulatory proteins

27
Q

________ degrade proteins marked for destruction

A

Proteasomes

28
Q

How many proteasomes in each cell?

A

30,000-50,000

29
Q

What happens to cyclin proteins after the adult stem cell advances to the next cell cycle phase?

A

Cyclin proteins must be degraded

30
Q

What protein is attached to the cyclin proteins?

A

Ubiquitin

31
Q

Proteasomes degrade what and release what?

A

Proteasomes degrade the marked cyclin proteins and release the amino acids

32
Q

_______ proteasomes that can’t degrade cyclin increase cancer risk

A

Defective proteasomes

33
Q

Defective cell cycle regulation has…

A

Medical consequences
-Abnormal growth
-Benign tumors, malignant tumors
-Immune system dysfunction