cell biology

1. Mitochondria ( Power house of cell)
Ahsan Bashir 19024160-005
Umair Asghar 19024160-009
Muhammad Zeeshan Ali Janjua 19024160-022
Muhammad Shoaib Kazim 19024160-038

2. Ahsan Bashir
19024160-005

3. Introduction
 Double membrane bound organelle found in all
Eukayotic cell.
 Derived from Greek word “Mito” mean “thread”
“chondrion” mean “ granule like”.
 First Observed By Richard Altman (1894).
 Term mitochondria was coined by Carl Benda (1898)
 Mitochondria are know known to be more than Hub of Richard Altman
Energy metabolism.
 Basically found in all body cells except Red blood cells.
 They produce enzyme for the metabolic conversion of food
To energy.
Carl Benda

4. Origin Of Mitochondria
 There are two hypothesis about the origin of mitochondria
1. Endosymbiotic hypothesis
2. Autogenesis hypothesis
Endosymbiotic hypothesis:
 According to this theory, the large anaerobic prokaryotes ingested small
aerobic bacteria. This aerobic bacteria stabilize themselves with in and later
developed into mitochondria.
 The mitochondria became the site of aerobic respiration.

5. Cont…

6. Umair Asghar
19024160-009

7. Morphology of mitochondria
Feature Morphology
Size 0.05 – 1.0 µm in diameter.
Length 1 – 10 µm long
Number Depends on type, size and functional state of cell. E.g : an average
liver cell contain around 1500 mitochondria.
 Maximum (Liver cell)
 Minimum ( Ear cell)
Location They are present in all type of eukaryotic cell except red blood cells

8. Structure of Mitochondria:
 Outer membrane
 Intermembrane space
 Inner membrane
 Cristae
 Matrix

9. Outer membrane:
 Simple phospholipid bilayer
 It encloses the mitochondria
 Contain large number of integral protein structures called porins, which allows molecules
to freely diffuse from one side of the membrane to the other.
 The mitochondrial outer membrane can associate with the (ER) membrane.
 The ER-mitochondria calcium signaling and the transfer of lipids between the ER and
mitochondria.
 Ions, nutrient molecules, ATP, ADP etc. can pass through the outer membrane with ease.

10. Intermembrane space
 It is also known as Perimitochondrial space.
 The space between inner membrane and outer membrane.
 The space between inner and outer membrane is approximately 70 A.
 Because the outer membrane is freely permeable to small molecules, the concentration of
small molecules such as ions and sugars in the intermembrane space is the same as cytosol.

11. Inner membrane
 It is freely permeable only to oxygen, carbon dioxide and water.
 The inner mitochondrial membrane contain protein that performs redox reactions in
oxidative phosphorylation, ATP synthase, transport protein and mitochondrion fusion and
fission protein.
 Several antiport systems exist, allowing exchange of anions between the cytosol and the
mitochondrial matrix.

12. Cristae
 The folding of the inner membrane that allows more surface area, enhancing its
ability to produce ATP.
 The inner surface of cristae in the mitochondrial matrix contain small knob like
structure called F1 particle.
 The electron transport chain and chemiosmosis are the process which help to
produce ATP in final step of cellular respiration, occur in the cristae of mitochondria.

13. Mitochondrial matrix
 Contain enzymes for the synthesis of ATP, ribosomes, tRNAs and the
mitochondrial DNA.
 Matrix components can diffuse to inner membrane complexes and transport
proteins within short time.
 Kreb cycle and Oxidative phosphorylation occur in matrix.

15. Muhammad Zeeshan Ali Janjua
19024160-022

16. Mitochondrial Genome:
 Mitochondrial genome was discovered in 1960.
 This genome consist of a circular chromosome, 16.5 kb in size that is located inside the
mitochondrial organelle, not in the nucleus.
Here we discuss:
 Mitochondrial DNA
 Mitochondrial genetic system
 Biogenesis
 Inheritance of mitochondria

17. Mitochondrial DNA:
 Mitochondrial DNA are Small, Double stranded ,covalently closed ,
circular molecule.
 The DNA in the cell nucleus does not code for the construction
of mitochondria.
Mitochondrial DNA makes up less than 1% of the total cellular DNA.
 Most usually remains attached to inner mitochondrial membrane.
 Mitochondrial DNA consist of two strands:
 Heavy chain which contain Purines ( Adenine, Guanine)
 Light chain which contain pyrimidine ( Cytosine, thyamine, uracil)

18. Mitochondrial genetic system
 Mitochondria are unique in their own way containing their own circular DNA and their
own ribosomes.
 It has 16569 bp, encode 37 gene and no intron.
 Out of 37 genes, 13 genes encode protein, 22 for tRNA and 2 for ribosomal RNA
 This system consist of molecular machinery needed to replicate and gene contain
in DNA.
 This machinery includes the macromolecule needed for transcription and
translation.

19. Cont.…
Replication of mitochondrial DNA:
 Mitochondria show d-loop replication.
 Replication start at replication site of
H strand.
There are two model for DNA replication:
 Displacement replication
 Symmetric replication

20. Biogenesis:
 Mitochondrial biogenesis is the process by which cell increase mitochondrial mass.
 It was first described by john Holloszy in the 1960.
 Mitochondrial biogenesis is activated by numerous different signals during the time of
cellular stress.
 Similar to cells, mitochondria divide and fuse with other mitochondria maintaining their
number of cells.
 Our understanding of mitochondrial fission and fusion has improved in recent years with
the development of in vitro assays for their study and the identification of proteins
required for both events.
 The balance between fusion and fission is likely a major determinant of mitochondrial
number, length, and degree of interconnection.

22. Inheritance Of mitochondria
 Mitochondrial DNA is inherited maternally in most animals.
 Fathers only give genes to their children but mothers give both genes and cytoplasm
through their egg cell.
 Since mitochondria are in the cytoplasm and reproduce themselves they only are
inherited from mothers.
 Hence this pattern of mtDNA inheritance is well known as “ maternal inheritance”.

23. Homoplasmy and Heteroplasmy:
 One daughter cell may be chance receive mitochondria that contain only a pure population
of normal mtDNA or a pure population of mutant mtDNA is called homoplasmy.
 The daughter cell may receive a mixture of mitochondria some with and some without
mutation is called heteroplasmy.
Homoplasmy Heteroplasmy

24. .
Muhammad Shoaib Kazim
19024160-038

25. Function of mitochondria
 Energy transducer of the cell- synthesis ofATP
 Kreb Cycle
 ETC system
 Oxidative phosphorylation
 Extra mitochondrial inheritance:
 mtDNA contains plasma genes (extra chromosomalgenes)
 Transmitted from mother to the offspring

26. SITE OF SEVERAL METABOLIC REACTIONS
Structure Functions
Outer membrane  Oxidation of epinephrine
 Degradation of tryptophan
 Elongation of fatty acid
Inner membrane Oxidative phosphorylation
Matrix  Kreb cycle
 Detoxification of ammonia in urea cycle

27. Kreb Cycle
 It is also called citric acid cycle or Tricarboxylic (TCA) cycle.
 Occur in the matrix of mitochondria.
 Before entering this cycle, Pyruvate (C3) loses 1 carbon atom → acetic
acid (C2)
 Acetic acid + Coenzyme A (CoA) → Acetyl CoA

28. Cont.…
 In this cycle, Oxaloacetate (C4) + acetyl group (C2) = citrate (C6)
 The final product of this cycle is:
 2 CO2
 3NADH
 1 FADH2
 1 GTP

29. Oxidative Phosphorylation
 Synthesis of ATP in the presence of oxygen is called oxidative phosphorylation.
 Oxidative Phosphorylation occur in matrix of mitochondria
 Basically, 3 events occur in this reaction
1) Oxidation of coenzymes
2) Movement of protons
3) ATP synthesis by ATP sythase

30. Cont…
1. Oxidation of Coenzyme:
 The oxidation of co enzyme cause to move electrons
 The final electron acceptor is molecular oxygen → is reduced to water

31. Cont..
2. Movement of protons:
 Are pumped into the intermembrane space →electrochemical proton gradient (proton-
motive force)
 Protons have to flow back into the matrix trough ATP synthase

32. Cont..
3. ATP synthesis by ATP sythase:
 Protons flow trough the complex (chemiosmosis) which cause this kinetic energy rotates
the F1 subunit → synthesis of ATP from ADP + Pi .
 The final product is ATP

33. ATP production from bioorganic molecules
 1 g fatty acid:
9Kcal/37kJ
 1 g carbohydrate:
4Kcal/17kJ
 1 g protein:
4Kcal/17kJ

34. Additional functions
 Mitochondria play a central role in many other metabolic tasks:
• Regulation of the membrane potential
• Apoptosis (programmed cell death)
• Signaling (regulation of gene expression)
• Regulation of cellular metabolism
• Steroid synthesis

35. Mitochondrial disease
 Mutations in genes for mitochondrial proteins encoded by both mtDNAand nuclear DNA
causes disorders such as :
 Stoke
 Cardiomyopathy
 Neuropathy
 Hearing
 Blindness
 Myopathy ( Muscular weekness)