Ultrastructure of cells

Nature of science:

Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)

• Prokaryotes have a simple cell structure without compartmentalization.
• Eukaryotes have a compartmentalized cell structure.
• Electron microscopes have a much higher resolution than light microscopes.

Applications and skills:

• Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf.
• Application: Prokaryotes divide by binary fission.
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
• Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells.

Guidance:

• Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
• Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S ribosomes and a nucleus, mitochondria and other membrane-bound organelles are present in the cytoplasm. Some eukaryotic cells have a cell wall.

• Microscopes were invented simultaneously in different parts of the world at a time when information travelled slowly. Modern-day communications have allowed for improvements in the ability to collaborate, enriching scientific endeavour.

Theory of knowledge:

• The world that we inhabit is limited by the world that we see. Is there any distinction to be drawn between knowledge claims dependent upon observations made by sense perception and knowledge claims dependent upon observations assisted by technology?

Utilization:

• Syllabus and cross-curricular links:
• Physics
• Topic 4.4 Wave behaviour
• Topic C.1 Introduction to imaging Topic C.3 Fibreoptics

Aims:

• Aim 8: Developments in science, such as electron microscopy, can have economic benefits as they give commercial companies opportunities to make profits, but this can affect cooperation between scientists.