High School Biology

Cell Structure and Function细胞结构与功能

The cell is the fundamental unit of all life. This guide builds from the three tenets of cell theory through the prokaryote vs eukaryote distinction, the fluid-mosaic cell membrane and its three transport modes (diffusion, osmosis, active transport), the major organelles of animal and plant cells, the nucleus as the control center, microscopy and the surface-area-to-volume ratio that governs cell size, cell specialization and differentiation, and finally the hierarchy from molecule to biosphere. Worked examples and quiz questions draw on real biology throughout.细胞（cell，细胞）是一切生命的基本单位。本指南从细胞学说（cell theory，细胞学说）的三条原则出发，历经原核（prokaryote，原核细胞）与真核（eukaryote，真核细胞）之分、流动镶嵌细胞膜（cell membrane，细胞膜）及其三种运输方式（扩散、渗透、主动运输），再到动植物细胞器（organelle，细胞器）、核（nucleus，细胞核）的调控功能、显微镜与表面积体积比，直至细胞特化（cell specialization，细胞特化）与生命组织层次。全部例题与测验均以真实生物学情境为据。

7 sections7 节内容 US NGSS · ON · BC · ABUS NGSS · ON · BC · AB SBI4U organelle detail marked HonorsSBI4U 细胞器详解标为荣誉级
Read me first先读这里

How to use this guide如何使用本指南

Cell structure and function is the foundational unit in every biology curriculum we map to, and the four curricula agree on the core scope: cell theory, prokaryote vs eukaryote, the cell membrane and its transport modes, major organelles, the nucleus, and levels of organization. They diverge mainly on depth of organelle detail. US NGSS does not require organelle-by-organelle memorization (the HS-LS1-2 Assessment Boundary excludes "molecular or chemical reaction level" interactions). Ontario SBI4U B3.1 expects a named-organelle list including lysosomes, smooth/rough ER, and Golgi bodies — this is the Honors SBI4U track. British Columbia Life Sciences 11 and Ontario SBI3U B3.2 land in the middle: prokaryote/eukaryote comparison and cell specialization are fully required. The table below locates each section in your curriculum; each row cites the source document it was verified against.细胞结构与功能是我们对照的所有生物大纲中的基础单元；四套大纲在核心范围上高度一致：细胞学说、原核与真核之分、细胞膜及其运输方式、主要细胞器、细胞核、生命组织层次。它们的分歧主要在于细胞器细节的深度。US NGSS 不要求逐一记忆细胞器（HS-LS1-2 的评估边界排除"分子或化学反应层面"的互动）。安大略 SBI4U B3.1 要求命名的细胞器列表，含溶酶体、光面/糙面内质网与高尔基体——这是 荣誉 SBI4U 轨道。BC Life Sciences 11 与安大略 SBI3U B3.2 居中：原核/真核比较与细胞特化是完全必修内容。下表定位各节在你大纲中的位置；每行均注明所依据的来源文件。

If you are in…如果你在… Focus on these sections重点学习 Defer / lighter可推迟 / 减负 Source依据
🇺🇸 US NGSS HS Life Sciences美国 NGSS 生命科学 §1 (cell theory, pro/eukaryote), §2 (membrane concepts), §6 (specialization), §7 (hierarchical organization) — the HS-LS1-2 model expectation§1（细胞学说、原/真核）、§2（细胞膜概念）、§6（特化）、§7（层级组织）——HS-LS1-2 模型期望 §3 organelle detail: NGSS Assessment Boundary excludes "molecular or chemical reaction level" — read for understanding, not memorization§3 细胞器细节：NGSS 评估边界排除"分子或化学反应层面"——理解即可，无需死记 NGSS HS Life Science — HS-LS1-2 PE and Assessment Boundary— HS-LS1-2 表现期望及评估边界
🇨🇦 ON Grade 11 — SBI3U安大略 11 年级 — SBI3U §1 through §7 at the conceptual level. SBI3U B3.2 requires prokaryote/eukaryote comparison including organelles and metabolism§1 至 §7 概念层面。SBI3U B3.2 要求原核/真核比较，含细胞器与代谢 Named-organelle detail (B3.1) is SBI4U, not SBI3U — conceptual coverage suffices at Grade 11命名细胞器细节（B3.1）属 SBI4U，非 SBI3U——11 年级概念性覆盖即可 Ontario SBI3U/4U Biology — SBI3U Strand B B3.2— SBI3U B 单元 B3.2
🇨🇦 ON Grade 12 — SBI4U Honors安大略 12 年级 — SBI4U 荣誉 All 7 sections in full including the going-deeper organelle lists (B3.1: lysosomes, vacuoles, mitochondria, ribosomes, ER, Golgi) and fluid mosaic membrane detail (B3.6)全部 7 节完整学习，含深入细胞器列表（B3.1：溶酶体、液泡、线粒体、核糖体、内质网、高尔基体）与流动镶嵌膜细节（B3.6） Nothing — this unit is prerequisite for SBI4U Biochemistry and Metabolic Processes无 — 本单元是 SBI4U 生物化学与代谢过程的先修基础 Ontario SBI3U/4U Biology — SBI4U Strand B B3.1, B3.6— SBI4U B 单元 B3.1、B3.6
🇨🇦 BC Life Sciences 11BC Life Sciences 11 §1, §3, §5, §6, §7 are all core: Big Idea 1 ("interactions at the molecular and cellular levels") and Content bullet "cell structure and function: prokaryotic and eukaryotic; unicellular and multicellular; cell specialization"§1、§3、§5、§6、§7 均为核心：大概念 1（"分子和细胞层面的互动"）及内容条目"细胞结构与功能：原核与真核；单细胞与多细胞；细胞特化" Deep fluid-mosaic membrane biochemistry (§2 going-deeper): BC Life Sciences 11 names transport modes but not the full SBI4U B3.6 biochemical detail深入流动镶嵌膜生化（§2 深入内容）：BC Life Sciences 11 涉及运输方式但不含 SBI4U B3.6 的完整生化细节 BC Life Sciences 11 / Anatomy 12 — Life Sciences 11 Big Ideas + Content— Life Sciences 11 大概念 + 内容
🇨🇦 AB Biology 20 / 30阿尔伯塔 Biology 20 / 30 All sections at the conceptual level as preparation for Biology 20 Unit D (human systems) and Biology 30 Unit C GO1 (cell cycle). Alberta has no standalone cell-structure unit, so use this guide as the missing foundation全部各节概念层面，为 Biology 20 Unit D（人体系统）与 Biology 30 Unit C GO1（细胞周期）作准备。阿尔伯塔无独立细胞结构单元，以本指南补足基础 Nothing — treat the whole guide as foundational context for both Biology 20 and 30无 — 将全指南视为 Biology 20 与 30 的基础背景 Alberta Biology 20/30 — Biology 20 Unit D GO1; Biology 30 Unit C GO1— Biology 20 Unit D GO1；Biology 30 Unit C GO1

Once you have located your row, use the two cards below for the approach that fits your timeline.找到所在行后，用下面两张卡片选择适合你时间安排的方式。

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If you are cramming the night before如果你在临阵磨枪

Know the three tenets of cell theory; the prokaryote vs eukaryote split (no nucleus/membrane-bound organelles vs yes); the three transport modes (diffusion: passive, with concentration gradient; osmosis: water through semipermeable membrane; active transport: against gradient, requires ATP); and the seven levels of biological organization. Read every cram-cheat box. Skip the going-deeper sections on fluid mosaic details and microscope optics.掌握细胞学说三条原则；原核（无核/无膜性细胞器）与真核（有核/有膜性细胞器）之分；三种运输方式（扩散：被动，顺浓度梯度；渗透：水穿过半透膜；主动运输：逆梯度，需 ATP）；以及七个生命组织层次。读每个速记框，跳过流动镶嵌细节与显微镜光学的深入内容。

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If you are going for the top mark如果你目标顶分

Be precise about why a cell can only be so large: the surface-area-to-volume ratio decreases as a cell grows, limiting the rate at which materials can enter and waste can leave. Know which organelles are plant-only (cell wall, chloroplast, central vacuole) and which are shared. For SBI4U, link organelle function to biochemistry: mitochondria as the site of aerobic respiration, chloroplasts for photosynthesis, ribosomes for translation. Distinguish simple diffusion from facilitated diffusion from active transport by energy requirement and directionality.精准掌握细胞为何只能长到一定大小：随细胞生长，表面积体积比降低，限制了物质进出速率。了解哪些细胞器为植物专有（细胞壁、叶绿体、中央液泡），哪些共享。SBI4U 轨道需将细胞器功能与生化挂钩：线粒体是有氧呼吸场所，叶绿体负责光合作用，核糖体负责翻译。以能量需求与方向性区分简单扩散、促进扩散与主动运输。

Honors flag.荣誉级标记。 The going-deeper organelle detail in §3 (named list including lysosomes, smooth/rough ER, Golgi bodies) and the full fluid-mosaic membrane biochemistry in §2 carry the Honors SBI4U chip, because Ontario SBI4U B3.1/B3.6 expects this depth while SBI3U, NGSS, and BC Life Sciences 11 do not. If your curriculum is NGSS or SBI3U, read these sections for conceptual grounding but do not memorize the named lists.§3 的深入细胞器细节（含溶酶体、光面/糙面内质网、高尔基体的命名列表）与 §2 的完整流动镶嵌膜生化标注 荣誉 SBI4U，因为安大略 SBI4U B3.1/B3.6 要求这一深度，而 SBI3U、NGSS 与 BC Life Sciences 11 不作此要求。若你的大纲是 NGSS 或 SBI3U，阅读这些部分以获得概念基础，但无需背诵命名列表。
Section 1 · Cell theory and cell types第 1 节 · 细胞学说与细胞类型

Cell Theory and Prokaryotic vs Eukaryotic Cells细胞学说与原核细胞 vs 真核细胞

The three tenets of cell theory — biology begins here.细胞学说三条原则 — 生物学从这里出发。
  • All living things are made of one or more cells.一切生物由一个或多个细胞构成。
  • The cell is the basic unit of life.细胞是生命的基本单位。
  • All cells arise from pre-existing cells (biogenesis).所有细胞由已有细胞产生（生源论）。

Prokaryote vs eukaryote (SBI3U B3.2; BC Life Sciences 11 Content; NGSS HS-LS1-2 framing):原核 vs 真核（SBI3U B3.2；BC Life Sciences 11 内容；NGSS HS-LS1-2 框架）：

  • Prokaryotes (bacteria, archaea): no membrane-bound nucleus; no membrane-bound organelles; DNA is a circular chromosome in the cytoplasm; smaller (1–10 μm); reproduce by binary fission.原核细胞（细菌、古菌）：无膜性细胞核；无膜性细胞器；DNA 以环状染色体存在于细胞质；较小（1–10 μm）；以二分裂方式繁殖。
  • Eukaryotes (animals, plants, fungi, protists): membrane-bound nucleus containing linear chromosomes; membrane-bound organelles (mitochondria, ER, etc.); larger (10–100 μm).真核细胞（动物、植物、真菌、原生生物）：具膜性细胞核，内含线状染色体；具膜性细胞器（线粒体、内质网等）；较大（10–100 μm）。
Worked Example 1 · Classifying cells例题 1 · 细胞分类

A student examines two cells under a microscope. Cell A has a clearly visible nucleus and numerous small organelles. Cell B has no visible nucleus and is about one-tenth the diameter of Cell A. Classify each cell and give two reasons for each classification.一名学生在显微镜下观察两种细胞。细胞 A 有清晰可见的细胞核和大量小型细胞器；细胞 B 无可见的细胞核，直径约为细胞 A 的十分之一。请分类每种细胞，并各给出两条理由。

Cell A is eukaryotic.细胞 A 为真核细胞。 Evidence: (1) membrane-bound nucleus visible; (2) numerous membrane-bound organelles present. Larger size is consistent but not definitional.依据：(1) 可见膜性细胞核；(2) 存在大量膜性细胞器。体积较大与此一致，但非定义性标准。

Cell B is prokaryotic.细胞 B 为原核细胞。 Evidence: (1) no membrane-bound nucleus; (2) much smaller size (~1–10 μm typical of bacteria). All bacteria are prokaryotes; the absence of a nucleus is the defining criterion.依据：(1) 无膜性细胞核；(2) 体积小得多（细菌典型 1–10 μm）。所有细菌均为原核生物；无细胞核是定义性标准。

Which of the following is a feature shared by ALL living cells, prokaryotic and eukaryotic alike?下列哪项是所有活细胞（原核与真核）共同具备的特征？
§1 · Q1
A membrane-bound nucleus膜性细胞核
A cell membrane (plasma membrane)细胞膜（质膜）
Mitochondria线粒体
A cell wall细胞壁
Every cell, prokaryotic or eukaryotic, is bounded by a plasma membrane. Nuclei and mitochondria are eukaryote-only; cell walls are absent in animal cells.每个细胞，无论原核还是真核，都由质膜包裹。细胞核与线粒体为真核细胞专有；动物细胞无细胞壁。
The plasma membrane is universal. A nucleus is a eukaryotic feature; mitochondria are eukaryotic; cell walls are absent in animal cells.质膜是普遍特征。细胞核属真核；线粒体属真核；动物细胞无细胞壁。
Which statement about prokaryotic cells is correct?关于原核细胞，下列哪项表述正确？
§1 · Q2
They have a nucleus but no mitochondria有细胞核，但无线粒体
They have mitochondria but no cell membrane有线粒体，但无细胞膜
They have DNA but no membrane-bound nucleus有 DNA，但无膜性细胞核
They are always larger than eukaryotic cells总比真核细胞更大
Prokaryotes carry DNA (a circular chromosome in the cytoplasm) but lack a membrane-bound nucleus. They also lack membrane-bound organelles and are generally smaller than eukaryotes.原核生物携带 DNA（在细胞质中呈环状染色体），但无膜性细胞核。同样无膜性细胞器，通常比真核细胞更小。
Prokaryotes have no nucleus (membrane-bound or otherwise) and no mitochondria. They do have a cell membrane and do contain DNA. They are generally smaller than eukaryotes.原核生物无细胞核（无论是否有膜），也无线粒体。它们有细胞膜，也含 DNA。通常比真核细胞更小。
Going deeper — evidence for the endosymbiotic theory (why mitochondria and chloroplasts were once free-living prokaryotes)深入 — 内共生理论的证据（线粒体与叶绿体曾是自由生活的原核生物）

Lynn Margulis proposed that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by a host cell but not digested. Key evidence: (1) both organelles have their own circular DNA, like bacteria; (2) both have double membranes (the inner membrane from the original bacterium, the outer from the engulfment event); (3) both replicate by binary fission independently of cell division; (4) ribosomal RNA sequences of mitochondria closely match proteobacteria, and chloroplast sequences match cyanobacteria. This endosymbiotic origin explains why both organelles are exclusively eukaryotic — only a cell large enough to engulf another cell could have acquired them.林恩·马古利斯提出，线粒体与叶绿体起源于被宿主细胞吞噬却未被消化的自由生活细菌。关键证据：(1) 两种细胞器均有自己的环状 DNA，与细菌相似；(2) 均具双层膜（内膜来自原始细菌，外膜来自吞噬事件）；(3) 均以二分裂方式独立于细胞分裂而复制；(4) 线粒体的核糖体 RNA 序列与变形菌高度相似，叶绿体序列则与蓝藻相近。这种内共生起源解释了为何两种细胞器均仅存在于真核细胞——只有足够大、能吞噬另一细胞的细胞才能获得它们。

Section 2 · Cell membrane and transport第 2 节 · 细胞膜与物质运输

The Cell Membrane and Transport细胞膜与物质运输

The fluid-mosaic model and three transport modes.流动镶嵌模型与三种运输方式。
  • Fluid mosaic model:流动镶嵌模型： the cell membrane (plasma membrane) is a phospholipid bilayer. Phospholipids have a hydrophilic head and two hydrophobic tails. Proteins float ("mosaic") in the fluid bilayer. Cholesterol stabilizes fluidity.细胞膜（质膜）是磷脂双分子层。磷脂分子有亲水头部与两条疏水尾部。蛋白质以"镶嵌"方式漂浮在流动的双分子层中。胆固醇稳定流动性。
  • Diffusion (passive):扩散（被动）： net movement of molecules from high to low concentration (down the concentration gradient). No energy (ATP) required. Small nonpolar molecules (O₂, CO₂) cross freely.分子从高浓度区向低浓度区的净移动（顺浓度梯度）。不需要能量（ATP）。小的非极性分子（O₂、CO₂）可自由穿越。
  • Osmosis:渗透： diffusion of water across a selectively permeable membrane from a region of lower solute concentration (higher water concentration) to a region of higher solute concentration (lower water concentration).水分子穿过半透膜从溶质浓度较低（水浓度较高）的区域向溶质浓度较高（水浓度较低）的区域扩散。
  • Active transport:主动运输： movement of molecules against their concentration gradient. Requires a carrier protein and ATP. Example: the sodium-potassium pump in nerve cells.分子逆浓度梯度的移动。需要载体蛋白和 ATP。例如：神经细胞中的钠钾泵。
Worked Example 2 · Osmosis in a red blood cell例题 2 · 红细胞中的渗透

A red blood cell is placed in a solution with a lower solute concentration than the cell's cytoplasm (a hypotonic solution). Predict and explain what happens to the cell, naming the transport process involved.将一个红细胞置于溶质浓度低于细胞质的溶液中（低渗溶液）。预测并解释细胞将发生什么变化，并说明涉及的运输方式。

Process: osmosis.过程：渗透。 The outside solution is hypotonic (lower solute = higher water concentration). Water moves by osmosis down its concentration gradient, from outside the cell to inside the cell.外部溶液为低渗（溶质较少 = 水浓度较高）。水分子沿浓度梯度通过渗透作用从细胞外向细胞内移动。

Result: the cell swells and may lyse (burst).结果：细胞膨胀，可能发生溶解（破裂）。 In an isotonic solution, the net water movement is zero and the cell retains its normal shape. In a hypertonic solution, water leaves the cell and it shrinks (crenation). These three outcomes (lysis / normal / crenation) appear as a classic exam question.在等渗溶液中，水的净移动为零，细胞保持正常形态。在高渗溶液中，水从细胞外流，细胞皱缩（锯齿状红细胞）。这三种结果（溶解／正常／皱缩）是经典考试题型。

Which transport process moves molecules against their concentration gradient and requires ATP?哪种运输方式逆浓度梯度移动分子且需要 ATP？
§2 · Q1
Simple diffusion简单扩散
Osmosis渗透
Active transport主动运输
Facilitated diffusion促进扩散
Active transport moves substances against their concentration gradient and requires ATP. Diffusion and osmosis are passive (no ATP needed) and move down the gradient.主动运输逆浓度梯度移动物质，需要 ATP。扩散与渗透是被动的（无需 ATP），沿梯度方向移动。
Active transport is the only mode that works against the concentration gradient and requires energy (ATP). The others are passive.主动运输是唯一逆浓度梯度工作且需要能量（ATP）的方式。其余均为被动运输。
A plant cell is placed in distilled water (a hypotonic solution). What happens?将植物细胞置于蒸馏水（低渗溶液）中。会发生什么？
§2 · Q2
Water enters by osmosis; the cell becomes turgid but the cell wall prevents lysis水通过渗透进入细胞；细胞变得膨胀，但细胞壁阻止溶解
Water leaves; the cell shrinks (plasmolysis)水外流；细胞皱缩（质壁分离）
No net water movement; cell stays the same水无净移动；细胞不变
The cell bursts immediately because it has no cell wall细胞立刻破裂，因为没有细胞壁
Distilled water has a lower solute concentration than the cell, so water enters by osmosis (turgidity). Unlike animal cells, plant cells have a rigid cell wall that provides turgor pressure and prevents lysis.蒸馏水溶质浓度低于细胞内，故水通过渗透进入（细胞膨胀）。与动物细胞不同，植物细胞有坚硬细胞壁，提供膨压，阻止溶解。
Water moves by osmosis into the cell (lower solute outside means higher water concentration outside). The cell wall of a plant cell prevents it from bursting.水通过渗透进入细胞（外部溶质较少意味着外部水浓度较高）。植物细胞的细胞壁阻止其破裂。
Going deeper — facilitated diffusion, endocytosis and exocytosis (SBI4U B3.6)深入 — 促进扩散、胞吞与胞吐（SBI4U B3.6）

Facilitated diffusion uses a channel or carrier protein to move molecules down their gradient. It is passive (no ATP), but unlike simple diffusion, it is specific (a glucose transporter only moves glucose) and can be saturated. SBI4U B3.6 adds endocytosis (cell engulfs large particles by forming a vesicle) and exocytosis (vesicles fuse with the membrane to secrete large molecules). These bulk-transport modes require ATP and are how cells manage molecules too large for membrane proteins.促进扩散借助通道蛋白或载体蛋白使分子沿梯度方向移动。它是被动的（无需 ATP），但与简单扩散不同，它具有特异性（葡萄糖载体只转运葡萄糖）且可以饱和。SBI4U B3.6 还涉及胞吞（细胞通过形成囊泡吞噬大颗粒）与胞吐（囊泡与细胞膜融合以分泌大分子）。这些大颗粒运输方式需要 ATP，是细胞处理过大而无法通过膜蛋白分子的方式。

Section 3 · Organelles第 3 节 · 细胞器

Organelles: Animal vs Plant Cells细胞器：动物细胞与植物细胞

Core organelles — know each one's job.核心细胞器 — 掌握各自功能。
  • Nucleus:细胞核： houses the DNA; site of transcription. Controls cell activities.储存 DNA；转录场所。控制细胞活动。
  • Mitochondria:线粒体： site of aerobic cellular respiration; produce ATP. Present in both animal and plant cells.有氧细胞呼吸的场所；产生 ATP。动植物细胞均有。
  • Ribosomes:核糖体： site of protein synthesis (translation). Present in all cells, including prokaryotes.蛋白质合成（翻译）的场所。所有细胞（包括原核细胞）均有。
  • Cell membrane:细胞膜： controls what enters and leaves the cell. Present in all cells.控制物质进出细胞。所有细胞均有。
  • Chloroplasts (plant/algae only):叶绿体（仅植物／藻类）： site of photosynthesis; contain chlorophyll. Absent in animal cells.光合作用场所；含叶绿素。动物细胞中无。
  • Cell wall (plant, fungi, bacteria):细胞壁（植物、真菌、细菌）： rigid outer layer for support and protection. Made of cellulose in plants. Absent in animal cells.坚硬外层，提供支撑与保护。植物细胞壁由纤维素构成。动物细胞中无。
  • Central vacuole (plant cells):中央液泡（植物细胞）： large fluid-filled sac; stores water, ions, and waste; maintains turgor pressure.大型充液囊；储存水、离子和废物；维持膨压。
T
Animal vs Plant: what each has that the other lacks动物细胞 vs 植物细胞：各自独有的结构
Structure结构Animal cell动物细胞Plant cell植物细胞
Cell wall细胞壁No无Yes (cellulose)有（纤维素）
Chloroplasts叶绿体No无Yes有
Central vacuole中央液泡No (small vacuoles)无（有小液泡）Yes (large)有（大型）
Nucleus细胞核Yes有Yes有
Mitochondria线粒体Yes有Yes有
Ribosomes核糖体Yes有Yes有
Which organelle is the site of aerobic cellular respiration?哪种细胞器是有氧细胞呼吸的场所？
§3 · Q1
Chloroplast叶绿体
Ribosome核糖体
Nucleus细胞核
Mitochondrion线粒体
Mitochondria are the site of aerobic cellular respiration, producing ATP. Chloroplasts perform photosynthesis; ribosomes make proteins; the nucleus houses DNA.线粒体是有氧细胞呼吸的场所，产生 ATP。叶绿体进行光合作用；核糖体合成蛋白质；细胞核储存 DNA。
Mitochondria are the "powerhouses" of the cell. Chloroplasts capture light energy; ribosomes build proteins; the nucleus stores DNA.线粒体是细胞的"能量工厂"。叶绿体捕获光能；核糖体构建蛋白质；细胞核储存 DNA。
A student observes a cell with a cell wall, chloroplasts, and a large central vacuole. This cell is most likely from which organism?一名学生观察到一个具有细胞壁、叶绿体和大型中央液泡的细胞。该细胞最可能来自哪类生物？
§3 · Q2
A mammal哺乳动物
A flowering plant开花植物
A bacterium细菌
A fungus真菌
Cell wall + chloroplasts + large central vacuole = plant cell. Mammals lack all three; bacteria are prokaryotic (no chloroplasts, no central vacuole); fungi have cell walls but no chloroplasts.细胞壁 + 叶绿体 + 大型中央液泡 = 植物细胞。哺乳动物三者均无；细菌为原核（无叶绿体、无中央液泡）；真菌有细胞壁但无叶绿体。
The combination of cell wall + chloroplasts + large central vacuole is unique to plant cells.细胞壁 + 叶绿体 + 大型中央液泡的组合是植物细胞所独有的。
Going deeper — the endomembrane system: ER, Golgi, lysosomes (SBI4U B3.1)深入 — 内膜系统：内质网、高尔基体、溶酶体（SBI4U B3.1）

The rough endoplasmic reticulum (rough ER) is studded with ribosomes and packages proteins destined for secretion or for the membrane. Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification. The Golgi apparatus receives vesicles from the ER, modifies the proteins inside (e.g. adds sugar chains), and ships them to the cell surface or to lysosomes. Lysosomes are membrane-bound sacs containing digestive enzymes; they break down worn-out organelles (autophagy) and foreign particles. The entire sequence — synthesis (rough ER) → modification (Golgi) → delivery (vesicle) — is the secretory pathway, which Ontario SBI4U B3.1 expects students to explain.糙面内质网（糙面 ER）表面附有核糖体，负责包装准备分泌或插入膜中的蛋白质。光面 ER 无核糖体，参与脂质合成与解毒。高尔基体接收来自 ER 的囊泡，对内部蛋白质进行修饰（如添加糖链），再将其运送至细胞表面或溶酶体。溶酶体是含消化酶的膜性囊泡，负责降解老化细胞器（自噬）和外来颗粒。合成（糙面 ER）→ 修饰（高尔基体）→ 输送（囊泡）的整个流程即分泌途径，是安大略 SBI4U B3.1 要求学生解释的内容。

Section 4 · The nucleus and genetic control第 4 节 · 细胞核与基因调控

The Nucleus and the Control of the Cell细胞核与细胞的调控

The nucleus is the control center of the eukaryotic cell.细胞核是真核细胞的控制中心。
  • Nuclear envelope:核膜： double membrane that surrounds the nucleus. Nuclear pores allow controlled transport of RNA and proteins.包围细胞核的双层膜。核孔允许 RNA 和蛋白质的受控运输。
  • Chromatin / chromosomes:染色质 / 染色体： DNA wound around histone proteins. In non-dividing cells the DNA is loosely coiled chromatin; during cell division it condenses into visible chromosomes.缠绕组蛋白的 DNA。在非分裂细胞中，DNA 以松散卷曲的染色质形式存在；细胞分裂时凝缩成可见的染色体。
  • Nucleolus:核仁： a dense region inside the nucleus where ribosomal RNA (rRNA) is made. Disappears during cell division and reforms afterwards.细胞核内的致密区域，合成核糖体 RNA（rRNA）。细胞分裂期间消失，之后重新形成。
  • Information flow:信息流： DNA (nucleus) → mRNA transcription → mRNA exits through nuclear pores → translation at ribosomes → protein.DNA（细胞核）→ mRNA 转录 → mRNA 通过核孔输出 → 在核糖体翻译 → 蛋白质。
What is the function of nuclear pores in eukaryotic cells?真核细胞中核孔的功能是什么？
§4 · Q1
To allow mRNA and proteins to pass in and out of the nucleus允许 mRNA 和蛋白质进出细胞核
To replicate DNA复制 DNA
To produce ATP for the nucleus为细胞核产生 ATP
To break down damaged DNA分解受损 DNA
Nuclear pores are protein channels in the nuclear envelope that regulate molecular movement: mRNA exits the nucleus to be translated; proteins (such as transcription factors) enter the nucleus to regulate gene expression.核孔是核膜上的蛋白质通道，调控分子的进出：mRNA 离开细胞核进行翻译；蛋白质（如转录因子）进入细胞核调控基因表达。
Nuclear pores control molecular traffic between the nucleus and cytoplasm. mRNA must exit to reach ribosomes; regulatory proteins must enter to control transcription.核孔控制细胞核与细胞质之间的分子运输。mRNA 必须离开才能到达核糖体；调控蛋白必须进入才能控制转录。
The nucleolus is a region inside the nucleus that primarily produces:核仁是细胞核内的一个区域，主要产生：
§4 · Q2
DNA copies for replication用于复制的 DNA 拷贝
Lipids for the cell membrane用于细胞膜的脂质
Ribosomal RNA (rRNA)核糖体 RNA（rRNA）
ATP for cellular respiration用于细胞呼吸的 ATP
The nucleolus synthesizes ribosomal RNA (rRNA) and assembles ribosome subunits. These are exported through nuclear pores to the cytoplasm, where they function in translation.核仁合成核糖体 RNA（rRNA）并组装核糖体亚基。这些亚基通过核孔输出至细胞质，在那里参与翻译。
The nucleolus makes rRNA, the RNA component of ribosomes. It is not involved in DNA replication, lipid synthesis, or ATP production.核仁合成 rRNA，即核糖体的 RNA 组成部分。它不参与 DNA 复制、脂质合成或 ATP 生成。
Section 5 · Microscopy and cell size第 5 节 · 显微镜与细胞大小

Microscopy, Cell Size, and the Surface-Area-to-Volume Ratio显微镜、细胞大小与表面积体积比

Why cells must stay small: the SA:V argument.细胞为何必须保持小体积：SA:V 论证。

For a cube of side length $l$:对于边长为 $l$ 的正方体：

$$ \text{Surface area} = 6l^2 \qquad \text{Volume} = l^3 \qquad \text{SA:V ratio} = \frac{6l^2}{l^3} = \frac{6}{l} $$
  • As $l$ increases, SA:V ratio decreases. A larger cell has proportionally less surface area to exchange materials per unit of cytoplasm.随 $l$ 增大，SA:V 比值减小。较大的细胞每单位细胞质所对应的物质交换表面积成比例减少。
  • Nutrients must enter and wastes must leave through the surface. If the cell is too large, the interior starves of nutrients and accumulates toxic waste faster than diffusion can cope.营养物质必须通过表面进入，废物必须通过表面排出。若细胞过大，内部的营养供给不足，废物积累速度超过扩散能力。
  • This explains why cells divide before growing too large (cell cycle), and why large organisms need specialised transport systems (circulatory system) rather than relying on diffusion alone.这解释了为何细胞在长得过大之前便会分裂（细胞周期），以及为何大型生物需要专门的运输系统（循环系统），而非单纯依赖扩散。

Microscopy types:显微镜类型： Light microscope — max ~1,000× magnification, resolves down to ~0.2 μm; can view living cells with stains. Electron microscope (TEM/SEM) — up to 500,000×; reveals organelle ultrastructure; cells must be dead and fixed.光学显微镜 — 最高约 1,000 倍放大，分辨率约 0.2 μm；可借助染料观察活细胞。电子显微镜（TEM/SEM）— 最高 500,000 倍；显示细胞器超微结构；细胞须死亡固定。

Worked Example 3 · Surface-area-to-volume ratio calculation例题 3 · 表面积体积比计算

Compare the SA:V ratios of two cuboidal cells: Cell A has side length $2\ \mu\text{m}$ and Cell B has side length $8\ \mu\text{m}$. Which cell exchanges materials more efficiently?比较两个正方体细胞的 SA:V 比：细胞 A 边长 $2\ \mu\text{m}$，细胞 B 边长 $8\ \mu\text{m}$。哪个细胞物质交换效率更高？

Cell A ($l = 2$):细胞 A（$l = 2$）：

$$ \text{SA} = 6(2)^2 = 24\ \mu\text{m}^2 \qquad \text{V} = (2)^3 = 8\ \mu\text{m}^3 \qquad \text{SA:V} = 24/8 = 3.0\ \mu\text{m}^{-1}. $$

Cell B ($l = 8$):细胞 B（$l = 8$）：

$$ \text{SA} = 6(8)^2 = 384\ \mu\text{m}^2 \qquad \text{V} = (8)^3 = 512\ \mu\text{m}^3 \qquad \text{SA:V} = 384/512 = 0.75\ \mu\text{m}^{-1}. $$

Conclusion:结论： Cell A's SA:V ratio (3.0) is four times larger than Cell B's (0.75). Cell A exchanges materials far more efficiently. Cell B would struggle to supply its larger volume by diffusion alone.细胞 A 的 SA:V 比（3.0）是细胞 B（0.75）的四倍。细胞 A 物质交换效率远高于细胞 B。细胞 B 仅靠扩散难以满足其更大体积的需求。

As a spherical cell doubles its radius, what happens to its surface-area-to-volume ratio?当球形细胞半径加倍时，其表面积体积比如何变化？
§5 · Q1
It doubles加倍
It is halved减半
It stays the same不变
It quadruples变为四倍
For a sphere SA $\propto r^2$ and V $\propto r^3$, so SA:V $\propto 1/r$. Doubling the radius halves the SA:V ratio. The cell becomes less efficient at exchanging materials.球体 SA $\propto r^2$，V $\propto r^3$，故 SA:V $\propto 1/r$。半径加倍，SA:V 比减半。细胞物质交换效率降低。
SA:V $\propto 1/r$ for a sphere. Doubling $r$ therefore halves the ratio.球体 SA:V $\propto 1/r$。$r$ 加倍则比值减半。
Section 6 · Cell specialization第 6 节 · 细胞特化

Cell Specialization and Differentiation细胞特化与分化

Specialization: same DNA, different jobs (BC Life Sciences 11; SBI3U; NGSS HS-LS1-2).特化：相同 DNA，不同职责（BC Life Sciences 11；SBI3U；NGSS HS-LS1-2）。
  • Differentiation:分化： the process by which a less-specialized cell becomes more specialized. All cells in a multicellular organism share the same DNA, but different genes are expressed in different cell types.较不特化的细胞变为更特化细胞的过程。多细胞生物体内所有细胞共享相同的 DNA，但不同类型的细胞表达不同的基因。
  • Examples of specialized cells:特化细胞示例：
    • Red blood cells: no nucleus (maximizes space for haemoglobin); biconcave disc shape (increases SA for gas exchange).红细胞：无细胞核（最大化血红蛋白空间）；双凹圆盘形（增大气体交换表面积）。
    • Muscle cells: contain many mitochondria for ATP; long and fibrous for contraction.肌肉细胞：含大量线粒体提供 ATP；细长纤维状以便收缩。
    • Root hair cells (plants): long extensions to maximize surface area for water and ion absorption.根毛细胞（植物）：具长延伸，最大化水分和离子吸收表面积。
    • Neurons: long axons to transmit signals over large distances; many mitochondria at synapses.神经元：具长轴突，可远距离传递信号；突触处有大量线粒体。
  • Stem cells:干细胞： undifferentiated cells that can divide and become specialized. Embryonic stem cells are pluripotent; adult stem cells are more restricted.未分化的细胞，可分裂并特化。胚胎干细胞具多能性；成体干细胞分化能力更受限。
Red blood cells in mammals lack a nucleus. What is the main advantage of this specialization?哺乳动物的红细胞没有细胞核。这种特化的主要优势是什么？
§6 · Q1
It allows the cell to replicate its DNA more quickly使细胞能更快复制其 DNA
It prevents the cell from being attacked by the immune system防止细胞被免疫系统攻击
It makes the cell transparent so oxygen can pass through使细胞透明，让氧气可以穿过
It provides more space for haemoglobin, increasing oxygen-carrying capacity为血红蛋白提供更多空间，增加携氧能力
Without a nucleus (and without mitochondria), more of the cell's volume is available for haemoglobin, the protein that binds and transports oxygen. This is a clear example of structure fitting function.没有细胞核（也没有线粒体），细胞中更多体积可用于储存血红蛋白——结合并运输氧气的蛋白质。这是结构适应功能的典型例子。
The lack of a nucleus frees up internal space for haemoglobin, the oxygen-carrying protein. The trade-off is maximized oxygen transport.无核腾出内部空间用于储存血红蛋白（携氧蛋白）。换来了最大化的氧气运输能力。
All cells in a multicellular organism have the same DNA. Why do different cell types look and function so differently?多细胞生物体内所有细胞的 DNA 相同，为何不同细胞类型的外观和功能差异如此之大？
§6 · Q2
Different genes are expressed (switched on) in different cell types不同细胞类型中不同的基因被表达（开启）
Different cells contain different sets of chromosomes不同细胞含有不同的染色体组
Mutations accumulate differently in each cell type over time随时间推移，各细胞类型中积累的突变不同
Some cells copy more DNA during S phase than others某些细胞在 S 期复制更多 DNA
All somatic cells in an organism contain the same genome (barring mutation). Differentiation occurs because gene expression is regulated: transcription factors activate or silence specific genes in each cell type, producing different proteins and therefore different structures and functions.生物体内所有体细胞含有相同的基因组（不考虑突变）。分化的发生是因为基因表达受到调控：转录因子在每种细胞类型中激活或沉默特定基因，产生不同的蛋白质，从而形成不同的结构和功能。
Somatic cells all carry the same DNA. The difference is which genes are turned on or off in each cell type (gene regulation / differential gene expression).体细胞均携带相同的 DNA。区别在于每种细胞类型中哪些基因被开启或关闭（基因调控 / 差异基因表达）。
Section 7 · Levels of organization第 7 节 · 生命组织层次

Levels of Biological Organization生命的组织层次

The hierarchy from molecule to biosphere (BC Life Sciences 11 Content; NGSS HS-LS1-2).从分子到生物圈的层次（BC Life Sciences 11 内容；NGSS HS-LS1-2）。
  1. Molecule — e.g. DNA, haemoglobin, glucose.分子 — 如 DNA、血红蛋白、葡萄糖。
  2. Organelle — e.g. mitochondrion, nucleus, ribosome.细胞器 — 如线粒体、细胞核、核糖体。
  3. Cell — the basic unit of life. Prokaryotic or eukaryotic.细胞 — 生命的基本单位。原核或真核。
  4. Tissue — a group of similar cells performing the same function. E.g. muscle tissue, epithelial tissue, xylem.组织 — 执行相同功能的同类细胞群。如肌肉组织、上皮组织、木质部。
  5. Organ — two or more tissue types working together. E.g. the heart (muscle + connective + epithelial + nervous tissue), a leaf.器官 — 两种或多种组织共同工作。如心脏（肌肉 + 结缔 + 上皮 + 神经组织）、叶片。
  6. Organ system — organs working together for a common function. E.g. circulatory system, digestive system, shoot system of a plant.器官系统 — 共同完成某种功能的器官集合。如循环系统、消化系统、植物茎叶系统。
  7. Organism — a complete individual. Unicellular (e.g. amoeba) or multicellular (e.g. human, oak tree).生物体 — 完整的个体。单细胞（如变形虫）或多细胞（如人类、橡树）。

Above the organism: population → community → ecosystem → biosphere. These are the ecology levels (covered in the Ecology guide).生物体以上：种群 → 群落 → 生态系统 → 生物圈。这些是生态层次（见《生态学》指南）。

Why the hierarchy matters for biology.为何层次结构在生物学中至关重要。

NGSS HS-LS1-2 frames the entire cell-biology unit around this hierarchy: cells provide functions within tissues; tissues within organs; organs within organ systems; and organ systems within the organism. The Assessment Boundary explicitly excludes the molecular level — the focus is on the structural-functional model, not chemical reactions. Understanding the hierarchy is also the gateway to understanding how a disease at the cell level (e.g. cancer: uncontrolled cell division) propagates its effects upward through tissue, organ, and system.NGSS HS-LS1-2 以这一层次结构为框架贯穿整个细胞生物学单元：细胞在组织中发挥功能；组织在器官中发挥功能；器官在器官系统中发挥功能；器官系统在生物体中发挥功能。评估边界明确排除分子层面——重点是结构-功能模型，而非化学反应。理解层次结构也是理解细胞层面疾病（如癌症：不受控制的细胞分裂）如何向上传播影响至组织、器官与系统的关键。

Which correctly lists the levels of biological organization from smallest to largest?下列哪项正确列出了从最小到最大的生命组织层次？
§7 · Q1
Cell → tissue → molecule → organ → organism细胞 → 组织 → 分子 → 器官 → 生物体
Tissue → cell → organ system → organ → organism组织 → 细胞 → 器官系统 → 器官 → 生物体
Molecule → organelle → cell → tissue → organ → organ system → organism分子 → 细胞器 → 细胞 → 组织 → 器官 → 器官系统 → 生物体
Organelle → cell → organism → tissue → organ细胞器 → 细胞 → 生物体 → 组织 → 器官
The correct order from smallest to largest is: molecule → organelle → cell → tissue → organ → organ system → organism (and then population, community, ecosystem, biosphere above that).从小到大的正确顺序为：分子 → 细胞器 → 细胞 → 组织 → 器官 → 器官系统 → 生物体（其上还有种群、群落、生态系统、生物圈）。
Remember: molecule → organelle → cell → tissue → organ → organ system → organism.记住：分子 → 细胞器 → 细胞 → 组织 → 器官 → 器官系统 → 生物体。
Exam Tactics考试策略

Exam Strategy and Common Pitfalls考试策略与常见陷阱

Identification questions辨认题
  • Always name the organelle AND state its function.始终同时说明细胞器名称及其功能。 "Mitochondrion" alone is rarely full marks; the complete answer is "mitochondrion — site of aerobic respiration, produces ATP."仅写"线粒体"很少能得满分；完整答案是"线粒体——有氧呼吸场所，产生 ATP"。
  • Prokaryote vs eukaryote is based on the nucleus, not size alone.原核与真核的区分基于细胞核，而非仅靠大小。 The defining criterion is the absence (prokaryote) or presence (eukaryote) of a membrane-bound nucleus.定义性标准是有无膜性细胞核：无 = 原核，有 = 真核。
Transport questions运输题
  • Identify the gradient first, then pick the mode.先判断梯度方向，再选运输方式。 Down the gradient with no ATP = diffusion or osmosis. Against the gradient with ATP = active transport. The word "pump" (e.g. Na/K pump) is a hint for active transport.顺梯度且无 ATP = 扩散或渗透。逆梯度且需 ATP = 主动运输。"泵"（如钠钾泵）是主动运输的提示词。
  • Osmosis is specifically about water.渗透专指水分子。 Do not say "glucose moves by osmosis." Osmosis applies only to the movement of water (solvent) across a selectively permeable membrane.不要说"葡萄糖通过渗透移动"。渗透仅适用于水（溶剂）穿过半透膜的移动。
SA:V ratio questionsSA:V 比题
  • Bigger cell = lower SA:V = less efficient.细胞越大 = SA:V 越低 = 效率越低。 This is the reason cells divide. Larger cells cannot supply their interior by diffusion fast enough.这是细胞分裂的原因。较大的细胞无法通过扩散足够快地供给内部。
  • Show your working.展示计算过程。 For a cube: SA $= 6l^2$, V $= l^3$, SA:V $= 6/l$. Always include units.正方体：SA $= 6l^2$，V $= l^3$，SA:V $= 6/l$。记得带单位。
Active Recall主动复习

Flashcards闪卡

0 / 14 flipped0 / 14 已翻
Three tenets of cell theory?细胞学说三条原则？
1. All living things are made of cells. 2. The cell is the basic unit of life. 3. All cells come from pre-existing cells.1. 一切生物由细胞构成。2. 细胞是生命的基本单位。3. 所有细胞由已有细胞产生。
Prokaryote vs eukaryote — key difference?原核与真核 — 关键区别？
Prokaryote: no membrane-bound nucleus; no membrane-bound organelles. Eukaryote: has both.原核：无膜性细胞核；无膜性细胞器。真核：两者均有。
What is diffusion?什么是扩散？
Net movement of molecules from high to low concentration (down the gradient). Passive — no ATP required.分子从高浓度到低浓度的净移动（顺梯度）。被动 — 无需 ATP。
What is osmosis?什么是渗透？
Diffusion of water across a selectively permeable membrane from lower solute concentration to higher solute concentration.水分子穿过半透膜从溶质浓度低的一侧向溶质浓度高的一侧扩散。
Active transport — how is it different from diffusion?主动运输 — 与扩散有何不同？
Moves molecules against their concentration gradient. Requires a carrier protein and ATP. Example: Na+/K+ pump.逆浓度梯度移动分子。需要载体蛋白和 ATP。例：Na+/K+ 泵。
Function of mitochondria?线粒体的功能？
Site of aerobic cellular respiration. Produces ATP from glucose and oxygen.有氧细胞呼吸的场所。利用葡萄糖和氧气产生 ATP。
Function of chloroplasts?叶绿体的功能？
Site of photosynthesis. Capture light energy and use it to convert CO2 and H2O into glucose and O2. Plant and algae cells only.光合作用场所。捕获光能，将 CO2 和 H2O 转化为葡萄糖和 O2。仅植物和藻类细胞有。
Three structures plants have that animal cells lack?植物细胞有而动物细胞没有的三种结构？
Cell wall (cellulose), chloroplasts, large central vacuole.细胞壁（纤维素）、叶绿体、大型中央液泡。
SA:V ratio formula for a cube (side $l$)?正方体（边长 $l$）的 SA:V 比公式？
$$\frac{\text{SA}}{\text{V}} = \frac{6l^2}{l^3} = \frac{6}{l}$$ Larger cell → smaller ratio → less efficient transport.细胞越大 → 比值越小 → 运输效率越低。
Role of the nucleus?细胞核的作用？
Houses the DNA; site of transcription. Controls all cell activities by directing protein synthesis.储存 DNA；转录场所。通过指导蛋白质合成控制细胞一切活动。
What is cell differentiation?什么是细胞分化？
The process by which cells with the same DNA become specialized for different functions by expressing different genes.具有相同 DNA 的细胞通过表达不同基因而特化为不同功能的过程。
Correct order of levels of organization (cell to organism)?组织层次的正确顺序（细胞到生物体）？
Cell → Tissue → Organ → Organ system → Organism细胞 → 组织 → 器官 → 器官系统 → 生物体
Fluid mosaic model: two key components?流动镶嵌模型：两个关键成分？
Phospholipid bilayer (fluid) + embedded proteins (mosaic). Cholesterol stabilizes the bilayer's fluidity.磷脂双分子层（流动）+ 镶嵌蛋白（镶嵌）。胆固醇稳定双分子层的流动性。
Why is a red blood cell specialized?红细胞为何是特化细胞？
No nucleus → more space for haemoglobin. Biconcave disc → increased SA for O2/CO2 exchange. Flexible → fits through capillaries.无核 → 更多空间储存血红蛋白。双凹圆盘 → 增大 O2/CO2 交换表面积。柔软 → 可通过毛细血管。
Mixed Practice综合练习

Practice Quiz综合测验

Which of the following structures is found in both prokaryotic and eukaryotic cells?下列哪种结构在原核细胞和真核细胞中均存在？
Q1
Nuclear envelope核膜
Ribosomes核糖体
Mitochondria线粒体
Endoplasmic reticulum内质网
Ribosomes (for protein synthesis) are present in all cells — prokaryotic and eukaryotic. They are smaller in prokaryotes (70S) than in eukaryotes (80S), but both types perform translation. The nuclear envelope, mitochondria, and ER are exclusively eukaryotic.核糖体（用于蛋白质合成）存在于所有细胞（原核与真核）中。原核细胞中的核糖体（70S）比真核细胞（80S）更小，但两类均进行翻译。核膜、线粒体和内质网仅见于真核细胞。
Ribosomes are the only structure present in both prokaryotic and eukaryotic cells. The nuclear envelope, mitochondria, and ER are eukaryotic-only.核糖体是唯一在原核和真核细胞中均存在的结构。核膜、线粒体和内质网仅见于真核细胞。
A cell with side length $4\ \mu\text{m}$ divides into two equal daughter cells (each side length $\approx 3.17\ \mu\text{m}$). Does the SA:V ratio increase or decrease after division?边长 $4\ \mu\text{m}$ 的细胞分裂为两个相等的子细胞（各边长 $\approx 3.17\ \mu\text{m}$）。分裂后 SA:V 比增大还是减小？
Q2
Increases — smaller cells have a higher SA:V ratio增大 — 较小的细胞 SA:V 比更高
Decreases — two cells have more surface area to maintain减小 — 两个细胞需要维持更多表面积
Stays the same — total volume is conserved不变 — 总体积守恒
Cannot be determined without more information没有更多信息无法判断
SA:V $= 6/l$ for a cube. Original: $6/4 = 1.5$. After division: $6/3.17 \approx 1.89$. The ratio increases, making each daughter cell more efficient at exchanging materials — this is why cells divide before growing too large.正方体 SA:V $= 6/l$。原始：$6/4 = 1.5$。分裂后：$6/3.17 \approx 1.89$。比值增大，使每个子细胞物质交换效率更高 — 这正是细胞在长得过大之前便会分裂的原因。
Smaller cells have higher SA:V. Since SA:V $= 6/l$, decreasing $l$ increases the ratio.细胞越小 SA:V 越高。因为 SA:V $= 6/l$，$l$ 减小则比值增大。
Iodine solution moves from outside a potato cell into the cell, down its concentration gradient, without using energy. What type of transport is this?碘液顺浓度梯度从马铃薯细胞外移动至细胞内，不消耗能量。这是哪种运输方式？
Q3
Active transport主动运输
Osmosis渗透
Exocytosis胞吐
Diffusion扩散
The iodine moves down its concentration gradient without ATP — this is simple diffusion. Osmosis is specifically for water. Active transport would move against the gradient and require ATP.碘顺浓度梯度移动且无需 ATP — 这是简单扩散。渗透专指水分子移动。主动运输逆梯度且需 ATP。
Down the gradient, no ATP = diffusion. Osmosis is only for water.顺梯度，无 ATP = 扩散。渗透仅适用于水。
A student claims: "Cell differentiation changes the DNA sequence in specialized cells." Is this claim correct?一名学生声称："细胞分化改变了特化细胞中的 DNA 序列。"这一说法正确吗？
Q4
Yes — muscle cells have muscle-specific DNA正确 — 肌肉细胞具有肌肉特异性 DNA
Yes — differentiation deletes genes that are not needed正确 — 分化会删除不需要的基因
No — all somatic cells share the same genome; differentiation changes which genes are expressed, not the DNA sequence不正确 — 所有体细胞共享相同基因组；分化改变的是哪些基因被表达，而非 DNA 序列
No — differentiation only changes the cell membrane, not the nucleus不正确 — 分化只改变细胞膜，不影响细胞核
Differentiation does NOT alter the DNA sequence. All somatic cells in an organism carry the same genome. What changes is gene expression: regulatory proteins switch specific genes on or off, producing different proteins in different cell types.分化不改变 DNA 序列。生物体内所有体细胞携带相同的基因组。改变的是基因表达：调控蛋白开启或关闭特定基因，在不同细胞类型中产生不同蛋白质。
Differentiation changes gene expression (which genes are turned on/off), not the underlying DNA sequence. Every somatic cell retains the full genome.分化改变基因表达（哪些基因开/关），而非底层 DNA 序列。每个体细胞保留完整基因组。
Which level of biological organization directly consists of multiple similar cells grouped together?哪个生命组织层次直接由多个相似细胞聚集而成？
Q5
Organelle细胞器
Tissue组织
Organ器官
Organ system器官系统
A tissue is a group of similar cells that perform the same function. Organs consist of multiple tissue types; organ systems consist of multiple organs; organelles are inside cells.组织是一群执行相同功能的同类细胞。器官由多种组织类型构成；器官系统由多个器官构成；细胞器位于细胞内部。
A tissue = group of similar cells. An organ = multiple tissue types. An organ system = multiple organs. Organelles are sub-cellular structures.组织 = 同类细胞群。器官 = 多种组织类型。器官系统 = 多个器官。细胞器是细胞内的亚细胞结构。
Self-check自查

Readiness Checklist准备就绪清单

Tick each item when you can do it cold, without notes, on a first attempt.能在无笔记、首次尝试下完成，再勾选每一项。

0 / 11 mastered已掌握 0 / 11
Next Steps后续衔接

What This Feeds Into本单元的去向

Cell structure and function is the foundational layer that every later biology topic builds on. The organelles and membrane transport you learned here reappear directly in the Biochemistry guide (Unit 2 — enzyme function, ATP structure), Cellular Energetics (Unit 3 — photosynthesis in chloroplasts, aerobic respiration in mitochondria), Cell Division (Unit 4 — chromosomes in the nucleus, the cell cycle), and Human Anatomy and Physiology (Unit 10 — specialised cells within organ systems).细胞结构与功能是后续所有生物学主题构建的基础层。你在此处学到的细胞器与膜运输将直接出现在《生物化学》（第 2 单元——酶的功能、ATP 结构）、《细胞能量学》（第 3 单元——叶绿体中的光合作用、线粒体中的有氧呼吸）、《细胞分裂》（第 4 单元——细胞核中的染色体、细胞周期）与《人体解剖与生理》（第 10 单元——器官系统中的特化细胞）中。

Within High School Biology.在 HS Biology 内部。

The Biochemistry guide (Unit 2) extends the cell membrane discussion into lipid bilayer chemistry and enzyme catalysis. Cellular Energetics (Unit 3) uses the mitochondrion and chloroplast in detail for respiration and photosynthesis. Cell Division (Unit 4) opens with the nucleus and chromatin introduced here. Molecular Genetics (Unit 6) picks up DNA transcription from the nucleus. Human Anatomy and Physiology (Unit 10) applies cell specialization to the tissue and organ system level.《生物化学》（第 2 单元）将细胞膜讨论延伸至脂质双分子层化学与酶催化。《细胞能量学》（第 3 单元）详细利用线粒体与叶绿体讲解呼吸与光合作用。《细胞分裂》（第 4 单元）以本指南介绍的细胞核与染色质为开篇。《分子遗传学》（第 6 单元）接续细胞核中的 DNA 转录。《人体解剖与生理》（第 10 单元）将细胞特化应用于组织与器官系统层面。

Feeds into AP Biology and IB Biology.衔接 AP Biology 与 IB Biology。

This guide is the direct foundation for AP Biology Unit 2 (Cell Structure and Function) and IB Biology HL Topic B1 (Molecules and Cells). Both courses assume fluency with organelle identification, membrane transport modes, and the prokaryote/eukaryote distinction from day one. AP Biology goes further with membrane protein types (channel, carrier, receptor) and the fluid mosaic model in quantitative terms. IB Biology HL adds ultrastructure detail from electron micrographs. Neither course exists yet in this repo; treat this guide as the prerequisite and revisit it when those products ship.本指南是 AP Biology 第 2 单元（细胞结构与功能）和 IB Biology HL Topic B1（分子与细胞）的直接基础。两门课程从第一天起就默认学生熟悉细胞器辨认、膜运输方式和原核/真核之分。AP Biology 进一步涉及膜蛋白类型（通道、载体、受体）与定量的流动镶嵌模型。IB Biology HL 增加了来自电子显微照片的超微结构细节。目前这两门课程均未收录于本仓库中；将本指南视为先修材料，待相关产品上线后再作衔接。

DINGRUI SCHOLARS

High School Biology · Cell Structure and Function · v1高中生物 · 细胞结构与功能 · v1