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Ketone oxidation

This figure shows the reactions in which ketone is oxidized to acetyl-CoA.
When glucose is limited, ketone bodies can be oxidized to produce acetyl CoA to be used in the Krebs cycle to generate energy.


When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis    , creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocytes (liver cells). When you eat more glucose or carbohydrates than your body needs, your system uses acetyl CoA to turn the excess into fat. Although there are several metabolic sources of acetyl CoA, it is most commonly derived from glycolysis. Acetyl CoA availability is significant, because it initiates lipogenesis. Lipogenesis begins with acetyl CoA and advances by the subsequent addition of two carbon atoms from another acetyl CoA; this process is repeated until fatty acids are the appropriate length. Because this is a bond-creating anabolic process, ATP is consumed. However, the creation of triglycerides and lipids is an efficient way of storing the energy available in carbohydrates. Triglycerides and lipids, high-energy molecules, are stored in adipose tissue until they are needed.

Although lipogenesis occurs in the cytoplasm, the necessary acetyl CoA is created in the mitochondria and cannot be transported across the mitochondrial membrane. To solve this problem, pyruvate is converted into both oxaloacetate and acetyl CoA. Two different enzymes are required for these conversions. Oxaloacetate forms via the action of pyruvate carboxylase, whereas the action of pyruvate dehydrogenase creates acetyl CoA. Oxaloacetate and acetyl CoA combine to form citrate, which can cross the mitochondrial membrane and enter the cytoplasm. In the cytoplasm, citrate is converted back into oxaloacetate and acetyl CoA. Oxaloacetate is converted into malate and then into pyruvate. Pyruvate crosses back across the mitochondrial membrane to wait for the next cycle of lipogenesis. The acetyl CoA is converted into malonyl CoA that is used to synthesize fatty acids. [link] summarizes the pathways of lipid metabolism.

Lipid metabolism

This figure shows the different reactions that take place for lipid metabolism.
Lipids may follow one of several pathways during metabolism. Glycerol and fatty acids follow different pathways.

Chapter review

Lipids are available to the body from three sources. They can be ingested in the diet, stored in the adipose tissue of the body, or synthesized in the liver. Fats ingested in the diet are digested in the small intestine. The triglycerides are broken down into monoglycerides and free fatty acids, then imported across the intestinal mucosa. Once across, the triglycerides are resynthesized and transported to the liver or adipose tissue. Fatty acids are oxidized through fatty acid or β-oxidation into two-carbon acetyl CoA molecules, which can then enter the Krebs cycle to generate ATP. If excess acetyl CoA is created and overloads the capacity of the Krebs cycle, the acetyl CoA can be used to synthesize ketone bodies. When glucose is limited, ketone bodies can be oxidized and used for fuel. Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis. Acetyl CoA is used to create lipids, triglycerides, steroid hormones, cholesterol, and bile salts. Lipolysis is the breakdown of triglycerides into glycerol and fatty acids, making them easier for the body to process.

Questions & Answers

For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
Favour Reply
Name at least three reasons to study anatomy and physiology.
Structure Funtion
what is anatomy
Favour Reply
anatomy is a study of the human body
study of the structure and shape of the body and its parts
Ok, thanks
-For us to be a knowleagble about how the form(structures) works together to perform its functions. -Fo us to know the importance of each structure and its function. -To do the right procedure when we examined the structure of the body.
An anatomy and physiology student performing a dissection of the heart on her very first day, well because alliens doesn't any have idea about the structures and functions of the human body they are not knowleagble enough unlike those students.
the study of human bodys structure
the study of large organs in the body
study the mirco particles of the body
the study of the humab bodys function
study the regions of the body
name the regions of the body
Head and neck Thorax Abdomen
Briefly describe the activity of digestion in the mouth
Zen Reply
Please the difference between apoptosis and necrosis?
apoptosis is predefined cell suicide,where the cell actively destroys itself,maintaining a smooth functioning in the body. whereas necrosis is an accidental cell death occurring due to the controlled external factors in the external environment of the cell
Apoptosis is non detrimental while Necrosis is detrimental
Apoptosis is physiological pro
Apoptosis occur due to physiological change while Necrosis occur due to pathological change/is pathological.
Apoptosis is cause by Ageing while Necrosis is cause by pathogenic agent such as bacteria, viruses , Dangerous chemical such as toxins.
Apoptosis is programmed cell death while necrosis is an abnormal lysis of the cell characterised by unusual dismantling of the nucleus and entire cell at large
Apoptosis is when the cell kills itself. This occurs when the cell becomes old or abnormal. Necrosis is cell death, not caused by the cell itself, but other factors esp. decreased supply of oxygen and nutrients (blood). This can be caused by external factors like diseases or injuries.
Apoptosis is described as an active, programmed process of autonomous cellular dismantling that avoids eliciting inflammation. Necrosis has been characterized as passive, accidental cell death resulting from environmental perturbations with uncontrolled release of inflammatory cellular contents.
what are the types of nerve lesions
Kanimba Reply
neurapraxia (class l) axonotmesis (class ll) neurotmesis class lll)
there are three types of nerves in the body
what is inflammatory
Santuno Reply
It's a biological response triggered by a variety factors, including pathogens, damaged cells and toxic compounds.
It can be as well be de as defense mechanism that's vital to health
Why do Ladies. Experience hormonal imbalance after using family planning
Abdallah Reply
function of squamous epithelial
Helena Reply
wbc is a component of blood. it is also known as leucocytes, it is among the formed element of blood, there are 5 types of wbc, the neutrophils, the lymphocytes, the monocytes, the eosinophils and the basophils. it's function is to fight against disease
Faith Reply
Whole blood count
complete blood count
They're responsible for immunity
what are about openstax
Divya Reply
how many cells are in human
Gratel Reply
they are over 3billion cells in a human body
Is there fixed in amount ? because day by day it's increase as well as decrease also.
Red cells
Red cells to be in touch with the people
Then what about WBC ?
what about WBC ?
white blood cells are one of the most important constituant of our blood the total WBC are counts in blood is 8000/cubicmm wbc provide immunity to our body from foreign particle
what about WBC ?
They are responsible for immunity
What exactly is your question Khusali please?
I think the cells multiply while every day since the white blood cells fight diseases and pathogens I'm sure they multiply too
what is the function of clans..1.pituitary glands 2.Thyroid glands ..3.parathyroid glands ..4 suprenenal....5.testes...6.ovaries...7.placenta
Muyangana Reply
The pituitary gland is called the master gland because it releases hormones that act on other glands in the body to stimulate them to release other hormones. However, the pituitary gland has its own master which is the hypothalamus; it acts on the pituitary by also releasing hormones.
is that's all about Axal skeletal?
Jelle Reply
what is adipose
benita Reply
adipose means composed of animal fat I guess
were you satisfied with the answer?
adipose is used to store fats in animals adipose tissue are there which stores fats
otieno ur answer is correct
Correct otieno

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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