Hydrogen bonds between functional groups within the same molecule or between different molecules are important to the function of many macromolecules and help them to fold properly and maintain the appropriate shape needed to function correctly. Hydrogen bonds are also involved in various recognition processes, such as DNA complementary base pairing and the binding of an enzyme to its substrate. Biological macromolecules, the large molecules necessary for life, include carbohydrates, lipids, nucleic acids, and proteins.
Nutrients are the molecules that living organisms require for survival and growth but that animals and plants cannot synthesize themselves. Animals obtain nutrients by consuming food, while plants pull nutrients from soil. Sources of biological macromolecules : Foods such as bread, fruit, and cheese are rich sources of biological macromolecules.
Many critical nutrients are biological macromolecules. Staudinger was the first to propose that many large biological molecules are built by covalently linking smaller biological molecules together. Living organisms are made up of chemical building blocks : All organisms are composed of a variety of these biological macromolecules.
Biological macromolecules play a critical role in cell structure and function. Most but not all biological macromolecules are polymers, which are any molecules constructed by linking together many smaller molecules, called monomers. Typically all the monomers in a polymer tend to be the same, or at least very similar to each other, linked over and over again to build up the larger macromolecule.
These simple monomers can be linked in many different combinations to produce complex biological polymers, just as a few types of Lego blocks can build anything from a house to a car. Monomers and polymers : Many small monomer subunits combine to form this carbohydrate polymer.
Examples of these monomers and polymers can be found in the sugar you might put in your coffee or tea. Regular table sugar is the disaccharide sucrose a polymer , which is composed of the monosaccharides fructose and glucose which are monomers.
If we were to string many carbohydrate monomers together we could make a polysaccharide like starch. The molecule sucrose common table sugar : The carbohydrate monosaccharides fructose and glucose are joined to make the disaccharide sucrose.
Biological macromolecules all contain carbon in ring or chain form, which means they are classified as organic molecules. They usually also contain hydrogen and oxygen, as well as nitrogen and additional minor elements. Each of these types of macromolecules performs a wide array of important functions within the cell; a cell cannot perform its role within the body without many different types of these crucial molecules.
Because these biomolecules are typically large, we call them macromolecules. Many biologically relevant macromolecules are formed by linking together a great number of identical, or very similar, smaller organic molecules. The smaller molecules act as building blocks and are called monomers , and the macromolecules that result from their linkage are called polymers.
Cells and cell structures include four main groups of carbon-containing macromolecules: polysaccharides , proteins , lipids , and nucleic acids. The first three groups of molecules will be studied throughout this chapter. The biochemistry of nucleic acids will be discussed in Biochemistry of the Genome. Of the many possible ways that monomers may be combined to yield polymers, one common approach encountered in the formation of biological macromolecules is dehydration synthesis.
In this chemical reaction, monomer molecules bind end to end in a process that results in the formation of water molecules as a byproduct:. Figure 5 shows dehydration synthesis of glucose binding together to form maltose and a water molecule. Table 2 summarizes macromolecules and some of their functions. Figure 5. In this dehydration synthesis reaction, two molecules of glucose are linked together to form maltose.
In the process, a water molecule is formed. Which of the following is the name for molecules whose structures are nonsuperimposable mirror images? Two molecules containing the same types and numbers of atoms but different bonding sequences are called enantiomers. Skip to main content. Microbial Biochemistry. Search for:. Organic Molecules Learning Objectives Identify common elements and structures found in organic molecules Explain the concept of isomerism Identify examples of functional groups Describe the role of functional groups in synthesizing polymers.
Clinical Focus: Cristina, Part 1 Cristina is a year-old student who visited her doctor, complaining about an itchy skin rash.
What kinds of substances would you expect to find in a moisturizing cream? What physical or chemical properties of these substances would help alleviate itching and inflammation of the skin? Think about It Describe the most abundant elements in nature. What are the differences between organic and inorganic molecules? Think about It We say that life is carbon based. What makes carbon so suitable to be part of all the macromolecules of living organisms? Think about It What is the byproduct of a dehydration synthesis reaction?
Key Concepts and Summary The most abundant elements in cells are hydrogen, carbon, oxygen, nitrogen, phosphorus, and sulfur. Life is carbon based. Each carbon atom can bind to another one producing a carbon skeleton that can be straight, branched, or ring shaped. Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules.
Proteins may be structural, regulatory, contractile, or protective; they may serve in transport, storage, or membranes; or they may be toxins or enzymes. Each cell in a living system may contain thousands of different proteins, each with a unique function.
Their structures, like their functions, vary greatly. They are all, however, polymers of amino acids, arranged in a linear sequence. The functions of proteins are very diverse because there are 20 different chemically distinct amino acids that form long chains, and the amino acids can be in any order.
For example, proteins can function as enzymes or hormones. Enzymes , which are produced by living cells, are catalysts in biochemical reactions like digestion and are usually proteins.
Each enzyme is specific for the substrate a reactant that binds to an enzyme upon which it acts. Enzymes can function to break molecular bonds, to rearrange bonds, or to form new bonds.
An example of an enzyme is salivary amylase, which breaks down amylose, a component of starch. Hormones are chemical signaling molecules, usually proteins or steroids, secreted by an endocrine gland or group of endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction.
For example, insulin is a protein hormone that maintains blood glucose levels. Proteins have different shapes and molecular weights; some proteins are globular in shape whereas others are fibrous in nature. For example, hemoglobin is a globular protein, but collagen, found in our skin, is a fibrous protein. Protein shape is critical to its function. Changes in temperature, pH, and exposure to chemicals may lead to permanent changes in the shape of the protein, leading to a loss of function or denaturation to be discussed in more detail later.
All proteins are made up of different arrangements of the same 20 kinds of amino acids. Amino acids are the monomers that make up proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom bonded to an amino group —NH 2 , a carboxyl group —COOH , and a hydrogen atom. Every amino acid also has another variable atom or group of atoms bonded to the central carbon atom known as the R group.
The R group is the only difference in structure between the 20 amino acids; otherwise, the amino acids are identical. The chemical nature of the R group determines the chemical nature of the amino acid within its protein that is, whether it is acidic, basic, polar, or nonpolar. Each amino acid is attached to another amino acid by a covalent bond, known as a peptide bond, which is formed by a dehydration reaction. The carboxyl group of one amino acid and the amino group of a second amino acid combine, releasing a water molecule.
The resulting bond is the peptide bond. The products formed by such a linkage are called polypeptides. While the terms polypeptide and protein are sometimes used interchangeably, a polypeptide is technically a polymer of amino acids, whereas the term protein is used for a polypeptide or polypeptides that have combined together, have a distinct shape, and have a unique function.
The Evolutionary Significance of Cytochrome cCytochrome c is an important component of the molecular machinery that harvests energy from glucose. For example, scientists have determined that human cytochrome c contains amino acids. For each cytochrome c molecule that has been sequenced to date from different organisms, 37 of these amino acids appear in the same position in each cytochrome c.
This indicates that all of these organisms are descended from a common ancestor. On comparing the human and chimpanzee protein sequences, no sequence difference was found.
When human and rhesus monkey sequences were compared, a single difference was found in one amino acid. In contrast, human-to-yeast comparisons show a difference in 44 amino acids, suggesting that humans and chimpanzees have a more recent common ancestor than humans and the rhesus monkey, or humans and yeast.
As discussed earlier, the shape of a protein is critical to its function. To understand how the protein gets its final shape or conformation, we need to understand the four levels of protein structure: primary, secondary, tertiary, and quaternary.
The unique sequence and number of amino acids in a polypeptide chain is its primary structure. The unique sequence for every protein is ultimately determined by the gene that encodes the protein. Any change in the gene sequence may lead to a different amino acid being added to the polypeptide chain, causing a change in protein structure and function. What is most remarkable to consider is that a hemoglobin molecule is made up of two alpha chains and two beta chains that each consist of about amino acids.
The molecule, therefore, has about amino acids. The structural difference between a normal hemoglobin molecule and a sickle cell molecule—that dramatically decreases life expectancy in the affected individuals—is a single amino acid of the This can lead to a myriad of serious health problems, such as breathlessness, dizziness, headaches, and abdominal pain for those who have this disease.
Folding patterns resulting from interactions between the non-R group portions of amino acids give rise to the secondary structure of the protein.
Both structures are held in shape by hydrogen bonds. In the alpha helix, the bonds form between every fourth amino acid and cause a twist in the amino acid chain. The R groups are attached to the carbons, and extend above and below the folds of the pleat. The pleated segments align parallel to each other, and hydrogen bonds form between the same pairs of atoms on each of the aligned amino acids.
The unique three-dimensional structure of a polypeptide is known as its tertiary structure. This structure is caused by chemical interactions between various amino acids and regions of the polypeptide. Primarily, the interactions among R groups create the complex three-dimensional tertiary structure of a protein. There may be ionic bonds formed between R groups on different amino acids, or hydrogen bonding beyond that involved in the secondary structure. When protein folding takes place, the hydrophobic R groups of nonpolar amino acids lay in the interior of the protein, whereas the hydrophilic R groups lay on the outside.
The former types of interactions are also known as hydrophobic interactions. In nature, some proteins are formed from several polypeptides, also known as subunits, and the interaction of these subunits forms the quaternary structure. Weak interactions between the subunits help to stabilize the overall structure.
For example, hemoglobin is a combination of four polypeptide subunits. Each protein has its own unique sequence and shape held together by chemical interactions. If the protein is subject to changes in temperature, pH, or exposure to chemicals, the protein structure may change, losing its shape in what is known as denaturation as discussed earlier.
Denaturation is often reversible because the primary structure is preserved if the denaturing agent is removed, allowing the protein to resume its function. Sometimes denaturation is irreversible, leading to a loss of function. One example of protein denaturation can be seen when an egg is fried or boiled. The albumin protein in the liquid egg white is denatured when placed in a hot pan, changing from a clear substance to an opaque white substance.
Not all proteins are denatured at high temperatures; for instance, bacteria that survive in hot springs have proteins that are adapted to function at those temperatures. Nucleic acids are key macromolecules in the continuity of life. Many of these critical nutrients are biological macromolecules, or large molecules, necessary for life. These macromolecules polymers are built from different combinations of smaller organic molecules monomers.
What specific types of biological macromolecules do living things require? How are these molecules formed?
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