O-LevelBiologyEnzymes5090/21 · May/June 2022 · Q45 Marks
The human liver contains a high concentration of enzymes called transaminases. These enzymes are important in the metabolism of amino acids. Amino acids are absorbed from the alimentary canal and carried to the liver by a blood vessel.
- (a)Name the part of the alimentary canal where absorption occurs and the blood vessel that carries the amino acids to the liver. part of alimentary canal blood vessel[2]
- (b)There are different types of transaminase. Each type has a specific active site. Explain why this means that each type catalyses a specific reaction.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.
- [1] ileum / small intestine;
- [1] hepatic portal vein ;
- [3] any three from: lock and key; shape AW + active site / enzyme / amino acids different shapes ; complementary / fits / matches ; binds AW to a substrate / enzyme-substrate complex / ES complex ; wrongly shaped substrates cannot fit + active site ;
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