Key term
OCR A-Level Biology B H422
The Developing Cell: Cell Division and Cell Differentiation
The Developing Individual: Meiosis, Growth and Development
The Development of Species: Evolution and Classification
Cells and Microscopy
Topic overviewMicroscopy and the cell theoryBlood smears, staining and microscope drawingsBlood cells and their structureMagnification and measuring cellsHaemocytometer cell counts and dilutionsFlow cytometry in blood analysisUltrastructure of the animal cellPlant and prokaryotic cellsMembrane lipids and the fluid mosaic modelMovement of molecules across membranesThe roles of membranes and the secretion of proteins
Water and Its Importance in Plants and Animals
Proteins and Enzymes
Nucleic Acids
Patterns of Inheritance
Population Genetics and Epigenetics
Gene Technologies
The Principles and Importance of Homeostasis
The Hormonal Control of Blood Glucose and the Management of Diabetes
Kidney Functions and Malfunctions
Topic overviewExcretion and the gross structure of the kidneyThe nephron: ultrafiltration and selective reabsorptionInvestigating the composition of urine, plasma and filtrateOsmoregulation and the action of ADHThe kidney as an endocrine gland and kidney failureDialysis, transplantation and the future of transplant surgery
The Cellular Basis of Cancer and Treatment
Respiratory Diseases and Treatment
Cellular Respiration
Metabolism and Exercise
Topic overviewThe consequences of exercise on the bodyAerobic fitness and VO₂ maxTraining, F.I.T.T. factors and investigating fitnessEnhancing athletic performanceHaemoglobin and the transport of oxygenOxygen dissociation curves of different respiratory pigmentsOxygen deficit and oxygen debtThe structure of skeletal muscleThe sliding filament theory of muscle contraction
Pathogenic Microorganisms
The Immune System
Controlling Communicable Diseases
Photosynthesis, Food Production and Management of the Environment
Topic overviewChloroplast ultrastructure and photosynthetic pigmentsThe light-dependent stage of photosynthesisThe Calvin cycleInvestigating the factors affecting photosynthesisThe Hill reaction and DCPIPUsing TP and GP to build carbohydrates, lipids and amino acidsThe compensation point and crop productionMicroorganisms, the nitrogen cycle and biosensorsBiomass transfer and efficiency in food productionRuminants in the human food chainFarms as ecosystems and the conflict with conservationDeflected succession and measuring biodiversity
The Impact of Population Increase
Planning and Implementing Practical Work
Analysing and Evaluating Practical Results
Practical Skills, Apparatus and Techniques
Topic overviewInvestigative approaches and working safelyFollowing instructions, recording and presenting dataResearch, referencing and processing data with softwareMeasuring mass, volume, time, temperature, length and pHColorimeters and potometersLaboratory glassware and serial dilutionsLight microscopy, graticules and biological drawingQualitative reagents for biological moleculesChromatography and electrophoresisAseptic technique and dissectionWhole-organism responses, fieldwork sampling and data logging
Fertility and Assisted Reproduction
The Effects of Ageing on the Reproductive System
Plant Reproduction
The Nervous System and the Identification and Consequences of Damage
Topic overviewOrganisation of the nervous system and nervous tissueThe structure and function of the human brainThe structure of motor, sensory and relay neuronesResting potential and the action potentialSynapses and the integration of responsesReflexes, reaction times and their investigationBrain scans and the consequences of nervous system damageDrugs, brain function and dependency
Monitoring Visual Function
The Effect of Ageing on the Nervous System
The Heart and Monitoring Heart Function
Transport Systems in Mammals
Gas Exchange in Mammals and Plants
Nucleic Acids
- 4 subtopics
- 12 things to know
- Components 01, 02 and 03
What Nucleic Acids covers
Nucleic Acids is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers nucleotides, ADP and ATP, the structure of DNA and its extraction, DNA replication and the genetic code and RNA, transcription and translation.
Where it is assessed
Components 01, 02 and 03
Every module can be assessed on any of the three papers.
Check the OCR specification ↗The 4 subtopics
Each one has its own page.
- Nucleotides, ADP and ATPRecall questions on the components of a nucleotide, ribose and deoxyribose, purine and pyrimidine bases, phosphodiester bonds and the sugar–phosphate backbone, the structure of ATP and ADP, the hydrolysis of ATP, and why ATP is the universal energy currency.Open →
- The structure of DNA and its extractionRecall questions on the antiparallel double helix, base pairing and hydrogen bonds, purines pairing with pyrimidines, Chargaff's rules and base percentage calculations, why DNA suits its role, and extracting DNA from onion with detergent, salt, protease and ice-cold ethanol.Open →
- DNA replication and the genetic codeRecall questions on semi-conservative replication, the roles of helicase and DNA polymerase, template strands and proofreading, mutations as random changes, and the genetic code as a triplet, non-overlapping, degenerate and universal code that determines protein structure.Open →
- RNA, transcription and translationRecall questions on how RNA differs from DNA, messenger, transfer and ribosomal RNA, codons and anticodons, RNA polymerase and the steps of transcription, how translation begins, extends and ends, working out template and anticodon sequences, and several ribosomes on one messenger RNA.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Why must the ethanol used to precipitate DNA be ice-cold?
Key term
Name two features of replication that keep the error rate very low.
Process
What is the sequence of events in transcription?
Key term
How does translation begin?
Key term
How is the polypeptide chain extended during translation?
Key term
Name the three components of a nucleotide.
Key term
What are the base pairing rules in DNA?
Key term
What is the role of helicase in DNA replication?
Key term
Which pentose sugar is found in a DNA nucleotide and which in an RNA nucleotide?
Key term
How many hydrogen bonds hold each base pair together?
Key term
Why is each strand of the original molecule described as a template?
Take Nucleic Acids further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Nucleotide vs Nucleic acid
Nucleotide: the repeating monomer, made of a phosphate group, a pentose sugar and a nitrogen-containing base. Nucleic acid: the polymer built by joining many of those monomers into a long chain by condensation reactions.
Purine vs Pyrimidine
Purine: a base built from two fused nitrogen-containing rings; adenine and guanine are the two of this kind. Pyrimidine: a base built on a single nitrogen-containing ring; cytosine, thymine and uracil are of this kind.
Phosphodiester bond vs Hydrogen bond
Phosphodiester bond: the strong covalent link formed by condensation between the phosphate of one nucleotide and the sugar of the next, holding a single strand together. Hydrogen bond: the weak attraction between complementary bases, easily broken and holding the two strands of a double helix to one another.
Questions from this topic
Each one with the model answer underneath.
- 1
Name the three components of a nucleotide.
Model answer
A pentose sugar, a phosphate group and a nitrogen-containing base.
- 2
Which pentose sugar is found in a DNA nucleotide and which in an RNA nucleotide?
Model answer
Deoxyribose in DNA and ribose in RNA.
- 3
How does deoxyribose differ chemically from ribose?
Model answer
Deoxyribose has one fewer oxygen atom, carrying a hydrogen where ribose carries a hydroxyl group on carbon 2.
- 4
Name the two purine bases and state how they are recognised.
Model answer
Adenine and guanine; each has a double ring structure of two joined nitrogen-containing rings.
- 5
Name the pyrimidine bases found in nucleic acids and state their common structural feature.
Model answer
Cytosine, thymine and uracil; each has a single nitrogen-containing ring.
- 6
Which base occurs in DNA but not RNA, and which occurs in RNA but not DNA?
Model answer
Thymine occurs only in DNA and uracil only in RNA.
What is inside Levo
Six ways to work the same material.
Nucleic Acids revision questions
- What does Nucleic Acids cover in OCR A-Level Biology B?
- 4 subtopics: nucleotides, adp and atp, the structure of dna and its extraction, dna replication and the genetic code and rna, transcription and translation. Each one has its own page with questions and model answers.
- How is Nucleic Acids organised?
- By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Nucleic Acids, 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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