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Edexcel AS-Level Biology B 9BI0
Biological Molecules
Topic overviewMonosaccharides, disaccharides and polysaccharidesGlycosidic bonds and condensation reactionsStarch, glycogen and cellulose structureTriglycerides and phospholipidsSaturated and unsaturated fats and lipid propertiesAmino acid structure and the peptide bondPrimary, secondary, tertiary and quaternary structureFibrous and globular proteinsThe structure of DNADNA replication and gene mutationsThe structure of RNATranscription and translationEnzymes as globular proteinsFactors affecting enzyme activityMeasuring the rate of enzyme activityUnits, uncertainty and experimental errorEnzyme inhibitionInorganic ionsThe properties of water
Cells, Viruses and Reproduction of Living Things
Topic overviewCell theory and eukaryotic cell structureProkaryotic cells and Gram stainingMicroscopy, magnification and resolutionSignificant figures, estimates and mathematical symbolsVirus structure and classificationThe lytic cycle and latencyTreating viral disease and the ethics of untested drugsThe cell cycle and its regulationMitosis and the behaviour of chromosomesMitosis in growth, repair and root tip squashesMeiosis, genetic variation and chromosome mutationsGametogenesis in mammalsFertilisation and early embryo developmentPollen and embryo sac formationDouble fertilisation in flowering plantsInvestigating pollen tube growth
Classification and Biodiversity
Exchange and Transport
Topic overviewSurface area to volume ratioThe fluid mosaic modelDiffusion, osmosis and facilitated diffusionActive transport, endocytosis and exocytosisGas exchange in insects, fish and mammalsDissecting the insect gas exchange systemGas exchange in flowering plantsThe structure of the heart and blood vesselsThe double circulatory systemThe cardiac cycleMyogenic stimulation and ECG tracesThe composition of bloodThe functions of blood and clottingAtherosclerosis and its risk factorsHaemoglobin and the Bohr effectOxygen dissociation curvesFormation of tissue fluidThe lymphatic systemXylem and phloem structureApoplastic and symplastic pathwaysThe cohesion-tension theoryMeasuring transpiration with a potometerTranslocation and the mass flow hypothesis
Biological Molecules
- 19 subtopics
- 59 things to know
- Papers 1, 2 and 3
What Biological Molecules covers
The first topic and the chemical foundation of the rest of the course: carbohydrates, lipids and proteins, the structure of DNA and RNA and how a gene becomes a protein, how enzymes work and what alters their rate, and the roles of inorganic ions and water.
Where it is assessed
Papers 1, 2 and 3
Examined on every paper.
Check the Pearson Edexcel specification ↗The 19 subtopics
Each one has its own page. Edexcel AS Biology B students sit this topic in the first year.
- Monosaccharides, disaccharides and polysaccharidesRecall questions on monosaccharides, glucose as a hexose and ribose as a pentose, alpha and beta glucose, hydrolysis of glycosidic bonds, the structure of amylose, and why glucose and branched amylopectin suit rapid energy release.Open →
- Glycosidic bonds and condensation reactionsRecall questions on disaccharides and polysaccharides, condensation and the glycosidic bond, the monosaccharides in sucrose, lactose and maltose, the amylose and amylopectin in starch, 1,4 and 1,6 links, and glycogen branching.Open →
- Starch, glycogen and cellulose structureRecall questions on amylose and amylopectin, the branching of glycogen, and how the beta linkage in cellulose produces its strength.Open →
- Triglycerides and phospholipidsRecall questions on glycerol, fatty acids and the ester bond formed by condensation in a triglyceride, the phosphate group of a phospholipid, its hydrophilic head and hydrophobic tails, how phospholipids form a bilayer, and what bilayer fluidity allows.Open →
- Saturated and unsaturated fats and lipid propertiesRecall questions on saturated and unsaturated fatty acids, how double bonds and kinks affect packing and whether a lipid is solid or liquid, why lipids release more energy per gram, and their insolubility, waterproofing and insulation.Open →
- Amino acid structure and the peptide bondRecall questions on the general structure of an amino acid, the R group, and how a peptide bond forms.Open →
- Primary, secondary, tertiary and quaternary structureRecall questions on primary structure and why it determines folding, the alpha helix and beta pleated sheet, the ionic, disulfide and hydrogen bonds that stabilise tertiary structure, and what holds quaternary structure together.Open →
- Fibrous and globular proteinsRecall questions on fibrous and globular proteins, collagen's glycine-rich triple helix, its hydrogen bonds, cross-links and tensile strength, and haemoglobin's alpha and beta chains, haem groups, solubility and cooperative binding.Open →
- The structure of DNARecall questions on the nucleotide, complementary base pairing, the antiparallel double helix, and the bonds that hold it.Open →
- DNA replication and gene mutationsRecall questions on helicase, DNA ligase and DNA polymerase in semi-conservative replication, then gene mutations: deletions, insertions, substitutions and frameshifts, and the base change behind sickle cell anaemia and its effect on red blood cells.Open →
- The structure of RNARecall questions on the phosphodiester bond, the ribose, phosphate and bases of an mRNA nucleotide, the single-stranded structure of mRNA, the cloverleaf shape of tRNA, anticodons, and how a tRNA carries its amino acid.Open →
- Transcription and translationRecall questions on the gene as a sequence coding for a polypeptide, non-coding DNA, transcription of the antisense strand by RNA polymerase in the nucleus, translation at the ribosome, and the triplet, degenerate and non-overlapping genetic code with its start and stop codons.Open →
- Enzymes as globular proteinsRecall questions on enzymes as globular proteins and biological catalysts, the induced fit model and the enzyme-substrate complex, activation energy, the active site and specificity, and intracellular and extracellular enzymes.Open →
- Factors affecting enzyme activityRecall questions on how temperature and pH affect rate and cause denaturation, the effect of substrate and enzyme concentration, Vmax, why initial rate matters, and using proportionality, y = mx + c and gradients to predict rates.Open →
- Measuring the rate of enzyme activityRecall questions on measuring product formed or substrate used, drawing a tangent to find initial rate, and controlling the variables.Open →
- Units, uncertainty and experimental errorRecall questions on converting between nanometres, micrometres and millimetres, uncertainty and resolution, calculating and combining percentage error in enzyme experiments, accuracy and precision, random and systematic errors, and using uncertainty to evaluate conclusions.Open →
- Enzyme inhibitionRecall questions on competitive and non-competitive inhibitors, where each binds, why only competitive inhibition is overcome by adding more substrate, and end-product inhibition as negative feedback.Open →
- Inorganic ionsRecall questions on why plants need nitrate ions for DNA and amino acids, calcium ions for calcium pectate in the middle lamella, magnesium ions for chlorophyll and phosphate ions for ADP and ATP, and the deficiency symptoms of each.Open →
- The properties of waterRecall questions on the polarity of water and hydrogen bonding, its high specific heat capacity, its solvent properties, surface tension, incompressibility and hydrostatic support, maximum density at 4 °C, and why floating ice protects aquatic life.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Why do unsaturated lipids tend to be liquid at room temperature?
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What chains and prosthetic groups make up a haemoglobin molecule, and how many oxygen molecules can it bind?
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State the complementary base-pairing rules in DNA.
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Describe a tRNA molecule: the components of its nucleotides, its shape, and its anticodon.
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Explain why enzyme activity decreases at pH values above or below the optimum.
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What is Vmax in enzyme kinetics?
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How do competitive inhibitors reduce enzyme activity, and why can excess substrate overcome them?
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What is calcium pectate and where is it found in plant cells?
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What role do phosphate ions play in forming ADP and ATP in plants?
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What partial charges do the oxygen and hydrogen atoms carry in a water molecule, and why?
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Why does water have a high specific heat capacity, and how does this help terrestrial organisms?
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What defines a monosaccharide?
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What monosaccharide units form maltose?
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What alcohol molecule is used as the backbone in triglyceride synthesis?
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What distinguishes an unsaturated fatty acid from a saturated one?
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Why is glycine important in collagen structure?
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What are disulfide bonds and how do they form?
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How many alpha chains are present in a haemoglobin molecule?
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Define a gene in terms of its molecular structure and function.
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What is the sense strand of DNA and why is it given that name?
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What is the universal start codon and which amino acid does it code for?
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Give two examples of intracellular reactions catalysed by enzymes.
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What is a disaccharide?
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What type of glucose and glycosidic bonds make up cellulose?
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Why is starch suitable for long-term energy storage in plants?
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How many fatty acid molecules combine with glycerol to form a triglyceride?
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What is bonded to the central carbon atom of an amino acid?
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What type of reaction occurs when a peptide bond forms, and what is released?
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Besides the sugar and phosphate, what third component completes a DNA nucleotide?
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Guanine belongs to which structural class of nitrogenous bases?
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What type of covalent bond links the phosphate group of one nucleotide to the sugar of the next?
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What type of protein are enzymes, and what structural feature is essential to their function?
Who and when
According to the induced fit hypothesis, what happens when a substrate first approaches the active site?
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When determining initial rate from a graph, where should the tangent be drawn?
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Describe an alternative method for measuring initial rate using time measurements.
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What is the role of an enzyme as a biological catalyst?
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In alpha glucose, where is the hydroxyl group on carbon-1 positioned relative to the ring?
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Define a polysaccharide.
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How does the helical structure of amylose contribute to its storage function?
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Which functional group on glycerol participates in the bond formation during triglyceride synthesis?
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Describe the shape of saturated fatty acid chains and explain how this affects molecular packing.
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What functional group containing nitrogen is found in all amino acids?
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What is a polypeptide?
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Where do hydrogen bonds form in proteins and what structures do they contribute to?
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To which category of bases does thymine belong?
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What phosphorus-containing group is present in every DNA nucleotide?
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What phosphorus-containing component is present in each mRNA nucleotide?
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Adenine is classified as which category of nitrogenous base?
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What effect does the altered haemoglobin have on red blood cells in sickle cell anaemia?
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Why is the sickle cell allele common in some regions?
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In the induced fit model, what occurs to the active site when the substrate binds?
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What is the dependent variable in an enzyme activity investigation?
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How are uncertainties combined when a measurement is the difference between two readings, such as the start and end marks on a syringe?
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What is the difference between accuracy and precision in experimental results?
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How can error bars or uncertainty ranges be used to judge whether two mean rates of enzyme activity really differ?
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Where do non-competitive inhibitors bind, and what effect does this have?
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Why do plants require nitrate ions for DNA synthesis?
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Why is oxygen more electronegative than hydrogen in a water molecule?
Take Biological Molecules further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Condensation vs Hydrolysis
Condensation: reaction joining molecules while releasing water. Hydrolysis: reaction splitting molecules through the addition of water.
Primary structure vs Tertiary structure
Primary structure: amino-acid sequence of a polypeptide. Tertiary structure: overall three-dimensional folding of one polypeptide.
Competitive inhibitor vs Non-competitive inhibitor
Competitive inhibitor: molecule occupying the active site. Non-competitive inhibitor: molecule binding elsewhere and altering active-site shape.
Questions from this topic
Each one with the model answer underneath.
- 1
What defines a monosaccharide?
Model answer
A single sugar unit that cannot be hydrolysed into simpler carbohydrates.
- 2
How many carbon atoms does glucose contain, and what type of sugar is it classified as?
Model answer
Six carbon atoms; it is a hexose sugar.
- 3
In alpha glucose, where is the hydroxyl group on carbon-1 positioned relative to the ring?
Model answer
Below the plane of the ring.
- 4
How does the position of the hydroxyl group on carbon-1 in beta glucose differ from alpha glucose?
Model answer
In beta glucose, the hydroxyl group on carbon-1 is positioned above the plane of the ring.
- 5
How many carbon atoms does ribose contain, and what category of sugar is it?
Model answer
Five carbon atoms; it is a pentose sugar.
- 6
How does hydrolysis break down disaccharides or polysaccharides?
Model answer
A molecule of water is added across the glycosidic bond, breaking it and releasing monosaccharides.
What is inside Levo
Six ways to work the same material.
Biological Molecules revision questions
- Is Biological Molecules examined at AS in Edexcel Biology B?
- Yes. It sits in Papers 1, 2 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 Edexcel AS-Level Biology B?
- 19 subtopics: monosaccharides, disaccharides and polysaccharides, glycosidic bonds and condensation reactions, starch, glycogen and cellulose structure, triglycerides and phospholipids, saturated and unsaturated fats and lipid properties, amino acid structure and the peptide bond, primary, secondary, tertiary and quaternary structure, fibrous and globular proteins, the structure of dna, dna replication and gene mutations, the structure of rna, transcription and translation, enzymes as globular proteins, factors affecting enzyme activity, measuring the rate of enzyme activity, units, uncertainty and experimental error, enzyme inhibition, inorganic ions and the properties of water. Each one has its own page with questions and model answers.
- How is Biological Molecules organised?
- By the Edexcel 9BI0 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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