2.59 explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen

Red blood cells carry oxygen around the body. In order to do this they have haemoglobin- which is made from iron- that can bond to oxygen. Red blood cells are enucleate (they have no nucleus) to make room for the haemoglobin. There are no mitochondria as the cells respire anaerobically so the cells don't use any oxygen.
They are biconcave; they are a flat disk with a dip in the middle. The shape of a flat disk enables them to pass through narrow capillaries  They have a dip in the middle to increase the surface area and decrease the distance for diffusion meaning that diffusion of oxygen happens quickly.