2.1 The Cell

Introduction

  • The basic structural and functional unit of all known organisms.
  • Smallest unit of life that can replicate independently.

Plant Cell: Cell Organelles and their Functions

  • Cell Wall: Rigid outer layer (cellulose); structural support, protection, maintains shape.
  • Cell Membrane: Semi-permeable; controls substance movement.
  • Plastids: (e.g., Chloroplasts) Sites of photosynthesis; pigment synthesis, food storage.
  • Nucleus: Control center; contains DNA; controls cell activities.
  • Vacuole: Large, central; stores water, nutrients, waste; maintains turgor pressure.
  • Cytoplasm: Jelly-like substance; site of metabolic reactions.

Animal Cell: Cell Organelles and their Functions

  • Cell Membrane: Thin, flexible outer boundary; controls substance passage, cell communication.
  • Plastids: Absent (no photosynthesis).
  • Nucleus: Control center; contains DNA; controls cell activities.
  • Vacuole: Several small, temporary (if any); temporary storage/transport.
  • Cytoplasm: Jelly-like substance; site of metabolic reactions.

Differences between Plant and Animal Cells

Feature Plant Cell Animal Cell
Cell Wall Present (rigid, cellulose) Absent
Cell Membrane Present (inside cell wall) Present (outer boundary)
Plastids Present (e.g., chloroplasts) Absent
Nucleus Present (often pushed to periphery) Present (usually central)
Vacuole One large, central Several small, temporary (if any)
Cytoplasm Present Present