Most Peroxisome Functions are Linked to Hydrogen Peroxide Metabolism

Question 1

in animals, where are peroxisomes most prominent?

Answer 1

-in the liver and kidney tissues

Question 2

Five general categories of peroxisome function…?

Answer 2

1. hydrogen peroxide metabolism
2. detoxification of harmful compounds
3. oxidation of fatty acid
4. metabolism of nitrogen containing compounds
5. catabolism of unusual substances

Question 3

Five general categories of peroxisome function: Hydrogen peroxide metabolism (4)

• oxidases do what?
• what happens next?
• catalase can also?
• end result?

Answer 3

• oxidases generate H2O2 in peroxisomes
• the H2O2 is detoxified by catalase
• catalase can function as a peroxisome
• end result if H2O2 is degraded while still inside the peroxisome

Question 4

Five general categories of peroxisome function: Detoxification of harmful compounds (2)

• as a peroxidase, catalase can do what?
• what may be a vital peroxisomal function?

Answer 4

• as a peroxidase, catalase can use a variety of substances as electron donors (methanol, ethanol, formic acid, etc…)
• because all of these compounds are harmful to cells, their oxidative detoxification by catalase maybe a vital peroxisomal function

Question 5

Five general categories of peroxisome function: Oxidation of fatty acids (4)

• peroxisomes contain?
• in animal cells they oxidize…?
• what happens after they oxidize the long chain fatty acids?
• in plants and yeast..

Answer 5

• peroxisomes contain enzymes for β- oxidation of fatty acids
• in animal cells they oxidize long chain fatty acids
• once the fatty acids are fewer than 16 carbons in length, the rest of the oxidation occurs in the mitochondria
• in plants and yeast, fatty acids are completely oxidized by peroxisomes

Question 6

Five general categories of peroxisome function: Metabolism of nitrogen containing compounds

• most animals require?
• aminotransferases catalyze what?

Answer 6

• most animals (not primates) require urate oxidase to oxidize urate, formed during catabolism of nucleic acids and some proteins
• aminotransferases catalyze the transfer of amino groups from amino acids to α-ketoacids in the degradation and synthesis of amino acids

Question 7

Five general categories of peroxisome function: Catabolism of unusual substances

• what are D-amino groups?
• in some cells, peroxisomes also contain?
• xenobiotics include….

Answer 7

• D-amino groups are rare substances for which the cell has no degradative pathways, except in peroxisomes
• in some cells, peroxisomes also contain enzymes that break down xenobiotics, which are compounds foreign to living organisms
• xenobiotics includes short chain hydrocarbons such as alkanes