MITOCHONDRIA STRUCTURE

By

Prof. DR. IR. CHANIF MAHDI, MS.

DEPARTEMENT OF CHEMISTRY

BRAWIJAYA UNIVERSITY

Diagrame of the mitochondria structure

Mitochondria

Mitochondria contain two membranes,

separated by space. Inside the space enclosed

by inner membrane is the matrix.

These appears moderatly dense and one may

find strands of DNA, Ribosome, or small granula

in the matrix.

The above diagrame shows the diagram of the

mitochondrial membranes and the enclosed

compartement.

Contd

Mitochondria is the Power of house of the cell.

How are mitochondria organized to be power house.

The food we eat is oxidized to produce high energy electrons that converted to store energy. This energy is stored in high energy phosphat bond in a molecule called Adenosine Triphosphate (ATP).

ATP is converted from Adenosine Diphosphat by adding the phophat group with high energy bond.

Various reaction in the cells can be either use energy ( where by the ATP is converted back to ADP( releasing the high energy bond).

REAKSI PEMBENTUKAN ENERGI

C6 (H2O)6 + H2O O2 + 4H+ + 4 e

NADP+ + 2 H+ + 2 e NADPH + H+ + Energi

Energi + ADP + H3 PO4 ATP

Why are mitochondria important

The food we eat must first be converted to basic

chemicals that the cell can use. Some of the

best energy supplaying foods contain sugar or

carbohydrates.

The sugars are broken down by enzymes that

split them into into simplest form sugar which

called glucose . Then glucose enters the cell by

special molecules in the membrane called “

Glucose transporter”.

Contd

Once inside the cell, glucose is broken down to

make ATP in two pathways.

The first pathways requires no oxygen and is

called “ anaerobic metabolism” this pathway is

called glycolysis and it occur in the cytoplasm,

outside of mitochondria.

During glycolysis, glucose is broken down into

pyruvate.

Contd

Each reaction is designed to produce some

hydogen ions (electron) that can be used to

make energy packet ( ATP ). However, only 4

ATP molecules can be made by one molecule of

glucose run through this pathway.

That is why mitochondria and oxygen are so

important.We need to continou the breakdown

with the Krebs cycle inside the mitochondria in

orde to enough ATP to run all the cell function.

Figure 2. Mitochondria as power house of the cell

Figure : Glycolysis diagrame

Figure : Anaerob and aerob meabolism

Figure 2. Information

Pyruvat is carried into the mitochondria and it converted into Acetyl Coa which enter the Krebs cycle. This first reaction produce carbon dioxide, because it involves the removal of one carbon from pyruv, atc.

How does the Krebs Cycles work. The whole idea behind respiration in the mitochondria is

to use the Krebs ( also called the Citric acid Cycle ) to get many electron ( in the form of hydrogen ions ), are then used to drive pumps that produce ATP. The energy carried by ATP is than used for all kind of cellular function, like movement, transport, entry and exit products, devision, etc.

Contd

First, you need pyruvate, which is made by

glycolysis from glucose. Next you need some

carrier molecule for the electrons. There are two

types of these : one called Nicotinamide Adenin

Dinucleotide ( NAD+ ), and the other is called

Flavin Adenin Dinucleotid ( FAD+ ), The third

molecule, of course is oxygen.

Pyruvat is a 3 carbon molecule. After inter the

mitochondria, it is broken down to a 2 carbon

molecule by special enzyme. This release

contd

molecule are called acetyl Coa and it enters the Krebs Cycle by joining to 4 carbon molecule called Citric acid ( 2 carbon + 4 carbon = 6 carbon). That is where the citric acid cycle got it name. ( from the first reaction, that make citric acid).

Citric acid is then broken down, and modified in a

stepwise fashion ( See text for details), and as the happens, hidrogen ions and carbon molecules are released.

The carbon molecules are used to make more carbon dioxide and the hydrogen ions are picked up by NAD and FAD.

Contd

Eventually the process produces the 4 carbon

oxalo acetat again. The reason, the process

called cycle, is because its ends up always

where it started, with oxalo acetat available to

combine with more acetyl Coa.

Oxydative Phosphorilation

First some basic difinition. When you take hydrogen ion

or electron away from molecule, you “ oxydaze” that

molecule. When you give hydrogen ion or electron to a molecule, you “ reduce” that molecule.

So, oxidative phosphorilation ( very simply) mean, the

process that couples the removal of hydrogen ion from

molecule and giving phosphat molecule to another

molecule. How does this apply to mitochondria?

Contd

As the Krebs cycle runs, hydrogen ion ( or electron ), are

donated to the two carrier molecules in the 4 of the

steps. They are picked up by either NAD or FAD, and this molecules became NADH and FADH ( becauce they

now are carrying a hydrogen ion). The following

diagrame shows what heppens next ( Figure 3).

Figure 3.

More information Figure 3

The electron are carried chemically to the respiratory or electron

transport chain found in the mitochondria crestae ( see diagram

above and bellow).

The NADH and FADH essentially serve as Ferry in the lateral plane

of the membrane diffusing from one complex to the next.

At each site is the hydrogen (or proton) pump which transfers

hydrogen from one side of the membrane the other. This creates a

gradient a cross the inner membrane with a higher concentration of

hydrogen ion in the intercrestae space ( The space between inner

and outer membranes). ( Figure 4). The diagram shows the

individual complexes in electron transport chain.

The following diagram shows the individual complex in

the electron transport chain. The elecron are carried

from complex to complex by ubiquinon and cytochrome

C.

In the third pump in the series catalyzes the transfer of

electron to oxygen to make water. This semiosmotic pumping creates.

An electrochemical proton gradient a cross the membrane which is used to drive the “Energy Producing

Machine”. The ATP Synthase this molecule is found in

small elementary particle that project from crestae. See

figure 5 ).

Figure 4.

More information figure 5

As started above, this process requires oxygen, which is

called “ aerobic metabolism” The ATP Synthase uses

energy of the hydrogen ion ( also called proton) gradient

to form ATP from ADP and Phosphat. It also produces

water from hydrogen and oxygen. Thus, each compartement of the mitochondria is specialized for one

phase of this reaction.

How oxidation is coupled to phophorilation

To Review :

NAD and FAD remove the electron that are donated

during some of the steps of the Krebs or citric acid cycle.

Figure 5

Contd

They carried the electron to one electron transport Pump and donate them to the pump. So NAD and FAD are “ Oxidized” because they loss the hydrogen ion to the pump. The pump then transport the hidrogens ion to space between two membranes, where they accumalate in high enough concentration fuel to the ATP pumps. With sufficient fuel, they “ Phosphorylate” the ADP : That is how “ oxidation” is coupled to phosphorilation”.

The hydrogen that get pumped back into the matrix by ATP pump than combine with oxygen to make water. And that is very important because, without oxygen, they will accumulate and the concentration gradient needed to turn the ATP pump will not allow the pump work.

So, Why do we need mitochondria

The whole idea behind process to get as much ATP out of glucose (or other food product) as posible. If we have no oxygen, we get only 4 molecule ATP s for energy packet each glucose molecule (in glycolysis).

However, if we have oxygen, then we get to run Krebs cycles to product many more hydrogen ion, can run those ATP pumps, from the Krebs cycle we get 24- 28 ATP molecules out of one molecule of glucose converted to pyruvate.

So you can see how much more energy we can get out of a molecule of glucose, if mitochondria are working, and if we have oxygen.

Importance of the crestae

Not only do they contain and organize the electron

transport chain and the ATP pump, they also servte to

separate the matrix from the space that will contain the

hydogen ion, allowing the gradient needed to drive the

pump.

As shown in the above diagam, the molecules in the electron transport chain are found as cluster organized in

the crestae. These membrane sheves maybe more

numerous in mitochondria that are active in production

ATP ( Gambar 6 ).

More information of figure 6

Mitochondria can be separated and the inner and outer

membrane can be dissociated. This will result in a

fraction containing only the inner membrane and matrix.

These have been called : Mitoplast”. They are functional

and have helped us learn more about the compartementation of mitochondria.

Figure 6 Cyochrome C lying just outside the inner membrane

Figure 7 Cytochrome is on the inner membrane