OCR · A-Level · Biology
Course version: H420 · Version from Sept 2025
(g) the ultrastructure of eukaryotic cells and the functions of the…
Full specification wording
Cell structure: (g) the ultrastructure of eukaryotic cells and the functions of the different cellular components
Ultrastructure means the fine internal detail of a eukaryotic cell as revealed by an electron microscope.
Checked against the OCR H420 specification (opens in a new tab) on .
- Point 6 of 10
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Ultrastructure means the fine internal detail of a eukaryotic cell as revealed by an electron microscope. You must know each component and its function. The nucleus contains chromatin and a nucleolus and controls the cell via transcription of DNA. Mitochondria have a double membrane with folded cristae and carry out aerobic respiration, releasing ATP. Rough endoplasmic reticulum, studded with ribosomes, synthesises and transports proteins; smooth ER synthesises lipids. The Golgi apparatus modifies proteins and packages them into vesicles. Ribosomes are the site of protein synthesis. Lysosomes contain hydrolytic enzymes that digest material. The cell surface membrane controls exchange, and the cytoskeleton maintains shape and moves components. Chloroplasts in plant cells carry out photosynthesis, and the cellulose cell wall gives support.
What earns the marks
- The nucleus contains chromatin and a nucleolus and controls cell activities through DNA.
- Mitochondria have a double membrane with folded cristae and are the site of aerobic respiration, producing ATP.
- Rough endoplasmic reticulum bears ribosomes and synthesises and transports proteins; smooth ER synthesises lipids.
- The Golgi apparatus modifies proteins and packages them into vesicles for transport or secretion.
- Ribosomes are the site of protein synthesis; lysosomes contain hydrolytic enzymes for digestion.
- Chloroplasts carry out photosynthesis and the cellulose cell wall provides structural support in plant cells.
Common mistakes and how to put them right
Mixing up rough and smooth ER.
Put it right by linking each structure to its function.
Saying the Golgi apparatus synthesises proteins.
Put it right by stating it modifies and packages proteins made on the rough ER.
Describing mitochondria as having a single membrane.
Put it right by stating the double membrane with folded cristae.
Exam tips
- Pair every named structure with its function so answers cover both parts of the criterion.
- Use correct structural detail such as double membrane, cristae and ribosomes to gain credit.
- Distinguish plant-only components such as chloroplasts and the cellulose cell wall from those in animal cells.
Try the lesson
The start of the Cell structure: (g) the ultrastructure of eukaryotic cells and the functions of the different cellular components lesson, made from checked teaching notes for this specification point.
Have a go first
Which cellular component controls the movement of substances into and out of a eukaryotic cell?
Listen
Ultrastructure means the fine internal detail of a eukaryotic cell as revealed by an electron microscope. You must know each component and its function. The nucleus contains chromatin and a nucleolus and controls the cell via transcription of DNA. Mitochondria have a double membrane with folded cristae and carry out aerobic respiration, releasing ATP. Rough endoplasmic reticulum, studded with ribosomes, synthesises and transports proteins; smooth ER synthesises lipids. The Golgi apparatus modifies proteins and packages them into vesicles. Ribosomes are the site of protein synthesis. Lysosomes contain hydrolytic enzymes that digest material. The cell surface membrane controls exchange, and the cytoskeleton maintains shape and moves components. Chloroplasts in plant cells carry out photosynthesis, and the cellulose cell wall gives support. A strong answer earns marks for these points. The nucleus contains chromatin and a nucleolus and controls cell activities through DNA. Mitochondria have a double membrane with folded cristae and are the site of aerobic respiration, producing ATP. Rough endoplasmic reticulum bears ribosomes and synthesises and transports proteins; smooth ER synthesises lipids. The Golgi apparatus modifies proteins and packages them into vesicles for transport or secretion. A common slip: Mixing up rough and smooth ER: rough ER has ribosomes and makes proteins, smooth ER makes lipids. Instead, linking each structure to its function. Exam tip: Pair every named structure with its function so answers cover both parts of the criterion.
See it
Key words
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Nucleus
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Mitochondria
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Golgi apparatus
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See every definition
- Nucleus
- Contains chromatin and a nucleolus and controls the cell via transcription of DNA.
- Mitochondria
- Have a double membrane with folded cristae and carry out aerobic respiration, releasing ATP.
- Golgi apparatus
- Modifies proteins and packages them into vesicles.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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