# Original fact and model cards · cells, jobs and scale

These are **authored teaching summaries and invented diagrams in words**, not microscopy images or laboratory observations. Function statements were checked against the official QCAA Topic 1 list and the government cell sources in the [ledger](SOURCE-AND-RIGHTS.md). Read a model's completeness label before classifying it. An organelle's presence in a typical teaching diagram is not a universal rule for every specialised cell.

## Card A · features shared across cells

The standard living-cell models compared here share a **plasma membrane** separating inside from outside, **cytoplasm**, **DNA** and **ribosomes** that assemble proteins. Some specialised mature cells differ from canonical diagrams, including mature mammalian red blood cells, which lack a nucleus; this is a comparison rule for the modelled cells, not a universal checklist for every mature cell. Ribosomes are cell structures but **not membrane-bound**. Cell walls are not a safe single test for prokaryote versus eukaryote: several different groups can have them. A drawing may omit a structure to stay readable; an omission in an **incomplete** drawing is not evidence of biological absence.

## Card B · two organisation patterns

**Prokaryotic cells**, including bacteria and archaea, lack a membrane-bound nucleus. Their DNA occupies a nucleoid region; they still have ribosomes, cytoplasm and a plasma membrane. **Eukaryotic lineages** have a membrane-bound nucleus and other internal membrane-bound compartments in typical cells; some specialised mature cells are exceptions. Plants, animals and fungi are eukaryotes. Do not decide “prokaryote” merely because a faint or simplified image did not label a nucleus. A complete inventory or stronger observation is needed.

## Card C · nine named structures, one useful job each

| Structure | Carefully bounded job for these lessons |
| --- | --- |
| Nucleus | Membrane-bound compartment containing most of a typical eukaryotic cell's DNA. |
| Ribosomes | Assemble proteins; free in cytoplasm or attached to rough ER. Not membrane-bound themselves. |
| Mitochondria | In many eukaryotic cells, carry out steps of aerobic respiration that make ATP available; not a food-making machine. |
| Rough ER | Ribosome-studded membrane network involved in making/processing many proteins destined for membranes or secretion. |
| Smooth ER | Membrane network involved in lipid synthesis and other functions that vary by cell. No surface ribosomes. |
| Golgi apparatus | Modifies, sorts and packages many products from the ER. |
| Lysosomes | In many animal-cell models, membrane compartments that break down and recycle material. Plant cells can use lytic vacuoles for related work; do not say plants universally lack recycling. |
| Vacuoles | Membrane compartments with varied jobs; a large central vacuole in many plant cells helps water balance. Animal cells can also have smaller vacuoles. |
| Chloroplasts | In photosynthetic plant cells, organelles where photosynthesis takes place. Not every plant cell has chloroplasts. |

**One route, not every protein:** In an illustrative secretory cell, a protein made by a ribosome attached to rough ER can pass through ER processing and Golgi sorting before leaving the cell. Other proteins follow other routes; the diagram is not a complete transport account.

## Card D · four invented schematic inventories

1. **Pond bacterium model — comparison features fully stated:** plasma membrane, cytoplasm, DNA in a nucleoid region, ribosomes; **no membrane-bound nucleus or mitochondria**. It is a fictional schematic, not a cultured organism. The list does not claim to enumerate every real cellular feature.
2. **Leaf mesophyll model — comparison features fully stated:** plasma membrane, cytoplasm, DNA including in a membrane-bound nucleus, ribosomes, mitochondria, chloroplasts and a large central vacuole. It illustrates one photosynthetic eukaryotic cell type, not every cell in a leaf; the list is not exhaustive.
3. **Human intestinal lining model — comparison features fully stated:** plasma membrane, cytoplasm, DNA including in a membrane-bound nucleus, ribosomes, mitochondria, rough ER, smooth ER and Golgi apparatus. Other structures have not been inventoried. No diagnosis, real tissue image or actual organelle count is implied.
4. **Unfinished sketch — INCOMPLETE:** plasma membrane and ribosomes are labelled; the rest of the drawing has been left blank. **Classification is undetermined** from this sketch. The blank space is not a negative observation.

## Card E · organisation grows beyond a cell

One **intestinal epithelial cell** can be considered as part of **epithelial tissue** contributing to the **small intestine**, an **organ** in the **digestive system**. The small intestine contains several tissues; one epithelial cell or tissue does not by itself make the whole organ. Similarly, a **cardiac muscle cell** belongs to **cardiac muscle tissue** within the **heart**, one organ of the **circulatory system**. The hierarchy explains a contribution, not a claim that all cells in an organ are identical. A plant example can be built locally after checking its tissue and system terms.

## Card F · how to read a model honestly

Use `stated feature → supported comparison → model limit`. A **complete comparison inventory** can support presence/absence for the named features within that invented card; it does not establish all properties of a real species. An **incomplete sketch** supports only the labels it shows. None of these cards reports measurements, organelle counts, an experiment or a clinical finding.

SubjectNest original cards © NeuroForgeIO Pty Ltd 2026, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).