What is an Animal Cell?
An animal cell is a eukaryotic cell surrounded by a flexible plasma membrane. Unlike plant cells, animal cells lack a rigid cell wall, allowing them to take on various shapes. The interior is filled with cytoplasm — a gel-like matrix in which all organelles are suspended. Every process that keeps you alive happens inside trillions of these microscopic units.
The Nucleus: Control Centre
The nucleus is the largest organelle and serves as the cell's control centre. Enclosed by a double membrane called the nuclear envelope, it houses the cell's genetic material in the form of DNA organised into chromosomes. The nucleus directs all cellular activities by controlling which proteins are synthesised.
HSC Exam Focus
For HSC Biology, practise writing organelle functions in one clear sentence. Common exam questions ask you to compare animal and plant cell structures, or explain why a particular organelle is abundant in a specific tissue type (e.g., why liver cells have many mitochondria).
Interactive 3D Animal Cell
Explore the complete animal cell in three dimensions. Rotate to view any angle, click each organelle to learn its structure and function, and use Guided Tour to step through all 9 major components.
Mitochondria: The Powerhouse
Mitochondria are double-membraned organelles responsible for producing ATP through cellular respiration. The inner membrane is folded into cristae, greatly increasing the surface area for oxidative phosphorylation. Each cell may contain hundreds to thousands of mitochondria depending on its energy demands.
Cellular Respiration Equation
Key Organelles and Their Functions
Summary table of the major organelles found in animal cells.
| Organelle | Structure | Primary Function |
|---|---|---|
| Nucleus | Double-membrane envelope with pores | Stores DNA; controls gene expression |
| Mitochondria | Double membrane, cristae inside | Produces ATP via cellular respiration |
| Ribosomes | Two protein-rRNA subunits | Synthesises proteins |
| Endoplasmic Reticulum | Network of membranes (rough/smooth) | Protein & lipid synthesis and transport |
| Golgi Apparatus | Stack of flattened membrane sacs | Processes, packages, and ships proteins |
| Lysosome | Single membrane vesicle | Intracellular digestion using enzymes |
| Centrosome | Two centrioles at right angles | Organises spindle fibres during cell division |
| Cell Membrane | Phospholipid bilayer with proteins | Controls entry and exit of substances |
Biochemistry Bridge
Mitochondria connect directly to HSC Chemistry: the electron transport chain uses redox reactions to pump H⁺ ions across the inner membrane, creating a proton gradient that drives ATP synthase — an application of electrochemical principles studied in Chemistry Chapter 3.
Endoplasmic Reticulum and Golgi Apparatus
The endoplasmic reticulum (ER) is a network of membranous tunnels extending from the nucleus. Rough ER is studded with ribosomes and manufactures secretory proteins. Smooth ER synthesises lipids and detoxifies chemicals. The Golgi apparatus receives proteins from rough ER, modifies them (e.g., adding carbohydrate chains), and packages them into vesicles for export or internal use.
InstaTest
InstaTest: Organelle Functions
Test your understanding of organelle functions with a 5-question MCQ sprint before moving to the next section.