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Carbohydrate digestion

The average American diet is about 50 percent carbohydrates, which may be classified according to the number of monomers they contain of simple sugars (monosaccharides and disaccharides) and/or complex sugars (polysaccharides). Glucose, galactose, and fructose are the three monosaccharides that are commonly consumed and are readily absorbed. Your digestive system is also able to break down the disaccharide sucrose (regular table sugar: glucose + fructose), lactose (milk sugar: glucose + galactose), and maltose (grain sugar: glucose + glucose), and the polysaccharides glycogen and starch (chains of monosaccharides). Your bodies do not produce enzymes that can break down most fibrous polysaccharides, such as cellulose. While indigestible polysaccharides do not provide any nutritional value, they do provide dietary fiber, which helps propel food through the alimentary canal.

The chemical digestion of starches begins in the mouth and has been reviewed above.

In the small intestine, pancreatic amylase    does the ‘heavy lifting’ for starch and carbohydrate digestion ( [link] ). After amylases break down starch into smaller fragments, the brush border enzyme α-dextrinase    starts working on α-dextrin    , breaking off one glucose unit at a time. Three brush border enzymes hydrolyze sucrose, lactose, and maltose into monosaccharides. Sucrase splits sucrose into one molecule of fructose and one molecule of glucose; maltase    breaks down maltose and maltotriose into two and three glucose molecules, respectively; and lactase    breaks down lactose into one molecule of glucose and one molecule of galactose. Insufficient lactase can lead to lactose intolerance.

Carbohydrate digestion flow chart

This flow chart shows the steps in digestion of carbohydrates. The different levels shown are starch and glycogen, disaccharides and monosaccharides. Under each type of sugar, examples and the enzymes responsible for digestion are listed.
Carbohydrates are broken down into their monomers in a series of steps.

Protein digestion

Proteins are polymers composed of amino acids linked by peptide bonds to form long chains. Digestion reduces them to their constituent amino acids. You usually consume about 15 to 20 percent of your total calorie intake as protein.

The digestion of protein starts in the stomach, where HCl and pepsin break proteins into smaller polypeptides, which then travel to the small intestine ( [link] ). Chemical digestion in the small intestine is continued by pancreatic enzymes, including chymotrypsin and trypsin, each of which act on specific bonds in amino acid sequences. At the same time, the cells of the brush border secrete enzymes such as aminopeptidase    and dipeptidase    , which further break down peptide chains. This results in molecules small enough to enter the bloodstream ( [link] ).

Digestion of protein

This diagrams shows the human digestive system and identifies the role of each organ in protein digestion. A text call-out next to each organ details the specific function.
The digestion of protein begins in the stomach and is completed in the small intestine.

Digestion of protein flow chart

This flow chart shows the different steps in the digestion of protein. The four steps shown are protein, large polypeptides, short peptides and amino acids and amino acids.
Proteins are successively broken down into their amino acid components.

Lipid digestion

A healthy diet limits lipid intake to 35 percent of total calorie intake. The most common dietary lipids are triglycerides, which are made up of a glycerol molecule bound to three fatty acid chains. Small amounts of dietary cholesterol and phospholipids are also consumed.

Questions & Answers

yellow marrow has been identified as
Raychelle Reply
Which of the following accurately describe external resipration
Gwendolyn Reply
from the heart to the lungs
Phee
I think it's not outside organ of respiratory all respiratory organ are inside of human body
Moha
diffusion of CO2 and oxygen at a pulmonary capillary surrounding an alveolar sac.
Jeremiah
In other words, from the external environment to the lungs (alveoli) then to the pulmonary capillary then to the heart. So this is a stage of inhalation. inhale = external respiration.
Jeremiah
What kind of discussion
horyaal Reply
what is the function of the placenta
Nchimunya Reply
The placenta acts to provide oxygen and nutrientsto the fetus, whilst removing carbon dioxide and other waste products.
Moha
Also it's the barrier through which the mother is connected to the fetus.
Samuel
I want to discuss... atherosclerosis.., everything about it, about to treatment n prevention at age 50 +
Doctors
Please participate in discussion
Doctors
ok let's discuss now
Moha
first define the word artherosclerosis
Moha
a disease of the arteries characterized by the deposition of fatty material on their inner walls.
tabe
hardening of the arteries, due to fats..
jenelyn
Q = which type of fat utilized for this.., I.e LDL, HDL, TG, VLDL...?
Doctors
Atherosclerosis is a condition of deposition of plaque inside the artries
Arvind
Plaque include such as fat, chalestrol, calcium etc
Arvind
Thank you kumar...., is there any way that we can protect these plaques without any medicines., I. e exercises n food stuffs
Doctors
go to the gym
Moha
what is chylomicrons?
Moha
how can plaque buildup in The angina or vessels ?
Moha
Atherosclerosis is a condition of deposition of plaque inside the artries
Doctors
atherosclerosis can also be caused by tortuousness of arteries with old age as contributing factor.
edward
You tube Prof Fink...he is an amazing lecturer and does a brilliant job on arteriosclerosis
Jacqueline
what are cell
Chigozie Reply
The basic structural and functional unit of any living thing. Each cell is a small container of chemicals and water wrapped in a membrane. 
Yusuf
cell is the structural and functional basic unit of life
Zaid
So every living thing was Created From a Cell
Anthony
from a fusion of two cells , the sperm and the egg
Shikoh
What is the only bone that doesn't have any articulation?
Jimmy
that magical fusion of cells
OBED
why body immune system attack and destroy the body own cell during type 1 diabetes?
Sanamacha Reply
It's an autoimmune disease... targeting the pancreas
Claudia
what are the three genetic defects of pregnancy?
Belinda Reply
structure of fallopian tubes
Akash Reply
what z the role played by the transport system
zinitha Reply
how fats are digested in the human body
Nabukwasi Reply
Fat digestion begins in the stomach but some argue in that it starts in the mouth. Reason is because the sublingual gland secretes an enzyme called lingual lipase. However, this enzyme is not activated until it comes into contact with gastric fluids (HCl). In the stomach, HCl breaks down the lipid..
Jeremiah
due to body heat
Mule
into smaller molecules. Going from a triglyceride and a fatty acid to a monoglyceride and a a fatty acid no longer bound to one another. This is known as lipolysis.
Jeremiah
After lipolysis in the stomach from gastric and lingual lipase, an acidic chyme is produced after stomach churning the bolus. The chyme exits the stomach at the pyloric sphincter and enters the first section of the small intestine known as the duodenum.
Jeremiah
in the duodenum. An alkaline mucus from goblet cells neutralizes the acidic chyme to prevent acid burns. After that, the pancreas and gallbladder secrete a number of enzymes to continue lipolysis. Bile from the gallbladder enters the duodenum via common bile duct. The acinar cells in the pancreas...
Jeremiah
secretes pancreatic lipase after enteroendocrine cells in the duodenum secrete a stimulator hormone called CCK. Cck stimulates bile synthesis and secretion as well as pancreatic lipase.
Jeremiah
Bile emuslifies the lipid, allowing the lipases to continue lipolysis
Jeremiah
this breakdown continues until it reaches the jejunum of the small intestines. At this point, the lipid has been broken down small enough to absorbed into the blood stream. So villi in the jejunum, absorb the contents.
Jeremiah
ileum, the last small intestine region, absorbs anything that wasn't absorbed previously. Like minerals, vitamins, bile salts, water soluble material. Villi here complete that task. Fatty acid and glycerol however, are absorbed by lacteals. small lymph vessels. And are transported to the liver.
Jeremiah
That concludes lipid digestion. Anything else that remains is deficated after it travels through the large intestines.
Jeremiah
parents with blood group AB & 0,,,what will b the blood group of their offspring
imran
what are the different branches of anatomy
Nabukwasi
hopefully that helped.
Jeremiah
which ion is low of blood level?
Ezra Reply
what is coagulation?
feng Reply
liquid turning to solid... blood clots.
Kristy
coagulation : liquid blood into blood clots caused with a coagulant.
jaime
when the blood turn from liquid form to solid
June
it said to coagulate by the action of active plasma protein called *fibrin*
Hassan
I.e liquid inform of blood when to solid
Hassan
it is the process by which blood becomes more viscous or becomes thick
CHRISTOPHER
cloting of blood cells
Kabange
clot of blood
Moses
the process of forming semi solid lumps in a liquid
rida
conversion of blood to solid state
Ezra
semi solid., rather than solid form
Doctors
what is pivot functioned
Ever
to less thefriction
Hirsi
how to calculate the micrograph
Ampong Reply
it can be used to knw the disease condition
Akbar Reply
which gland secret tears
Opoku
lacrimal glands
Diego
explain the blood supply to the brain
Brenda Reply
There are two paired arteries which are responsible for the blood supply to the brain; the vertebral arteries, and the internal carotid arteries. These arteries arise in the neck, and ascend to the cranium.
Sabrina
two arteries main vertebral arteries & internal carotid artery
Akbar

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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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