Barriers and white blood cells
הוצג| English | משמעות |
|---|---|
| phagocytosis/ˌfæɡəsɪˈtəʊsɪs/ | פיגוציטוז |
| antitoxin/ˌæntɪˈtɒksɪn/ | אנטיתוקסין |
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.
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: 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?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Antitoxins are specific molecules released by white blood cells that bind and neutralise bacterial toxins. Red cells carry oxygen, and magnification is an observation tool, not a defence.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
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.
In the lab: 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?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- 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.
Your turn: A model traps 42 of 60 incoming particles. Calculate the trapped percentage.
A model traps 42 of 60 incoming particles. Calculate the trapped percentage.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 70 %. Known: 42 of 60 particles trapped. Use percentage = trapped / incoming x 100. Percentage = 42/60 x 100 = 70%. Real defence depends on particle properties and ciliary function too.
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.
Not true: An antibody is the same thing as an antibiotic. An antibody is a protein your immune cells make against a specific antigen; an antibiotic is a drug that kills bacteria. One is part of you, the other is a medicine - they are not interchangeable.
- Skin forms a physical barrier; a clot helps seal a break.
- White blood cells defend against pathogens by phagocytosis, producing antibodies and producing antitoxins.
- Watch for: antibodies and antitoxins are not antibiotics.
An antibody is a protein your immune cells make against a specific antigen; an antibiotic is a drug that kills bacteria.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. An antibody is a protein your immune cells make against a specific antigen; an antibiotic is a drug that kills bacteria. One is part of you, the other is a medicine - they are not interchangeable.
Engulfing and digesting a pathogen by a cell: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
phagocytosis means Engulfing and digesting a pathogen by a cell.