Process
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
Gas Exchange in Mammals and Plants
- 5 subtopics
- 15 things to know
- Components 01, 02 and 03
What Gas Exchange in Mammals and Plants covers
Gas Exchange in Mammals and Plants 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 tissues of the mammalian gas exchange system, gas exchange in the alveoli, pulmonary ventilation and lung volumes, expired air resuscitation and gas exchange and stomata in terrestrial plants.
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 5 subtopics
Each one has its own page.
- Tissues of the mammalian gas exchange systemRecall questions on the path of air to the alveoli, squamous alveolar epithelium, ciliated epithelium and goblet cells, C-shaped cartilage rings in the trachea, smooth muscle and elastic fibres in the airways and lungs, and recognising these tissues in stained sections.Open →
- Gas exchange in the alveoliRecall questions on the thin barrier and large surface area of the alveoli, the factors setting the rate of diffusion, how ventilation and blood flow keep gradients steep, surfactant and premature babies, elastic fibres, smooth muscle and cilia, the moist surface, and emphysema.Open →
- Pulmonary ventilation and lung volumesRecall questions on tidal volume and breathing rate, calculating pulmonary ventilation rate, vital capacity and residual volume, peak expiratory flow rate in asthma, FEV1 and airway obstruction, and how ventilation changes during exercise and with body size.Open →
- Expired air resuscitationRecall questions on why exhaled breath supplies oxygen, opening an airway, giving an effective breath, how the technique differs for a baby, and the devices used instead of mouth-to-mouth.Open →
- Gas exchange and stomata in terrestrial plantsRecall questions on gas exchange by leaves by day and night, air spaces in the spongy mesophyll, lenticels, the structure of stomata and guard cells and how they open and close, the cost of closing stomata in drought, nail varnish impressions, and estimating stomatal density.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
How is expired air resuscitation given to an adult, how is each breath checked, and what differs for a baby?
Key term
Explain how the wall structure of a guard cell causes the pore to open when the cell gains water.
Key term
Which two cell layers must oxygen cross to pass from alveolar air into the blood?
Key term
State the equation for pulmonary ventilation rate.
Key term
Name in order the structures air passes through between the trachea and the site of gas exchange.
Key term
State the three factors that determine the rate of diffusion across a gas exchange surface.
Numbers
A person has a tidal volume of 0.45 dm³ and takes 14 breaths per minute. Calculate the pulmonary ventilation rate.
Key term
Why can breathing out into a casualty supply them with oxygen?
Key term
Why does a plant not need a transport system for respiratory gases?
Key term
Why is the alveolar epithelium made of squamous rather than columnar cells?
Key term
Explain how blood flow through the alveolar capillaries helps maintain the concentration gradients.
Key term
Why is peak expiratory flow rate reduced during an asthma attack?
Key term
How is the airway of an unresponsive adult opened before rescue breaths are given?
Key term
Which gases diffuse into and out of a leaf at night?
Take Gas Exchange in Mammals and Plants further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Ventilation vs Gas exchange
Ventilation: the bulk movement of air into and out of the lungs, which keeps the concentration gradients at the alveoli steep. Gas exchange: the diffusion of oxygen and carbon dioxide across the alveolar wall between the air and the blood.
Residual volume vs Vital capacity
Residual volume: the air left in the lungs even after the most forceful possible breath out, which keeps the alveoli from collapsing and sticking shut. Vital capacity: the largest amount of air that can be breathed out after taking the deepest possible breath in, typically about 4.5 dm³ in a healthy adult.
PEFR vs FEV1
PEFR: the greatest rate at which air can be forced out of the lungs at one instant during a single sharp exhalation. FEV1: the amount of air a person can breathe out during the first second of a maximal forced exhalation.
Questions from this topic
Each one with the model answer underneath.
- 1
Name in order the structures air passes through between the trachea and the site of gas exchange.
Model answer
The trachea, then the bronchi, then the bronchioles, and finally the alveoli.
- 2
Describe the appearance of the squamous epithelial cells lining an alveolus.
Model answer
They are extremely flattened cells with a bulging nucleus, forming a layer well under 1 μm thick.
- 3
Why is the alveolar epithelium made of squamous rather than columnar cells?
Model answer
Flattened cells give a much shorter diffusion distance between the air and the blood, so gases cross faster.
- 4
Describe the structure of the ciliated epithelial tissue lining the airways.
Model answer
It is made of column-shaped cells whose exposed surface bears many cilia, with mucus-secreting goblet cells scattered among them.
- 5
What is the function of the cilia in the ciliated epithelium of the airways?
Model answer
They beat rhythmically to sweep the mucus, with any trapped dust and pathogens, up towards the throat where it is swallowed.
- 6
What is the role of the goblet cells in the airway lining?
Model answer
They secrete mucus, which traps dust particles, pollen and pathogens in the incoming air.
What is inside Levo
Six ways to work the same material.
Gas Exchange in Mammals and Plants revision questions
- What does Gas Exchange in Mammals and Plants cover in OCR A-Level Biology B?
- 5 subtopics: tissues of the mammalian gas exchange system, gas exchange in the alveoli, pulmonary ventilation and lung volumes, expired air resuscitation and gas exchange and stomata in terrestrial plants. Each one has its own page with questions and model answers.
- How is Gas Exchange in Mammals and Plants organised?
- By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Gas Exchange in Mammals and Plants, 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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