VCE Biology Unit 1: How Do Cells Function?

Cell Cycle and Cell Growth, Death, and Differentiation

  • Key Concepts:

  • Focus on binary fission in prokaryotes and eukaryotic cell cycle (mitosis and cytokinesis).

DNA Structure and Replication

  • DNA Composition:

  • DNA is a polymer of nucleotides (A, T, C, G).

  • Each nucleotide has:

    • Pentose sugar.

    • Nitrogen base.

    • Phosphate group.

  • Structure: Two strands, complementary and antiparallel (A-T, C-G pairing).

  • DNA Replication Process:

  • Leading Strand:

    • DNA polymerase III synthesizes in 5' to 3' direction.

  • Lagging Strand:

    • Needs RNA primers from primase for synthesis.

    • Forms Okazaki fragments.

    • DNA polymerase I replaces RNA with DNA.

    • Ligase joins fragments to form continuous strand.

Binary Fission in Prokaryotes

  • Definition: A process where one parent cell divides to form two identical daughter cells.

  • Steps:

  1. DNA Replication starts at the origin and proceeds to the terminus.

  2. Chromosome Attachment to cell membrane.

  3. Cell Elongation as wall material is added.

  4. Z-ring Formation using FtsZ protein, which constricts the cell.

  5. Septum Formation and degradation of cell wall leading to cytokinesis, resulting in two genetically identical cells.

Important Definitions

  • Replisome: Complex of enzymes like helicase, primase, DNA polymerase.

  • Okazaki Fragments: Short DNA segments on the lagging strand.

  • Cytokinesis: Division of the cytoplasm during cell division.

Summary of Key Points

  • DNA is essential for cell replication.

  • Prokaryotic reproduction mainly via binary fission (DNA replication, cell growth, division).

  • Understanding of these processes is foundational for the upcoming study of the eukaryotic cell cycle.