Barriers and white blood cells
| English | 中文 | Pinyin |
|---|---|---|
| phagocytosis/ˌfæɡəsɪˈtəʊsɪs/ | 吞噬作用 | tūn shì zuò yòng |
| antitoxin/ˌæntɪˈtɒksɪn/ | 抗毒素 | kàng dú sù |
What would explain this observation?
- The body first tries to stop pathogens entering. Once pathogens cross a barrier, white blood cells can respond through several distinct mechanisms.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Skin forms a physical barrier; a clot helps seal a break. Nose hairs and mucus trap particles. Mucus in the trachea and bronchi traps pathogens, and cilia move it away from the lungs towards the throat. Stomach acid kills many swallowed pathogens. These defences are nonspecific because they do not target one particular antigen.
- phagocytosis 吞噬作用: Engulfing and digesting a pathogen by a cell; antitoxin 抗毒素: A substance that neutralizes a toxin.
Which response directly neutralizes a bacterial toxin?
White blood cells defend against pathogens by phagocytosis, producing antibodies and producing antitoxins. In phagocytosis a cell engulfs and digests a pathogen. Antibodies bind to particular antigens associated with a pathogen; antitoxins neutralize toxins. Explain the target before choosing the mechanism: removing a bacterium and neutralizing its toxin are different actions.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- White blood cells defend against pathogens by phagocytosis, producing antibodies and producing antitoxins. In phagocytosis a cell engulfs and digests a pathogen. Antibodies bind to particular antigens associated with a pathogen; antitoxins neutralize toxins. Explain the target before choosing the mechanism: removing a bacterium and neutralizing its toxin are different actions.
- Use labelled barrier diagrams and paper antigen–antibody models. Match a named defence to its location and effect. Then trace a pathogen that has crossed a barrier to a suitable immune response. This is a model exercise; do not test disinfectants on students’ skin or collect body samples.
Which two habits make the investigation or model in this case more defensible?
Use labelled barrier diagrams and paper antigen–antibody models. Match a named defence to its location and effect. Then trace a pathogen that has crossed a barrier to a suitable immune response. This is a model exercise; do not test disinfectants on students’ skin or collect body samples.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a fictional observation shows 80 particles entering a model airway and 62 trapped in mucus. The remaining count is 18 and the trapped proportion is 62/80×100 = 77.5%. The model illustrates interception, but real defence depends on particle properties, ciliary function and many additional processes.
A model traps 42 of 60 incoming particles. Calculate the trapped percentage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model traps 42 of 60 incoming particles. Calculate the trapped percentage.
The result is 70 %. Known: a fictional observation shows 80 particles entering a model airway and 62 trapped in mucus. The remaining count is 18 and the trapped proportion is 62/80×100 = 77.5%. The model illustrates interception, but real defence depends on particle properties, ciliary function and many additional processes.
Check the conclusion and its limits
- Antibodies and antitoxins are not antibiotics. Red blood cells mainly transport oxygen and do not replace the white-cell roles here. A barrier lowers entry risk but is not an absolute guarantee that no pathogen will ever enter.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
An antibody is the same thing as an antibiotic. This claim is false: Antibodies and antitoxins are not antibiotics. Red blood cells mainly transport oxygen and do not replace the white-cell roles here. A barrier lowers entry risk but is not an absolute guarantee that no pathogen will ever enter.
Barriers and white blood cells: White blood cells defend against pathogens by phagocytosis, producing antibodies and producing antitoxins. In phagocytosis a cell engulfs and digests a pathogen. Antibodies bind to particular antigens associated with a pathogen; antitoxins neutralize toxins. Explain the target before choosing the mechanism: removing a bacterium and neutralizing its toxin are different actions.
An antibody is the same thing as an antibiotic.
Antibodies and antitoxins are not antibiotics. Red blood cells mainly transport oxygen and do not replace the white-cell roles here. A barrier lowers entry risk but is not an absolute guarantee that no pathogen will ever enter.
Engulfing and digesting a pathogen by a cell: write the technical term.
phagocytosis means Engulfing and digesting a pathogen by a cell.