Name: protein breakdown and amino acid use
Uploaded: 2026-08-26T08:20:16.635Z
Duration: 1 min 31 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Protein Digestion

- [Instructeur] Vertering van eiwitten begint primair in de maag, de sterk zure omgeving die de eiwitstructuur kan verstoren, waardoor peptidebindingen in een polypeptideketen worden blootgelegd.
 Bijvoorbeeld, het maag-enzym pepsine verbreekt de bindingen om kleinere peptidefragmenten, kortere ketens van aminozuren, te vormen.
 Terwijl de peptiden naar de twaalfvingerige darm gaan, activeert het binnenkomen van chymus verschillende andere enzymen, zoals trypsine, die de peptidebindingen blijven afbreken, waardoor een verscheidenheid aan kortere peptiden ontstaat.
Het epitheeloppervlak van de dunne darm scheidt verschillende peptidasen af, dit zijn enzymen die korte peptideketens in afzonderlijke aminozuren breken.
 Deze aminozuren worden vervolgens opgenomen in de bloedbaan, waar ze door het hele lichaam kunnen worden vervoerd om te worden gebruikt voor eiwitsynthese of worden getransporteerd naar de lever, waar ze worden gebruikt om energie te produceren.

eiwitvertering

De eiwitvertering begint in de maag, waar de zeer zure omgeving de eiwitstructuur gemakkelijk kan verstoren door de peptidebindingen van polypeptideketens bloot te leggen. Nadat polypeptideketens door een reeks spijsverteringsenzymen in individuele aminozuren zijn opgedeeld, worden de aminozuren via de bloedbaan naar de lever getransporteerd om energie te produceren.

<h4>Pepsine</h4>

Pepsine is een protease, of eiwitverterend enzym, dat in de maag wordt geproduceerd en een van de belangrijkste spijsverteringsenzymen in het menselijke spijsverteringsstelsel is. In combinatie met chymotrypsine en trypsine die vrijkomen in de dunne darm, verbreekt pepsine de verbindingen tussen specifieke soorten aminozuren om kortere polypeptideketens te vormen. Andere enzymen, peptidasen genoemd, splitsen vervolgens aminozuur voor aminozuur af van de uiteinden van deze polypeptideketens. De dunne darm kan de resulterende aminozuren gemakkelijk opnemen.

<h4>Het lever- en eiwitmetabolisme</h4>

De lever speelt een essenti&#xEB;le rol in de stofwisseling van eiwitten. Levercellen veranderen verteerde aminozuren uit de dunne darm, zodat ze kunnen worden gebruikt om energie te produceren of koolhydraten en vetten te maken. Een bijproduct van dit proces is een giftige stof, ammoniak genaamd, die door de lever wordt omgezet in een veel minder giftige stof, ureum genaamd. Ureum wordt vervolgens in het bloed afgegeven en naar de nieren getransporteerd, die ureum via de urine uit het lichaam afscheiden.

Eiwitvertering

Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of ...

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Education

JoVE Core

Biology

Biologie

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Genetica

Nutrition and Digestion

Voeding en Spijsvertering

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

protein breakdown and amino acid use

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body.

Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter polypeptide chains.

Next, peptidases remove one amino acid at a time from the ends of those chains. The small intestine absorbs the resulting amino acids easily. They then travel through the bloodstream to the liver.

The liver uses these digested amino acids for protein metabolism. Liver cells can change them so they can be used to make energy, carbohydrates, or fats. During this process, ammonia is produced. The liver converts ammonia into urea, a much less toxic substance. Urea enters the blood, goes to the kidneys, and leaves the body in urine.

Protein Breakdown and Amino Acid Use

overview of human digestion

Saliva, Stomach Acid, and Gut Health

The human digestive system is monogastric, which means the stomach has one chamber for digestion. Several other animals also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter focuses on the human digestive system. Saliva is a watery fluid released by the salivary glands into the mouth. It is about 99.5% water and also contains electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes in saliva begin...

anatomy of the intestines

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The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination. The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of...

accessory organs

Digestive Glands and Enzymes

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion. The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach. The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum,...

carbohydrate digestion

Carbohydrate Breakdown in the Digestive Tract

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further. Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple...

protein digestion

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body. Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter...

lipid digestion

Lipases and Bile in Fat Breakdown

Lipases and bile help the body break down lipids, which are large molecules that do not mix well with water. Because most digestive enzymes are water-based, lipids need special steps before the body can use them. Lingual lipase is an enzyme made by acinar cells in the sublingual gland. It is found in saliva, but it has only a small role in the mouth. Its best pH, or acidity level, is 3.5-6.0, so it becomes active after chewed food reaches the acidic stomach. Gastric lipase is another acidic...

neural regulation

Brain and Gut Control of Digestion

Brain and gut control digestion through a cephalic phase and the enteric nervous system. The cephalic phase begins when the brain sees or smells food. It sends impulses through cranial nerves to the salivary glands and stomach so the body is ready to eat. This first response is a conditioned, or learned, reaction to familiar foods. Appetite also changes the response. People may make more saliva and hear more stomach rumbling when they think about apple pie than broccoli. The hypothalamus and...

hormonal regulation

Digestive Hormones and Stomach Control

Digestive hormones control when the stomach makes acid and when food moves into the small intestine. They work with the neuroendocrine system, which links nerve signals and hormone release during digestion. In the stomach, proteins are detected by sensory neurons in the enteric nervous system. This stimulates the pyloric gland to release gastrin. Gastrin then helps trigger histamine release, and together they start hydrochloric acid production. The acid helps break food down into chyme. As the...

key terms and concepts

Follow protein digestion from the stomach to the liver, including pepsin, peptidases, amino acid absorption, and urea formation for excretion.

Protein Breakdown and Amino Acid Use | JoVE K12

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SC.912.L.14.46

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Structure and Function

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Protein Breakdown and Amino Acid Use

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