Mitochondria : Powerhouse of the Cell

Exploring the Powerhouse of the Cell: Mitochondria Unveiled

This PowerPoint presentation is tailored for Bachelor of Science students, offering a comprehensive exploration of mitochondria, the cellular powerhouses. Covering fundamental concepts such as structure, function, and cellular respiration, the presentation delves into the pivotal role mitochondria play in energy production. Additionally, it discusses the evolutionary origins, dynamic nature, and the intricate interplay between mitochondria and other cellular components. With engaging visuals and concise explanations, this presentation aims to provide a solid foundation for students to comprehend the significance of mitochondria in cellular biology.

1. Topic : Mitochondria
B.Sc. Sem 1 - Kishan Kumar Jha Cell Biology

2. Mitochondria (plural) ( Greek: Mitos : thread, Chondrion : Granule ) Richard altmann Carl Benda First observed by Richard Altmann (1884), A Dutch Pathologist. Term coined by Carl Benda (1898), A Microbiologist. ‘Granular thread like body’ Found in cytoplasm of the cell

3. De Novo Hypothesis: ( Backwith and harvey 1914 ) New mitochondria develops from the material present in cytoplasm. In 1951, Harvey centrifuged sea urchin eggs and cut it into 2 halves, one with mitochondria and another without mitochondria but consisting nuclei, which later developed mitochondria. Probably from the RNAs and DNAs of old Mitochondria. Biogenesis Origin from non mitochondrial membranes Later on, Some scientists Suggested that mitochondria is developed from nuclear envelope, plasma membrane, golgi apparatus and Endoplasmic reticulum Sea urchin

4. Origin from Pre–Existing Mitochondria Payne (1952) found mitochondria frequently present in adrenal cortex of fowl. He thought that new mitochondria Develop by growth and constriction of division of pre-existing mitochonddia, this theory was supported by luck and Rich (1964). Now all workers believes that mitochondria is semi autonomous body.

5. Endosymbiotic theory of mitochondria The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis and became incorporated into the cytoplasm.

6. Definition of Mitochondria : Mitochondria are cell organelles of aerobic eukaryotes which take part in oxidative phosphorylation and Krebs cycle of aerobic respiration.

7. Structure of Mitochondria: A mitochondrion contains two membranes, Each of them is 60-75 A in thickness and structure of a mitochondrion have two chambers, outer and inner. Adhesion site

8. The inner membrane is in-folded variously to form involutions called cristae . They are meant for increasing the physiologically active area of the inner membrane.
The density of cristae indicates the intensity of respiration.
The inner membrane as well as its cristae possess small tennis-racket like particles called elementary particles, F0 – F1 particles or oxysomes (ATP Synthetase).

9. Outer membrane Membrane is smooth, bears protien lined channels. Enzymes are fewer and outer Membrane is in contact with cytoplasm. Foldings are absent,proteins are roughly equal to lipids. Cardiolipids absent. ETS absent, Permeable to most Biochemicals Inner membrane Membrane contains number of particles. Porins are absent. Carrier and other transport proteins are present. Contain Number of enzymes, inner surface is in contact with matrix of the organelle. Protein content is upto 75% while Lipid content is low,Cardiolipins present. ETS present, It is selectively Permeable Difference between outer and inner mitochondrial membranes :

10. Shape and Size of Mitochondria: .The size of the mitochondria is variable. Normally, they have a length of 5 -10 µm and a diameter of 0.6-2.0 µm . Chemical Composition. Proteins. 60-70%, Lipids 25-35%, RNA 5-7%, DNA. Small quantity. Minerals. Traces, Granules Manganese and Calcium phosphate.

11. Cells of dormant seeds have very few mitochondria. Those of germinating seeds have several mitochondria. In general green plant cells contain less number of mitochondria as compared to non-green plant cells and animal cells.
The position of mitochondria in a cell depends upon the requirement of energy and amino acids.

12. They are called power houses of cell because they produce ATP (Adenosine triphosphate) Mitochondria are easily distinguishable under light microscope though ultrastructure can be studied only under electron microscope. Mitochondria are absent in prokaryotes, anaerobic eukaryotes And red blood corpuscles of mammals.

13. Outer Chamber (Peri-mitochondrial Space): forms the core of the mitochondrion. The inner chamber contains a semi-fluid matrix. The matrix has protein particles, ribosomes, RNA, DNA (mitochondrial or mDNA), enzymes of Krebs or TCA cycle (except succinate dehydrogense which is membrane based), amino acid synthesis and fatty acid metabolism, crystals of calcium phosphate and manganese. The chamber is the space that lies be­tween the outer and inner membrane of the mitochondrial envelope. Usually, it is 60-100 A wide. Inner chamber :

14. Mitochondria resemble the ribosomes of prokaryotes. DNA is naked. It is commonly circular but can be linear. DNA makes the mitochondrion semi-autonomous. Mitochondria show a large degree of autonomy or independence in their functioning: 1. Mitochondria have their own DNA which can replicate independently.

2. Mitochondrial DNA produces its own mRNA, tRNA and rRNA.

3. The organelles possess their own ribosomes.

15. 4. Mitochondria synthesise some of their own structural proteins. However, most of the mitochondrial proteins are synthesised under instructions from cell nucleus. 5. New mitochondria develop by division/binary fission of pre-existing mitochondria. However, mitochondria are not fully autonomous. Both their structure and functioning are partially controlled by nucleus of the cell and availability of materials from cytoplasm.

16. Mitochondria are believed to be symbionts in the eukaryotic cells which became associated with them quite early in the evolution. Functions of Mitochondria: 1. Mitochondria are miniature biochemical factories where food stuffs or respiratory substrates are completely oxidized to carbon dioxide and water. The energy liberated in the process is initially stored in the form of reduced coenzymes and reduced prosthetic groups.

17. 3. The matrix or inner chamber of the mitochondria has enzymes for the synthesis of fatty acids. Enzymes required for the elongation of fatty acids have been reported in the outer mitochondrial chamber.
4. Synthesis of many amino acids occurs in the mitochondria. The first formed amino acids are glutamic acid and aspartic acid. They are synthesized from a-ketoglutaric acid and oxaloacetic acid respectively. Other amino acids are produced by transformation and tran­samination or transfer of amino group (—NH2) from glutamic acid and aspartic acid.

5. Mitochondria may store and release Calcium when required.

6. An organism generally receives mitochondria from its mother (maternal inheritance).