Animal & Plant Cells (Cambridge (CIE) AS Biology)

Electron Micrographs: Animal Cells

• 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

Electron Micrographs: Plant 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

Structure of Animal & 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