Biology by Bradford
2.2.AExchange at the surface
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2.2 Cell Size: revision map
The subtopic in the middle and four tasks round it: label a diagram, complete a table and fill 11 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Cell Size
AP Biology ยท Unit 2 Cell Structure and FunctionHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name2.2.AGetting more surface
Cells that exchange a lot have features that raise the surface area without raising the volume much. Small intestine cells have , root hair cells extend long thin projections, and mitochondria fold their inner membrane into cristae. Flattened or elongated cells, and cells with a large central vacuole pushing the cytoplasm to a thin layer, also keep distances short. Compartmentalization adds membrane surface inside the cell too.
Topic 2.2Cell Size
2.2.ACubes as cells
| Side length | Surface area | Volume | Surface area to volume |
|---|---|---|---|
| 1 unit | 1 | 6 : 1 | |
| 2 units | 24 | 3 : 1 | |
| 3 units | 27 | 2 : 1 |
As a cell grows, its volume rises faster than its surface area, so the ratio of surface area to volume .
2.2.AWhy cells stay small
Materials such as oxygen and nutrients enter, and wastes leave, across the , so the supply a cell can get depends on its surface area. The demand depends on its volume. A cell with a small cannot exchange enough and its interior is too far from the surface for diffusion to reach quickly. This limits cell size, and it is why large organisms are made of many small cells.
Word bank 5468cytoplasmfallsmicrovillinucleusplasma membranesurface area to volume ratio
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
TableCubes as cells
Side length Surface area Volume Surface area to volume 1 unit 6 1 6 : 1 2 units 24 8 3 : 1 3 units 54 27 2 : 1 As a cell grows, its volume rises faster than its surface area, so the ratio of surface area to volume falls.
LabelExchange at the surface
- plasma membrane
- nucleus
- microvilli
- cytoplasm
GapsWhy cells stay small
Materials such as oxygen and nutrients enter, and wastes leave, across the plasma membrane, so the supply a cell can get depends on its surface area. The demand depends on its volume. A cell with a small surface area to volume ratio cannot exchange enough and its interior is too far from the surface for diffusion to reach quickly. This limits cell size, and it is why large organisms are made of many small cells.
GapsGetting more surface
Cells that exchange a lot have features that raise the surface area without raising the volume much. Small intestine cells have microvilli, root hair cells extend long thin projections, and mitochondria fold their inner membrane into cristae. Flattened or elongated cells, and cells with a large central vacuole pushing the cytoplasm to a thin layer, also keep distances short. Compartmentalization adds membrane surface inside the cell too.