Like all the other biomolecules, carbohydrates are often built into long chains by stringing together smaller units. This works like adding beads to a bracelet to make it longer. The general term for a single unit or bead is a monomer. The term for a long string of monomers is a polymer. Examples of carbohydrates include the sugars found in milk lactose and table sugar sucrose. Depicted below is the structure of the monomer sugar glucose, a major source of energy for our body.
Sphere Stick Surface Rotate. Carbohydrates have several functions in cells. They are an excellent source of energy for the many different activities going on in our cells.
Some carbohydrates may have a structural function. For example, the material that makes plants stand tall and gives wood its tough properties is a polymer form of glucose known as cellulose. Other types of sugar polymers make up the stored forms of energy known as starch and glycogen.
Starch is found in plant products such as potatoes and glycogen is found in animals. A short molecule of glycogen is shown below. You can manipulate the molecule yourself to take a good look. Stick Line Space-Filling Rotate. Carbohydrates are essential for cells to communicate with each other. They also help cells adhere to each other and the material surrounding the cells in the body. The ability of the body to defend itself against invading microbes and the removal of foreign material from the body such as the capture of dust and pollen by the mucus in our nose and throat is also dependent on the properties of carbohydrates.
Learn more about how Dr. Michael Pierce is using carbohydrates to investigate cancer. Like the carbohydrates, proteins are composed of smaller units. The monomers that make up proteins are called amino acids. There are around twenty different amino acids. The structure of the simplest amino acid , glycine, is shown below. Sphere Stick Rotate. The term lipid refers to a wide variety of biomolecules including fats, oils, waxes and steroid hormones.
The largest group of amino acids have nonpolar side chains. Several other amino acids have side chains with positive or negative charges, while others have polar but uncharged side chains. The chemistry of amino acid side chains is critical to protein structure because these side chains can bond with one another to hold a length of protein in a certain shape or conformation.
Charged amino acid side chains can form ionic bonds, and polar amino acids are capable of forming hydrogen bonds. Hydrophobic side chains interact with each other via weak van der Waals interactions. The vast majority of bonds formed by these side chains are noncovalent.
In fact, cysteines are the only amino acids capable of forming covalent bonds, which they do with their particular side chains. Because of side chain interactions, the sequence and location of amino acids in a particular protein guides where the bends and folds occur in that protein Figure 1.
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. When connected together by a series of peptide bonds, amino acids form a polypeptide, another word for protein. The polypeptide will then fold into a specific conformation depending on the interactions dashed lines between its amino acid side chains.
Figure Detail. Figure 2: The structure of the protein bacteriorhodopsin Bacteriorhodopsin is a membrane protein in bacteria that acts as a proton pump. Its conformation is essential to its function. The overall structure of the protein includes both alpha helices green and beta sheets red. The primary structure of a protein — its amino acid sequence — drives the folding and intramolecular bonding of the linear amino acid chain, which ultimately determines the protein's unique three-dimensional shape.
Hydrogen bonding between amino groups and carboxyl groups in neighboring regions of the protein chain sometimes causes certain patterns of folding to occur. Known as alpha helices and beta sheets , these stable folding patterns make up the secondary structure of a protein. Most proteins contain multiple helices and sheets, in addition to other less common patterns Figure 2.
The ensemble of formations and folds in a single linear chain of amino acids — sometimes called a polypeptide — constitutes the tertiary structure of a protein. Finally, the quaternary structure of a protein refers to those macromolecules with multiple polypeptide chains or subunits. The final shape adopted by a newly synthesized protein is typically the most energetically favorable one. As proteins fold, they test a variety of conformations before reaching their final form, which is unique and compact.
Folded proteins are stabilized by thousands of noncovalent bonds between amino acids. In addition, chemical forces between a protein and its immediate environment contribute to protein shape and stability.
For example, the proteins that are dissolved in the cell cytoplasm have hydrophilic water-loving chemical groups on their surfaces, whereas their hydrophobic water-averse elements tend to be tucked inside. In contrast, the proteins that are inserted into the cell membranes display some hydrophobic chemical groups on their surface, specifically in those regions where the protein surface is exposed to membrane lipids. 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. 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. For example, proteins are composed of monomers called amino acids. They are linked together to form a polypeptide chain, which folds into a three dimensional 3D structure to constitute a functional protein Figure 1.
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