Key term
AQA AS-Level Biology 7402
Biological Molecules
Topic overviewMonomers, polymers, condensation and hydrolysisMonosaccharides, disaccharides and glycosidic bondsAlpha and beta glucose, amylose and amylopectinHow starch, glycogen and cellulose suit their functionsCellulose microfibrils and tests for sugars and starchTriglycerides, fatty acids and phospholipid structureProperties of lipids and the emulsion testThe general structure of amino acidsPeptide bonds, polypeptides and bonds in proteinsLevels of protein structure, the biuret test and chromatographyActivation energy, induced fit and enzyme specificityEnzyme and substrate concentration and inhibitionpH, temperature, initial rates and measurement uncertaintyDNA, RNA and the components of a nucleotideBase pairing in DNA and RNAPhosphodiester bonds and the DNA double helixDoubts about DNA, base ratios and RNA structureSemi-conservative replication, helicase and DNA polymeraseSteps of replication and the Meselson-Stahl experimentATP structure, hydrolysis and resynthesisWater as a metabolite, solvent and coolantHydrogen, iron, sodium and phosphate ions
Cells
Topic overviewCell-surface membrane, nucleus and mitochondriaChloroplasts, Golgi apparatus and lysosomesRibosomes, endoplasmic reticulum, cell walls and vacuolesCell specialisation, levels of organisation and organelle rolesProkaryotic cell structure and virus particlesOptical and transmission electron microscopesScanning electron microscopes, magnification and graticulesCell fractionation, homogenisation and ultracentrifugationOrder of sedimentation, artefacts and fractionation conditionsThe cell cycle, interphase and the stages of mitosisSpindle fibres, cytokinesis and uncontrolled cell divisionBinary fission, viral replication and root tip squashesMitotic index, mitosis stages and size calculationsThe fluid-mosaic model and cholesterolSimple diffusion, facilitated diffusion and membrane proteinsOsmosis, water potential and active transportCo-transport in the ileum and adaptations for rapid transportTransport rates, dilution series and membrane permeabilityAntigens, cell recognition and phagocytosisAntigen-presenting cells, T cells and clonal selectionAntibody structure, agglutination and antigen-antibody complexesMemory cells, vaccination and active and passive immunityHIV structure and replicationAIDS, monoclonal antibodies, ELISA and clinical trials
Organisms Exchange Substances with Their Environment
Topic overviewSurface area to volume ratio, metabolic rate and calculationsGas exchange in single-celled organisms, insects and fishLeaf gas exchange, insect water loss and xerophytesTrachea, bronchi, alveoli and lung dissectionInspiration, expiration and pulmonary ventilation rateLung disease, correlation, insect tracheae and Spearman's rankDigestion of carbohydrates and lipidsEndopeptidases, exopeptidases and dipeptidasesCo-transport of amino acids, micelles and chylomicronsHaemoglobin, red blood cells and the dissociation curveCooperative binding, the Bohr effect and different haemoglobinsDouble circulation and the major blood vesselsHeart chambers, the cardiac cycle and heart dissectionArteries, arterioles, veins and capillariesTissue fluid, cardiovascular risk factors and semilunar valvesXylem structure and the cohesion-tension theoryPhloem structure, companion cells and translocationMass flow from source to sink, tracers and ringingEvaluating mass flow, potometers and transpiration rate
Genetic Information, Variation and Relationships Between Organisms
Topic overviewProkaryotic and eukaryotic DNA, chromosomes and histonesDNA in mitochondria and chloroplasts, genes and lociFeatures of the genetic code, exons and intronsGenome, proteome, mRNA and tRNATranscription, RNA polymerase and splicingTranslation at the ribosome and the role of tRNAGene mutations, mutagens and chromosome non-disjunctionMeiosis, independent segregation and crossing overMeiosis compared with mitosis and random fertilisationGenetic diversity and the spread of advantageous allelesDirectional and stabilising selectionDefining adaptations and how antibiotic resistance spreadsSelection on birth weight, aseptic technique and antimicrobialsClassifying anatomical, physiological and behavioural adaptationsDefining a species, courtship and phylogenetic classificationThe taxonomic hierarchy, binomial names and molecular evidenceSpecies richness, the index of diversity and farmingComparing genetic diversity, standard deviation and the t-test
Biological Molecules
- 22 subtopics
- 64 things to know
- Papers 1 and 3
What Biological Molecules covers
Biological Molecules is examined on Paper 1 of AQA Biology, which covers topics 1 to 4, and on Paper 3, which can draw on any topic. 283 recall questions across 22 subtopics.
Where it is assessed
Papers 1 and 3
Topics 1 to 4, then the synoptic paper.
Check the AQA specification ↗The 22 subtopics
Each one has its own page. AQA AS Biology students sit this topic in the first year.
- Monomers, polymers, condensation and hydrolysisRecall questions on monomers and polymers, the monomers of carbohydrates, proteins and nucleic acids, and condensation and hydrolysis reactions as the making and breaking of bonds with water.Open →
- Monosaccharides, disaccharides and glycosidic bondsRecall questions on monosaccharides as the monomers of carbohydrates, the condensation reaction that forms a glycosidic bond, and the monosaccharides that make up maltose, sucrose and lactose.Open →
- Alpha and beta glucose, amylose and amylopectinRecall questions on the alpha and beta isomers of glucose, which isomer builds glycogen, starch and cellulose, and the chain shape and glycosidic bonds of amylose and amylopectin.Open →
- How starch, glycogen and cellulose suit their functionsRecall questions on how the helical, insoluble structure of starch suits storage in plants, why the branching of glycogen allows rapid energy release in animals, and how cellulose chains are bonded together.Open →
- Cellulose microfibrils and tests for sugars and starchRecall questions on cellulose microfibrils in plant cell walls, Benedict's test for reducing sugars, the hydrolysis step in the test for non-reducing sugars, and the iodine test for starch.Open →
- Triglycerides, fatty acids and phospholipid structureRecall questions on how glycerol and three fatty acids condense to form a triglyceride with ester bonds, saturated and unsaturated fatty acids, and how a phospholipid differs from a triglyceride.Open →
- Properties of lipids and the emulsion testRecall questions on why triglycerides are hydrophobic and energy-rich stores, how amphipathic phospholipids form bilayers, and each step and result of the emulsion test for lipids.Open →
- The general structure of amino acidsRecall questions on amino acids as the monomers of proteins, the central carbon with its amine group, carboxyl group, hydrogen and R group, and how the twenty common amino acids differ.Open →
- Peptide bonds, polypeptides and bonds in proteinsRecall questions on the condensation reaction that forms a peptide bond, dipeptides and polypeptides, and the hydrogen bonds, ionic bonds and disulfide bridges that hold a protein's structure.Open →
- Levels of protein structure, the biuret test and chromatographyRecall questions on the primary, secondary, tertiary and quaternary structure of proteins, why shape matters, the biuret test for proteins, and separating amino acids by chromatography.Open →
- Activation energy, induced fit and enzyme specificityRecall questions on how enzymes lower activation energy, the induced-fit model and why it replaced the lock-and-key model, enzyme-substrate complexes and why enzymes are specific.Open →
- Enzyme and substrate concentration and inhibitionRecall questions on how enzyme and substrate concentration affect the rate of reaction, saturation of active sites, and how competitive and non-competitive inhibitors affect rate and Vmax.Open →
- pH, temperature, initial rates and measurement uncertaintyRecall questions on how pH and temperature affect enzyme activity and denaturation, finding initial rate with a tangent, and accuracy, precision, uncertainty, percentage error and controls in enzyme investigations.Open →
- DNA, RNA and the components of a nucleotideRecall questions on the roles of DNA and RNA, nucleotides as the monomers of nucleic acids, the pentose sugar, phosphate group and organic base, and deoxyribose in DNA.Open →
- Base pairing in DNA and RNARecall questions on complementary base pairing of adenine, thymine, guanine and cytosine in DNA, uracil replacing thymine in RNA, and how the pentose sugars of DNA and RNA differ.Open →
- Phosphodiester bonds and the DNA double helixRecall questions on phosphodiester bonds formed by condensation between nucleotides, the double helix of two polynucleotide strands held by hydrogen bonds, and how RNA compares in length and strands.Open →
- Doubts about DNA, base ratios and RNA structureRecall questions on why scientists first doubted that DNA carried the genetic code, calculating base percentages from complementary pairing, and ribose and the polynucleotide structure of RNA.Open →
- Semi-conservative replication, helicase and DNA polymeraseRecall questions on what semi-conservative replication means, how DNA helicase breaks hydrogen bonds to separate the strands, how free nucleotides pair with the template, and the role of DNA polymerase.Open →
- Steps of replication and the Meselson-Stahl experimentRecall questions on the sequence of semi-conservative replication, the conservative, semi-conservative and dispersive models, and how Meselson and Stahl used nitrogen isotopes and banding patterns to test them.Open →
- ATP structure, hydrolysis and resynthesisRecall questions on ATP as a nucleotide derivative, its hydrolysis by ATP hydrolase to release energy and phosphorylate compounds, and its resynthesis by ATP synthase in photosynthesis and respiration.Open →
- Water as a metabolite, solvent and coolantRecall questions on water in condensation and hydrolysis reactions, its high heat capacity and latent heat of vaporisation, cohesion and surface tension from hydrogen bonding, and water as a polar solvent.Open →
- Hydrogen, iron, sodium and phosphate ionsRecall questions on inorganic ions in organisms, hydrogen ions and pH, iron ions in haemoglobin, sodium ions in the co-transport of glucose and amino acids, and phosphate ions in DNA and ATP.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
What is a triglyceride made from, and what bond joins the parts?
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What are monomers and polymers, and how are they joined?
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What fundamental principle underlies the biochemistry of all living organisms, regardless of their diversity?
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What type of chemical reaction joins two monosaccharides together to form a glycosidic bond?
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How many monosaccharide units are joined together to form a disaccharide?
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What are the names of the two isomers of glucose?
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In α-glucose, where is the hydroxyl group on carbon-1 positioned relative to the ring?
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What is the main function of starch in plants?
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Explain how the structure of glycogen differs from amylopectin in terms of branching.
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What is the function of cellulose in plants?
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Describe the colour change observed in a positive Benedict's test for reducing sugars.
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Name the two main groups of lipid you need to know.
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Explain how the amphipathic nature of phospholipids enables them to form bilayers in water.
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Explain why the insolubility of triglycerides makes them suitable for energy storage in cells.
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In the general structure of an amino acid, what is at the centre to which all other groups are attached?
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What nitrogen-containing group is bonded to the central carbon in an amino acid?
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What type of chemical reaction joins two amino acids together, and what bond is formed?
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What small molecule is released when a condensation reaction occurs between amino acids?
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Define the primary structure of a protein.
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What effect does an enzyme have on the activation energy of a reaction?
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Define activation energy.
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Why does increasing enzyme concentration increase the rate of reaction when substrate is in excess?
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What happens to the rate of reaction at low substrate concentrations as substrate concentration increases?
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What is meant by the optimum pH of an enzyme?
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What happens to an enzyme at extreme pH values?
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What is the role of RNA in relation to genetic information?
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What two types of molecule make up ribosomes?
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How does the pentose sugar in DNA differ from that in RNA?
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What is the name of the bond that links adjacent nucleotides in a polynucleotide chain?
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What type of chemical reaction forms a phosphodiester bond between two nucleotides?
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In double-stranded DNA, if 30% of the bases are adenine, what percentage would be thymine?
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What type of macromolecule is RNA in terms of its basic structural organisation?
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What does semi-conservative replication mean in terms of the composition of each new DNA molecule?
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What must happen to the DNA double helix before replication can begin?
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What is released when a phosphodiester bond forms between adjacent nucleotides during replication?
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Which enzyme unwinds the double helix, and how does it separate the strands?
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What type of molecule is ATP classified as?
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How many phosphate groups are present in a single molecule of ATP?
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Why is water considered essential at the cellular level?
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What role does water play in condensation reactions?
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Do all inorganic ions occur at the same concentration in organisms?
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How do hydrogen ions affect the acidity of a solution?
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Define the term monomer.
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Which two monosaccharides condense together to form maltose?
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How does the position of the hydroxyl group on carbon-1 in β-glucose differ from α-glucose?
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Why does the highly branched structure of glycogen allow rapid energy release?
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Which disaccharides are classified as reducing sugars?
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How many glycerol molecules are required to form one triglyceride?
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Which biochemical test is used to detect the presence of lipids?
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What acidic group is bonded to the central carbon atom of an amino acid?
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How many polypeptide chains may a functional protein contain?
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What is the secondary structure of a protein, and what bonds maintain it?
Who and when
According to the induced-fit model, what occurs to the active site when the substrate binds?
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What happens to active sites as substrate concentration increases?
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What is the optimum temperature of an enzyme?
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What type of biological molecule is DNA classified as, in terms of its structure?
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Describe the overall three-dimensional shape of a DNA molecule.
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Explain why RNA is classified as a polynucleotide.
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What type of bonds are broken to separate the two polynucleotide strands during DNA replication?
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What becomes available for replication once DNA helicase has acted?
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What nucleotide is produced when ATP undergoes hydrolysis?
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What role does water play in hydrolysis reactions?
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What would happen to pH if hydrogen ion concentration in a solution increased?
Take Biological Molecules further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Monomer vs Polymer
Monomer: a small molecular unit that joins to form larger molecules. Polymer: a large molecule assembled from many repeating molecular units.
Condensation vs Hydrolysis
Condensation: bond formation accompanied by water release. Hydrolysis: bond breaking through addition of water.
Saturated fatty acid vs Unsaturated fatty acid
Saturated fatty acid: a lipid component containing no carbon-carbon double bonds. Unsaturated fatty acid: a lipid component containing at least one carbon-carbon double bond.
Questions from this topic
Each one with the model answer underneath.
- 1
What fundamental principle underlies the biochemistry of all living organisms, regardless of their diversity?
Model answer
The biochemical basis of life is similar for all living things, despite the extensive variety of life both past and present.
- 2
Define the term monomer.
Model answer
Monomers are the smaller units from which larger molecules are made.
- 3
What is a polymer?
Model answer
A polymer is a molecule made from a large number of monomers joined together.
- 4
Name a type of monomer that serves as the building block for carbohydrates.
Model answer
Monosaccharides.
- 5
What monomers are joined together to form proteins?
Model answer
Amino acids.
- 6
Which type of monomer is used to build nucleic acids?
Model answer
Nucleotides.
What is inside Levo
Six ways to work the same material.
Biological Molecules revision questions
- Is Biological Molecules examined at AS in AQA Biology?
- Yes. It sits in Papers 1 and 3, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.
- What does Biological Molecules cover in AQA AS-Level Biology?
- 22 subtopics: monomers, polymers, condensation and hydrolysis, monosaccharides, disaccharides and glycosidic bonds, alpha and beta glucose, amylose and amylopectin, how starch, glycogen and cellulose suit their functions, cellulose microfibrils and tests for sugars and starch, triglycerides, fatty acids and phospholipid structure, properties of lipids and the emulsion test, the general structure of amino acids, peptide bonds, polypeptides and bonds in proteins, levels of protein structure, the biuret test and chromatography, activation energy, induced fit and enzyme specificity, enzyme and substrate concentration and inhibition, ph, temperature, initial rates and measurement uncertainty, dna, rna and the components of a nucleotide, base pairing in dna and rna, phosphodiester bonds and the dna double helix, doubts about dna, base ratios and rna structure, semi-conservative replication, helicase and dna polymerase, steps of replication and the meselson-stahl experiment, atp structure, hydrolysis and resynthesis, water as a metabolite, solvent and coolant and hydrogen, iron, sodium and phosphate ions. Each one has its own page with questions and model answers.
- How is Biological Molecules organised?
- By the AQA 7402 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Biological Molecules, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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