B2.3.7 Adaptations to increase surface area-to-volume ratios of cells (HL) Notes

Cells Adapt to Maximize Surface Area for Efficient Exchange

1. As cells increase in size, their surface area-to-volume ratio (SA:V) decreases.
2. This decrease makes it harder for them to exchange materials efficiently with the environment.
3. To overcome this limitation, cells have evolved various adaptations that increase their surface area, allowing them to absorb nutrients, expel waste, and exchange gases more effectively.

Why Surface Area-to-Volume Ratio Matters

Exchange Efficiency

1. High SA:V Ratio: Facilitates the rapid diffusion of molecules and ensures that cells can quickly take in nutrients and expel waste.
2. Low SA:V Ratio: May hinder exchange processes, leading to an accumulation of waste and insufficient nutrient uptake.

Metabolic Demands

1. The cell’s volume determines its metabolic needs.
2. The cell’s surface area determines its ability to meet those needs.

Evolutionary Pressure

1. Cells have evolved specialized structures to maximize SA:V to survive and function efficiently.

Key Adaptations to Increase Surface Area-to-Volume Ratios

1. Flattening of Cells

1. Flattening a cell can increase the surface area exposed to the environment without significantly increasing the cell's volume.
2. This is particularly useful for cells that are involved in gas exchange or nutrient absorption.

Why Flattening Helps

1. Flattening cells (or giving them an overall shape like the biconcave shape of RBCs).
2. This allows for more surface area in contact with the surroundings, which aids in faster diffusion of gases and nutrients.

2. Microvilli

1. Microvilli are small, finger-like projections on the surface of cells.