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

A digest&#xE3;o de prote&#xED;nas come&#xE7;a primariamente no est&#xF4;mago. 
O ambiente altamente &#xE1;cido que pode quebrar a estrutura proteica expondo as liga&#xE7;&#xF5;es de pept&#xED;deos dentro de uma cadeia polipept&#xED;dica. 
Por exemplo, a enzima estomacal pepsina quebra as liga&#xE7;&#xF5;es para formar fragmentos menores de pept&#xED;deos, cadeias menores de amino&#xE1;cidos. 
&#xC0; medida que os pept&#xED;deos se movem para o duodeno, a entrada de quimo ativa v&#xE1;rias outras enzimas, como a tripsina, que continuam a quebrar as liga&#xE7;&#xF5;es pept&#xED;dicas criando uma variedade de pept&#xED;deos ainda menores. 
A superf&#xED;cie epitelial do intestino delgado secreta v&#xE1;rias proteases que s&#xE3;o enzimas que quebram cadeias curtas de pept&#xED;deos em amino&#xE1;cidos individuais. 
Esses amino&#xE1;cidos s&#xE3;o ent&#xE3;o absorvidos na corrente sangu&#xED;nea onde podem ser carregados por todo o corpo e usados para s&#xED;ntese proteica ou transportados para o f&#xED;gado onde s&#xE3;o usados para produzir energia.

Goodman, Barbara E. "Insights sobre Digestão e Absorção dos Principais Nutrientes em Humanos". Avanços na Educação em Fisiologia 34, nº 2 (1º de junho de 2010): 44–53. [<a href="https://doi.org/10.1152/advan.00094.2009" target="__blank">Fonte</a>]

digestão proteica

A digest&#xE3;o proteica come&#xE7;a no est&#xF4;mago, onde o ambiente altamente &#xE1;cido pode facilmente corromper a estrutura proteica expondo as liga&#xE7;&#xF5;es de pept&#xED;deos das cadeias de polipept&#xED;deos. Depois de as cadeias de polipept&#xED;deos serem quebradas em amino&#xE1;cidos individuais por uma s&#xE9;rie de enzimas digestivas, os amino&#xE1;cidos s&#xE3;o transportados para o f&#xED;gado atrav&#xE9;s da corrente sangu&#xED;nea para produzir energia.
 
 <h4>Pepsina</h4>
 
 A pepsina &#xE9; uma protease, ou enzima que digere prote&#xED;nas, que &#xE9; produzida no est&#xF4;mago e &#xE9; uma das principais enzimas digestivas do sistema digestivo humano. Trabalhando em conjunto com a quimotripsina e a tripsina libertadas no intestino delgado, a pepsina corta os elos entre tipos espec&#xED;ficos de amino&#xE1;cidos para formar cadeias de polipept&#xED;deos mais curtas. Outras enzimas, chamadas peptidases, separam ent&#xE3;o um amino&#xE1;cido de cada vez das extremidades dessas cadeias de polipept&#xED;deos. O intestino delgado pode facilmente absorver os amino&#xE1;cidos resultantes.
 
 <h4>O F&#xED;gado e o Metabolismo Proteico</h4>
 
 O f&#xED;gado desempenha um papel essencial no metabolismo das prote&#xED;nas. As c&#xE9;lulas hep&#xE1;ticas alteram amino&#xE1;cidos digeridos do intestino delgado para que possam ser usados para produzir energia ou produzir carboidratos e gorduras. Um subproduto desse processo &#xE9; uma subst&#xE2;ncia t&#xF3;xica chamada amon&#xED;aco, que o f&#xED;gado converte ent&#xE3;o em uma subst&#xE2;ncia muito menos t&#xF3;xica chamada ureia. A ureia &#xE9; ent&#xE3;o libertada no sangue e transportada para os rins, que excretam a ureia para fora do corpo atrav&#xE9;s da urina.

Digestão Proteica

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

Biologia

Genetics

Genética

Nutrition and Digestion

Nutrição e Digestão

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

Small and Large Intestine Functions

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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A coleção JoVE Core dá vida à biologia através de mais de 300 vídeos de animação concisos e fáceis de entender que explicam conceitos-chave de biologia, além de mais de 150 vídeos de Cientistas em ação que mostram experimentos reais em pesquisa realizados nos laboratórios atualmente.

Next Generation Science Standards

High School

Life Science

HS-LS1-2

Florida Department of Education

SC.912.L.14

SC.912.L.14.46

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New York State Science Learning Standards

Structure and Function

HS-LS1-2.

structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

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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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a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

9-12.HA.1.2.a

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Components ...

Classification of Bones

The bones of the human skeletal system are of varied shapes, sizes, and functions. They can be classified based on their shape and function into four ...

Overview of the Axial Skeleton

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Joints

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3. Develop and use a model to illustrate how the structures of the skeletal system contribute to its function. Examples: Create a diagram or 3D model to illustrate bone shape, joint types, and bones in the appendicular and axial skeletons. Use models to illustrate the role of the skeletal system in movements around joints, support of a body structure, and protection of soft tissues.

9-12.HA.1.3

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Intramembranous ossification is one of the two processes involved in the development of bones within an embryo. The flat bones of the face, most of the ...

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a. Obtain, evaluate, and communicate information describing the growth and development of the skeletal system.

9-12.HA.1.3.a

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b. Construct an explanation of the relationships between the skeletal system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain the role of spongy bone in hematopoiesis (cardiovascular system) and leukopoiesis (immune system). Explain how the storage of minerals in bone contributes to homeostasis.

9-12.HA.1.3.b

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Skeletal muscle names are based on various factors, such as location, physical traits, and functions.
Often, muscle names indicate their location. For ...

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Depending on their function, a muscle or group ...

Fascicle Arrangement in Skeletal Muscles

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4. Develop and build a three-dimensional model to illustrate the structures of the muscular system, including muscle locations, origins, and insertions, and explain their roles in movement and support. Example: Design and build a model of a lever to illustrate the relationship between bones and muscles and explain their roles in body movement and support.

9-12.HA.1.4

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Excitation-Contraction Coupling in Skeletal Muscles

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Relaxation of Skeletal Muscles

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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.

9-12.HA.1.4.a

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b. Obtain, evaluate, and communicate information to explain muscle fatigue and tone in terms of muscle cell physiology.

9-12.HA.1.4.b

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5. Obtain, evaluate, and communicate information explaining the relationship between the structures and functions of the central nervous system and the peripheral nervous system.

9-12.HA.1.5

Action Potential

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b. Construct an explanation of the role of reflex arcs, the central nervous system, and special senses in the response to stimuli to maintain homeostasis and guide behavior. Example: smelling a strong odor initiating a sneeze response using a reflex arc; pupil diameter changing in relation to the amount of light entering the eye Clarification: Discussion of the anatomy and physiology of the sensory organs is not required.

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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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