Topic 1 of 8 · Form 5
Cell structure, biological molecules and enzymes
Light and electron microscopy (magnification and resolution; calibration with eyepiece graticule and stage micrometer); ultrastructure of eukaryotic cells (nucleus, RER, SER, Golgi, mitochondria, ribosomes, lysosomes, centrioles, chloroplasts, cell wall); prokaryotic cells; viruses.
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Cell structure
Light and electron microscopy (magnification and resolution; calibration with eyepiece graticule and stage micrometer); ultrastructure of eukaryotic cells (nucleus, RER, SER, Golgi, mitochondria, ribosomes, lysosomes, centrioles, chloroplasts, cell wall); prokaryotic cells; viruses.
Worked example: An eyepiece graticule division equals 2.5 µm at ×400. A cell spans 18 divisions. Find its actual length.
18 × 2.5 = 45 µm
Biological molecules
Carbohydrates (α- and β-glucose, glycosidic bonds, starch, glycogen, cellulose), lipids (triglycerides, phospholipids), proteins (peptide bonds; primary to quaternary structure; haemoglobin and collagen), water and its properties. Tests for reducing and non-reducing sugars, starch, lipids and proteins.
Enzymes
Active site, specificity, induced fit; factors affecting rate; Vmax and Km; competitive and non-competitive inhibition; immobilised enzymes.
Check yourself
- Why do electron microscopes have higher resolution than light microscopes?
- Describe the test for a non-reducing sugar.
- What does a low Km indicate?
Show answers
- Electrons have a much shorter wavelength than light.
- After a negative Benedict's test, boil with dilute HCl, neutralise with NaHCO₃, then repeat Benedict's – brick-red precipitate.
- High affinity of the enzyme for its substrate.
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