Peroxisomes are small organelles found in the cytoplasm of cells. They contain enzymes that break down fatty acids and reactive oxygen species. Specifically, peroxisomes contain catalase which breaks down hydrogen peroxide into water and oxygen. They also play roles in photosynthesis, beta-oxidation of fatty acids, and producing bile acids. Certain genetic diseases can result from defects in peroxisome function, such as Zellweger syndrome.

2. PEROXISOMES
PRESENTED: ABIGAIL GREAVES AND SHANIAH HOLDER

3. STRUCTURE

4. STRUCTURE
• Small vesicles found around the cell.
• They have a single celled membrane that contains digestive
enzymes.
• They have the thickest membrane of all organelles.
• A lipid bilayer surrounds it.

5. • Contains a urate
oxylase crystalline core.
• Contains more than 50
enzymes
• They self-replicate by
enlarging and then dividing

6. CONTRAST BETWEEN PEROXISOMES AND OTHER
ORGANELLES
• Like vacuoles, peroxisomes digest and store material.
• Like lysosomes, peroxisomes have similar structure.
• Unlike lysosomes, peroxisomes require oxygen to work.
• Like mitochondria and choroplast, proteins from the peroxisomes are
translated to the cytoplasm
• Unlike mitochondria and choroplast, peroxisomes do not contain genetic
material.

7. FUNCTION OF PEROXISOMES
 AIDS IN THE OXIDATION OF TOXIC MOLECULES
 CONTRIBUTES TO THE BIOSYNTHESIS OF PLASMOLOGENS WHICH ARE AN
ABUNDANT CLASS OF PHOSPHOLIPIDS IN MYELIN
 RECYCLES CARBON DURING PHOTORESPIRATION IN PLANT CELLS

8. FUNCTIONS CONT’D
 BREAK DOWN FATTY ACIDS AND AMINO ACIDS TO BE USED FOR THE
FORMATION OF MEMBRANES AND FUEL FOR RESPIRATION
 AIDS IN THE FORMATION AND BREAKDOWN OF REACTIVE OXYGEN
SPECIES
 PRODUCES BILE ACIDS NEEDED FOR ABSORPTION OF FATS AND LIPID-
SOLUBLE VITAMINS

9. IMPORTANCE OF PEROXISOMES IN CELLS
PEROXISOMES ARE IMPORTANT TO THE CELL
SINCE THEY PROVIDE A MAJOR SOURCE OF
METABOLIC ENERGY

10. ENZYMES IN PEROXISOMES
 THE ENZYMES IN PEROXISOMES ARE :
1) CATALASE
DESTROYS EXCESS HYDROGEN PEROXIDE IN OXIDATION REACTIONS
2) D- AMINO ACID OXIDASE
OXIDISES D-AMINO ACIDS TO IMINO ACIDS (AMMONIA & HYDROGEN PEROXIDE)
3) URIC ACID OXIDASE
CATALYZES THE OXIDATION OF URIC ACID TO SOLUBLE ALLANTOIN IN PLANTS

11. FAT METABOLISM

12. FAT METABOLISATION
• The enzymes in the peroxisomes break down long fatty acids by
oxidation.
• Uric acid and amino acids are broken down.
• The fatty acids are decomposed to acetyl CoA which provides
energy.

13. • Hydrogen peroxide is produced.
• Peroxisomes produce catalase which break down hydrogen
peroxide to water and oxygen.
• A peroxisomal protein prevents oxalate build up

14. BETA OXIDATION

15. • Beta oxidation occurs in the liver and mitochondria.
• Long chain fatty acids are broken down to create acetyl Coenzyme A
• Acetyl coenzyme A combines with oxaloacetate to form citrate
• Fatty acids enter the citric acid cycle directly
• Hydrogen peroxide is a by product of beta oxidation

16. PEROXISOME ROLE IN PHOTOSYNTHESIS
• Takes part in photorespiration where carbon is recovered.
• Glycolate, a chemical which is received by the peroxisomes.
• Glycolate is turned to another enzyme called glycine and sent to the
mitochondria.

17. • In the mitochondria it turned into serine and passed back to the
peroxisome.
• In the peroxisome is then turned to glycerate and sent to the
chloroplast.
• No energy is gained.

19. CONVERSION OF
REACTIVE O2 SPECIES
H2O2

20.  REACTIVE OXYGEN SPECIES ACT AS SIGNAL MEDIATORS
 OVER PRODUCTION OF “ROS” CAN CAUSE CELL DEATH, PATHOLOGICAL
CONDITIONS AND DAMAGING CELLULAR EFFECTS.
 PEROXISOMES CONTAIN A NUMBER OF ENZYMES AND ANTIOXIDANTS
WHICH AID IN THE FORMATION AND BREAKDOWN OF REACTIVE OXYGEN
SPECIES

21. PEROXISOMES AID IN THE
PRODUCTION AND DEGENRATION OF
H2O2 WITH THE ENZYMES CATALASE
AND D-AMINO OXIDASE.

22. STEP 1
 PEROXISOMES USE O2 AND H2O2 TO PERFORM OXIDATIVE REACTIONS.
 D- AMINO OXIDASE CATALYZES THE REACTION WHICH USES MOLECULAR
O2 TO COMBINE WITH HYDROGEN ATOMS FROM SUBSTRATES TO FORM
HYDROGEN PEROXIDE
FORMULA : RH2 + O2  R + H2O2

23. STEP 2
 THE ENZYME CATALASE USES H2O2 TO OXIDISE PHENOLS, FORMALDEHYDE &
ALCOHOL
FORMULA: H2O2 + RIH2  RI + 2H2O
 WHEN EXCESS H2O2 ACCUMULATES THROUGH THE CELL CATALASE
CATALYZES H2O2 TO H2O AND O2
FORMULA: 2H2O2  2H2O + O2

24. DID YOU KNOW?
PEROXISOMES ARE PRESENT IN GERMINATING
SEEDS WHERE IT PLAYS A ROLE IN CONVERTING
FATTY ACIDS STORED IN SEED LIPIDS INTO
SUGAR NEEDED FOR GROWTH OF A YOUNG
PLANT.

25. URIC ACID OXIDASE

26.  ABSENT IN HUMANS
 CATALYZES THE OXIDATION OF URIC ACID TO 5-HYDROXYISOURATE
FORMULA: URIC ACID + O2 + H2O  5-HYDROXYISOURATE + H2o2
 OTHER ENZYMES SUCH AS HIU HYDROLASE AND OHCU DECARBOXYLASE
CONVERT THE 5-HYDROXYISOURATE TO ALLANTOIN AND CARBON DIOXIDE
FORMULA: 5-HYDROXYISOURATE +H2O  ALLANTOIN + CO2

27. PEROXISOME DISEASES

28. ZELLWEGER SYNDROME
• It is rare, inherited condition
• Peroxisomal enzymes are unable to cross the membrane barrier and enter
the matrix of the peroxisomes.
• Skeletal abnormalities and seizures are common symptoms.

29. • It is caused by mutations in 12 different genes involved in the
creation and proper function of peroxisomes.
• Various test are used to detect at birth.
• There are no cures

30. DISEASE: X-LINKED ADRENOLEUKODYSTROPHY
 CAUSED BY A MUTATION ON GENE XQ28
THAT ENCODES A PEROXISOMAL
MEMBRANE PROTEIN ALD PROTEIN
 WITHOUT ALD PROTEIN, LONG CHAINS
OF FATTY ACIDS ACCUMULATE IN
ADRENAL CORTEX AND GLIAL CELLS
 THIS RESULT IN ADRENAL TROPHY,
VISUAL LOSS AND SPASTICITY.

32. QUESTION
 WHAT ENZYME FOUND IN THE PEROXISOME DEGRADES HYDROGEN
PEROXIDE
A) HYDROGEN PEROXIDE CONVERTASE
B) CATALASE
C) DEGRADASE
D) HYDROGEN PEROXIDE OXIDASE

35. REFERENCES
• https://bscb.org/learning-resources/softcell-e-learning/peroxisome/
• https://rarediseases.info.nih.gov/diseases/7917/zellweger-syndrome
• https://biologydictionary.net/peroxisome/
• https://scienceaid.net/the_Structure_and_Function_of_Peroxisomes
• https://www.ncbi.nlm.nih.gov/books/NBK9930/