6/7. Tocoferol (vitamin E), Oxidative stress, free radicals, antioxidants Flashcards
Structure:
-
Metabolism:
- Comes into the body as esters, but need to be hydrolyzed before absorption with bile, then the route is through lymph and then blood. There is no special transport system, but they are often associated with chylomicrons or lipoproteins. It is stored in liver and brown adipose tissue.
Deficiency:
- Lipid peroxides in adipose tissue of animals with deficiency. -Oxidation of polyunsaturated FA (permeability may change) - Lack in food: Rats: estrus disturbance, death of fetus, sterility (epithelium degradation) Sheep/cattle: white muscle disease (hyalin degradation), muscular dystrophy in newborns. Poultry: hemorrhage and necrosis in cerebellum. If selenium is not present it can also lead to increased capillary permeability (subcutaneous edema)
Characteristics of tocoferol:
- Excellent antioxidant -Naturally occuring -Stable in heat in abcense of O2 -UV and radiation destroys the vitamin’s activity
Excretory routes:
- With bile (Vit E metabolites) -Some with urine ( water soluble metabolites)
Biochemical function of tocoferol (short explaination):
- Strong antioxidant effect -Prevents the non-enzymatic oxidation of polyunsaturated FA by molecular oxygen and free radicals.
Explain the first line defense:
Vitamin E is the first line of defense, it protects against peroxidation of cellular and subcellular membrane lipid. It is a chain breaker and inhibits destruction. another effect it has is on lysosomal enzymes, lysosoes has many enzymes which has a hydrolytic degrading effect on the organisms. Prevents these catabolic enzymes ( prevent activation) Protects the proteins in the tissue from hydrolytic degradation.
Explain the second line of defense:
Even though we have the frist line of defense some free radicals might pass, then they will be met by the second line of defense, the glutathione peroxidase. It is a cytoplasmic enzyme with selenium as an intergral component, they destroy lipid peroxides before they cause damage. They mix the toxic lipid peroxide (R-O-OH) with glutathione (2 HS-G) —> hydroxy compound(R-OH) + oxidized glutatione (G-S-S-G) + H2O
What is oxidative stress?
- A balance between free radicals and antioxidants is necessary for proper physiological function. If free radicals overwhelm the body’s ability to regulate them, a condition known as oxidative stress happens. Reason for oxidative stress might be high production of free radicals or decreased intensity for the antioxidants. Can lead to acute chronic diseases.
Explain ROS:
- Reactive oxygen species (ROS) are chemically reactive chemical species containing oxygen. Examples include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. In a biological context, ROS are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. -During times of environmental stress (e.g., UV or heat exposure), ROS levels can increase dramatically. This may result in significant damage to cell structures. Known as oxidative stress. The production of ROS is strongly influenced by stress factor responses in plants, these factors that increase ROS production include drought, salinity, chilling, nutrient deficiency, metal toxicity and UV-B radiation. ROS are also generated by exogenous sources such as ionizing radiation.
Explain RNS:
-Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide (•NO) and superoxide (O2•−) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. Reactive nitrogen species act together with reactive oxygen species (ROS) to damage cells, causing nitrosative stress. Therefore, these two species are often collectively referred to as ROS/RNS. Reactive nitrogen species are also continuously produced in plants as by-products of aerobic metabolism or in response to stress.
Explain RCS:
- Reactive chloride species are produced during bacterial infection and inflammation. -Hipochloride acid (HOCl) - non free
What is the effect of all the free and non-free radicals in general?
-Cell functions -Signalling -Antibacterial role -Cell division -inflammation -Vasodilation -Apoptosis
How do free radicals affect the body?
Free radicals are toxic byproducts of oxygen metabolism that can cause significant damage to living cells and tissues in a process called “oxidative stress.” The vitamins and minerals the body uses to counteract oxidative stress are called antioxidants.
What are free radicals?
The body is under constant attack from oxidative stress. Oxygen in the body splits into single atoms with unpaired electrons. Electrons like to be in pairs, so these atoms, called free radicals, scavenge the body to seek out other electrons so they can become a pair. This causes damage to cells, proteins and DNA.
