Question

________________are able to detoxify substances such as hydrogen peroxide by enzymatic action

What are the steps in the cell cycle? How is the cell cycle regulated? What happens in cancer cells?

Answer 1

• Catalase is an enzyme that are able to detoxify substances such as hydrogen peroxide by enzymatic action.
• When the reaction occur oxygen gas bubbles escape and create foam.

Steps of cell cycle are :-

1) G1 phase

• Increase in the size of cell.
• Duplication of cellular content.

2) S phase

• DNA replication.
• Each of the 46 chromosomes (23 pairs) is replicated by the cell.

3) G2 phase

• Cell prepares for cell division

4) M phase

• Mitosis followed by cytokinesis .
• Formation of two identical daughter cells.
• Phases of M phase :- Prophase , metaphase , anaphase and telophase.
• Cytokinesis is process of parent cell becoming 2 daughter cells.

Regulation

• Progression of cell through cell cycle is controlled by checkpoints at different stages .
• These detect if a cell contains damaged DNA and ensure those cells do not replicate.
• The key checkpoint is restriction point (R) located at G1.
• If damaged DNA is detected at any checkpoint,it leads to activation of the checkpoint results in increased protein p53 production.
• Cell cycle is also regulated by cyclins which control cell progression by activating cyclin-dependent kinase (CDK) enzymes.
• In cancer cell there occur mutation in a protein that regulate cell cycle .eg p53 it can lead to cancerous cells and the rapid multiplication of these cells.