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The breakdown of fatty acids, called fatty acid oxidation    or beta (β)-oxidation    , begins in the cytoplasm, where fatty acids are converted into fatty acyl CoA molecules. This fatty acyl CoA combines with carnitine to create a fatty acyl carnitine molecule, which helps to transport the fatty acid across the mitochondrial membrane. Once inside the mitochondrial matrix, the fatty acyl carnitine molecule is converted back into fatty acyl CoA and then into acetyl CoA ( [link] ). The newly formed acetyl CoA enters the Krebs cycle and is used to produce ATP in the same way as acetyl CoA derived from pyruvate.

Breakdown of fatty acids

This figure shows the reactions that break down fatty acids. The top panel shows the conversion of fatty acids into carnitine. The bottom panel shows the conversion of carnitine into acetyl-CoA.
During fatty acid oxidation, triglycerides can be broken down into acetyl CoA molecules and used for energy when glucose levels are low.


If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies    . These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starvation or when patients suffer from uncontrolled diabetes and cannot utilize most of the circulating glucose. In both cases, fat stores are liberated to generate energy through the Krebs cycle and will generate ketone bodies when too much acetyl CoA accumulates.

In this ketone synthesis reaction, excess acetyl CoA is converted into hydroxymethylglutaryl CoA (HMG CoA)    . HMG CoA is a precursor of cholesterol and is an intermediate that is subsequently converted into β-hydroxybutyrate, the primary ketone body in the blood ( [link] ).


This pathway shows the production of beta-hydroxybutyrate from acetyl-CoA.
Excess acetyl CoA is diverted from the Krebs cycle to the ketogenesis pathway. This reaction occurs in the mitochondria of liver cells. The result is the production of β-hydroxybutyrate, the primary ketone body found in the blood.

Ketone body oxidation

Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO 2 and acetone. The acetone is removed by exhalation. One symptom of ketogenesis is that the patient’s breath smells sweet like alcohol. This effect provides one way of telling if a diabetic is properly controlling the disease. The carbon dioxide produced can acidify the blood, leading to diabetic ketoacidosis, a dangerous condition in diabetics.

Ketones oxidize to produce energy for the brain. beta (β)-hydroxybutyrate    is oxidized to acetoacetate and NADH is released. An HS-CoA molecule is added to acetoacetate, forming acetoacetyl CoA. The carbon within the acetoacetyl CoA that is not bonded to the CoA then detaches, splitting the molecule in two. This carbon then attaches to another free HS-CoA, resulting in two acetyl CoA molecules. These two acetyl CoA molecules are then processed through the Krebs cycle to generate energy ( [link] ).

Questions & Answers

There was this time when the teacher is explaining about something that involves calculating.When the teacher calculate that (2×4)-(1×-3)=11.I was confused and think that the answer is wrong, so I asked the teacher.Then,I realized I calculate wrongly and then my head feels hot. Why?
Dicky Reply
I mean... (2 x 4)- (1 x -3) = 11
But since I don't really care about it. My head slowly goes back to normal.
blood is unique it is the only flueid tissue in the body
this is fascinating
for real
what is blood
sujon Reply
lol. the red substance in your body. that circulates food nutrients and oxygen
Blood is composed of plasma and formed elements. The plasma is about 55% of blood and is about 80-90% water usually. The other 20-10% accounts for solutes such as ions, nutrients, gases, and hormones.
Blood is a fluid type of connective tissue and it's formed elements (cells) include RBC, WBC, and plalets.
what is sasamoid bone?
hafeez Reply
how many types of bone on the base of shape
i want join the conversation
juwar Reply
feel free to do so
where are you from ?
hi what's up
well hello
Im from kashmir,but I'm studying in punjab
I'm studying pharmacy at JUST University in jordan
so am i emad 😅
I am Javed Ali
hello i am hafeez from gilgit
explain the mechanism(release and control) of hormonal interplay for fluid and electrolyte.
Cassie Reply
There are three main ways in which hormones may be released. Humoral stimulus - occurs when their is an inbalance in electrolytes in the body. Neural stimulus - occurs when autonomic nerve fibers stimulate glands to release hormones.
Hormonal stimulus - occurs when a hormone causes another hormone to be released from another gland.
what are the main pumps found in the cell membrane
pauline Reply
sodium potassium pump
Differences between ligaments and catilage
joy Reply
differences between catilage and ligaments
Both are different types of connective tissues. Second difference is that cartilage contains chondroblasts rather than fibroblasts. Their is also slight differences on their extracrullar matrix. For ex, cartilages tend to contain more collagen than tendons and ligaments.
Both types of connective tissue also function differently. Ligaments connect bone to bone, while cartilage have a variety of function like cushioning bones and giving structural support like on the nose and ears.
explain the causes of the refractory period of a nerve fiber
Sophia Reply
Refractory period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation. Brief pause in stimulus or excitation.
To add on, the brief pause is produced because of the event of establishing a resting membrane potential that needs to be produced before depolarization (another action potential) can occur again.
The refractory period also gives a chance for neurotransmitters to be replenished on the axon terminal.
what is hypoxia
Akas Reply
I guess it's low supply the oxygen to the tissues
A condition in which tissues (especially the blood) are deprived of an adequate supply of oxygen
hanifa pia uko hapa
Hypoxia is the lack of oxygen concentration in the blood. Therefore, tissues will receive a low concentration of oxygen. Usually our bodies respond to Hypoxia by stimulating erythropoiesis in red bone marrow.
hypoxia is the lack of oxygen in blood absolutely.
hypoxia: is a condition in wich the concentration of oxygen goes down in tissue or all over the body but the low concentration of oxygen in blood is called hypoxiemia.
where is present Glenoid Cavity ?
A- Reply
what is the muscular tissue
Md Reply
muscular tissue is a type of tissue that provide to help in cotraction to aur body.
What's the difference in epithelial, connective, muscular and muscle tissue
and it's similarities
what is limb bone
Akshu Reply
this are bone attaching or joining to the axial bone.axial bone including skull,vertebrate and ribcage
how many bones make up the skull?
22 bones
where is present Glenoid cavity ?
how many bone in skull
almost there are 8 bones in skull
Explain the stages of mitosis and cell division
Bella Reply
Bella, this is a very long process to detail by text. However, to keep it brief, mitosis has four phases in order: prophase, metaphase, anaphase, and telophase which sometimes followed by cytokinesis. Note that some cells do not always do the cytokinesis phase.
As a result, some of the cells in the body are multinuclear (osteoclasts for ex).
explain further
difference between mitosis and meosis
In mitosis, two genetically exact daughter cells (somatic cells) are produced and they are diploid. In meiosis, four genetically unique cells (gametes) are produced and they are haploid.
Meiosis only occurs in reproductive organs. Mitosis is a type of asexual reproduction and is involved in tissue growth and regeneration(repair).
mitosis > Diploid to Diploid meiosis > Diploid to Haploid
systems of human body
Udezue Reply

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