Animal & Plant Cells (CIE AS Biology)

• Exam questions will not always contain neat diagrams of cellular structures, but may instead present images taken using microscopes
  • Such images are known as micrographs
• It is possible to identify organelles in micrographs of animal cells on the basis of their shape, location, and size relative to other organelles, e.g.
  • The nucleus will always be the largest organelle
  • Mitochondria are the next largest, and are often cylindrical with a folded inner membrane
    • Note that mitochondria are not always cylindrical, but can also be circular; their shape will depend on their age, and on the angle at which they were sliced during specimen preparation
  • RER will be near the nucleus, and ribosomes can sometime be seen
  • Lysosomes and vesicles will be smaller than mitochondria

Exam questions may present micrograph images of cells

• Plant cell micrographs can be interpreted using the same techniques as animal cells
  • Large, seemingly empty spaces inside cells will be vacuoles
  • The nucleus will be the largest dark region in the cell
  • Chloroplasts are the next-largest organelles, and grana are often visible

Vacuoles and chloroplasts can be easily recognised inside plant cells

• Animal and plant cells have many common structures:
  • Cell surface membrane
  • Cytoplasm
  • Nucleus
  • Mitochondria
  • Rough and smooth endoplasmic reticulum
  • Golgi bodies
  • Vesicles and lysosomes
  • Ribosomes
  • Microtubules
• Plant cells are larger and more regular in shape than animal cells, and have the following additional structures
  • Cellulose cell wall
  • Large permanent vacuoles
  • Chloroplasts
  • Plasmodesmata
• The only structures found in animal cells but not plant cells are centrioles and microvilli

Animal and plant cell ultrastructure diagrams

Plant cells have a larger, more regular structure in comparison to animal cells