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VICBiologyQuick questions
Unit 1: How do organisms regulate their functions?
Quick questions on Cell size and the surface area to volume ratio: VCE Biology Unit 1
9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the geometry?Show answer
For any 3D shape, as linear size increases, volume increases faster than surface area.
What is why this matters for cells?Show answer
The plasma membrane is the only surface across which a cell exchanges materials with its environment: oxygen and nutrients in, carbon dioxide and waste out, heat transferred. The cell's metabolic demand is proportional to its volume (more cytoplasm means more metabolism). The cell's exchange capacity is proportional to its surface area.
What is strategies cells use?Show answer
When a cell grows too large, it has three options:
What is why organelles solve the problem?Show answer
Membrane-bound organelles partition the eukaryotic cell into compartments, each with its own surface area for specialised reactions:
What is multicellularity as the next step?Show answer
Beyond the single-cell limit, organisms became multicellular. Trillions of small cells, each with high SA:V, are organised into tissues and organs. Specialised transport systems (blood vessels in animals, xylem and phloem in plants) deliver nutrients and oxygen far past the diffusion limit of any single cell.
What is mixing up SA:V and SA times V?Show answer
It is a ratio, not a product.
What is saying "big cells die"?Show answer
Big cells either divide, change shape, or evolve internal compartments. Cells in your body actively manage their size.
What is forgetting that organelles solve the problem?Show answer
The key insight is that eukaryotes evolved internal membranes precisely because their large outer surface alone is not enough.
What is forgetting that shape matters?Show answer
Two cells of equal volume can have very different SA:V. Flat cells, thin cells and folded cells (microvilli on intestinal cells) all maximise SA:V.