Describe the role of cilia in the airways.

Cilia beat to sweep mucus and the pathogens trapped in it up to the throat, where it is swallowed.

Explain why a smoker is more likely to get a chest infection.

Smoke damages the cilia, so mucus carrying trapped pathogens is no longer swept out of the airways.

Where are lysozymes found, and what do they do?

Lysozymes are enzymes in tears and saliva that break down the cell walls of bacteria and kill them.

Explain how hydrochloric acid in the stomach defends the body against pathogens.

Its very low pH denatures the enzymes of pathogens swallowed in food and mucus, killing them.

Edexcel GCSE Combined Science Biology 1SC0

Key Concepts in Biology

Topic overview Eukaryotic and prokaryotic cells Specialised cells and their adaptations Microscopes and magnification calculations Size, scale and units in cell biology Enzyme action and denaturation Factors affecting enzyme activity Enzymes in synthesis and digestion, and rate calculations Diffusion, osmosis and active transport Osmosis in potatoes and percentage change in mass

Cells and Control

Topic overview Mitosis and the cell cycle Why mitosis matters: growth, repair and cancer Growth, differentiation and percentile charts Stem cells and their use in medicine Neurones, receptors and the reflex arc

Genetics

Topic overview Meiosis and the formation of gametes DNA structure, genes and the genome Extracting DNA from fruit Alleles, genotype and phenotype Monohybrid crosses and sex determination Probability and ratios from genetic crosses Causes of variation: genes and environment The Human Genome Project Genetic variation and the effects of mutation

Natural Selection and Genetic Modification

Topic overview Natural selection and antibiotic resistance Fossil evidence for human evolution Stone tool evidence for human evolution Five kingdoms and the three domains Selective breeding Genetic engineering and modern agriculture

Health, Disease and the Development of Medicines

Topic overview Health, disease and susceptibility Pathogens and common infections How pathogens spread, and the virus life cycle Sexually transmitted infections Physical barriers and chemical defences The immune system, immunisation and herd immunity Antibiotics and developing new medicines Lifestyle factors and non-communicable disease Treatments for cardiovascular disease

Plant Structures and Their Functions

Topic overview Photosynthesis as an endothermic reaction Limiting factors in photosynthesis Light intensity and the rate of photosynthesis Root hair cells, xylem and phloem Transpiration and translocation Factors affecting the rate of transpiration

Animal Coordination, Control and Homeostasis

Topic overview Hormones, endocrine glands and homeostasis The menstrual cycle and its hormones Hormonal and barrier contraception Controlling blood glucose, and type 1 diabetes Type 2 diabetes and body mass

Exchange and Transport in Animals

Topic overview Why multicellular organisms need exchange surfaces Alveoli and gas exchange The blood and its components Arteries, veins and capillaries The heart and the circulatory system Cellular respiration as an exothermic reaction Aerobic and anaerobic respiration compared Investigating the rate of respiration Cardiac output, stroke volume and heart rate

Ecosystems and Material Cycles

Topic overview Levels of organisation and interdependence Abiotic and biotic factors in a community Parasitism and mutualism Sampling with quadrats and transects Estimating population size from field data Human impact on ecosystems and biodiversity The carbon cycle The water and nitrogen cycles

Health, Disease and the Development of Medicines

Physical barriers and chemical defences

3 things to know
Paper 1

Overview

The skin as a physical barrier, mucus and cilia in the airways and why smokers get more chest infections, lysozymes in tears and saliva, hydrochloric acid in the stomach, and how a cut in the skin raises the risk of infection.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe the physical barriers that keep pathogens out of the body and why smoking weakens one of those barriers.

Key term

Describe how the skin protects the body from pathogens.

Key term

Explain how mucus in the airways protects the lungs.

Questions from this subtopic

Each one with the model answer underneath.

1
Describe how the skin protects the body from pathogens.
Model answer
The skin is a physical barrier of tough dead cells that pathogens cannot pass through unless it is broken.
2
Explain how mucus in the airways protects the lungs.
Model answer
Sticky mucus traps pathogens and dust particles before they can reach the lungs.
3
Describe the role of cilia in the airways.
Model answer
Cilia beat to sweep mucus and the pathogens trapped in it up to the throat, where it is swallowed.
4
Explain why a smoker is more likely to get a chest infection.
Model answer
Smoke damages the cilia, so mucus carrying trapped pathogens is no longer swept out of the airways.
5
Where are lysozymes found, and what do they do?
Model answer
Lysozymes are enzymes in tears and saliva that break down the cell walls of bacteria and kill them.
6
Explain how hydrochloric acid in the stomach defends the body against pathogens.
Model answer
Its very low pH denatures the enzymes of pathogens swallowed in food and mucus, killing them.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Key Concepts in Biology

Cells and Control

Genetics

Natural Selection and Genetic Modification

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Type 2 .

diabetescancercholera

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

ANitrates cause an algal bloom that blocks the light.

BWater plants die and decay.

CThe decomposers use up the dissolved oxygen.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

A millimetre is 10⁻³ of a metre.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Health, Disease and the Development of Medicines, 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.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.