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Biological molecules official content
Biological molecules official content develops AQA A-Level Biology knowledge through Monomers and polymers, Carbohydrates, Lipids, General properties of proteins, Many proteins are enzymes, Structure of DNA and RNA. Students should connect molecular detail, cell-level mechanisms, organism-level outcomes and ecological or genetic consequences where relevant, rather than treating each objective as an isolated definition. The topic overview should help learners locate every learning objective, recognise the main command words and prepare for data-led questions. Focus on precise biological vocabulary, cause-and-effect chains, and evidence from practical work or experimental observations. Useful revision links include monomers, smaller, molecules, polymers, together., Identify, monosaccharides,, nucleotides, examples, monomers.. Strong answers should state the biological principle, apply it to the named context, interpret any data carefully and finish with a clear consequence or evaluation. Common mistakes include giving GCSE-level descriptions, missing the scale of organisation, or using a correct term without explaining why it matters in this A-Level context.
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10
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90 min
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49 objective pages available
Monomers and polymers4 objectives
- Define monomers as smaller units from which larger molecules are made.
- Define polymers as molecules made from many monomers joined together.
- Identify monosaccharides, amino acids and nucleotides as examples of monomers.
- Distinguish condensation reactions from hydrolysis reactions using bond formation, bond breaking and water.
Carbohydrates6 objectives
- Describe monosaccharides as monomers from which larger carbohydrates are made.
- Explain how condensation between monosaccharides forms glycosidic bonds and disaccharides.
- Relate the structures of starch, glycogen and cellulose to their functions in plant and animal cells.
- Use and interpret Benedict's, non-reducing sugar and iodine tests for carbohydrates.
- Link chromatography and colorimetry opportunities to carbohydrate investigation.
- Required practical 11: produce a dilution series of glucose and use colorimetry to create a calibration curve for identifying glucose concentration in an unknown sample.
Lipids5 objectives
- Describe triglycerides and phospholipids as groups of lipid.
- Explain how condensation between glycerol and fatty acids forms ester bonds.
- Recognise saturated and unsaturated fatty acids from diagrams.
- Explain different properties of triglycerides and phospholipids using their structures.
- Use and interpret the emulsion test for lipids.
General properties of proteins5 objectives
- Describe amino acids as monomers from which proteins are made.
- Explain how condensation between amino acids forms peptide bonds, dipeptides and polypeptides.
- Relate primary, secondary, tertiary and quaternary structure to protein function.
- Explain roles of hydrogen bonds, ionic bonds and disulfide bridges in protein structure.
- Use and interpret the biuret test for proteins.
Many proteins are enzymes5 objectives
- Explain that enzymes lower activation energy and catalyse reactions.
- Describe the induced-fit model of enzyme action using active sites and enzyme-substrate complexes.
- Explain effects of enzyme concentration, substrate concentration, inhibitors, pH and temperature on enzyme-controlled reaction rates.
- Appreciate how models of enzyme action have changed over time.
- Required practical 1: investigate the effect of a named variable on the rate of an enzyme-controlled reaction.
Structure of DNA and RNA5 objectives
- Describe DNA and RNA as polymers of nucleotides.
- Identify the components of DNA and RNA nucleotides.
- Explain phosphodiester bond formation between nucleotides.
- Describe the DNA double helix and complementary base pairing.
- Use base-frequency information to infer complementary DNA base frequencies.
DNA replication5 objectives
- Explain why semi-conservative replication maintains genetic continuity.
- Describe unwinding of DNA and hydrogen-bond breakage by DNA helicase.
- Describe complementary base pairing on exposed template strands.
- Explain the role of DNA polymerase in joining adjacent nucleotides.
- Evaluate scientific work validating the Watson-Crick model of DNA replication.
ATP5 objectives
- Describe ATP as a nucleotide derivative formed from ribose, adenine and three phosphate groups.
- Explain hydrolysis of ATP to ADP and inorganic phosphate.
- Explain how ATP hydrolysis can be coupled to energy-requiring reactions.
- Explain how inorganic phosphate can phosphorylate compounds.
- Describe ATP resynthesis by condensation of ADP and inorganic phosphate.
Water5 objectives
- Explain water as a metabolite in condensation and hydrolysis reactions.
- Explain water as a solvent for metabolic reactions.
- Link high heat capacity to buffering temperature change.
- Link large latent heat of vaporisation to cooling.
- Explain cohesion and surface tension in biological contexts.
Inorganic ions4 objectives
- Describe inorganic ions as dissolved components of cytoplasm and body fluids.
- Explain that ion roles depend on ion properties and concentrations.
- Recognise roles of hydrogen ions in pH.
- Recognise roles of iron ions in haemoglobin, sodium ions in co-transport, and phosphate ions in DNA and ATP.
Key terms
Exam tips
- Clarify definitions: Ensure you can clearly define key terms like monomer and polymer, and understand their roles in biological molecules.
- Use diagrams to illustrate polymer structures: When explaining concepts related to polymers, include diagrams to visualize monomer arrangements and bonding.
Common mistakes
- Confusing monomers with polymers: Remember that monomers are the individual building blocks, while polymers are the larger structures formed from these monomers.
- Confusing monomers with polymers: Remember that polymers are composed of many repeating monomer units, which are the basic building blocks.
Practice preview
- Which of the following is a monomer of carbohydrates?
- Explain how monomers are related to the formation of polymers.
- A student conducts an experiment to determine the effect of temperature on the rate of starch polymerization from glucose monomers. Describe the independent, dependent, and control variables in this experiment.
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