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

Die Proteinverdauung beginnt zun&#xE4;chst im Magen.
 Die stark s&#xE4;urehaltige Umgebung kann die Proteinstruktur aufbrechen, wodurch Peptidverbindungen innerhalb einer Polypeptinkette freigelegt werden.
 Zum Beispiel bricht das Magenenzym Pepsin die Verbindungen auf, um kleinere Peptidfragmente zu bilden, k&#xFC;rzere Ketten von Aminos&#xE4;uren.
 Wenn die Peptide in den Zw&#xF6;lffingerdarm weiterwandern, aktiviert der Speisebrei mehrere andere Enzyme wie Trypsin, die die Peptinverbindungen weiter aufbrechen, was in einer Reihe noch k&#xFC;rzerer Peptide resultiert.
 Die epitheliale Oberfl&#xE4;che des D&#xFC;nndarms sondert verschiedene Peptidasen ab, Enzyme, die kurze Peptidketten in einzelne Aminos&#xE4;uren aufbrechen.
 Diese Aminos&#xE4;uren werden dann ins Blut aufgenommen, wo sie durch den K&#xF6;rper transportiert werden k&#xF6;nnen, um f&#xFC;r die Proteinsynthese genutzt zu werden oder zur Leber transportiert zu werden, wo sie der Energiegewinnung dienen.

Goodman, Barbara E. "Einblicke in die Verdauung und Absorption der wichtigsten Nährstoffe beim Menschen." Fortschritte in der physiologischen Ausbildung 34, Nr. 2 (1. Juni 2010): 44–53. [<a href="https://doi.org/10.1152/advan.00094.2009" target="__blank">Quelle</a>]

eiweißverdauung

Im Magen beginnt die Proteinverdauung. Dort st&#xF6;rt das stark saure Milieu leicht Proteinstrukturen, indem es die Peptidbindungen der Polypeptidketten freilegt. Nachdem die Polypeptidketten durch eine Reihe von Verdauungsenzymen in einzelne Aminos&#xE4;uren aufgespalten wurden, werden die Aminos&#xE4;uren &#xFC;ber die Blutbahn zur Energiegewinnung zur Leber transportiert.
 
 <h4>Pepsin</h4>
 
 Pepsin ist eine Protease oder ein eiwei&#xDF;verdauendes Enzym, das im Magen produziert wird. Es stellt eines der wichtigsten Verdauungsenzyme im menschlichen Verdauungssystem dar. Zusammen mit Chymotrypsin und Trypsin, die im D&#xFC;nndarm freigesetzt werden, spaltet Pepsin Bindungen zwischen bestimmten Arten von Aminos&#xE4;uren, wodurch k&#xFC;rzere Polypeptidketten entstehen. Andere Enzyme, die Peptidases, spalten dann einzelne Aminos&#xE4;uren von den Enden der Polypeptidketten ab. Der D&#xFC;nndarm kann die entstandenen Aminos&#xE4;uren leicht absorbieren.
 
 <h4>Die Leber und der Proteinstoffwechsel</h4>
 
 Die Leber spielt eine wesentliche Rolle beim Stoffwechsel von Proteinen. Die Leberzellen ver&#xE4;ndern die verdauten Aminos&#xE4;uren aus dem D&#xFC;nndarm, so dass sie zur Energiegewinnung oder zur Herstellung von Kohlenhydraten und Fetten verwendet werden k&#xF6;nnen. Ein Nebenprodukt dieses Prozesses ist eine giftige Substanz namens Ammoniak, welches die Leber in einen viel weniger giftigen Stoff umwandelt, den Harnstoff. Der Harnstoff wird dann in das Blut abgegeben und zu den Nieren transportiert, die den Harnstoff durch den Urin aus dem K&#xF6;rper ausscheiden.

Eiweißverdauung

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

Lehre

JoVE Core

Biology

Biologie

Genetics

Genetik

Nutrition and Digestion

Ernährung und Verdauung

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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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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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Next Generation Science Standards

High School

Life Science

HS-LS1-2

Florida Department of Education

SC.912.L.14

SC.912.L.14.46

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-2.

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2. Obtain, evaluate, and communicate information to describe how the structures of the integumentary system and its accessory organs contribute to its function. Examples: how the layers of the skin contribute to homeostasis, the role of glands in thermoregulation and in hydration of skin and mucous membranes, the protective functions of hair and nails

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9-12.HA.1.3.a

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9-12.HA.1.4

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a. Model the cellular physiology of skeletal muscle, including how the cell functions in muscle contraction and relaxation. Example: Use straws and paper to create a model of a sarcomere to illustrate how the fibers move during contraction and relaxation.

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9-12.HA.1.4.b

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9-12.HA.1.5

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c. Construct an explanation of the role of neurotransmitters in the functions and behavior of the nervous system. Clarification: Discussion of classes of neurotransmitters is not required.

9-12.HA.1.5.c

Protein Breakdown and Amino Acid Use

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