Animal Cell Structure
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of basic cell theory (from GCSE) and the general distinction between living and non-living structures. You can test your knowledge on these below.
What is the function of the nucleus in an animal cell?
The nucleus contains DNA, which controls the activities of the cell by regulating protein synthesis.
What organelle is responsible for releasing energy in animal cells?
The mitochondria are responsible for producing ATP through aerobic respiration.
What is one difference between animal and plant cells?
Animal cells lack a cell wall, chloroplasts or a permanent vacuole.
Topic Explainer Videos
Check out this @LauraDoesBiology video that explains animal cell structure or read the full notes below. Once you've gone through the whole note, try out the practice questions!
The Major Structures in an Animal Cell and their Functions
Animal cells are eukaryotic cells, meaning they have a membrane-bound nucleus and organelles.
Plasma Membrane (Cell Surface Membrane)
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Composed of a phospholipid bilayer with embedded proteins.
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Function: Partially permeable- controls the movement of substances in and out of the cell via diffusion, osmosis, active transport, and facilitated diffusion.
Nucleus
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Enclosed by a nuclear envelope (double membrane) with nuclear pores.
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Contains chromatin (DNA + proteins) and a nucleolus, which synthesises ribosomes.
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Function: Controls cell activities by storing genetic material (DNA).
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DNA codes for polypeptides.
Mitochondria
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Have a double membrane; the inner membrane is folded into cristae to increase the surface area for ATP production.
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The matrix contains enzymes for aerobic respiration.
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Mitochondria have their own circular DNA and their own 70s ribosomes.
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Function: Produces ATP (energy carrier) via aerobic respiration.
Ribosomes
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Small organelles composed of RNA and protein, found either free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (RER).
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Function: Site of protein synthesis.
Endoplasmic Reticulum (ER)
- Rough ER: A 3D system of sheet-like membranes spreading through the cell.
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The membranes form a series of flattened sacs called cisternae.
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The Rough ER has ribosomes attached to its surface, involved in protein synthesis.
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The RER provides a large surface area to synthesise proteins.
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It also transports proteins and packages them into vesicles before they move to the golgi body.
- Smooth ER: A 3D system of sheet-like membranes spreading through the cell.
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The membranes form a series of flattened sacs called cisternae.
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Similar to the RER but with no ribosomes attached.
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The SER synthesises, stores and transports lipids and carbohydrates.
Golgi Apparatus
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A series of flattened sacs (similar to the endoplasmic reticulum but more compact) that modify, sort, and package proteins and lipids into vesicles for secretion.
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Function: Modifies and processes proteins and lipids.
Lysosomes
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Small vesicles containing digestive/ hydrolytic enzymes.
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Function: Breakdown of waste materials and cellular debris.
Centrioles
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Found in pairs near the nucleus.
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Function: Involved in cell division, helping to organise the mitotic spindle.
Cytoskeleton
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A network of protein microtubules and microfilaments.
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Function: Provides mechanical strength to the cell, supports organelles, and enables vesicle movement within the cell.
Key Terms
- Organelle: A specialised structure within a cell.
- Eukaryotic cell: A cell containing a nucleus and membrane-bound organelles.
- Mitochondria: The site of aerobic respiration and ATP production.
- Golgi apparatus: Modifies and packages proteins for secretion.
- Lysosomes: Contain enzymes to digest waste and foreign materials.
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Exam Tip
Linking Structure to Function: Parts of the cell will be referred to in other questions, you need to recognise the functions of these parts and how it links to the context of the question.
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Describe the role of the Golgi apparatus in protein secretion. (3 marks)
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The Golgi apparatus modifies proteins (e.g., adding carbohydrates to form glycoproteins).
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It packages proteins into vesicles.
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Vesicles transport proteins to the plasma membrane for exocytosis.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!