Which macromolecules are polar

Proteins are a class of macromolecules that can perform a diverse range of functions for the cell. They help in metabolism by providing structural support and by acting as enzymes, carriers or as hormones. The building blocks of proteins are amino acids. Proteins are organized at four levels: primary, secondary, tertiary, and quaternary. Protein shape and function are intricately linked; any change in shape caused by changes in temperature, pH, or chemical exposure may lead to protein denaturation and a loss of function.

Nucleic acids are molecules made up of repeating units of nucleotides that direct cellular activities such as cell division and protein synthesis. Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. Explain what happens if even one amino acid is substituted for another in a polypeptide chain. Provide a specific example. Answer the question s below to see how well you understand the topics covered in the previous section.

Each of these four macromolecules of life, or biomolecules, performs a variety of duties; as you might expect, their different roles are exquisitely related to their various physical components and arrangements. A macromolecule is a very large molecule, usually consisting of repeated subunits called monomers , which cannot be reduced to simpler constituents without sacrificing the "building block" element.

While there is no standard definition of how large a molecule must be to earn the "macro" prefix, they generally have, at a minimum, thousands of atoms. You have almost certainly seen this kind of construction in the non-natural world; for example, many kinds of wallpaper, while elaborate in design and physically expansive on the whole, consist of adjoining subunits that are often less than a square foot or so in size.

Even more obviously, a chain can be regarded as a macromolecule in which the individual links are the "monomers. An important point about biological macromolecules is that, with the exception of lipids, their monomer units are polar, meaning that they have an electric charge that is not distributed symmetrically. Schematically, they have "heads" and "tails" with different physical and chemical properties.

Because the monomers join head-to-tail to each other, macromolecules themselves are also polar. Also, all biomolecules have high amounts of the element carbon.

You may have heard the kind of life on Earth in other words, the only kind we know for certain exists anywhere referred to as "carbon-based life," and with good reason.

But and nitrogen, oxygen, hydrogen, and phosphorus are indispensable to living things as well, and a host of other elements are in the mix to lesser degrees.

It is a near-certainty that when you see or hear the word "carbohydrate," the first thing you think of is "food," and perhaps more specifically, "something in food a lot of people are intent on getting rid of. But in fact, carbohydrates are far more than just a source of energy for living things. Carbohydrate molecules all have the formula CH 2 O n , where n is the number of carbon atoms present.

This means that the C:H:O ratio is For example, the simple sugars glucose, fructose and galactose all have the formula C 6 H 12 O 6 the atoms of these three molecules are, of course, arranged differently. Carbohydrates are classified as monosaccharides, disaccharides and polysaccharides. A monosaccharide is the monomer unit of carbohydrates, but some carbohydrates consist of only one monomer, such as glucose, fructose and galactose.

Usually, these monosaccharides are most stable in a ring form, which is depicted diagrammatically as a hexagon. Disaccharides are sugars with two monomeric units, or a pair of monosaccharides.

These subunits can be the same as in maltose, which consists of two joined glucose molecules or different as in sucrose, or table sugar, which consists of one glucose molecule and one fructose molecule.

Bonds between monosaccharides are called glycosidic bonds. Polysaccharides contain three or more monosaccharides. The longer these chains are, the more likely they are to have branches, that is, to not simply be a line of monosaccharides from end to end. Examples of polysaccharides include starch, glycogen, cellulose and chitin. Starch tends to form in a helix, or spiral shape; this is common in high-molecular-weight biomolecules in general.

Cellulose, in contrast, is linear, consisting of a long chain of glucose monomers with hydrogen bonds interspersed between carbon atoms at regular intervals.

Cellulose is a component of plant cells and gives them their rigidity. Humans cannot digest cellulose, and in the diet it is usually referred to as "fiber.

Chitin is a modified carbohydrate, as it is "adulterated" with ample nitrogen atoms. Glycogen is the body's storage form of carbohydrate; deposits of glycogen are found in both liver and muscle tissue. Starch is the stored form of sugars in plants and is made up of amylose and amylopectin both polymers of glucose. Plants are able to synthesize glucose, and the excess glucose is stored as starch in different plant parts, including roots and seeds.

The starch that is consumed by animals is broken down into smaller molecules, such as glucose. The cells can then absorb the glucose. Glycogen is the storage form of glucose in humans and other vertebrates, and is made up of monomers of glucose. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever glucose levels decrease, glycogen is broken down to release glucose. Cellulose is one of the most abundant natural biopolymers.

The cell walls of plants are mostly made of cellulose, which provides structural support to the cell. Wood and paper are mostly cellulosic in nature.

Cellulose is made up of glucose monomers that are linked by bonds between particular carbon atoms in the glucose molecule. Every other glucose monomer in cellulose is flipped over and packed tightly as extended long chains. This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Cellulose passing through our digestive system is called dietary fiber. While the glucose-glucose bonds in cellulose cannot be broken down by human digestive enzymes, herbivores such as cows, buffalos, and horses are able to digest grass that is rich in cellulose and use it as a food source.

In these animals, certain species of bacteria reside in the rumen part of the digestive system of herbivores and secrete the enzyme cellulase. The appendix also contains bacteria that break down cellulose, giving it an important role in the digestive systems of ruminants.

Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal. Carbohydrates serve other functions in different animals. Arthropods, such as insects, spiders, and crabs, have an outer skeleton, called the exoskeleton, which protects their internal body parts. This exoskeleton is made of the biological macromolecule chitin , which is a nitrogenous carbohydrate. It is made of repeating units of a modified sugar containing nitrogen. Thus, through differences in molecular structure, carbohydrates are able to serve the very different functions of energy storage starch and glycogen and structural support and protection cellulose and chitin.

Registered Dietitian: Obesity is a worldwide health concern, and many diseases, such as diabetes and heart disease, are becoming more prevalent because of obesity. This is one of the reasons why registered dietitians are increasingly sought after for advice. Registered dietitians help plan food and nutrition programs for individuals in various settings. They often work with patients in health-care facilities, designing nutrition plans to prevent and treat diseases.

For example, dietitians may teach a patient with diabetes how to manage blood-sugar levels by eating the correct types and amounts of carbohydrates. Dietitians may also work in nursing homes, schools, and private practices. In addition, registered dietitians must complete a supervised internship program and pass a national exam. Those who pursue careers in dietetics take courses in nutrition, chemistry, biochemistry, biology, microbiology, and human physiology.

Dietitians must become experts in the chemistry and functions of food proteins, carbohydrates, and fats. Lipids include a diverse group of compounds that are united by a common feature. This is because they are hydrocarbons that include only nonpolar carbon-carbon or carbon-hydrogen bonds. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of lipids called fats. Lipids also provide insulation from the environment for plants and animals. For example, they help keep aquatic birds and mammals dry because of their water-repelling nature.

Lipids are also the building blocks of many hormones and are an important constituent of the plasma membrane. Lipids include fats, oils, waxes, phospholipids, and steroids.

A fat molecule, such as a triglyceride, consists of two main components—glycerol and fatty acids. Glycerol is an organic compound with three carbon atoms, five hydrogen atoms, and three hydroxyl —OH groups. In a fat molecule, a fatty acid is attached to each of the three oxygen atoms in the —OH groups of the glycerol molecule with a covalent bond.

During this covalent bond formation, three water molecules are released. The three fatty acids in the fat may be similar or dissimilar. These fats are also called triglycerides because they have three fatty acids. Some fatty acids have common names that specify their origin.

For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogaea , the scientific name for peanuts.

Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated.

Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. When the hydrocarbon chain contains a double bond, the fatty acid is an unsaturated fatty acid. Most unsaturated fats are liquid at room temperature and are called oils.

If there is one double bond in the molecule, then it is known as a monounsaturated fat e. Saturated fats tend to get packed tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid contained in meat, and the fat with butyric acid contained in butter, are examples of saturated fats.

Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell. In plants, fat or oil is stored in seeds and is used as a source of energy during embryonic development.

Unsaturated fats or oils are usually of plant origin and contain unsaturated fatty acids. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats.

Unsaturated fats help to improve blood cholesterol levels, whereas saturated fats contribute to plaque formation in the arteries, which increases the risk of a heart attack. In the food industry, oils are artificially hydrogenated to make them semi-solid, leading to less spoilage and increased shelf life. Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis -conformation in the hydrocarbon chain may be converted to double bonds in the trans -conformation.

This forms a trans -fat from a cis -fat. The orientation of the double bonds affects the chemical properties of the fat. Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans -fats. Many fast food restaurants have recently eliminated the use of trans -fats, and U. Essential fatty acids are fatty acids that are required but not synthesized by the human body. Consequently, they must be supplemented through the diet.

Omega-3 fatty acids fall into this category and are one of only two known essential fatty acids for humans the other being omega-6 fatty acids. They are a type of polyunsaturated fat and are called omega-3 fatty acids because the third carbon from the end of the fatty acid participates in a double bond. Salmon, trout, and tuna are good sources of omega-3 fatty acids. Omega-3 fatty acids are important in brain function and normal growth and development.

They may also prevent heart disease and reduce the risk of cancer. Like carbohydrates, fats have received a lot of bad publicity. However, fats do have important functions. Fats serve as long-term energy storage. They also provide insulation for the body. Phospholipids are the major constituent of the plasma membrane. Like fats, they are composed of fatty acid chains attached to a glycerol or similar backbone. Instead of three fatty acids attached, however, there are two fatty acids and the third carbon of the glycerol backbone is bound to a phosphate group.

The phosphate group is modified by the addition of an alcohol. A phospholipid has both hydrophobic and hydrophilic regions. The fatty acid chains are hydrophobic and exclude themselves from water, whereas the phosphate is hydrophilic and interacts with water. Cells are surrounded by a membrane, which has a bilayer of phospholipids. The fatty acids of phospholipids face inside, away from water, whereas the phosphate group can face either the outside environment or the inside of the cell, which are both aqueous.

Unlike the phospholipids and fats discussed earlier, steroids have a ring structure. Although they do not resemble other lipids, they are grouped with them because they are also hydrophobic. All steroids have four, linked carbon rings and several of them, like cholesterol, have a short tail.

Cholesterol is a steroid. Cholesterol is mainly synthesized in the liver and is the precursor of many steroid hormones, such as testosterone and estradiol.

It is also the precursor of vitamins E and K. Cholesterol is the precursor of bile salts, which help in the breakdown of fats and their subsequent absorption by cells. Although cholesterol is often spoken of in negative terms, it is necessary for the proper functioning of the body. It is a key component of the plasma membranes of animal cells. 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. 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. 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. Major types include fats and oils, waxes, phospholipids, and steroids. Fats and oils are a stored form of energy and can include triglycerides. Fats and oils are usually made up of fatty acids and glycerol. Proteins are a class of macromolecules that can perform a diverse range of functions for the cell.

They help in metabolism by providing structural support and by acting as enzymes, carriers or as hormones. The building blocks of proteins are amino acids. Proteins are organized at four levels: primary, secondary, tertiary, and quaternary.

Protein shape and function are intricately linked; any change in shape caused by changes in temperature, pH, or chemical exposure may lead to protein denaturation and a loss of function. Nucleic acids are molecules made up of repeating units of nucleotides that direct cellular activities such as cell division and protein synthesis.

Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. Explain what happens if even one amino acid is substituted for another in a polypeptide chain. Provide a specific example. Ophardt, C. In Biological Chemistry. Gunawardena, G. Snell, Foster D. Review Questions: 1. What are the monomers that make up proteins called? Where is the linkage made that combines two amino acids?

The alpha-helix and the beta-pleated sheet are part of which protein structure? Which of the following may cause a protein to denature? Key Concepts and Summary Lipids are composed mainly of carbon and hydrogen, but they can also contain oxygen, nitrogen, sulfur, and phosphorous.

They provide nutrients for organisms, store carbon and energy, play structural roles in membranes, and function as hormones, pharmaceuticals, fragrances, and pigments. Fatty acids are long-chain hydrocarbons with a carboxylic acid functional group. Their relatively long nonpolar hydrocarbon chains make them hydrophobic. Fatty acids with no double bonds are saturated ; those with double bonds are unsaturated.

Fatty acids chemically bond to glycerol to form structurally essential lipids such as triglycerides and phospholipids. Triglycerides comprise three fatty acids bonded to glycerol, yielding a hydrophobic molecule. Phospholipids contain both hydrophobic hydrocarbon chains and polar head groups, making them amphipathic and capable of forming uniquely functional large scale structures. Biological membranes are large-scale structures based on phospholipid bilayers that provide hydrophilic exterior and interior surfaces suitable for aqueous environments, separated by an intervening hydrophobic layer.

These bilayers are the structural basis for cell membranes in most organisms, as well as subcellular components such as vesicles. Isoprenoids are lipids derived from isoprene molecules that have many physiological roles and a variety of commercial applications. A wax is a long-chain isoprenoid that is typically water resistant; an example of a wax-containing substance is sebum, produced by sebaceous glands in the skin.

Steroids are lipids with complex, ringed structures that function as structural components of cell membranes and as hormones.

Bacteria produce hopanoids, structurally similar to cholesterol, to strengthen bacterial membranes. Fungi and protozoa produce a strengthening agent called ergosterol. Multiple Choice Which of the following describes lipids? Critical Thinking Microorganisms can thrive under many different conditions, including high-temperature environments such as hot springs.

Short Answer Describe the structure of a typical phospholipid. Introduction Glyceraldehyde can exist in two isomeric forms that are mirror images of each other which are shown below. Introduction The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups. Di- and Poly-Carbohydrates Monosaccharides contain one sugar unit such as glucose , galactose , fructose , etc.

Disaccharides contain two sugar units. In almost all cases one of the sugars is glucose, with the other sugar being galactose, fructose, or another glucose.