toxiology of biochem PDF

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1. Draw a diagram of a typical mitochondrion. Label the important components and show where the important reactions carried out by the organelle occur.

 Mitochondria are well-defined cytoplasmic organelles of the cell which take part in a variety of cellular metabolic functions 

The components of mitochondria are as follows: Outer membrane    

It is smooth and is composed of equal amounts of phospholipids and proteins. It has a large number of special proteins known as the porins. The porins are integral membrane proteins and they allow the movement of molecules that are of 5000 daltons or less in weight to pass through it. The outer membrane is freely permeable to nutrient molecules,ions, energy molecules like the ATP and ADP molecules.

Inner membrane      

The inner membrane of mitochondria is more complex in structure. It is folded into a number of folds many times and is known as the cristae. This folding help to increase the surface ares inside the organelle. The cristae and the proteins of the inner membrane aids in the production of ATP molecules. Various chemical reactions takes place in the inner membrane of the mitochondria. Unlike the outer membrane, the inner membrane is strictly permeable, it is permeable only to oxygen, ATP and it also helps in regulating transfer of metabolites across the membrane.

Intermembrane space 

It is the space between the outer and inner membrane of the mitochondria, it has the same composition as that of the cell's cytoplasm.

Matrix 

The matrix of the mitochondria is a complex mixture of proteins and enzymes. These enzymes are important for the synthesis of ATP molecules, mitochondrial ribosomes, tRNAs and mitochondrial DNA.

2. List the functions of mitochondria.  Functions of mitochondria depends on the cell type in which they are present. 

   

The most important function of the mitochondria is to produce energy. The simpler molecules of nutrition are sent to the mitochondria to be processed and to produce charged molecules. These charged molecules combine with oxygen and produce ATP molecules. This process is known as oxidative phosphorylation. Mitochondria help the cells to maintain proper concentration of calcium ions within the compartments of the cell. The mitochondria also help in building certain parts of blood and hormones like testosterone and estrogen. The liver cells mitochondria have enzymes that detoxify ammonia. The mitochondria also play important role in the process of apoptosis or programmed cell death. Abnormal death of cells due to the dysfunction of mitochondria can affect the function of organ.

3. Describe the evolution of mitochondria

4. What are reactive oxygen species (ROS) and how are they generated?  Reactive Oxygen Species (ROS) is a phrase used to describe a number of reactive molecules and free radicals derived from molecular oxygen.  The production of oxygen based radicals is the bane to all aerobic species. These molecules, produced as byproducts during the mitochondrial electron transport of aerobic respiration or by oxidoreductase enzymes and metal catalyzed oxidation, have the potential to cause a number of deleterious events. It was originally thought that only phagocytic cells were responsible for ROS production as their part in host cell defense mechanisms.  Most reactive oxygen species are generated as by-products during mitochondrial electron transport. In addition ROS are formed as necessary intermediates of metal catalyzed oxidation reactions. Atomic oxygen has two unpaired electrons in separate orbits in its outer electron shell. This electron structure makes oxygen susceptible to radical formation. The sequential reduction of oxygen through the addition of electrons leads to the formation of a number of ROS including: superoxide; hydrogen peroxide; hydroxyl radical; hydroxyl ion; and nitric oxide

5) How are mitochondria believed to be involved in the process of aging?

6) How can mutations in nuclear DNA and mitochondrial DNA both give rise to mitochondrial disorders?

7) What is the role of carnitine in mitochondria? What is the key enzyme involved in this process and what does it do?

 Carnitine acyltransferase I, which is located on the outer mitochondrial membrane, transfers the fatty acyl group from fatty acyl ‐CoA to the hydroxyl (OH) group of carnitine. The acyl ‐ carnitine then moves across the intermembrane space to a translocase enzyme, which, in turn, moves the

acyl‐carnitine to carnitine acyltransferase II, which exchanges the carnitine for Coenzyme A

8) What is the most common site in the mitochondria that shows abnormalities?

9) How are mitochondria involved with Leber’s Hereditary Optic Neuropathy?

10) What are the symptoms of pyruvate carboxylase deficiency?

11) What are Ragged red fibres? 12) Which complex of the respiratory chain does Kearns-Sayre syndrome affect?

13) Leigh’s syndrome can be caused by abnormalities of which enzyme and which complexes?

14) Is Leigh’s disease curable? How is it treated?

15) What is pronuclear transfer and how might it be used to treat mitochondrial disorders?...