Name: protein building blocks and folding
Uploaded: 2023-04-30T10:34:00.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-1

What are Proteins?

Una proteína es una cadena de aminoácidos, compuestos que contienen grupos amina y carboxilo, junto con diferentes cadenas laterales denotadas como R, unidas a un carbono central.
Los aminoácidos están unidos a través de enlaces peptídicos covalentes, y la serie repetida de átomos a lo largo del núcleo se denomina columna vertebral polipeptídica.
La secuencia comienza en el extremo N, con un grupo amino libre, NH3<span style="color: rgb(0, 0, 0); font-family: Arial; font-size: 13px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-thickness: inicial; text-decoration-style: inicial; text-decoration-color: inicial; Pantalla: en línea !importante; flotación: ninguno;" >+, y termina con el extremo C, un grupo carboxilo libre, COO<span style="color: rgb(0, 0, 0); familia-fuente: Arial; tamaño de fuente: 13px; estilo-fuente: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; espaciado entre letras: normal; huérfanos: 2; text-align: izquierda; text-indent: 0px; text-transform: none; white-space: pre-wrap; viudas: 2; espaciado entre palabras: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-thickness: inicial; text-decoration-style: inicial; text-decoration-color: inicial; Pantalla: en línea !importante; flotación: ninguno;" >-.
Cada proteína es única, dependiendo del número de aminoácidos y sus cadenas laterales.
Hay 20 cadenas laterales diferentes, que se dividen en uno de cuatro grupos. Los aminoácidos ácidos, como los ácidos aspártico y glutámico, tienen cadenas laterales con un grupo carboxilo. Debido a esto, actúan como ácidos a pH fisiológico.
Los aminoácidos básicos tienen un grupo amino en su cadena lateral y actúan como bases.
Varios aminoácidos son polares pero no cargados. Tienden a ser hidrófilos y constituyen la parte exterior de una proteína plegada, donde son libres de interactuar con el medio acuoso.
Por último, un gran grupo de aminoácidos contiene cadenas laterales no polares. Pueden ser simples, como en la glicina, o complejos, como la prolina y el triptófano.

¿qué son las proteínas?

Las proteínas son polímeros de aminoácidos unidos entre sí mediante enlaces peptídicos. Las proteínas y los polipéptidos se utilizan indistintamente para referirse a largas cadenas de aminoácidos. Sin embargo, los polipéptidos tienen un peso molecular inferior a 10.000 daltons, mientras que las proteínas tienen un peso molecular mayor. Los polipéptidos con menos de 20 aminoácidos se denominan oligopéptidos o simplemente péptidos. Las interacciones entre las cadenas laterales de aminoácidos constituyentes de las proteínas las ayudan a plegarse en una estructura tridimensional estable llamada estructura nativa. La estructura nativa de una proteína es su forma funcionalmente activa.

Los residuos de aminoácidos son los componentes básicos de las proteínas

Un aminoácido es una molécula que contiene un grupo carboxilo (–COOH), un grupo amino (–NH2), una cadena lateral, llamada grupo R, y un átomo de hidrógeno unido al mismo átomo de carbono o al carbono α. Las propiedades químicas del grupo R determinan la estructura final de la proteína a medida que interactúan entre sí y con las moléculas de agua polares. Por ejemplo, el aminoácido más simple, la glicina, tiene un único átomo de hidrógeno como grupo R. Otros aminoácidos portan grupos R más complejos, de modo que pueden atraer o repeler el agua (hidrófilos o hidrófobos), portar una carga negativa (ácida) o positiva (básica) y formar enlaces de hidrógeno (polares).

La identidad de cada aminoácido también está determinada por su grupo R específico. El código genético eucariota especifica sólo 20 aminoácidos utilizados en la síntesis de proteínas de todos los aminoácidos conocidos. Cada uno de estos 20 aminoácidos está representado de forma única mediante abreviaturas que utilizan un código de tres letras (p. ej., Gly, Val, Pro) o de una letra (p. ej., G, V, P).

La síntesis de proteínas es una reacción de deshidratación.

Durante la síntesis de polipéptidos, se forman enlaces peptídicos covalentes entre el grupo amino (grupo –NH2) de un aminoácido y el grupo carboxilo (–COOH) del aminoácido adyacente mediante la eliminación de agua. La síntesis de proteínas es una reacción de deshidratación. El enlace covalente resultante es un enlace peptídico. El polipéptido recién formado consta de un grupo amino libre en un extremo, llamado extremo N, y un grupo carboxilo libre en el otro extremo, llamado extremo C. La secuencia de aminoácidos siempre se lee desde el extremo N al extremo C.

El pH del medio circundante determina la función química de los aminoácidos.

Los aminoácidos tienen un grupo básico y uno ácido. Por tanto, pueden actuar como base (receptor de iones de hidrógeno) o como ácido (donante de iones de hidrógeno). Sin embargo, sus propiedades químicas dependen del pH del medio circundante. A pH bajo (p. ej., pH 2), tanto el grupo carboxilo como el amino están protonados (–NH3, –COOH), por lo que el aminoácido actúa como una base. En un pH alcalino (p. ej., pH 13), tanto los grupos carboxilo como amino se desprotonan (–NH2, –COO-) y el aminoácido actuará como un ácido. A un pH neutro (es decir, en la mayoría de los entornos fisiológicos, ~pH 7,4), el grupo amino se protona (–NH3+) y el grupo carboxilo se desprotona (–COO-), dando lugar a un zwitterión, una molécula con dos carga positiva y negativa. Esta propiedad química de los aminoácidos en pH fisiológico les permite formar enlaces de hidrógeno con el entorno acuoso circundante y, por lo tanto, contribuye a estructuras proteicas más complejas.

Las proteínas muestran una enorme diversidad en su estructura, composición y, por tanto, en su función. Ayudan a proporcionar soporte estructural a la célula (p. ej., en forma de colágeno), ayudan en el movimiento celular (p. ej., en forma de proteínas actina y miosina en los músculos), ayudan a catalizar reacciones biológicas (como enzimas), transportan moléculas a través de la membrana celular (como canales) y defiende a los vertebrados contra los invasores (como anticuerpos).

¿Qué son las proteínas?

Las proteínas son polímeros de aminoácidos unidos entre sí por enlaces peptídicos. Las proteínas y los polipéptidos se utilizan indistintamente para referirse a largas cadenas de aminoácidos ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Protein Structure

Estructura de las proteínas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

protein building blocks and folding

Proteins are built from amino acids linked by peptide bonds. Long chains of amino acids are often called polypeptides, and the terms proteins and polypeptides are sometimes used the same way. In this context, polypeptides with a molecular weight below 10,000 daltons are called polypeptides, while proteins have a higher molecular weight. Very short chains with fewer than 20 amino acids are called peptides or oligopeptides.

Amino acids are the basic units of proteins. Each amino acid has a carboxyl group, an amino group, a hydrogen atom, and a side chain called the R-group attached to the same carbon, called the alpha-carbon. The R-group helps determine the amino acid’s identity and its chemical behavior. Some R-groups are hydrophilic or hydrophobic, some are acidic or basic, and some are polar and can form hydrogen bonds. Glycine is the simplest amino acid because its R-group is just a hydrogen atom. The eukaryotic genetic code uses 20 amino acids for protein synthesis, and each one has a three-letter code and a one-letter code.

Protein synthesis is a dehydration reaction. During polypeptide formation, the amino group of one amino acid reacts with the carboxyl group of the next amino acid. This reaction removes water and forms a covalent peptide bond. The growing chain has a free amino end called the N-terminus and a free carboxyl end called the C-terminus. Amino acid sequences are read from the N-terminus to the C-terminus.

The pH of the surrounding medium changes how amino acids behave chemically. At low pH, both the amino and carboxyl groups are protonated, so the amino acid acts as a base. At alkaline pH, both groups are deprotonated, and the amino acid acts as an acid. At about pH 7.4, which is close to most physiological conditions, amino acids exist as zwitterions. A zwitterion has both a positive and a negative charge. This helps amino acids form hydrogen bonds with water and supports more complex protein structures.

Proteins fold because the side chains of their amino acids interact with one another and with water. These interactions help create a stable three-dimensional native structure, which is the active form of the protein. Protein shape is closely tied to function. Proteins can provide structural support, as collagen does, help cells move, as actin and myosin do in muscles, speed up reactions as enzymes, move molecules across cell membranes as channels, and defend vertebrates against invaders as antibodies.

Protein Building Blocks and Folding

what are proteins?

Proteins are built from amino acids linked by peptide bonds. Long chains of amino acids are often called polypeptides, and the terms proteins and polypeptides are sometimes used the same way. In this context, polypeptides with a molecular weight below 10,000 daltons are called polypeptides, while proteins have a higher molecular weight. Very short chains with fewer than 20 amino acids are called peptides or oligopeptides. Amino acids are the basic units of proteins. Each amino acid has a...

protein organization

Protein Folding Levels and Bonds

Proteins are built from amino acids and folded into shapes that support many cell jobs. They help with DNA replication, molecular transport, catalysis, and structural support. Their function depends on how their amino acids are arranged and folded. Protein structure is organized in levels. The primary structure is the amino acid sequence in a polypeptide chain. Amino acids are joined by peptide bonds, and the chain has two ends: the amino terminus, or N-terminus, and the carboxyl terminus, or...

protein folding

How Amino Acid Sequence Shapes Proteins

Proteins get their shape from the order of amino acids in a polypeptide chain. After a protein is made, the chain folds into a three-dimensional form that is needed for it to work. The way amino acids interact with one another guides this folding. Protein structure matters because proteins do many jobs in cells. They can speed up chemical reactions, help with immune defense, store materials, carry substances, send cell signals, support movement, and provide structure. A protein usually works...

protein families

Protein Families and Superfamilies

Protein families and superfamilies group proteins with shared features. These groups help scientists organize proteins by common structure, function, or evolutionary history. The classification can show how related proteins are connected across different organisms. A protein family usually includes proteins that are closely related. A superfamily is a broader group that can include several families with more distant relationships. These categories help explain why some proteins share similar...

conservation of protein domains

Protein Domains Shared Across Proteins

Protein domains are shared structural and functional parts of proteins. A domain is a region that can often be found in more than one protein, even when the full proteins are different. This conservation means that a protein domain may keep a similar shape or role across related proteins. Because of that, scientists can compare proteins by looking for domains that stay the same. Conserved domains help reveal how proteins are related and how they may work. The topic of protein domain...

globular and fibrous proteins

Protein Shapes: Globular vs Fibrous

Proteins can have globular or fibrous shapes, and these shapes help explain how they work in the body. Globular proteins are compact and usually fold into rounded forms. Fibrous proteins are long, extended molecules that often provide support and structure. The shape of a protein is tied to its function. Globular proteins often take part in chemical jobs in cells, while fibrous proteins are better suited for strength and stability. These structural differences make the two groups easy to...

intrinsically disordered proteins

Flexible Protein Regions and Disorder

Intrinsically disordered proteins have flexible regions that do not settle into one fixed shape. Instead, these proteins can remain dynamic and change form as they move through the cell. This flexibility is an important part of their structure and function. Many proteins need a stable folded shape to work properly. Intrinsically disordered proteins are different because they may lack a single rigid structure under normal conditions. Their shifting shape can help them take part in cell...

protein complex assembly

Protein Complex Formation and Function

Protein complex formation explains how proteins join together to carry out specific jobs in cells. These groups are called protein complexes, and they can form in more than one way. Some complexes are homomeric, which means they contain the same kind of protein subunit. Others are heteromeric, which means they contain different protein subunits. The assembly process helps show how protein shape and subunit choice affect function. When proteins combine, the resulting complex can behave...

conjugated proteins

Conjugated Proteins and Their Bound Groups

Conjugated proteins are proteins that include a nonprotein part called a prosthetic group. This added group helps give the protein its full structure or function. The video explains how the protein part and the bound group work together. Several common types of conjugated proteins are named by the kind of group attached. Nucleoproteins contain nucleic acids. Glycoproteins contain carbohydrate groups, and lipoproteins contain lipid groups. Other examples include phosphoproteins, which have...

amyloid fibrils

Amyloid Fibrils and Protein Aggregation

Amyloid fibrils are protein aggregates with a very specific structure. They are made when proteins misfold and stick together in long, ordered fibers. This structure makes them different from many other protein clumps. Amyloid fibrils are important in biology because they are linked to protein aggregation. Protein aggregation means proteins build up into groups instead of staying properly folded and separate. In many cases, this process is associated with disease and abnormal cell function. <br...

key terms and concepts

Learn how amino acids join to form proteins, how peptide bonds work, and how pH and side-chain interactions shape protein structure and function.

Protein Building Blocks and Folding | JoVE K12

cell biology

JoVE Core Biología Celular ilustra procesos celulares complejos mediante completos vídeos animados fáciles de entender. Esta colección se centra en los componentes esenciales de las células y su funcionamiento, incluyendo los orgánulos y las membranas, el transporte celular y el metabolismo energético celular. Todo este material se complementa con los vídeos de científicos en acción, que muestran la aplicación de la biología celular en experimentos reales de investigación.

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Proteins: From Genes to Degradation

Amyloid Fibrils

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protein-complexes-with-interchangeable-parts

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Structural Protein Function

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Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

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Homeostatic Imbalance

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pH Homeostasis

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HS-LS1-3

Protein Building Blocks and Folding

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