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AS Biology ­ Revision Notes
Unit 1 ­ Core Principles
1. Carbohydrates have the general formula (CH2O)x.
2. The simplest carbohydrates are monosaccharides, e.g. glucose (C 6H12O6), and are monomers.
3. Monosaccharides can join together to form disaccharides in a condensation reaction, forming a

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e. It has a high specific heat capacity ­ it absorbs a lot of energy with little change in
temperature. So it is thermally very stable.

Cells And Transport
1. Prokaryotic cells have no nuclear membrane ­ the nucleic acids are free in the cytoplasm.

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c. The distance over which diffusion takes place.
d. The surface area.
surface area × concentration difference
25. Fick's Law says that: rate of diffusion =
distance between the two areas
26. Facilitated diffusion is still a passive process, but uses either:
a. Ion channels (i.e.…

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14. Extracellular digestion takes place in saprophytic fungi. In the mycelium, enzymes are secreted
from the hyphae. Digestion takes place on the food surface, and the products of digestion are
absorbed. Note that fungi are multinuclear (i.e. there are no cell membranes or walls).
15. In…

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c. Lungs ­ bronchial/alveolar network within the pleural cavity, e.g. most mammals.
4. All respiratory surfaces have the following properties:
a. Large surface area.
b. Short diffusion pathway (thin walls).
c. Well supplied with blood.
d. They are moist (as a consequence of thin walls).


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