If we were to string many carbohydrate monomers together we could make a polysaccharide like starch. 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.
All the molecules both inside and outside of cells are situated in a water-based i. Boundless vets and curates high-quality, openly licensed content from around the Internet.
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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. Because fat is the most calorie dense food and having a storable, high calorie compact energy source would be important to survival.
The nature of its fat also made it an important trade good. Like salmon, ooligan returns to its birth stream after years at sea. Its arrival in the early spring made it the first fresh food of the year. As you learned above all fats are hydrophobic water hating. To isolate the fat, the fish is boiled and the floating fat skimmed off. Importantly it is a solid grease at room temperature. Because it is low in polyunsaturated fats which oxidize and spoil quickly it can be stored for later use and used as a trade item.
Its composition is said to make it as healthy as olive oil, or better as it has omega 3 fatty acids that reduce risk for diabetes and stroke. It also is rich in three fat soluble vitamins A, E and K.
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. When two monosaccharides are linked together, they form disaccharides.
For example, sucrose is composed of glucose and fructose, whereas lactose contains glucose and galactose. These monosaccharides and disaccharides are used for short-term energy storage in living organisms.
Maltose is another disaccharide that is made up of two glucose molecules and is usually formed when polysaccharide chains such as starch and glycogen are broken down during digestion.
Starch is a polysaccharide that serves as an energy storage molecule in plants and is made up of two types of glucose polymers: amylose and amylopectin. Amylopectin makes up the bulk of the starch and is a branched polymer of glucose. Glycogen is virtually the same as starch, however it is synthesized, stored and used in animal liver and muscle tissues. Besides serving as energy stores, carbohydrates also have other functions in organisms.
The five-carbon monosaccharides, ribose and deoxyribose, are integrated into the nucleic acid structure and are present in every living cell. Moreover, the polysaccharide cellulose, which is a long polymer made up of glucose, serves as a rigid structural material in plants. Humans do not have digestive enzymes to break down cellulose in food, which is also called dietary fiber. However, dietary fiber consumption helps to maintain a healthy gut flora, which in turn contributes to the health of digestive and immune systems 1.
Similar to plants, some animals and fungi use another polysaccharide, chitin, as a structural molecule. Arthropods use chitin to build and maintain their exoskeletons, whereas fungi incorporate it into their cell walls to maintain rigidity.
The second class of biological macromolecules are lipids, which include fats, oils, and waxes. Lipids are hydrophobic molecules that are almost entirely made up of carbon and hydrogen atoms. Often, lipids are grouped in three major categories; triglycerides, phospholipids, and steroids.
The most common type of lipid is triglycerides, which include fats from animals and oils from plants. Triglycerides generally serve as long-term energy storage molecules, except indigestible waxes, which are instead used as a waterproofing substance in both plants and animals. Triglycerides contain three fatty acid chains, which can be either saturated or unsaturated, connected to a glycerol molecule.
Saturated fatty acid chains are linear molecules with a maximum number of hydrogen atoms, where every carbon in the chain is connected via a single bond. On the other hand, unsaturated fatty acid chains have kinks due to the presence of at least one double bond.
While trans fats occur naturally, they are generated during industrial production of saturated vegetable oils with hydrogen. Similar to saturated fatty acids, trans fats stack very well due to their relative linearity. However, trans fats cause problems for human heart health, such as the damaging the lining of arteries and causing inflammation when digested 2. Phospholipids are similar to triglycerides, however, one of the fatty acid chains is replaced with a phosphate-containing polar group.
Therefore, phospholipids have a hydrophilic head and two hydrophobic fatty acid tails. These properties of phospholipids are crucial to the cell membrane structure and function. Steroids are lipids that are composed of fused carbon rings with varying functional groups.
Cholesterol is a steroid that is also a cell membrane component. Moreover, cholesterol is used to synthesize other steroids, including sex hormones such as estrogen and testosterone. Although cholesterol is essential for cell membrane structure and hormone synthesis, high levels of plasma cholesterol are implicated in plaque accumulation inside blood vessels and causing coronary disease 3. The third class of biological macromolecules are proteins, which are made up of chains of amino acids.
These groups link together, N-terminal to C-terminal, in a chain connected by peptide bonds. Proteins are important for maintaining body functions as enzymes, hormones, structural components and transport molecules, and play vital roles in muscle contractibility, immunity and blood clotting. However, issues can arise in protein structure and function, and these issues are often genetic.
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