Cell Cycle Overview

Cell Cycle

• The cell cycle is a series of events that lead to cell division and duplication. It's a precisely regulated process, ensuring accurate DNA replication and proper chromosome distribution to daughter cells.
• The cell cycle is broadly categorized into interphase and the mitotic (M) phase.
• Interphase, the longest phase, consists of the G1, S, and G2 phases.
  • G1 phase (Gap 1): The cell grows, synthesizes proteins and organelles, and prepares for DNA replication.
  • S phase (Synthesis): DNA replication occurs, creating two identical chromosome copies.
  • G2 phase (Gap 2): The cell continues to grow, synthesizes more proteins and organelles, and checks for DNA replication errors – vital quality control.
• The mitotic (M) phase involves nuclear division (mitosis) followed by cytoplasmic division (cytokinesis).
  • Mitosis: Duplicated chromosomes are separated and distributed into two daughter nuclei. It involves four key stages:
    • Prophase: Chromosomes condense, becoming visible; the nuclear envelope breaks down; the mitotic spindle begins to form.
    • Metaphase: Chromosomes align at the metaphase plate (center of the cell).
    • Anaphase: Sister chromatids separate and move to opposite poles of the cell.
    • Telophase: Chromosomes decondense; nuclear envelopes reform around each chromosome set; the mitotic spindle disappears.
  • Cytokinesis: The cytoplasm divides, creating two separate daughter cells. This process differs between animal and plant cells.
    • Animal cells: A cleavage furrow forms and deepens, eventually pinching the cell in two.
    • Plant cells: A cell plate forms, developing into a new cell wall, separating the two daughter cells.
• Crucial control mechanisms regulate the cell cycle. Checkpoints ensure that DNA replication is complete before mitosis begins, preventing errors.
• Uncontrolled cell growth (cancer) results from compromised cell cycle control mechanisms.

Unit of Life

• A cell serves as the fundamental structural and functional unit of all living organisms.
  • Every organism, whether unicellular or multicellular, is composed of one or more cells.
  • Cells carry out the essential functions of life.
• Types of Cells:
  • Prokaryotic cells lack membrane-bound organelles and a true nucleus. Their DNA is located in a region called the nucleoid. Examples include bacteria and archaea.
  • Eukaryotic cells possess membrane-bound organelles and a distinct nucleus containing the DNA. Examples include animal, plant, fungi and protist cells. Eukaryotic cells are typically larger than prokaryotic cells.
• Key Cellular Structures and their Functions:
  • Cell membrane: A semi-permeable boundary controlling material passage.
  • Nucleus: Houses the genetic material (DNA) and directs cellular activities.
  • Cytoplasm: The region between the nucleus and cell membrane, filled with organelles.
  • Mitochondria: Site of cellular respiration, producing energy.
  • Ribosomes: Involved in protein synthesis.
  • Endoplasmic reticulum (ER): Involved in protein and lipid synthesis. Rough ER (studded with ribosomes) folds and modifies proteins; smooth ER synthesizes lipids and detoxifies substances.
  • Golgi apparatus: Processes, packages, and modifies proteins for secretion or use within the cell.
  • Vacuoles/vesicles: Store substances and facilitate transport. Large central vacuoles are characteristic of plant cells.
  • Chloroplasts (plant cells only): Site of photosynthesis, converting light energy to chemical energy.
  • Cell wall (plant cells only): Provides support and protection to the cell.
• Multicellular Organization: Cells organize into tissues, organs, and organ systems, each with distinct functions.
  • Specialized structures and functions are crucial to individual cells.
  • Coordination and communication between cells are vital for organismal function.

Explore the complex processes of the cell cycle, detailing its stages including interphase and the mitotic phase. Understand critical components like G1, S, G2 phases, and how mitosis and cytokinesis lead to cell division. This quiz will test your knowledge of cellular replication and genetic material distribution.