Check All That Apply Dehydration synthesis reactions are required to synthesize polymers. Dehydration synthesis reactions are required to synthesize In dehydration synthesis, a hydrogen atom from one molecule joins with a hydroxyl group -OH from another molecule to form water, leaving two molecules bonded to the same oxygen Monosaccharides have a ratio of carbon: hydrogen: oxygen.
Glucose has the chemical formula of C 6 H 12 O 6. Following dehydration synthesis, the ratio is not exactly , although very close. This is because a water molecule has been Create an Account and Get the Solution.
Log into your existing Transtutors account. Have an account already? Click here to Login. No Account Yet? Click here to Sign Up. Waxes are made up of a hydrocarbon chain with an alcohol —OH group and a fatty acid. Examples of animal waxes include beeswax and lanolin. Plants also have waxes, such as the coating on their leaves, that helps prevent them from drying out. 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. They carry the genetic blueprint of a cell and carry instructions for the functioning of the cell.
DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. The other type of nucleic acid, RNA, is mostly involved in protein synthesis.
The DNA molecules never leave the nucleus, but instead use an RNA intermediary to communicate with the rest of the cell.
Other types of RNA are also involved in protein synthesis and its regulation. Each nucleotide is made up of three components: a nitrogenous base, a pentose five-carbon sugar, and a phosphate group. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to a phosphate group. DNA has a double-helical structure.
It is composed of two strands, or polymers, of nucleotides. The strands are formed with bonds between phosphate and sugar groups of adjacent nucleotides. The alternating sugar and phosphate groups lie on the outside of each strand, forming the backbone of the DNA.
The nitrogenous bases are stacked in the interior, like the steps of a staircase, and these bases pair; the pairs are bound to each other by hydrogen bonds. The bases pair in such a way that the distance between the backbones of the two strands is the same all along the molecule. The rule is that nucleotide A pairs with nucleotide T, and G with C, see section 9. Living things are carbon-based because carbon plays such a prominent role in the chemistry of living things.
The four covalent bonding positions of the carbon atom can give rise to a wide diversity of compounds with many functions, accounting for the importance of carbon in living things. Carbohydrates are a group of macromolecules that are a vital energy source for the cell, provide structural support to many organisms, and can be found on the surface of the cell as receptors or for cell recognition.
Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides, depending on the number of monomers in the molecule. Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Rather, the atoms within these proteins remain capable of making small movements. Even though proteins are considered macromolecules, they are too small to visualize, even with a microscope.
So, scientists must use indirect methods to figure out what they look like and how they are folded. The most common method used to study protein structures is X-ray crystallography. With this method, solid crystals of purified protein are placed in an X-ray beam, and the pattern of deflected X rays is used to predict the positions of the thousands of atoms within the protein crystal.
In theory, once their constituent amino acids are strung together, proteins attain their final shapes without any energy input. In reality, however, the cytoplasm is a crowded place, filled with many other macromolecules capable of interacting with a partially folded protein. Inappropriate associations with nearby proteins can interfere with proper folding and cause large aggregates of proteins to form in cells.
Cells therefore rely on so-called chaperone proteins to prevent these inappropriate associations with unintended folding partners. Chaperone proteins surround a protein during the folding process, sequestering the protein until folding is complete. For example, in bacteria, multiple molecules of the chaperone GroEL form a hollow chamber around proteins that are in the process of folding.
Molecules of a second chaperone, GroES, then form a lid over the chamber. Eukaryotes use different families of chaperone proteins, although they function in similar ways. Chaperone proteins are abundant in cells. These chaperones use energy from ATP to bind and release polypeptides as they go through the folding process.
Chaperones also assist in the refolding of proteins in cells. Folded proteins are actually fragile structures, which can easily denature, or unfold. Although many thousands of bonds hold proteins together, most of the bonds are noncovalent and fairly weak. Even under normal circumstances, a portion of all cellular proteins are unfolded. Increasing body temperature by only a few degrees can significantly increase the rate of unfolding. When this happens, repairing existing proteins using chaperones is much more efficient than synthesizing new ones.
Interestingly, cells synthesize additional chaperone proteins in response to "heat shock. All proteins bind to other molecules in order to complete their tasks, and the precise function of a protein depends on the way its exposed surfaces interact with those molecules. Proteins with related shapes tend to interact with certain molecules in similar ways, and these proteins are therefore considered a protein family. The proteins within a particular family tend to perform similar functions within the cell.
Proteins from the same family also often have long stretches of similar amino acid sequences within their primary structure. These stretches have been conserved through evolution and are vital to the catalytic function of the protein. For example, cell receptor proteins contain different amino acid sequences at their binding sites, which receive chemical signals from outside the cell, but they are more similar in amino acid sequences that interact with common intracellular signaling proteins.
Protein families may have many members, and they likely evolved from ancient gene duplications. These duplications led to modifications of protein functions and expanded the functional repertoire of organisms over time.
This page appears in the following eBook. Aa Aa Aa. Protein Structure. What Are Proteins Made Of? Figure 1: The relationship between amino acid side chains and protein conformation. The defining feature of an amino acid is its side chain at top, blue circle; below, all colored circles.
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