Question

What are proteins? Are proteins polymers? Explain. What molar mass ranges are shown by proteins? What fraction of our bodies is made up of proteins?

Short answer

Proteins are large, complex molecules that play critical roles in the body and are made up of amino acids. They are considered natural polymers as they are made up of amino acid monomers linked together by peptide bonds. The molar mass of proteins can range from approximately 5,000 g/mol to over 1,000,000 g/mol, depending on the size and composition. In the human body, proteins make up about 15% to 20% of the body mass and are the major solid constituent of cells. They are present in various body parts and play key roles in body functions, such as enzymes and antibodies.

Step-by-step solution

Definition of Proteins

Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body's tissues and organs. They are made up of hundreds or thousands of smaller units called amino acids, which are attached in long chains. Hence they are also known as polypeptides.

Proteins as Polymers

A polymer is a large molecule that is made up of repeating subunits linked together by covalent bonds. The small subunits that make up a polymer are called monomers. Given that proteins are built up from amino acid monomers linked together by peptide bonds, they can indeed be classified as polymers. Hence, proteins are considered to be natural polymers.

Molar Mass of Proteins

The molar mass of proteins varies widely. Proteins differ in size, comprising anywhere from 50 to several thousand amino acid residues. Consequently, their molar masses can range from approximately 5,000 g/mol for small proteins to over 1,000,000 g/mol for large protein complexes.

Fraction of Proteins in the Human Body

In the human body, depending on water content, proteins make up about 15% to 20% of the body mass. In fact, proteins are the major solid constituent of cells. They are present in every part of the body including, muscles, skin, hair, and other body parts. They also play key roles in various body functions, such as enzymes in metabolism and antibodies in the immune response.

Key concepts

Polymers

Polymers are giant molecules composed of numerous repeating units called monomers. These monomers are connected by covalent bonds, forming extensive chains that give polymers their unique properties. The concept of polymers encompasses both synthetic materials, like plastics, and natural ones, such as DNA and proteins.

Proteins fit into the category of natural polymers because they are made up of amino acids, which serve as their monomers. These amino acids join together in chains through peptide bonds, creating long strands or structures called polypeptides. Hence, the classification of proteins as polymers is well-founded, recognizing their complex yet repetitive nature.

• Made up of monomers
• Connected by covalent bonds
• Can be synthetic or natural
• Proteins are natural polymers

Amino Acids

Amino acids are the fundamental building blocks of proteins. There are 20 different amino acids that combine in various sequences to form almost endless possibilities of proteins, each with unique functions and structures. Each amino acid has a central carbon atom connected to four distinct groups: a hydrogen atom, a carboxyl group (-COOH), an amino group (-NH2), and a distinctive side chain, known as an R group.

The sequence and type of these amino acids determine a protein's three-dimensional structure and its specific function within the body. For instance, certain side chains make an amino acid hydrophobic or hydrophilic, influencing the protein's overall shape and solubility.

• 20 different amino acids
• Structure: Central carbon, hydrogen, carboxyl, amino, R-group
• Determine protein's shape and function
• Sequence matters

Molar Mass

The molar mass of proteins, which reflects the mass of one mole of protein molecules, can vary greatly. This variance is due to the diverse number of amino acids that comprise different proteins. Small proteins might only have a molar mass of a few thousand grams per mole, typically around 5,000 g/mol. In contrast, large proteins, or protein complexes, can have molar masses exceeding 1,000,000 g/mol.

The variability in size is due to the number of amino acid residues present, from as few as fifty to several thousand per protein. This range of molar masses highlights the vast diversity and specialization possible in protein function and structure.

• Reflects mass of one mole of protein
• Varies greatly depending on amino acid number
• Small: ~5,000 g/mol
• Large: over 1,000,000 g/mol

Human Body Composition

The human body is remarkably composed of various elements and compounds that come together to make life possible. One of the crucial components of this composition is protein, which constitutes about 15% to 20% of the body's mass. Proteins are the main solids found throughout the body, present in muscle tissue, skin, hair, and various organs.

Their roles are essential, performing functions such as forming enzymes to drive metabolic processes, and creating antibodies for immune defense. The diversity and abundance of proteins in the human body underscore their vital role in maintaining health and facilitating bodily functions.

• Proteins make up 15%-20% of body mass
• Present in muscles, skin, and organs
• Essential for bodily functions
• Provide structure and perform important roles