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Biochemical Pathways

Biochemical Pathways. How they are affected by mutations. Biochemical Pathways. All biochemical pathways are catalysed by enzymes. The coding for these enzymes is controlled by a gene. If an organism has a faulty gene, it may not be able to make the enzyme. Biochemical Pathways.

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Biochemical Pathways

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  1. Biochemical Pathways How they are affected by mutations.

  2. Biochemical Pathways • All biochemical pathways are catalysed by enzymes. • The coding for these enzymes is controlled by a gene. • If an organism has a faulty gene, it may not be able to make the enzyme.

  3. Biochemical Pathways • This means that the biochemical pathway would stop at that point and there would be an accumulation of the chemical prior to the faulty enzyme.

  4. Gene 1 Gene 2 Gene 3 Expression of gene 1 produces enzyme 1 Expression of gene 2 produces enzyme 2 Expression of gene 3 produces enzyme 3 Enzyme 1 Enzyme 2 Enzyme 3 A B C D A Biochemical Pathway

  5. Diseases of Inborn Errors of Metabolism

  6. Phenylketonuria - PKU • This is a serious disease, which if left untreated, can result in severe mental retardation. • It results from a defect in the enzyme E1 that converts phenylalanine to tyrosine. • This results in an accumulation of phenylalanine and other minor metabolic products in the body.

  7. Phenylketonuria - PKU • People with this disease are lightly pigmented, although there is usually enough tyrosine in their diets to allow them to make melanin. • All babies in NZ are tested for PKU at birth, and if it is present the children are put on a strict diet which can prevent the effects.

  8. Phenylketonuria - PKU • This diet greatly reduces the amount of phenylalanine accumulated. • Phenylalanine is one of the essential amino acids, which is not made by the body, so it can be controlled by diet. • A small amount of phenylalanine has to be given to maintain normal growth.

  9. Albinism • The most common type of Albinism is due to lack of the enzyme E3 that makes melanin from tyrosine. • Because Albino people cannot make melanin, they have white hair and pink eyes, and their eyes and skin are very sensitive to sunlight. • Albinism is widespread in the animal kingdom. (rats, rabbits, snakes, birds)

  10. In Humans

  11. In Other Animals

  12. Alkaptonuria • This is due to lack of enzyme E4 that processes homogentisic acid. • Its absence means that homogentisic acid accumulates in the tissues. • People with this condition appear normal as children, but are detected when their nappies start turning black

  13. Alkaptonuria • As they grow, they develop a blue-black discolouration of the ears, whites of the eyes, tips of the nose, and other areas where cartilage is just under the skin. • Their urine turns black after exposure to sunlight for several hours. • They often have severe arthritis, caused by accumulation of the metabolite in the cartilage of the joints.

  14. Phenylalanine Minor Metabolic Products E1 E3 Tyrosine Melanin E2 Homogentisic acid E4 E = enzyme Further metabolic Products

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