1.2 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)
Understandings:
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.
International-mindedness:
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?
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.
Essential idea: The structure of biological membranes makes
them fluid and dynamic.
