# CellNaut

> Free cell biology course: 10 illustrated lessons, 21 interactive 3D cell models, 18 labelled figures and a 92-term glossary, all sourced.

CellNaut is free to use. Lessons and topics are written in our own words from open textbooks such as OpenStax Biology 2e; every lesson lists its sources and the date it was last reviewed. Each lesson and topic below links to a plain Markdown version of the page. The complete text of all lessons, topics and glossary terms is in https://cellnaut.com/llms-full.txt.

## English

### Learn

- [What Is a Cell?](https://cellnaut.com/learn/what-is-a-cell.md): Meet the basic unit of life, the three ideas of cell theory, and the big divide between prokaryotic and eukaryotic cells.
- [Cell Size and Scale](https://cellnaut.com/learn/cell-size-and-scale.md): Learn the units of the microscopic world and why most cells stay small, with a little geometry.
- [The Plasma Membrane and Transport](https://cellnaut.com/learn/plasma-membrane-and-transport.md): How a membrane only a few molecules thick controls what enters and leaves, from simple diffusion to pumps and vesicles.
- [The Nucleus and the Endomembrane System](https://cellnaut.com/learn/nucleus-and-endomembrane.md): Follow a protein from the gene that codes for it, through the ER and Golgi, to its destination, and meet the lysosome clean-up crew.
- [Mitochondria and Chloroplasts](https://cellnaut.com/learn/energy-organelles.md): How cells make ATP and capture sunlight, and why these two organelles look like bacteria that moved in.
- [The Cytoskeleton and Cell Movement](https://cellnaut.com/learn/cytoskeleton-and-movement.md): The protein scaffolding that gives cells their shape, moves cargo, and powers everything from crawling immune cells to flexing muscles.
- [From DNA to Protein](https://cellnaut.com/learn/dna-to-protein.md): How a gene stored in DNA is copied into RNA and then read by a ribosome to build a protein.
- [The Cell Cycle and Mitosis](https://cellnaut.com/learn/cell-division.md): How a cell copies its DNA, divides it equally between two daughters, and what happens when the controls fail.
- [Cell Communication and the Neuron](https://cellnaut.com/learn/cell-communication.md): How cells send, receive, and respond to signals, and how a nerve cell passes a message across a synapse.
- [Specialized Cells and Tissues](https://cellnaut.com/learn/specialized-cells-and-tissues.md): A tour of the Studio's specimens in four groups (animal, plant, protist and fungus, and prokaryote), and how one genome builds cells with very different shapes and jobs.

### Topics

- [Neuron Synapse and Neurotransmitter Release](https://cellnaut.com/topics/neuron-synapse-transmission.md): A synapse is the junction where one neuron passes a message to the next cell.
- [Chloroplast and Photosynthetic Structures](https://cellnaut.com/topics/chloroplast-photosynthesis.md): A chloroplast turns light into sugar.
- [Antibody and Antigen Binding](https://cellnaut.com/topics/antibody-antigen-binding.md): An IgG antibody is a Y-shaped protein.
- [Alveoli and Gas Exchange](https://cellnaut.com/topics/alveoli-gas-exchange.md): The lungs end in millions of tiny air sacs called alveoli.
- [Glomerulus and Filtration](https://cellnaut.com/topics/nephron-glomerulus-filtration.md): In the kidney, blood is filtered in a ball of capillaries called the glomerulus.
- [Root Tip and Mitosis](https://cellnaut.com/topics/root-tip-mitosis.md): A root grows from its tip.
- [DNA Replication Fork](https://cellnaut.com/topics/dna-replication-fork.md): Before a cell divides it copies its DNA.
- [Meiosis and Homologous Chromosome Crossing Over](https://cellnaut.com/topics/meiosis-crossing-over.md): In prophase I of meiosis, homologous chromosomes pair up and swap segments.
- [Enzyme Catalysis and Active Site](https://cellnaut.com/topics/enzyme-catalysis-active-site.md): Enzymes are protein catalysts.
- [Bacterial Cell Structure](https://cellnaut.com/topics/bacterial-cell-structure.md): A bacterium is a prokaryote: it has no membrane-bound nucleus.
- [CRISPR-Cas9 Gene Editing](https://cellnaut.com/topics/crispr-cas9-gene-editing.md): Cas9 is a protein that cuts DNA, and a guide RNA tells it where.
- [Plant Vascular Bundle Transport](https://cellnaut.com/topics/plant-vascular-bundle-transport.md): A stem cross-section shows the plant's plumbing.
- [Animal Cell vs Plant Cell](https://cellnaut.com/topics/animal-vs-plant-cell.md): Animal and plant cells are both eukaryotic, so they share a nucleus, mitochondria and a membrane system.
- [Prokaryotic vs Eukaryotic Cells](https://cellnaut.com/topics/prokaryote-vs-eukaryote.md): The biggest divide in biology is whether a cell keeps its DNA inside a nucleus.
- [The Cell Cycle, Stage by Stage](https://cellnaut.com/topics/cell-cycle-stages.md): A dividing animal cell moves through a fixed order: interphase to prepare, then four stages of mitosis that share out the chromosomes, and finally cytokinesis that splits the cell in two.
- [The Cell Nucleus](https://cellnaut.com/topics/nucleus.md): The nucleus is the cell's control room.
- [The Plasma Membrane](https://cellnaut.com/topics/plasma-membrane.md): The plasma membrane is a double layer of lipids with proteins floating in it, a design called the fluid mosaic model.
- [The Plant Cell Wall](https://cellnaut.com/topics/cell-wall.md): A plant cell wall is a layered coat of cellulose fibres in a gel-like matrix, with a thin shared layer between neighbours.

### Studio

- [White Blood Cell](https://cellnaut.com/studio/whiteBlood): Immune Cell
- [Neuron](https://cellnaut.com/studio/neuron): Nerve Cell
- [Epithelial Cell](https://cellnaut.com/studio/epithelial): Human Tissue Cell
- [Animal Cell](https://cellnaut.com/studio/animal): Eukaryotic Cell
- [Muscle Cell](https://cellnaut.com/studio/muscle): Muscle Fiber
- [Red Blood Cell](https://cellnaut.com/studio/redBlood): Blood Cell
- [Sperm Cell](https://cellnaut.com/studio/sperm): Reproductive Cell
- [Egg Cell](https://cellnaut.com/studio/egg): Reproductive Cell
- [Stem Cell](https://cellnaut.com/studio/stem): Progenitor Cell
- [Cardiac Muscle Cell](https://cellnaut.com/studio/cardiac): Heart Muscle Cell
- [Osteocyte](https://cellnaut.com/studio/osteocyte): Mature Skeletal Cell
- [Fat Cell](https://cellnaut.com/studio/adipocyte): Storage Cell
- [Rod Photoreceptor](https://cellnaut.com/studio/rod): Light-Sensing Cell
- [Plant Cell](https://cellnaut.com/studio/plant): Eukaryotic Cell
- [Guard Cell](https://cellnaut.com/studio/guard): Plant Epidermal Cell
- [Root Hair Cell](https://cellnaut.com/studio/rootHair): Plant Absorptive Cell
- [Yeast Cell](https://cellnaut.com/studio/yeast): Fungal Cell
- [Paramecium](https://cellnaut.com/studio/paramecium): Single-Celled Protist
- [Chlamydomonas](https://cellnaut.com/studio/chlamydomonas): Single-Celled Alga
- [Bacteria Cell](https://cellnaut.com/studio/bacteria): Prokaryotic Cell
- [Cyanobacterium](https://cellnaut.com/studio/cyanobacteria): Photosynthetic Prokaryote

### Glossary / Resources

- [Glossary](https://cellnaut.com/glossary): Plain-language definitions of 92 cell biology terms, each linked to the lessons and 3D models that show it.
- [Resources](https://cellnaut.com/resources): Hand-picked open 3D cell models, illustrations, textbooks, atlases and communities for learning cell biology. Filter by category and language.
- [About](https://cellnaut.com/about): How CellNaut's cell biology lessons are written, reviewed and sourced, which open resources it builds on, and how the 3D models are licensed.

## 中文 (Chinese)

### 课程

- [细胞是什么？](https://cellnaut.com/zh/learn/what-is-a-cell.md): 认识生命的基本单位、细胞学说的三个观点，以及原核细胞与真核细胞这条最大的分界线。
- [细胞的大小与尺度](https://cellnaut.com/zh/learn/cell-size-and-scale.md): 认识微观世界的计量单位，并用一点几何知识理解为什么大多数细胞都很小。
- [细胞膜与物质运输](https://cellnaut.com/zh/learn/plasma-membrane-and-transport.md): 一层只有几个分子厚的膜，是如何控制物质进出的：从简单扩散，到泵和囊泡。
- [细胞核与内膜系统](https://cellnaut.com/zh/learn/nucleus-and-endomembrane.md): 跟随一个蛋白质，从编码它的基因出发，经过内质网和高尔基体，抵达目的地，并认识负责清理的溶酶体。
- [线粒体与叶绿体](https://cellnaut.com/zh/learn/energy-organelles.md): 细胞如何制造 ATP、如何捕获阳光，以及为什么这两种细胞器看起来像“搬进来住”的细菌。
- [细胞骨架与细胞运动](https://cellnaut.com/zh/learn/cytoskeleton-and-movement.md): 这套蛋白质支架赋予细胞形状、运送货物，并驱动从爬行的免疫细胞到收缩的肌肉的各种运动。
- [从 DNA 到蛋白质](https://cellnaut.com/zh/learn/dna-to-protein.md): 储存在 DNA 中的基因如何被复制成 RNA，再由核糖体读取并合成蛋白质。
- [细胞周期与有丝分裂](https://cellnaut.com/zh/learn/cell-division.md): 细胞如何复制自己的 DNA，把它平均分给两个子细胞，以及调控失灵时会发生什么。
- [细胞通讯与神经元](https://cellnaut.com/zh/learn/cell-communication.md): 细胞如何发送、接收并响应信号，以及神经细胞如何把信息传过突触。
- [特化细胞与组织](https://cellnaut.com/zh/learn/specialized-cells-and-tissues.md): 巡览工作室中的标本，按动物、植物、原生生物与真菌、原核生物四大类，了解同一个基因组如何构建出形状和功能迥异的细胞。

### 专题

- [神经突触与递质释放](https://cellnaut.com/zh/topics/neuron-synapse-transmission.md): 突触是神经元把信息传给下一个细胞的连接处。电信号到达轴突末端后，会触发囊泡释放化学信使，信使跨过一个极窄的间隙，打开接收细胞上的通道。
- [叶绿体与光合作用结构](https://cellnaut.com/zh/topics/chloroplast-photosynthesis.md): 叶绿体把光能变成糖。类囊体膜上的光反应捕获能量并释放氧气，基质中的卡尔文循环再利用这些能量，把二氧化碳合成为糖。
- [抗体与抗原结合](https://cellnaut.com/zh/topics/antibody-antigen-binding.md): IgG 抗体是一种 Y 形蛋白质。两条臂的末端与抗原的特定部位互相契合，尾部则提醒其他免疫细胞去处理被结合的目标。
- [肺泡与气体交换](https://cellnaut.com/zh/topics/alveoli-gas-exchange.md): 肺的末端是数以百万计的微小气囊，称为肺泡。每个肺泡都被毛细血管包围，空气与血液之间的壁极薄，氧气和二氧化碳在极短时间内就能扩散通过。
- [肾小球与滤过作用](https://cellnaut.com/zh/topics/nephron-glomerulus-filtration.md): 在肾脏中，血液在一团称为肾小球的毛细血管里被过滤。水和小分子溶质在压力下穿过三层滤过结构进入鲍曼囊，血细胞和大分子蛋白质则留在血液中。
- [根尖结构与有丝分裂](https://cellnaut.com/zh/topics/root-tip-mitosis.md): 根从尖端生长。细胞在分生区分裂，在伸长区变长，在分化区承担各自的功能，根冠则在根尖穿过土壤时保护它。
- [DNA 复制叉](https://cellnaut.com/zh/topics/dna-replication-fork.md): 细胞分裂前要复制 DNA。在复制叉处，双螺旋被解开，每条链都作为模板。一条新链连续合成，另一条则分成短片段合成。
- [减数分裂与同源染色体交换](https://cellnaut.com/zh/topics/meiosis-crossing-over.md): 在减数分裂 I 前期，同源染色体配对并交换片段。这种交叉互换把来自双亲的等位基因混合起来，使每个卵细胞或精子都带有独特的组合。
- [酶催化与活性位点](https://cellnaut.com/zh/topics/enzyme-catalysis-active-site.md): 酶是蛋白质催化剂。底物结合在活性位点上，酶使反应更容易发生，产物离开后酶又可以继续工作。
- [细菌细胞结构](https://cellnaut.com/zh/topics/bacterial-cell-structure.md): 细菌是原核生物，没有膜包被的细胞核。它的 DNA 位于拟核区，外面有细胞壁，常常还有荚膜，表面有菌毛和鞭毛。
- [CRISPR-Cas9 基因编辑](https://cellnaut.com/zh/topics/crispr-cas9-gene-editing.md): Cas9 是一种切割 DNA 的蛋白质，引导 RNA 告诉它切哪里。当引导 RNA 与匹配的序列配对后，Cas9 切断双链，细胞自身的修复系统再修复断口，这样就可以关闭某个基因或插入新的序列。
- [植物维管束运输](https://cellnaut.com/zh/topics/plant-vascular-bundle-transport.md): 茎的横切面展示了植物的“管道系统”。木质部向上运输水和矿物质，韧皮部把糖运到需要的地方，两者之间的形成层则产生新细胞。
- [动物细胞与植物细胞对比](https://cellnaut.com/zh/topics/animal-vs-plant-cell.md): 动物细胞和植物细胞都是真核细胞，都有细胞核、线粒体和膜系统。植物细胞多了坚硬的细胞壁、叶绿体和大液泡，这些结构让它适合固定不动、自己制造养分。
- [原核细胞与真核细胞对比](https://cellnaut.com/zh/topics/prokaryote-vs-eukaryote.md): 生物学里最大的分界，是细胞是否把 DNA 放在细胞核里。细菌这样的原核细胞个头小，没有膜包被的细胞器；真核细胞更大，把工作分配给许多隔间来完成。
- [细胞周期分阶段图解](https://cellnaut.com/zh/topics/cell-cycle-stages.md): 分裂中的动物细胞按固定顺序前进：先在间期做好准备，再经过四个有丝分裂时期分配染色体，最后由胞质分裂把细胞一分为二。请按顺序依次点击标记。
- [细胞核](https://cellnaut.com/zh/topics/nucleus.md): 细胞核是细胞的控制中心。带有核孔的双层膜包着染色质，内部的核仁负责组装核糖体的零件。它直接与粗面内质网相连。
- [细胞膜](https://cellnaut.com/zh/topics/plasma-membrane.md): 细胞膜是一层双层脂质，里面漂浮着蛋白质，这种设计称为流动镶嵌模型。它决定什么物质进出细胞，也让细胞感知周围环境。
- [植物细胞壁](https://cellnaut.com/zh/topics/cell-wall.md): 植物细胞壁是由纤维素纤维与凝胶状基质构成的分层外套，相邻细胞之间还有一层很薄的共用层。它抵抗细胞内水分的压力，支撑植物，并留有通道让相邻细胞相连。

### 三维工作室

- [白细胞](https://cellnaut.com/zh/studio/whiteBlood): 免疫细胞
- [神经元](https://cellnaut.com/zh/studio/neuron): 神经细胞
- [上皮细胞](https://cellnaut.com/zh/studio/epithelial): 人体组织细胞
- [动物细胞](https://cellnaut.com/zh/studio/animal): 真核细胞
- [肌细胞](https://cellnaut.com/zh/studio/muscle): 肌纤维
- [红细胞](https://cellnaut.com/zh/studio/redBlood): 血液细胞
- [精子](https://cellnaut.com/zh/studio/sperm): 生殖细胞
- [卵细胞](https://cellnaut.com/zh/studio/egg): 生殖细胞
- [干细胞](https://cellnaut.com/zh/studio/stem): 未分化细胞
- [心肌细胞](https://cellnaut.com/zh/studio/cardiac): 肌细胞
- [骨细胞](https://cellnaut.com/zh/studio/osteocyte): 成熟骨细胞
- [脂肪细胞](https://cellnaut.com/zh/studio/adipocyte): 储能细胞
- [视杆细胞](https://cellnaut.com/zh/studio/rod): 感光细胞
- [植物细胞](https://cellnaut.com/zh/studio/plant): 真核细胞
- [保卫细胞](https://cellnaut.com/zh/studio/guard): 植物表皮细胞
- [根毛细胞](https://cellnaut.com/zh/studio/rootHair): 植物吸收细胞
- [酵母细胞](https://cellnaut.com/zh/studio/yeast): 真菌细胞
- [草履虫](https://cellnaut.com/zh/studio/paramecium): 单细胞原生生物
- [衣藻](https://cellnaut.com/zh/studio/chlamydomonas): 单细胞藻类
- [细菌细胞](https://cellnaut.com/zh/studio/bacteria): 原核细胞
- [蓝细菌](https://cellnaut.com/zh/studio/cyanobacteria): 光合原核生物

### 术语表 / 资源

- [术语表](https://cellnaut.com/zh/glossary): 92 条细胞生物学术语的通俗释义，每条都链接到相关课程和 3D 模型。
- [资源](https://cellnaut.com/zh/resources): 精选的开放 3D 细胞模型、插图、教材、图谱和社区，可按类别与语言筛选。
- [关于](https://cellnaut.com/zh/about): 了解 CellNaut 的细胞生物学课程如何编写、审校和标注来源，基于哪些开放资源，以及 3D 模型的授权方式。

## Optional

- [Sitemap](https://cellnaut.com/sitemap.xml): every indexable page with language alternates
- [Source code](https://github.com/cclank/cell-architecture-studio): open source, MIT licensed