Mitochondria the power house of cell .ppt

### **Mitochondria: The Powerhouses of the Cell**

Mitochondria are integral to life on Earth as we know it. These tiny, double-membraned organelles are present in nearly every eukaryotic cell and serve as the primary site of energy production, making them critical for cellular survival. The term “powerhouse of the cell” aptly describes their role, as they generate most of the adenosine triphosphate (ATP) – the molecular fuel that powers many of the biochemical reactions necessary for life. However, mitochondria's importance goes beyond just energy production; they are also involved in a variety of cellular processes, such as signaling, apoptosis (programmed cell death), and metabolic regulation. This multifaceted functionality makes mitochondria a vital part of cellular biology and overall organismal health.

This comprehensive description will cover the mitochondrion's structure, its role in energy production and metabolism, its evolutionary history, the way it interacts with cellular processes, and its impact on human health and disease.

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### **1. Structure of Mitochondria**

Mitochondria possess a unique structure that reflects their complex functionality. These organelles are surrounded by two membranes: an outer membrane that encases the organelle and an inner membrane that is intricately folded into structures known as cristae. This dual-membrane system is key to their function.

- **Outer Membrane**: The outer membrane is smooth and contains proteins known as porins, which allow the passage of ions and small molecules. It serves as a gateway between the mitochondrion and the rest of the cell, controlling the entry of certain metabolites necessary for energy production and other functions.

- **Inner Membrane**: The inner membrane is highly specialized and forms cristae, which increase the surface area available for important reactions like oxidative phosphorylation. The inner membrane is impermeable to most ions and small molecules, a property that is crucial for maintaining the electrochemical gradients necessary for ATP production. Embedded within this membrane are proteins responsible for the electron transport chain, a series of reactions essential for cellular respiration.

- **Matrix**: Inside the inner membrane lies the mitochondrial matrix, a gel-like substance containing a variety of enzymes that participate in the citric acid cycle (Krebs cycle), a key component of energy metabolism. The matrix also contains mitochondrial DNA (mtDNA), ribosomes, and tRNAs, enabling mitochondria to carry out some of their own protein synthesis.

- **Mitochondrial DNA (mtDNA)**: One of the most unique aspects of mitochondria is that they contain their own DNA, separate from the nuclear DNA in the cell’s nucleus. Mitochondrial DNA is circular and resembles bacterial genomes, supporting the endosymbiotic theory of mitochondrial origin (more on that later). Mitochondrial DNA encodes for a small portion of the proteins required by the mitochondri

1. Mitochondria
Cristae
Intracristal space
Commonly between 0.75 
and 3 μm in
diameter

2. MAM: mitochondria-associated ER-membrane
 ER-mitochondria calcium signaling
 Involved in the transfer of lipids between the ER
and mitochondria
Outer membrane and Mitochondria-associated ER membrane

3. MAM plays
an important 
role during

the fission process
by wrapping the
damaged mitochondria with ER membrane,
thereby
promoting
Drp1 translocation to the 
ER-
mitochondria interface,
where it can
cleave mitochondria efficiently
and target
damaged mitochondria for
mitophagy.
Mitophagy is
the selective degradation of mitochondria by autophagy. It often
occurs
to defective mitochondria following damage.
dynamin-related protein 1= Drp1

4. Intermembrane space
also known as perimitochondrial space, enzyme of Krebs cycle
Inner membrane
ATP synthase, which generates ATP in the matrix
Outer membrane
Lipid and proteins

5. The inner mitochondrial membrane contains pr
oteins with five types of functions: 
1.Those
 that perform the redox reactions of oxidati
ve phosphorylation
2. ATP
 synthase, which generates ATP in the matri
x
3.Specific
 transport proteins that regulate
metabolite passage
 into and out of the matrix
4.
 Protein import machinery
5.
 Mitochondrial fusion and fission protein

6. Cristae
Expand the surface area of the inner mitochondrial
membrane, enhancing its ability to produce ATP
Matrix
Contains
•Special mitochondrial ribosomes, tRNA, and several
copies of the mitochondrial DNA genome,
•Enzymes, the major functions include oxidation of
pyruvate and fatty acids,
•Citric acid cycle occurs in it.
Powerhouse of the cell

7. Mitochondria as semi-autonomous organelle
Due to the following counts:
Mitochondria have
their own
 
DNA 
which
can replicate independently.
Themitochondrial DNA produces
its own 
mRNA, tRNA and rRNA.
The
organelles posses their own 
ribosomes,
 
called mitoribosomes.
Mitochondria synthesize some of their own structural proteins .

However,
most of the
 mitochondrial proteins are synthesized under
instructions from cell nucleus.

8. Origin
of mitochondria
Two
hypotheses (endosymbiotic and autogenous)
Endosymbiotic hypothesis
suggests that mitochondria
were
originally prokaryotic cells, capable of implementing
oxidative
mechanisms that were not possible for eukaryotic
cells;
they became endosymbionts living inside the
eukaryote.

Autogenous hypothesis:
mitochondria were born by
splitting
off a portion of DNA from the nucleus of the
eukaryotic
cell at the time of divergence with the
prokaryotes;
this DNA portion would have been enclosed
by
membranes.
 

9. Origin
of mitochondria
Since
mitochondria have many features in common with
bacteria
For
example,
circular DNA
The
membrane is double layered and is made up from
lipids,
just like a prokaryotes membrane.
The
inner folds of the mitochondrial membrane, cristae, are
very
similar to mesosomes found in bacteria
Ribosomes
similar to those found in bacteria, 70S in size
Endosymbiotic
hypothesis is more widely accepted.

10. The
inner folds of the mitochondrial membrane, cristae, are
very
similar to mesosomes found in bacteria

11. Cellular respiration
The set of metabolic reactions and processes that take
place in the cells of organisms to convert biochemical
energy from nutrients into adenosine triphosphate
(ATP), and then release waste products
ATP will be used in:
Locomotion or transportation of molecules across cell
membranes

12. Cellular respiration is considered an exothermic redox
reaction which releases heat.
Redox reactions involve the transfer of electrons
between species
The term "redox" comes from two concepts involved
with electron transfer:
Oxidation is the loss of electrons or an increase in
oxidation state
Reduction is the gain of electrons or a decrease in
oxidation state

13. Reduction and oxidation
In terms of the transfer of oxygen, hydrogen and electrons.
Oxidation
and reduction in terms of oxygen transfer
Definitions
•Oxidation
is gain of oxygen.
•Reduction
is loss of oxygen.
Because
both reduction and oxidation are going on side-by-side, this is known as
a redox reaction.
ferric oxide
Ferrous ion Fe2+
ferric ion Fe3+
 
Iron(III)
 oxide or ferric oxide is the inorganic compound with the formula Fe2O3.

14. Oxidation and reduction in terms of hydrogen
transfer
•Oxidation is loss of hydrogen
•Reduction is gain of hydrogen

AcetaldehydeEthanol

15. Oxidation and reduction in terms of electron
transfer
Oxidation is loss of electrons
Reduction is gain of electrons
:

-
-

16. Aerobic respiration requires oxygen in order to generate
ATP.
The products of this process are carbon dioxide and water.

17. Aerobic conditions produce pyruvate and anaerobic conditions produce lactate
NADH (reduced nicotinamide adenine dinucleotide)
10-2=8
ATP

18. NADH
1*2=2*3=6
in
the matrix of the mitochondria

19. NADH
3*2=6*3=18 ATP
FADH2
1*2=2*2=4 ATP
24
ATP
1*2=2 ATP
NADH
1*2=2*3=6
FADH is
the reduced form of flavin
adenine
dinucleotide (FAD).
FAD
is synthesized from riboflavin and
two
molecules of ATP

21. NADH
2*3=6 ATP, GLY
NADH
1*2=2*3=6 ATP, citrate
NADH
3*2=6*3=18 ATP, kreb cycle
FADH2
1*2=2*2=4 ATP, kreb cycle

22. high
energy molecules NADH, and FADH2 which
are
converted into ATP by
the mitochondrial electron
transport chain.

24. An electron transport chain (ETC)
is a series of
complexes
that transfer electrons from electron
donors to
electron acceptors via redox (both
reduction
and oxidation occurring simultaneously)
reactions,
and couples this electron transfer with the
transfer
of protons (H
+
 ions)
across a membrane.
This
drives the synthesis of adenosine
triphosphate (ATP).
ATP
stores energy chemically in the form of highly
strained
bonds

25. inner membrane

26. ubiquinone also
known as
Coenzyme
Q
10
Iron-rich compounds called cytochromes

27. NAD
(nicotinamide adenine dinucleotide)
FAD
(flavin adenine dinucleotide)

28. an
egg contains on average 200,000 mtDNA
molecules,
whereas a healthy human sperm
contains
on average 5 molecules
degradation
of sperm mtDNA in the male genital
tract,
in the fertilized egg, and, at least in a few
organisms,
failure of sperm mtDNA to enter the
egg.

this
single parent (uniparental inheritance) pattern
of
mtDNA inheritance is found in most animals,
most
plants and in fungi as well
Inheritance of mitochondrial DNA

29. Thanks
In
addition to supplying cellular energy,
mitochondria are
involved in other tasks, 
such as signaling, 
cellular
differentiation, 
and cell death, as well as maintaining

control of the cell cycle and cell growth

30. NADH
molecules are created by
glycolysis,
but they can only be
converted
into ATP in the mitochondrial
electron
transport chain.
This
requires them to enter the
mitochondria.
A step that is free in
some
organisms, and costs 2ATP in
others.
This is what causes the
differences
in the Net yield of aerobic
respiration

31. Cellular respiration can
be an 
anaerobic or

aerobic respiration,
depending on whether or not oxygen is
present. Anaerobic respiration makes
a total of 2 
ATP.
Aerobic respiration is much more
efficient and
can produce up
to 38 
ATP with
a single 
molecule of
glucose

32. The electron transport chain (ETC)
is a series of 
complexes
 that transfer electrons from electron
donors
 to 
electron
acceptors
 via redox (both
reduction and oxidation
occurring
simultaneously) reactions, and couples this electron
transfer
with the transfer of 
protons (H
+
 ions)
across a 
membrane. 
At
the 
inner
mitochondrial membrane
,
electrons from 
NADH
 and FADH
2
 pass
through the electron transport chain to
oxygen,
which is reduced to water.

33. The
electron transport chain comprises an 
enzymatic series
of electron donors and
acceptors.
Each 
electron
donor
 will
pass electrons to a
more electronegative acceptor,
which in turn donates these electrons to another
acceptor,
a process that continues down the series until electrons are passed to
oxygen,
the most electronegative and terminal electron acceptor in the chain.
Passage
of electrons between donor and acceptor releases energy, which is used
to
generate a 
proton
gradient
 across
the mitochondrial membrane by 
"pumping"

protons into
the intermembrane space, producing a thermodynamic state that has
the
potential to do work. This entire process is called 
oxidative

phosphorylation since
ADP is phosphrylated to ATP by using the electrochemical
gradient
established by the redox reactions of the electron transport chain

34. Schematic diagram of the electron transport chain (ETC) of mitochondria. Complex (C) I, II, III, IV, and V represent each
complex in the ETC chain. The ETC uses NADH and FADH2 to make ATP. These reducing equivalents for ETC are
generated during glycolysis, fatty acid breakdown, and in the Tricarboxylic Acid pathways (TCA), also known as the
Krebs cycle. The electron flow starting from NADH binding to complex I or from succinate/FADH2 binding to complex
II initiate electron flow that ultimately results in ATP production in Complex V, the ATPase. If these pathways
malfunction, ATP production is reduced, placing stress on the cell.