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
Practical Skills, Apparatus and Techniques
Colorimeters and potometers
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on zeroing a colorimeter and choosing its filter, building and reading a calibration curve, handling a cuvette, beetroot membrane work, and why potometer uptake overestimates transpiration.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Which colour filter would you select for measuring the absorbance of a red solution?
Key term
Why must the same filter be used for every reading within one investigation?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What does a colorimeter measure?
Model answer
It measures the absorbance of light by a solution, or the percentage of light transmitted through it.
- 2
How is a colorimeter set to zero before readings are taken?
Model answer
A cuvette containing the blank, usually distilled water or the solvent used, is placed in the instrument and the absorbance is set to zero.
- 3
How is the filter for a colorimeter chosen?
Model answer
The filter selected is the colour the solution absorbs most strongly, which is the complementary colour to the solution's own colour.
- 4
Which colour filter would you select for measuring the absorbance of a red solution?
Model answer
A green or blue-green filter, because a red solution absorbs green light most strongly.
- 5
Why must the same filter be used for every reading within one investigation?
Model answer
Absorbance depends on the wavelength of light used, so readings taken with different filters cannot be compared.
- 6
Describe how a calibration curve is produced for use with a colorimeter.
Model answer
The absorbance of a series of solutions of known concentration is measured, and absorbance is plotted against concentration.
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