Peroxisomes Degrade Fatty Acids and Toxic Compounds

All animal cells (except erythrocytes) and many plant cells contain peroxisomes, a class of roughly spherical organelles, 0.2-1.0 ^m in diameter (Figure 5-21). Peroxisomes contain several oxidases—enzymes that use molecular oxygen to oxidize organic substances, in the process forming hydrogen peroxide (H2O2), a corrosive substance. Peroxisomes also contain copious amounts of the enzyme catalase, which degrades hydrogen peroxide to yield water and oxygen:

In contrast with the oxidation of fatty acids in mitochondria, which produces CO2 and is coupled to the generation of ATP, peroxisomal oxidation of fatty acids yields acetyl groups and is not linked to ATP formation (see Figure 8-11). The energy released during peroxisomal oxidation is converted into heat, and the acetyl groups are transported into the cytosol, where they are used in the synthesis of cholesterol and other metabolites. In most eukaryotic cells, the peroxisome is the principal organelle in which fatty acids are oxidized, thereby generating precursors for important biosynthetic pathways. Particularly in liver and kidney cells, various toxic molecules that enter the bloodstream also are degraded in peroxisomes, producing harmless products.

In the human genetic disease X-linked adreno-leukodystrophy (ADL), peroxisomal oxidation of very long chain fatty acids is defective. The ADL gene encodes the peroxisomal membrane protein that trans

Nuclear

| 2 [im | Mitochondrion Nucleus membrane

Secretory vesicle

Nuclear

Secretory vesicle

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment