3.1 Chemical elements and water
• 4 elements most commonly found in living things (as we know them!)– Carbon– Hydrogen– Oxygen– Nitrogen
• What else do living things need? Why?
Water• Thermal properties– High specific heat (can absorb or release a lot of heat
without changing temp – temp stabilizer)– High heat of vaporization (cooling mechanism)
• Cohesive properties– Forms droplets– Surface tension (Jesus Christ lizard)– Moves as a column in plants– HSH and HHV
• Solvent properties– Glucose, amino acids, fibrinogen and hydrogencarbonate
ions (transport CO2) in blood
3.2 Carbs, lipids and proteins
• Carbohydrates – monosaccharides• Lipids – glycerol and fatty acids• Proteins (polypeptides) – amino acids• Nucleic acids – nucleotides
• Why are models of these molecules used? What do the molecules actually look like?
Lipids
• Why are they important?– Insulation– Adipose cells hold more or less– Energy storage – think about this primitively– Phospholipid – what is that?
3.3 DNA Structure• Nucleotide: a phosphate group O=P, a deoxyribose sugar and a
nitrogenous base• 4 Nitrogenous bases
– Adenine– Thymine– Guanine– Cytosine
• Nucleotides are covalently bonded• Complementary pairs are hydrogen bonds (T and C are much
smaller than A and G)– C-----G– A-----T
• Check out heinemann.co.uk/hotlinks; ex code 4242P and click on Weblink 3.4
3.4 DNA Replication
• Hydrogen bonds undone so DNA can be copied– Helicase is an enzyme that does this
Formation of 2 complementary strands
• Free nucleotides also present – can bond to end of strand– These covalent bonds are catalyzed by DNA
polymerase
Transcription
• Produces RNA using free nucleotides in nucleoplasm
• Only 1 strand of DNA is copied• mRNA is single stranded and shorter than DNA
(only 1 gene)• DNA has thymine and deoxyribose• RNA has uracil
• Figure 3.15 \/