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

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

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

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

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

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

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

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;

2.7 DNA replication, transcription and translation

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

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

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

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

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)

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

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

2.8 Cell respiration Aerobic vs anaerobic Respirometers

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

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

2.9 Photosynthesis Absorption and action spectra Limiting factors