B2.3 - cell size (3f) Flashcards
what happens to surface area and volume as a cell increases in size?
- the surface area increases by a factor of the squared width
- the volume increases by a factor of the cubed width
the mathematical ratio between surface area and volume therefore decreases with cell width
what are models?
models are simplified versions of complex systems
how can models be used for surface area and volumes of cells?
- in this case, surface-area-to-volume relationship can be modelled using cubes of different side lengths
- although the cubes have a simpler shape than real organisms, scale factors operate in the same way
what does the exchange and the need for exchange of materials depend on?
the exchange of materials across a cell surface depends on its area whereas the need for exchange depends on cell volume
- this constrains the size of cells; they are limited in the size they can reach that will still support the functions of life
- therefore, larger organisms have more cells, rather than bigger cells
how is cell size important for sperm cells?
small size is sufficient to deliver genetic material
- 3μm in diameter and 50μm in length
how is cell size important for egg cells?
large volume supplies the molecules and organelles to support early cell division during development
- 120μm in diameter
how is cell size important for muscle fibres?
long fibre means there are a lot of contractile units stacked, leading to greater shortening of the muscle when each unit contracts
- 10-50μm wide and 40-120mm in length
how is cell size important for neurons?
extremely long to rapidly transmit information via electrical impulses
- 3-18μm in diameter, 350μm - 1.5m in length
how is cell size important for erythrocytes?
small size allows movement through capillaries
- 7.5μm in diameter
how is cell size important for white blood cells?
larger size as it contains nuclei and organelles to carry out specific functions
- 12-15μm in diameter
