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

La digesti&#xF3;n de prote&#xED;nas
comienza principalmente

en el est&#xF3;mago, donde
gracias a los fuertes &#xE1;cidos

se rompen las estructuras prote&#xED;nicas,

exponiendo los enlaces pept&#xED;dicos
de una cadena de p&#xE9;ptidos.

Por ejemplo, la pepsina,
enzima del est&#xF3;mago,

rompe los enlaces para formar
fragmentos de p&#xE9;ptidos,

cadenas m&#xE1;s cortas de amino&#xE1;cidos.

Cuando los p&#xE9;ptidos se
dirigen al duodeno, el quimo

activa muchas otras
enzimas, como la tripsina,

que contin&#xFA;a separando
los enlaces pept&#xED;dicos,

dando lugar a una gran variedad
de p&#xE9;ptidos m&#xE1;s cortos.

La superficie epitelial
del intestino delgado

secreta diversas peptidasas,
enzimas que rompen

cadenas cortas de p&#xE9;ptidos y
las convierten en amino&#xE1;cidos.

Estos amino&#xE1;cidos, absorbidos
por el torrente sangu&#xED;neo,

son llevados a todo el
cuerpo y sirven para

sintetizar prote&#xED;nas, o llegan
directo al h&#xED;gado, donde

se aprovechan para producir energ&#xED;a.

Goodman, Barbara E. "Perspectivas sobre la digestión y la absorción de los principales nutrientes en los seres humanos". Avances en la Educación en Fisiología 34, no. 2 (1 de junio de 2010): 44–53. [<a href="https://doi.org/10.1152/advan.00094.2009" target="__blank">Fuente</a>]

digestión de proteínas

La digesti&#xF3;n de prote&#xED;nas comienza en el est&#xF3;mago, donde el ambiente altamente &#xE1;cido puede alterar f&#xE1;cilmente la estructura de las prote&#xED;nas al exponer los enlaces pept&#xED;dicos de las cadenas polipept&#xED;dicas. Despu&#xE9;s de que una serie de enzimas digestivas rompen las cadenas polipept&#xED;dicas en amino&#xE1;cidos individuales, los amino&#xE1;cidos se transportan al h&#xED;gado a trav&#xE9;s del torrente sangu&#xED;neo para producir energ&#xED;a. <h4>Pepsina</h4> La pepsina es una proteasa o enzima digestiva de prote&#xED;nas que se produce en el est&#xF3;mago y es una de las principales enzimas digestivas del sistema digestivo humano. Trabajando junto con la quimotripsina y la tripsina liberadas en el intestino delgado, la pepsina corta los enlaces entre tipos espec&#xED;ficos de amino&#xE1;cidos para formar cadenas polipept&#xED;dicas m&#xE1;s cortas. Otras enzimas, llamadas peptidasas, separan un amino&#xE1;cido a la vez de los extremos de estas cadenas polipept&#xED;dicas. El intestino delgado puede absorber f&#xE1;cilmente los amino&#xE1;cidos resultantes. <h4>El h&#xED;gado y el metabolismo de las prote&#xED;nas</h4> El h&#xED;gado juega un papel esencial en el metabolismo de las prote&#xED;nas. Las c&#xE9;lulas del h&#xED;gado alteran los amino&#xE1;cidos digeridos del intestino delgado para que puedan usarse para producir energ&#xED;a o producir carbohidratos y grasas. Un subproducto de este proceso es una sustancia t&#xF3;xica llamada amon&#xED;aco, que luego el h&#xED;gado convierte en una sustancia mucho menos t&#xF3;xica llamada urea. Luego, la urea se libera en la sangre y se transporta a los ri&#xF1;ones, que la excretan del cuerpo a trav&#xE9;s de la orina.

Digestión de proteínas

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

Educación

JoVE Core

Biology

Biología

Genetics

Genética

Nutrition and Digestion

Nutrición y digestión

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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JoVE Core Biología da vida a la biología a través de una serie con más de 300 lecciones de vídeo animadas, concisas y fáciles de entender, que explican conceptos clave de la biología, incluyendo también más de 150 vídeos de científicos en acción, que muestran experimentos reales realizados en laboratorios actuales de investigación.

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.

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

Structural Organization of the Human Body: An Overview

It is convenient to consider the body&#39;s structures in terms of fundamental levels of organization that increase in complexity: subatomic particles, ...

Tissues

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1. Obtain, evaluate, and communicate information to explain how differences in cellular structure (mitochondria, cytoskeletal structure, endoplasmic reticulum, cell membrane) lead to differences in the function and organization of the four tissue types (epithelial, connective, muscular, and nervous).

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Cells of the Epidermis

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Dermis
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Layers of the Epidermis

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Accessory Structures of the Skin: Sweat Glands

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Accessory Structures of the Skin: Hair and Hair Follicles

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Accessory Structures of the Skin: Nails

Nails are one of the important accessory structures of the skin. They are hard, protective structures that cover the dorsal surface of the distal ...

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

9-12.HA.1.2

Thermoregulation

The body regulates core temperature through negative feedback mechanisms.
When the core temperature drops, thermoreceptors send signals to the ...

Defense Mechanism Against Infection

Natural flora, body system defenses, and inflammation are natural barriers of the body against infectious agents regardless of previous exposure. Normal ...

Surface Membrane Barriers

Surface barriers such as the skin and mucous membranes are the body&#39;s initial defense against pathogens, offering physical and chemical protection.
...

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

Introduction to the Skeletal System

The skeletal system is the central framework of the body, consisting of different connective tissues: bones, cartilage, tendons, and ligaments.
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

bone-formation-by-endochondral-ossification

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Bone formation, or ossification, begins around the sixth to seventh week of embryonic development. Most bones develop from a cartilaginous template ...

bone-formation-by-intramembranous-ossification

Bone Formation by Intramembranous Ossification

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 ...

Bone Remodeling and Repair

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

9-12.HA.1.3.a

The Functions of the Skeletal System

The most apparent functions of the skeletal system are support, protection, and movement. However, bone tissue also performs several other critical ...

Skeleton and Calcium Homeostasis

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The Bone Matrix

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Overview of Hematopoiesis

Hematopoiesis, or hemopoiesis, is the production of the formed elements in blood from common progenitors, called hematopoietic stem cells, or HSCs.
During ...

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

The Muscular System

The muscular system includes the skeletal, smooth, and cardiac muscles that coordinate with each other to carry out functions like movement, digestion, ...

Naming Skeletal Muscles

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

Muscle Coordination and Action

The skeletal muscles can coordinate, oppose, or assist each other to facilitate voluntary body movements.
Depending on their function, a muscle or group ...

Fascicle Arrangement in Skeletal Muscles

Fascicles are bundles of muscle fibers in a skeletal muscle. Muscle fascicle arrangement is directly associated with the power and range of motion of ...

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

Microscopic Anatomy of Skeletal Muscles

Each skeletal muscle is composed of multiple bundles of elongated multinucleated muscle cells or muscle fibers.
These cells are enclosed by a plasma ...

The Sarcomere

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excitation-contraction-coupling-in-skeletal-muscles

Excitation-Contraction Coupling in Skeletal Muscles

Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at ...

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions ...

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

Muscle Recovery and Fatigue

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As contractions become vigorous, the compressed blood vessels impair the ...

Muscle Stimulation Frequency

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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

Organization of the Nervous System

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Functional Divisions of the Nervous System

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Anatomy of the Brain: Major Regions

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Peripheral Nervous System: Ganglia and Nerves

The peripheral nervous system consists of nerves, ganglia, and sensory receptors.
Each nerve has an outermost connective tissue layer called the ...

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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Propagation of Action Potentials

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Action Potential: Phases of Stimulation

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Voltage-gated Ion Channels

a. Use a model to illustrate the role of action potentials in neural transmission. Clarification: Discussions of sodium-potassium pumps and ion channels are not required.

9-12.HA.1.5.a

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One of the ...

Reflex Activity

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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.

9-12.HA.1.5.b

Neurotransmitters

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Chemical Synapses

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The Synapse

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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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