Notes on Healthy Tips and Cell Cycle in Biology

Healthy Tips for Screen Time

1. Sit Properly

   • Ensure your back is against the chair backrest.

2. Change Positions Regularly

   • Alternate between sitting on the couch, chair, or floor.

3. Maintain Adequate Lighting

   • Use dim lighting instead of complete darkness or bright lights to avoid eye damage.

4. Stretch Frequently

   • Use commercial breaks to stand, walk around, and perform gentle stretches.

5. Avoid Watching TV in Bed

   • This could lead to neck and back pain.

Cell Cycle Overview

• A cell cycle resembles a life cycle, representing stages a cell goes through from formation to reproduction.

Stages of the Cell Cycle

1. Interphase

   • G1 phase (First Gap): Active stage where the cell accumulates DNA building blocks and energy.
   • S phase (Synthesis): DNA replication occurs. Chromosomes form sister chromatids.
   • G2 phase (Second Gap): The cell prepares for mitosis, replenishing energy and duplicating organelles.

2. Mitotic Phase (M Phase)

   • Mitosis: Division of the nucleus and cytoplasm into two daughter cells.
   • Stages of Mitosis:
     • Prophase: Chromosomes condense.
     • Metaphase: Chromosomes align.
     • Anaphase: Chromatids separate.
     • Telophase: Nuclear envelopes reform.
   • Cytokinesis: Separation of cytoplasm forming two new cells.
     • Animal Cells: Contractile ring forms, creating a cleavage furrow.
     • Plant Cells: A cell plate forms separating the cells.

Cell Growth and Division Rates

• Cell Division: Varies across cell types.
  • Rapidly dividing cells (e.g., embryonic cells, tumor cells) can undergo immediate division.
  • Some cells enter a resting state (G0 phase) where division is not actively prepared, focusing on their specific roles (e.g., neurons, liver cells).

Duration of Cell Cycle Phases

• Typical human cells take approximately 24 hours to complete the cycle.
  • G1: ~11 hours
  • S: ~8 hours
  • G2: ~4 hours
  • M: ~1 hour
• Some cells cycle faster, taking about 9-10 hours (e.g., intestinal lining).

Quiz Summary

1. Most cell life spent in: Interphase.
2. Cell cycle description: A) Cells grow and develop during interphase, reproduce during mitotic phase.
3. Time to complete cell cycle: B) About one day.
4. DNA copying phase: A) S phase.
5. Plant cell division: A) New cell plate and wall forms in the middle.

Assignment

• Activity: Arrange the following in order:
  • Spindle fibers emerge from centrosomes.
  • Chromosomes condense and become visible.
  • Nucleolus disappears.
  • Nuclear envelope breaks down.

Conclusion

• More science explorations are upcoming.
• Remember, learning biology is fun!