1. condensation reactions involve joining subunits/molecules/monomers;
with the release of water;
hydrolysis reactions involve splitting molecules into subunits molecules/monomers;
with the addition of water;
example of condensation reaction; (e.g. amino acid + amino acid yields dipeptide + water)
example of hydrolysis reaction; (e.g. disaccharide + water yields two monosaccharides) Examples can be shown in words or chemical form.
5 marks

2. Year 12 Revision Topic 2: Molecular Biology
2.1 Molecules to metabolism
2.2 Water
2.3 Carbohydrates and lipids
2.4 Proteins
2.5 Enzymes
2.6 Structure of DNA and RNA
2.7 DNA replication, transcription and translation
2.8 Cell respiration
2.9 Photosynthesis

3. 2.6 Structure of DNA and RNA
Nucleotides
DNA vs RNA
Drawing DNA

4. Nucleotides Made up of Nitrogenous base Phosphate group
Pentose sugar (5 carbon atoms)
Many nucleotides together = nucleic acid

5. DNA or RNA?
Two strands
Deoxyribose
Uracil
One strand
Ribose
Thymine

6. DNA or RNA?
Two strands
Deoxyribose
Uracil
One strand
Ribose
Thymine

7. Draw a diagram showing the molecular structure of a section of the DNA molecule. 5 marks

8. Two polymers shown;
Sugar shown connected to base;
Sugar-phosphate backbone shown;
Sugar identified as deoxyribose;
Hydrogen bonding between bases shown;
Diagram shows complementary base pairing / Adenine bonded to Thymine, Cytosine with Guanine;
Covalent bonding between phosphate and sugar;

9. 2.7 DNA replication, transcription and translation

10. Complementary base pairs
Replication
DNA helicase
Free nucleotides
DNA polymerase
Complementary base pairs
Semi conservative
Hydrogen bonds

11. Replication During interphase of cell cycle DNA unwinds
Helicase: breaks H bonds
Strands separate
Free nucleotides bind with complementary base pairs
DNA polymerase: joins new nucleotides together
Two identical DNA strands
Semi conservative: each molecule contains a new strand and original strand of DNA

12. Transcription DNA cannot leave the nucleus
Want to get a gene out to make a protein
A copy must be transcribed into RNA
mRNA made

13. Complementary base pairs
Transcription
RNA polymerase
DNA unwinds
Complementary base pairs
Hydrogen bonds
Leaves nucleus
Free RNA nucleotides
Recoils

14. Transcription DNA unwinds H bonds break Strands separate
Free RNA nucleotides attracted to complementary base pairs
Nucleotides joined (RNA polymerase)
RNA leaves nucleus
DNA recoils as a double helix again (H bonds form)

15. Translation mRNA Ribosome Codon Anticodon tRNA Hydrogen bond Protein
Peptide bond
Polypeptide

16. Translation mRNA has left the nucleus into the cytoplasm
Ribsosome attaches to mRNA
3 bases = codon
tRNA has specific complementary anticodons
Anticodon attracted to mRNA – forms H bond
Second anticodon assembled
Peptide bond between amino acids
Carries on until stop codon reached
Polypeptide formed and released into cytoplasm

17. 2.8 Cell respiration
Aerobic vs anaerobic
Respirometers

18. Respiration
Controlled release of energy from organic compounds to produce ATP
Anaerobic
Glucose 🡪 lactate (animals)
Glucose 🡪 ethanol and carbon dioxide (yeast and plants)
Aerobic
Glucose + oxygen 🡪 Carbon dioxide and water

19. Respirometers
Controlled release of energy from organic compounds to produce ATP
Anaerobic
Glucose 🡪 lactate (animals)
Glucose 🡪 ethanol and carbon dioxide (yeast and plants)
Aerobic
Glucose + oxygen 🡪 Carbon dioxide and water

20. 2.9 Photosynthesis
Absorption and action spectra
Limiting factors