Biology · Cell structure
Explain that cells are the basic units of life
Use the units of measurement relevant to microscopy
Recognise the common structures found in cells as seen with a light microscope and outline their structures and functions
Compare the key structural features of animal and plant cells
Use a light microscope and make temporary preparations to observe cells
Calculate magnifications of images and actual sizes of specimens using drawings or micrographs
Explain the use of the electron microscope to study cells with reference to the increased resolution of electron microscopes
Recognise the common structures found in cells as seen with an electron microscope and outline their structures and functions
Outline briefly the role of ATP in cells
Describe the structure of bacteria and compare the structure of prokaryotic cells with eukaryotic cells
Describe the structure of viruses
Magnification
Ensure 'observed size of the image' and 'actual size' are in the same units before calculation. This formula can be rearranged to find any of the three variables if the other two are known.
Students often confuse magnification with resolution; magnification is about making an image larger, while resolution is about seeing more detail and distinguishing between two close points.
Students often think all organelles are membrane-bound, but some, like ribosomes and centrioles, are not.
Students often confuse the cell wall with the cell surface membrane; the cell wall is external, rigid, and freely permeable (in plants/bacteria), while the cell surface membrane is internal, thin, partially permeable, and present in all cells.
Students often think vacuoles are exclusive to plant cells, but animal cells can have small, temporary vacuoles, though they lack the large, permanent central vacuole of plants.
Students often think bacterial flagella have the same complex '9 + 2' microtubule structure as eukaryotic flagella, but bacterial flagella are much simpler and rotate like a propeller.
Students often think viruses are living cells, but they are acellular and obligate intracellular parasites, meaning they can only replicate inside living host cells.