Specialised Cells (DP IB Biology)

Increasing Surface Area : Volume

• It is crucial to maximise surface area to volume ratio in cells which require movement of substances across the membrane

• The larger the surface area compared to the volume of the cell, the faster the rate of substance movement

Red blood cells

• The function of a red blood cell (also known as an erythrocyte) is to deliver oxygen from the lungs to respiring cells

• They are flattened and biconcave shaped in order to maximise the surface area and minimise volume

• This means that oxygen can diffuse into the red blood cell more quickly in the lungs and out again at the respiring tissues

Adaptations of a Red Blood Cell Diagram

The biconcave shape and flattening of erythrocytes increases the surface area available for oxygen absorption

Proximal convoluted tubule cells

• The proximal convoluted tubules are tiny tubes found in the outer region of the kidney

• The tubules are responsible for reabsorption of vital substances e.g. glucose and mineral ions from the glomerular filtrate

• There are several adaptations to maximise surface area in the proximal convoluted tubule cells to ensure that the body reabsorb all the necessary substances

  • Microvilli - in the apical membrane

  • Invaginations - infoldings found in the basal membrane

Proximal Convoluted Tubule Cell Adaptations Diagram

The cells of the proximal convoluted tubule cells have invaginations and microvilli to increase surface area