(4) The attachment of the pyrimidine base to the ribose phosphate ring is catalyzed by orotate phosphoribosyl transferase (OPRT) and PRPP provides the ribose-5-phosphate moeity. Hydrolysis of the PP i that is split off of the PRPP makes this reaction irreversible.
Red Squirrels shed their coats twice a year, switching between a thinner coat in summer and a darker, thicker winter coat. 6. Males may live in an area of up to 17 hectares of woodland... thatâs about the same size as 34 football pitches! 7.
Some have a grey to dark grey-blue coat in the winter. The Arctic fox is the only canid that changes the colour of its coat in the summer. In addition to its thick coat, the Arctic fox is able to stay warm in the winter because it has short legs, a short muzzle and small rounded ears. These characteristics all reduce the amount of surface area it has for heat loss. Also, its feet are covered in fur, similar to the fur on a hare's foot.