<< Chapter < Page Chapter >> Page >

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

discuss nervers system in human being life.
Allen Reply
neuralgia what is other name of it
Muniba
how are neurons adapted to their function
Namiyaba Reply
machenic support production of blood cells locomotion protection of delicate organs
Ackson Reply
what are hormones?
Ackson
what is anatomy
Juma Reply
what are the functions of bones
Michael
To support and control the movements of the body
Mu
the study of human body is called anatomy
mishra
the study of human body is nt only anatomy but also physiology and histology
Evans
ooops lol I thought Michael was the one with the questions so sorry people. yes anatomy is the study of the body(structure)and it's physiology (functions).
Mu
what are the muscles of respiration?
Dorisha
Hi everyone, Why actyl choline decreases blood pressure although it affects adrenal gland leading it to secret adrenaline and noradrenaline which increase blood pressure?
cholinergic receptors are mostly under Parasympathetic response while adrenergic (norepinephrine) receptors are mostly sympathetic although they are cholinergic adrenergic receptors as well
Ayodeji
vocal cords
MT Reply
musah was admitted to your ward yesterday with traumatic amputation of the right thump . he complained this morning that he has not passed enough urine. Questions. 1) will you consider his complain to be pathological or physiological?. 2) in less than three sentences, justify your opinion. 3) Apply your understanding of the renin- angiotensin-aldosterone system to explain the factors and mechanisms accounting for his complains.
Ellen Reply
the mineral salt which break up a large portion of bone tissue is
Aurora Reply
calcium
Calcium
Sawda
please I need help. musah was admitted to your ward yesterday with traumatic amputation of the right thump. he complained this morning that he has not passed enough urine. Questions. 1). will you consider his complain to be pathological or physiological?.
Ellen
2). In less than three sentences, justify your opinion.
Ellen
Physiological
Ruth
musah copmlan to be physiological because of:-
Juma
cholesterol and triglycerides in simplest terms are fats (lipid) found in blood
Roy Reply
calcium is important for bone density and development. it also helps for safe / normal blood clotting, blood circulation to and from the heart, and muscle movement
Roy
please undertand me action potential ?
Josoph
minimum potential that must be overcomed to cause polarization and stimulate a neuronal response( generate impulse)
Ayodeji
what is muscle tissue
Rifat Reply
the muscle tissue is one of the 4 basic tissues in our body and is responsible for movement of our body
What Is difference between Ovary and Ovum
Sawda
ovary is female reproductive organ while ovum is a female gamete formed from ovary
Ubaidah
Thank You
Sawda
What Is Cholesterol and Triglycerides
Sawda
the mineral salt which break up a large portion of bone tissue
Aurora
in simple way muscle tissue is responsible for movement of our body.
Wellington
Hi Be Home Be safe , how are things doing hope all is well
Natarajan Reply
3 longitudinal bands of smooth muscles found in large intestines
Jamia
what's is sutures
Nimeshka Reply
what would I like to know
Roy Reply
anything u can tell me
Roy
anatomy mins
Manish
when two or more bones meet.
Joseph
Joints
Anita
I am interested in learning but it is a little threatening corona virus covid 19
Samnang Reply
I don't know about Corona virus
Vicky
what would you like to know?
Mbasa
what is a peripheral protien
Ayesha Reply
actually its located in between the lipid layer, it does not specify if it's closer to the inside or the outside of the cell
Justin
It is protein found in lipid bilayer but found attached with Cytoplasm aspect
Jamal

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask