📚 Cell Organelles: IB & CCEA Biology Exam Focus | IB CCEA 生物：细胞器考点精讲
Understanding cell organelles is fundamental to both IB and CCEA Biology. These membrane-bound or non-membrane-bound structures perform specialised functions that sustain cellular life, and questions on their structures, functions and interactions frequently appear in exams. This revision guide breaks down every organelle with clear explanations, exam-focused tips and comparative tables.
理解细胞器是 IB 和 CCEA 生物学的基础。这些有膜或无膜的结构执行维持细胞生命的专门功能，有关其结构、功能和相互作用的考题经常出现。本复习指南将逐一分解每个细胞器，提供清晰的解释、考试要点和对比表格。
1. Introduction to Organelles and Compartmentalisation | 细胞器与区室化简介
Eukaryotic cells contain membrane-bound organelles, which create distinct compartments for different metabolic processes. This compartmentalisation increases efficiency and prevents interference between reactions. In contrast, prokaryotic cells lack membrane-bound organelles, although they may have infoldings of the plasma membrane for specific functions.
真核细胞含有具膜细胞器，为不同的代谢过程创造了独立区室。这种区室化提高了效率，并防止反应间的相互干扰。相反，原核细胞缺乏具膜细胞器，尽管它们可能有质膜内陷用于特定功能。
Organelles can be classified as single-membrane bound (e.g., ER, Golgi, lysosomes, vacuoles), double-membrane bound (nucleus, mitochondria, chloroplasts) or non-membrane bound (ribosomes, centrioles). Exams often test your ability to identify organelles from electron micrographs and to describe their functions.
细胞器可分为单膜结合（如内质网、高尔基体、溶酶体、液泡）、双膜结合（细胞核、线粒体、叶绿体）或无膜结合（核糖体、中心粒）。考试经常测试你从电子显微照片中识别细胞器并描述其功能的能力。
2. The Nucleus | 细胞核
The nucleus is the largest organelle in eukaryotic cells and is enclosed by a nuclear envelope with nuclear pores. It contains chromatin (DNA and histone proteins) and the nucleolus, the site of ribosomal RNA (rRNA) synthesis and ribosome assembly.
细胞核是真核细胞中最大的细胞器，由带有核孔的核膜包围。它含有染色质（DNA 和组蛋白）以及核仁——核糖体 RNA (rRNA) 合成和核糖体组装的场所。
The nuclear pores regulate the passage of large molecules such as mRNA and proteins between the nucleus and cytoplasm. IB and CCEA questions often ask you to relate structure to function: the double membrane protects DNA from cytoplasmic reactions, while pores allow selective transport.
核孔调节大分子（如 mRNA 和蛋白质）在细胞核与细胞质之间的通过。IB 和 CCEA 题目常要求你将结构与功能联系起来：双层膜保护 DNA 免受细胞质反应影响，而核孔允许选择性运输。
The nucleolus is not membrane-bound and appears as a dense region within the nucleus. Ribosomal subunits are exported to the cytoplasm through nuclear pores.
核仁没有膜，表现为核内致密区域。核糖体亚基通过核孔输出到细胞质。
3. Mitochondria | 线粒体
Mitochondria are double-membrane organelles where aerobic respiration occurs. The inner membrane is highly folded into cristae, which increase surface area for oxidative phosphorylation. The matrix contains enzymes for the Krebs cycle, 70S ribosomes and a small circular DNA molecule.
线粒体是进行有氧呼吸的双膜细胞器。内膜高度折叠形成嵴，增大了氧化磷酸化的表面积。基质中含有克雷布斯循环的酶、70S 核糖体和小型环状 DNA 分子。
A key exam point is the relationship between the number of cristae and metabolic activity: cells with high energy demands, such as muscle cells, have mitochondria with many cristae. Questions may also require you to draw and label a mitochondrion from an electron micrograph.
一个关键考点是嵴的数量与代谢活性之间的关系：能量需求高的细胞（如肌细胞）具有嵴较多的线粒体。题目也可能要求你根据电子显微照片绘制并标注线粒体。
Mitochondria are the site of the link reaction, Krebs cycle and electron transport chain. You should be able to explain how the structure of the inner membrane facilitates chemiosmosis and ATP synthesis.
线粒体是链接反应、克雷布斯循环和电子传递链的发生场所。你应能解释内膜结构如何促进化学渗透和 ATP 合成。
4. Chloroplasts | 叶绿体
Chloroplasts are found in plant cells and some algae; they are the site of photosynthesis. Like mitochondria, they have a double membrane, as well as an internal membrane system of thylakoids stacked into grana. The stroma contains enzymes for the Calvin cycle, 70S ribosomes and circular DNA.
叶绿体存在于植物细胞和某些藻类中，是光合作用的场所。与线粒体一样，它们具有双层膜，以及由类囊体堆叠成基粒的内部膜系统。基质含有卡尔文循环的酶、70S 核糖体和环状 DNA。
Thylakoid membranes contain chlorophyll and other photosynthetic pigments organised into photosystems. The light-dependent reactions occur in the thylakoid membrane, while the light-independent reactions (Calvin cycle) take place in the stroma. Be prepared to identify and annotate a chloroplast diagram.
类囊体膜含有叶绿素及其他组织成光系统的光合色素。光依赖反应发生在类囊体膜上，而光非依赖反应（卡尔文循环）在基质中进行。准备好识别并标注叶绿体示意图。
5. Endoplasmic Reticulum (Rough and Smooth) | 内质网（粗面和滑面）
The endoplasmic reticulum (ER) is a network of membrane-bound channels and sacs. Rough ER has ribosomes attached to its cytoplasmic surface, giving it a ‘rough’ appearance under the microscope. It is involved in protein synthesis and folding, as well as the initial glycosylation of proteins destined for secretion.
内质网 (ER) 是由膜结合的通道和囊泡构成的网络。粗面内质网在其细胞质表面附有核糖体，因此在显微镜下呈现’粗糙’外观。它参与蛋白质合成和折叠，以及分泌蛋白的初始糖基化。
Smooth ER lacks ribosomes and is involved in lipid synthesis, carbohydrate metabolism, detoxification of drugs and poisons, and calcium ion storage. In muscle cells (sarcoplasmic reticulum), it plays a vital role in muscle contraction.
滑面内质网无核糖体，参与脂类合成、碳水化合物代谢、药物和毒物解毒以及钙离子储存。在肌细胞（肌质网）中，它对肌肉收缩至关重要。
6. Golgi Apparatus | 高尔基体
The Golgi apparatus consists of flattened membrane-bound cisternae, often with a forming (cis) face and a maturing (trans) face. It modifies, sorts and packages proteins and lipids for transport to lysosomes, secretion or incorporation into the plasma membrane.
高尔基体由扁平的膜结合潴泡组成，通常具有形成面（顺面）和成熟面（反面）。它对蛋白质和脂类进行修饰、分选和包装，以便运往溶酶体、分泌或整合到质膜中。
Vesicles from the ER fuse with the cis face, and secretory vesicles bud off from the trans face. Exam questions may ask you to describe the role of the Golgi in glycosylation, or to outline the path of a secreted protein (ER → Golgi → vesicle → plasma membrane).
来自内质网的囊泡与顺面融合，分泌囊泡从反面出芽。考试题目可能要求你描述高尔基体在糖基化中的作用，或概述分泌蛋白的路径（内质网 → 高尔基体 → 囊泡 → 质膜）。
7. Ribosomes | 核糖体
Ribosomes are non-membrane-bound organelles composed of rRNA and proteins. They exist as free ribosomes in the cytoplasm or bound to the rough ER. They translate mRNA into polypeptide chains during protein synthesis.
核糖体是无膜细胞器，由 rRNA 和蛋白质组成。它们以游离核糖体形式存在于细胞质中，或结合在粗面内质网上。它们在蛋白质合成期间将 mRNA 翻译为多肽链。
Eukaryotic ribosomes are 80S (composed of 60S and 40S subunits), whereas prokaryotic, mitochondrial and chloroplast ribosomes are 70S (50S + 30S). Distinguishing these is important for understanding antibiotic selectivity (e.g., tetracyclines target 70S ribosomes).
真核生物
Published by TutorHao | IB Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导