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By the end of this section, you will be able to:
  • Describe what defines each of the three metabolic states
  • Describe the processes that occur during the absorptive state of metabolism
  • Describe the processes that occur during the postabsorptive state of metabolism
  • Explain how the body processes glucose when the body is starved of fuel

You eat periodically throughout the day; however, your organs, especially the brain, need a continuous supply of glucose. How does the body meet this constant demand for energy? Your body processes the food you eat both to use immediately and, importantly, to store as energy for later demands. If there were no method in place to store excess energy, you would need to eat constantly in order to meet energy demands. Distinct mechanisms are in place to facilitate energy storage, and to make stored energy available during times of fasting and starvation.

The absorptive state

The absorptive state    , or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (anabolism exceeds catabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The digestion of carbohydrates begins in the mouth, whereas the digestion of proteins and fats begins in the stomach and small intestine. The constituent parts of these carbohydrates, fats, and proteins are transported across the intestinal wall and enter the bloodstream (sugars and amino acids) or the lymphatic system (fats). From the intestines, these systems transport them to the liver, adipose tissue, or muscle cells that will process and use, or store, the energy.

Depending on the amounts and types of nutrients ingested, the absorptive state can linger for up to 4 hours. The ingestion of food and the rise of glucose concentrations in the bloodstream stimulate pancreatic beta cells to release insulin    into the bloodstream, where it initiates the absorption of blood glucose by liver hepatocytes, and by adipose and muscle cells. Once inside these cells, glucose is immediately converted into glucose-6-phosphate. By doing this, a concentration gradient is established where glucose levels are higher in the blood than in the cells. This allows for glucose to continue moving from the blood to the cells where it is needed. Insulin also stimulates the storage of glucose as glycogen in the liver and muscle cells where it can be used for later energy needs of the body. Insulin also promotes the synthesis of protein in muscle. As you will see, muscle protein can be catabolized and used as fuel in times of starvation.

If energy is exerted shortly after eating, the dietary fats and sugars that were just ingested will be processed and used immediately for energy. If not, the excess glucose is stored as glycogen in the liver and muscle cells, or as fat in adipose tissue; excess dietary fat is also stored as triglycerides in adipose tissues.

[link] summarizes the metabolic processes occurring in the body during the absorptive state.

Questions & Answers

what is endocrin?
Asim Reply
why should there be an inhibition to the process of gastric production in the intestinal phase
Gloria
endocrine is a system through which the secretions of cell directly poured into blood.
Tanveer
why should there be an inhibition to the process of gastric production in the intestinal
Gloria Reply
what is a stimuli
Emily Reply
environment factor that cause a cell to respond
Quran
name the two types of melanin
Laila Reply
deference between RNA and DNA
Ali
.DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose.RNA stands for Ribonucleic Acid.  The sugar portion of RNA is Ribose.2.The helix geometry of DNA is of B-Form (A or Z also present).The helix geometry of RNA is of A-Form.3.DNA is a double-stranded molecule consisting o
ryaisha
DNA consists of nucleotide but RNA consists of nucleoside DNA is double standard but RNA is single standard.In DNA at the nitrogen bases adinine,guanine,cytocin and thymine is present but in case of RNA instead of thymine uracil is present.
Tanveer
what are rdna
Budumari
what is a heart
walker Reply
A heart is an organ in the circulatory system that pumps blood throughout the systemic regions
bernard
what is anatomy
Aisha
Anatomy is the study of internal and external structures and the relationship among body parts. (the study of structure).
Tomi
what is the physiology of the heart
nadine
guys help me with a pathophysiology of asthma
Luyando
asthma is a lungs related disorder in which there is difficulty in breathing due to some allergic factors, their is inflamation of alveoli of respiratory part of lungs.also decreases the surface area.
Tanveer
what is meaning of brain strock and its types?
Tanveer
the pathophysiology of asthma is complex and involves airway inflammation and bronchial hyperresponsiveness pathogenesis of asthma
Omkar
skin infection please explain
Hamza Reply
what is malignant melanoma
Akon Reply
cancerous cells 🙄
Sohan
yes benign is non-cancerous malignant is cancerous.
Joseph
that's a simple way of explaining it however you're different processes like mitosis etc a person can be at risk for developing cancer etc
Joseph
you can tell by an unusual growth of a mole, or change in size coloration with melanoma. which is abnormal growth of your squamous cells.
Joseph
Types of wandering connective tissues
Hassan Reply
what are the meaning of skin
PASHALINA Reply
study of external structure of human body is known as anatomy
VINAY Reply
what is Tau?
Vicki Reply
what is sliva
Saqlain Reply
what is gross
Kiran Reply
Describe the characteristics of tissue lining the respiratory passage way
arach Reply
please are they two types of antigens? one is foreign material and the other is a protein.... Please enlighten me cos i don't get it
shakainah Reply
what's a feedback
ivhil Reply
is the information or comment about something that one have done
Gaston

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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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