Everyone knows that energy is essential for sustaining life. How can you define energy in life? Have ever thought about ways of how carbohydrates like glucose from your diet can be used for extracting energy? A scientific field that focuses on energy production and flow though living cells and organisms is called bioenergetics. Energy metabolism covers various biochemical ways of energy transformation and regulatory mechanisms of over thousands chemical reactions. Without fine control of those metabolic processes, cells and organisms cannot maintain activities linked to life. This 7 week-course will give you a clear introduction to the basic fundamentals of energy metabolism. We will first establish the concept of energy metabolism and subsequently examine biochemical steps involved in energy production from glucose oxdiation as well as glucose synthesis via photosynthesis. We will also learn about metabolic reactions related to fat as well as regulatory actions among different organs. Finally, dysregulated energy metabolism in pathological conditions such as diabetes and cancer will be discussed. Everyone knows that energy is essential for sustaining life. How can you define energy in life? Have ever thought about ways of how carbohydrates like glucose from your diet can be used for extracting energy? A scientific field that focuses on energy production and flow though living cells and organisms is called bioenergetics. Energy metabolism covers various biochemical ways of energy transformation and regulation of thousands of chemical reactions. Without fine regulation of those metabolic processes, cells and organisms cannot maintain activities linked to life. This 7 week-course will give you a clear introduction to the basic fundamentals of energy metabolism. We will first establish the concept of energy metabolism and subsequently examine biochemical processes involved in energy production as well as photosynthesis. We will also learn about metabolic reactions related to fa as well as regulatory actions among different organs. Finally, dysregulated energy metabolism in pathological conditions such as diabetes and cancer will be discussed.
4. Oxidation of fatty acids
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來自 Korea Advanced Institute of Science and Technology 的課程
Biochemical Principles of Energy Metabolism
16 個評分
從本節課中
MODULE 5: FAT METABOLISM
與講師見面
Seyun KimAssistant Professor
Department of Biological Sciences
Hello everyone. Welcome back to my Coursera class,
Biochemical Principles of Energy Metabolism.
We are at session four in week five. Fat metabolism.
We've talked about many issues about fat metabolism so far.
We had post tissue and biochemical structures of
lipids and how fats can be digested from the diet and food,
or how fat molecules can be supplied from your stored fat in a deposit.
And it is time to talk about oxidation processes of fat molecules.
So the sources of fat obviously from the lipids, right?
And they are degraded or stored fats can be degraded and
transported to other tissues or dietary fats can be digested,
chemically digested and then through
the circulatory system they can be used for energy production.
And at peripheral tissues and those fatty acid are metabolically
activated first and then getting into mitochondria for food oxidation.
Again, so like a carbohydrate metabolism glucose degradation,
fat oxidative processes include mitochondria for major site for energy production.
And that was fatty acid getting into the transformed into
acetyl-CoA and this is
the basic starting point for fat degradation.
And citric acid cycle instead of mitochondria is
the key biochemical pathway for breakdown of fat.
So again, for the fatty acid this is like a overall review cartoon.
Fatty acid in the blood.
These hydrophobic molecules, they cannot just
freely localized or freely
available inside the blood.
So rather the albumin proteins,
the serum albumin is kind of carrier for fatty acid.
So target cells, the fatty acid can get
into the cytoplasm of target cells through the transporters.
There should be fatty acid transporters and
definitely fatty acid and activated and transformed into acetyl-CoA.
And that acetyl-CoA is used for energy production and the mitochondria is
the key organelle for this process like carbohydrate digestion,
carbohydrate oxidation pathway.
Okay. You are looking at palmitic acid,
one of highly abundant fatty acids, saturated fatty acid.
How many carbons? 16 carbons.
Okay, total 16 carbons.
So this palmitic acid,
16 carbon palmitic acid,
when they are oxidized into water and carbon dioxide,
total 106 ATP can be generated,
which is huge, right?
Through a specialized pathway called beta oxidation.
And we can subdivide into the steps in the very beginning.
We consume two ATP molecules,
so -2 ATP is kind of investment and activation step.
And then later on,
8 acetyl-CoA and reduced electron carrier FADH2 and NADH can be generated.
And out of these oxidation,
so total plus minus we can produce over 100 ATP molecules.
Step number one is fatty acid activation.
So, incoming fatty acid for degradation are supposed to be activated.
And this activation process include ATP consumption.
First we have to invest our free energy ATP.
So, reaction is like this,
the fatty acid and ATP they reacted with each other and
the pyrophosphate out of ATP can be released
and then fatty acid chain can be AMP modified, adenylated.
And these molecules and incoming Coenzyme A.
Again, this Coenzyme A is the key player.
It's like glucose degradation even in fat metabolism.
So, finally adenylate, fatty acyl-CoA
becomes fatty acyl-coenzyme A and then AMP is released.
Because these pyrophosphates, again energy containing molecules it can be further
degraded into two phosphate molecules and then generate more free energy.
And the hydrolysis of pyrophosphate
can drive these highly exergonic fatty acid activation biochemical process.
And that reaction of course inside cytosol of target cell, peripheral cells.
But the main oxidative process occurs
inside the mitochondria that beta oxidation takes place inside the mitochondria.
So, fatty acyl-CoA should
be transported into the mitochondria, mitochondrial matrix.
This transport process is a little bit complicated.
So acetyl-CoA becomes replaced by carnitine.
So another organic compound and carnitine,
fatty acid carnitine inside the mitochondrial matrix,
again getting back to the acetyl-CoA.
So you might be very curious about why this type of
complicated transport processes developed for fat oxidation.
Well, simply speaking fatty acyl-CoA cannot directly get into mitochondrial matrix.
On top of that,
this type of transport processes is one of
major regulatory points for fat metabolism homeostasis.
So what is it then that beta oxidation.
Again, this beta oxidation process takes place inside the mitochondria.
So you are looking at this very, very simplified cartoon.
Okay, fatty acyl-Coenzyme A can be biochemically cut into two carbons.
In each cycle, acetyl-CoA can be generated.
And then during this oxidative processes,
in addition to one acetyl-CoA and shortened fatty acyl-CoA product,
FADH2 and NADH can be generated.
And those reduced electron carriers inside the mitochondria,
they can be used to drive ATP throughout oxidative phosphorylation,
OXPHOS pathway we studied in the glucose degradation.
So beta oxidation pathway is like this.
So this pathway is composed of four steps, okay?
In particular, I want to give you why this is called beta oxidation.
So in the nomenclature of chemistry,
the first carbon from the carboxylic group is alpha carbon.
The second carbon from the carboxylic group is called beta carbon, okay?
So as you can imagine the beta oxidation pathway means
this beta carbon is continuously oxidized throughout this cycle.
First the hydrogenation then means oxidation
and one reduced FADH2 can be produced and then dehydration,
just look at those reduced state of this beta carbon, right?
So you see double bond now hydroxylated, oxidised,
partly oxidised and further oxidised.
And then NADH can be produced.
And now this from hydroxyl,
the beta carbon now ketone, right?
And then cleave's your reaction and the new Coenzyme A getting into this system and
the two carbon reduced fatty acyl chain can
be produced and then the terminal C2 part can be released acetyl-CoA.
So as you can imagine,
inside the mitochondria this reduced FADH2 and this NADH can be used
to drive the electron transport system and
oxidative phosphorylation and ultimately ATP synthesis.
And this acetyl-CoA getting into citric acid cycle.
So more ATP production can be done.
So, this is the summary cartoon.
Triglyceride fatty acid supplied
and these fatty acid getting into the mitochondria.
And fatty acyl-CoA throughout beta oxidation two carbons per cycle.
Acetyl-CoA C2, acetyl-CoA can be continuously produced and NADH and FADH2,
those reduced electron carriers can be produced.
And those are utilized for electron transport system and citric acid cycle.
And so every two carbons acetyl-CoA can be
successively generated until the entire saturated fatty acid
are fully oxidized into CO2 and water.
This is how the beta oxidation pathway can be operated inside your cells.
