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Biology Module 2 - Own Flashcards > 6.1 - The Cell Cycle > Flashcards

6.1 - The Cell Cycle Flashcards

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1
Q

What is the purpose of the cell cycle?

A

To produce two genetically identical daughter cells for growth, repair, and asexual reproduction.

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2
Q

How long is the cell cycle?

A

The length of the cell cycle is variable and depends on environmental conditions, the cell type, and the organism. For example, onion root-tip cells divide approximately every 20 hours, while human intestine epithelial cells divide roughly every 10 hours.

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3
Q

What are the two main phases of the cell cycle?

A

Interphase: Period of growth, normal metabolic activity, and preparation for division.
Mitotic (M) Phase: Includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).

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4
Q

What is interphase, and why is it important?

A

Interphase is the longest phase of the cell cycle where the cell grows, replicates DNA, and prepares for division. It is essential for ensuring the daughter cells have the correct genetic material and cellular components.

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5
Q

Why is interphase sometimes inaccurately referred to as the “resting phase”?

A

It is highly active, involving DNA replication, protein synthesis, organelle production, and metabolic processes. Cells are not dividing but are actively preparing for division.

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6
Q

What are the three stages of interphase, and what happens in each?

A

G1 - First Growth Phase (Growth)

S - Synthesis Phase (Synthesis, where DNA is replicated)

G2 - Second Growth Phase (Growth and preparation for mitosis)

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7
Q

What happens during the G1 (First Growth Phase) of interphase?

A

The cell grows and produces proteins needed for organelle synthesis.
Organelles replicate, and the cell increases in size.

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8
Q

What happens during the S (Synthesis Phase) of interphase?

A

DNA is replicated in the nucleus.

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9
Q

What happens during the G2 (Second Growth Phase) of interphase?

A

The cell continues to grow.
Energy stores are increased.
The replicated DNA is checked for errors.

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10
Q

What happens to mitochondria and chloroplasts during interphase?

A

Mitochondria: Grow and divide, increasing in number to meet the energy demands of the daughter cells.

Chloroplasts: Grow and divide in plant and algal cells to support photosynthesis.

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11
Q

What happens during the mitotic phase?

A
  1. Mitosis: The division of the nucleus into two identical nuclei.
  2. Cytokinesis: The division of the cytoplasm to form two separate daughter cells.
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12
Q

What are the stages of mitosis?

A

PMAT:
1. Prophase
2. Metaphase
3. Anaphase
4. Telaphase

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13
Q

What happens during the Prophase stage of mitosis?

A

Chromatin condenses into visible chromosomes.
The nuclear envelope breaks down.
Spindle fibers begin to form from centrioles.

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14
Q

What happens during the Metaphase stage of mitosis?

A

Chromosomes align along the metaphase plate.
Spindle fibers attach to centromeres.

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15
Q

What happens during the Anaphase stage of mitosis?

A

Sister chromatids are pulled apart to opposite poles by spindle fibers.

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16
Q

What happens during the Telophase stage of mitosis?

A

Chromatids reach the poles and decondense into chromatin.
Nuclear envelopes reform around each set of chromosomes.

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17
Q

What is the role of cytokinesis in the cell cycle?

A

Cytokinesis is the final stage of the cell cycle, where the cytoplasm divides to form two genetically identical daughter cells. In animal cells, the cytoplasm constricts, while in plant cells, a new cell wall is formed.

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18
Q

How does cytokinesis differ in animal and plant cells?

A

In animal cells: A cleavage furrow forms, pinching the cell into two.
In plant cells: A cell plate forms, which develops into a new cell wall.

19
Q

What is the G0 phase in the cell cycle?

A

A phase where cells leave the cycle temporarily or permanently.

20
Q

What are the reasons for a cell to enter G0?

A
  1. Differentiation: Specialized cells no longer divide and remain in G0.
  2. DNA Damage: Cells with damaged DNA may enter permanent arrest.
  3. Senescence: After a limited number of divisions, cells become inactive.
21
Q

Can cells re-enter the cell cycle from G0?

A

Yes, certain cells like lymphocytes can re-enter the cycle during an immune response.

22
Q

Why is control of the cell cycle important?

A

To ensure accurate DNA replication, error-free division, and proper chromosome segregation, preventing mutations and maintaining genetic stability.

23
Q

What mechanisms control the progression of the cell cycle?

A

Checkpoints, which monitor the accuracy of processes and allow progression only if criteria are met.

24
Q

What are the three main checkpoints in the cell cycle?

A

G1 Checkpoint (End of G1 Phase)
G2 Checkpoint (End of G2 Phase)
Spindle Assembly Checkpoint (Metaphase)

25
Q

What does the G1 Checkpoint check for? (4)

A
  1. Cell size.
  2. Nutrients.
  3. Growth factors.
  4. DNA damage.
26
Q

What happens if the G1 checkpoint is passed/not passed?

A

If passed, the cell proceeds to DNA replication (S phase). If not, the cell may enter G0.

27
Q

What does the G2 Checkpoint check for? (3)

A
  1. Cell size.
  2. Correct and complete DNA replication.
  3. DNA damage.
28
Q

What happens if the G2 checkpoint is passed?

A

If passed, the cell proceeds to mitosis.

29
Q

What does the Spindle Assembly (Metaphase) Checkpoint check for?

A

Chromosome attachment to spindle fibers.

  • Ensures accurate chromosome segregation before anaphase.
30
Q

What proteins regulate the cell cycle at checkpoints?

A

Cyclins and cyclin-dependent kinases (CDKs).

31
Q

What happens if errors are not corrected during the cell cycle?

A

Unrepaired errors can lead to mutations.
Faulty control mechanisms may result in uncontrolled cell division (cancer).

32
Q

What role does p53 play in the cell cycle?

A

p53 is a tumor suppressor protein that detects DNA damage, halts the cycle for repair, or triggers apoptosis if damage is irreparable.

33
Q

What enzyme type is responsible for passing a cell-cycle checkpoint? What do they do?

A

Kinases, which catalyze the addition of a phosphate group to a protein (phosphorylation).

34
Q

How does phosphorylation affect checkpoint proteins?

A

It changes their tertiary structure, activating them at specific points in the cell cycle.

35
Q

What are cyclins, and what is their role in cell-cycle regulation?

A

Cyclins are checkpoint proteins that activate kinases. Binding of a cyclin to the appropriate kinase forms a cyclin-dependent kinase (CDK) complex.

36
Q

How are CDK complexes activated, and what do they do?

A

Activated by enzymes.
Catalyze the phosphorylation of key cell-cycle proteins, ensuring progression through cell-cycle phases.

37
Q

How are cyclins removed when no longer needed?

A

Specific enzymes break down cyclins to signal progression into the next phase of the cycle.

38
Q

How can mutations in genes encoding checkpoint proteins contribute to cancer?

A

Mutations may disrupt cell-cycle regulation.
Leads to uncontrolled cell division and tumor formation.

39
Q

What is a tumor, and what are the two types?

A

Tumor: An abnormal mass of cells caused by uncontrolled division.

Benign Tumor: Non-invasive, does not spread.
Malignant Tumor: Invasive, grows unchecked, and spreads, forming the basis of cancer.

40
Q

How do mutations in cyclin genes lead to cancer?

A

Overexpression of cyclin genes results in excessive cyclin production, disrupting cell-cycle regulation and causing uncontrolled division.

41
Q

How can cyclin-dependent kinases (CDKs) be targeted in cancer treatment?

A

Chemical inhibitors can reduce CDK activity, slowing or halting cell division and tumor formation.

42
Q

Compare the roles of cyclins and enzyme inhibitors.

A

Cyclins: Promote cell-cycle progression by activating CDKs.
Enzyme Inhibitors: Reduce CDK activity, slowing or halting the cycle.

43
Q

What are the similarities between the role of cyclins and enzyme inhibitors?

A

Similarities: Both regulate CDK activity and affect the cell cycle.
Differences: Cyclins promote division, while enzyme inhibitors prevent it.

Biology Module 2 - Own Flashcards (23 decks)

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