Glyoxylate pathway

Question 1

What can do the glyoxylate pathway

Answer 1

1. Plants- possess the right enzymes to mediate conversion of acetyl-CoA to oxaloacetate

Question 2

What are the two areas of a plant involved in the glyoxylate pathway

Answer 2

1. Mitochondrion

2. Glyoxysome- membranous plant organelle

Question 3

What is the first step in the glyoxylate pathway

Answer 3

1. Mitochondrial oxaloacetate is converted to aspartate by aspartate aminotransferase
2. It is transported to the glyoxysome and converted back to oxaloacetate

Question 4

What is the second step in the glyoxylate pathway

Answer 4

1. Oxaloacetate is condensed with acetyl-CoA to form citrate

2. This is isomerised to isocitrate as in citric acid cycle

Question 5

What is the third step in the glyoxylate pathway

Answer 5

1. Glyoxysomal isocitrate lyase cleaves isocitrate to succinate and glyoxylate

Question 6

What happens to succinate

Answer 6

1. It is transported to the mitochondria where it enters the citric acid cycle for conversion back to oxaloacetate

Question 7

What happens to glyoxylate

Answer 7

1. It is converted back to oxaloacetate in 2 reactions

Question 8

What is the first reaction in converting glyoxylate to oxaloacetate

Answer 8

1. Malate synthase condenses glyoxylate with a second molecules of acetyl-CoA to form malate

Question 9

What is the second reaction in converting glyoxylate to oxaloacetate

Answer 9

1. Cytosolic malate dehydrogenase catalyses the oxidation of malate to oxaloacetate by NAD+
2. It can now be used in gluconeogenesis

Question 10

What is the overall reaction glyoxylate cycle

Answer 10

1. 2 Acetyl-CoA + 2NAD+ + FAD –> oxaloacetate + 2CoA + 2NADH + FADH2 + 2H+

Question 11

What is the use of the glyoxylate cycle in plants

Answer 11

1. Enables germinating seeds to convert their stored triglycerides through acetyl-CoA to glucose