🧬 Nucleus
- Controls all cell activities — the "control centre"
- Contains chromosomes made of DNA
- Surrounded by double nuclear membrane with pores
- Contains the nucleolus where ribosomes are assembled
- Sends instructions to ribosomes via mRNA
⚡ Mitochondria (singular: mitochondrion)
- Site of aerobic respiration
- Transfer energy from glucose, producing ATP
- Double membrane — inner membrane folded into cristae (increase surface area)
- Have their own DNA and ribosomes
- Cells with high energy demands (e.g. muscle cells) have many mitochondria
🏭 Ribosomes
- Site of protein synthesis
- Made of rRNA and protein
- Found free in cytoplasm (make cytoplasmic proteins) OR attached to membranes within the cell (make proteins for export)
- Present in ALL cells, including prokaryotic cells
- Translate mRNA code into a sequence of amino acids
📬 Golgi Apparatus
- Stack of flattened membrane sacs (cisternae)
- Receives newly made proteins from ribosomes
- Modifies and packages proteins (e.g. adds sugar chains)
- Sends finished proteins in vesicles to cell membrane for export OR to lysosomes
- Also makes lysosomes
🗑️ Lysosomes
- Membrane-bound sacs containing hydrolytic (digestive) enzymes
- Digest worn-out organelles (autophagy)
- Destroy engulfed bacteria in white blood cells
- Release their contents when cells are damaged or worn out
🧱 Cell Membrane
- Controls what enters and leaves the cell (selectively permeable)
- Made of a phospholipid bilayer with proteins embedded
- Site of cell signalling and receptor proteins
🌊 Cytoplasm
- Gel-like fluid filling the cell
- Site of many chemical reactions (e.g. glycolysis)
- Suspends and connects all organelles
- Contains dissolved chemicals needed for chemical reactions
This deep dive covers Animal Cell: Organelles and Their Functions within Cell Organelles for GCSE Biology. Revise Cell Organelles in Cell Biology for GCSE Biology with 12 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 14 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Cell Organelles
Scientists studying mitochondria use electron microscopes rather than light microscopes. Which statement correctly explains why electron microscopes are more useful for studying cell ultrastructure?
The diameter of a ribosome is approximately 0.00002 mm. (a) Write this diameter in standard form, in millimetres. (b) Convert this diameter into nanometres (nm).