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Proteins are one of four major macromolecule in living things. They are classified into specific groups based on their differing functions.

In the human body, proteins are responsible for carrying out most of the body's function. Our hair, fingernail, bones and muscle are all made of or by protein.

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Proteins are the workhorses of our bodies

Proteins make up about 42% of the dry weight of our bodies. The protein collagen-which holds our skin, tendons, muscles, and bones together-makes up about a quarter of the body's total protein.

All of our cells and even blood are packed with protein molecules. This watercolor painting by David S. Goodsell shows part of a red blood cell, in the upper left, filled with hemoglobin molecules. The right side of the painting shows blood serum, containing yellow, Y-shaped antibodies and other proteins. In purple, proteins poke through the blood cell's membrane.

Illustration by David S. Goodsell, The Scripps Research Institute. doi: 10.2210/rcsb_pdb/goodsell-gallery-003

A protein's three-dimensional shape is uniquely suited to its function. The 20 different amino acid building blocks can be arranged in different ways to form a nearly infinite assortment of protein shapes.

Different arrangements of amino acids can make proteins that are extremely strong, as in silk fibers, or flexible and elastic, as in the elastin in our skin. And like pieces of a jigsaw puzzle, proteins can interlock with other molecules. For example, each type of antibody in our blood has a unique arrangement of amino acids at its tips that can attach to a specific pathogen, marking it for destruction by the immune system.

Proteins need to physically interact with each other and with other molecules to do their work. These interactions might activate an enzyme, turn on a gene, or communicate a message from one cell to another.

Interactions between proteins depend not just on their shape but also on their chemical properties: positively and negatively charged amino acids are attracted to each other; hydrophobic residues cluster together, away from water. These physical properties allow proteins to interact in specific ways.

Multiple proteins can come together to build a molecular machine. In the proteasome shown above, proteins encoded by different genes come together to form a capsule where damaged and unneeded proteins are destroyed.

Cells are alive with motion, much of it driven by proteins. Many proteins are flexible and dynamic. Motor proteins, for example, bend and swing to literally walk across the cell's cytoskeleton. And when the neurotransmitter acetylcholine binds to its receptor, the entire protein molecule shifts, causing a hole to open up at its center. Sodium ions pass through the opening, starting a chain reaction that will fire a nerve signal across the brain.

Like us, plants and animals are made of proteins. When we eat them, we eat protein. High-protein foods such as beans, meat, fish, cheese, eggs, and nuts give us both energy and building blocks to grow and maintain a healthy body.

The proteins we eat are broken down into their individual amino acid building blocks. We reuse these amino acids to build new proteins.

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Proteins are the workhorses of our bodies Proteins make up about 42% of the dry weight of our bodies. The protein collagen-which holds our skin, tendons, muscles, and bones together-makes up about a quarter of the body's total protein. All of our cells and even blood are packed with protein molecules.

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The recipe of making proteins are found in segments of DNA called genes. Proteins are composed of chains of amino acids which are bonded covalently through a peptide bond. In total, there are 20 amino acids which make up one protein.

Amino acids are able to make up a variety of differing shapes. Due to the diverse arrangement of amino acid, the function of the protein is categorised based on its shape.

Chemically, an amino acid is composed of a central Carbon atom, with a carboxyl side group, amino side group, a Hydrogen atom and a 'R' group. The R group can be composed of anything, and it determines the amino acid's shape and properties.

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Proteins can be split into four different groups of organisation.

[Refer to Additional Resources on the right for visual representations]

Primary Structure
Consisting of a linear sequence, peptide bonds link amino acids into a long chain, thus creating a polypeptide chain.

Secondary Structure
Due to the polar attraction of peptide bonds, as a result hydrogen bonding occurs between C=O and N-H. Thus, the intermolecular force creates 2 possible shapes: a coil shapes alpha helix or a folded pleat beta pleated sheet.

Tertiary Structure
Tertiary structure involves the three-dimensional folding of a protein due to interactions of amino acid side chains. The tertiary structure shape is defined by the individual protein's hydrophobic effect. Polar hydrophilic group s will likely move towards the aqueous environment, whereas non-polar hydrophobic grou ps will clump together, standing as far away from aqueous solution.

Quaternary Structure
This structure consist of more than one polypeptide. Its visual representation looks like a clump of many tertiary structure.

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There is an incredible diverse type of proteins in the body. The body houses to more than tens of thousands of proteins, and each one has a differing function.

All these proteins are made of amino acid joined by peptide bonds. They all have the four levels of organization.

Catalyst: Catalytic proteins are large groups of proteins that speed up a biological reaction.

Transport: These proteins are responsible for transporting small molecules such as blood. Proteins residing in cell membrane transport molecules into or out of the cell.

Structural: Likes its name, these proteins provide structural support with its fibres. They give structure to bones, tendons, skin, hair, nails, claws and beaks.

Movement: This proteins gives organism the ability to move by muscle contraction, a process which requires the interactions between proteins actin and myosin.

Regulatory: This protein regulate cell activity. Proteins such as hormone carry signals between cells and regulate its activity. They also regulate cellular activity by altering genetic code.

Defence: Defensive proteins protect the body from diseases. Antibodies are proteins that fight against bacteria and viral infections.

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Functions Of Protein In The Body - How The Body Uses Proteins - Importance Of Protein

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In general, food products that provide proteins are red meat, seafood, eggs, beans and peas.

On a more specific chemical scale, examples include:
Catalyst - amylase, sucrase
Transport - hemoglobin, ion channel proteins
Structural - collagen, keratin
Movement - Myosin, actin
Regulatory - hormones, neurotransmitters
Defence - antibodies.

Enzymes
Many proteins are enzymes. An enzymes is a biological macromolecule that speed up the rate of a reaction. They do this by lowering the activation energy required for a reaction to take place.

Enzymes work by interacting with a substrate. Enzymes have indentations called an active side. During a reaction, the substrate fit into the enzyme, and the enzyme will adjust its active side to accommodate the substrate.

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More information on levels of organization

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More information on levels of organization

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primary secondary tertiary quaternary structure

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Protein Structure - Primary - Secondary - Tertiary - Quaternary - Structure of Protein

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This video looks into the different structures of proteins. We compare the structure of primary, secondary, tertiary and quaternary proteins. Diagrams are also included to help understand the key differences between these types of proteins at different levels.

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PROTEIN STRUCTURE -- OUTLINE. Retrieved from http://www.tusculum.edu/faculty/home/ivanlare/html/genetics/protein-master.html

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Lipids are one of four major macromolecule in living things. They are composed of carbon, hydrogen and oxygen.

Lipids are efficient for energy storage, thus they are known as the secondary source of long term energy after carbohydrate. In the human body, lipids are responsible for insulation against heat loss, cushioning major organs and make up cell membranes. In animals and plants, lipids provide water-repelling coat of furs, feathers, and leaves.

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Lipids are generally split into two categories, the first is glycerol, and the second is steroid.

[Refer to Additional Resources on the right for visual representations]

GLYCEROL

Triglyceride
Triglyceride are used for energy storage. It is composed of one glycerol and three fatty aci d. Fatty acids are made of a long hydrocarbon chain ending with an carboxyl group (C=O and OH). They can be either saturated or unsaturated. Saturated fatty acids have no double bond, whereas unsaturated fatty acids have one or more double bond.

The presence of double bonds affects the overall shape. Cis double bonds cause long hydrocarbons to bend at an angle, this causes a change in physical properties.

Phospholipids
Phospholipids is the main component of cell membranes. Similar to a triglyceride, this lipid is composed of one glycerol, 2 fatty acid, one phosphate group and one 'R' group. The R group determines the type of phospholipid. The "head" of a phospholipid is polar, making it hydrophilic, and the "tail" is non-polar, thus hydrophobic. Therefore, the opposing forces causes it to form a phospholipid bilayer in which the hydrophilic head faces the aqueous solution and the hydrophobic tails face in wards.

STEROIDS
Steroids are composed of four carbon rings attached to one another. Its function depends on the arrangement of atoms in the ring and the functional group attached.

Waxes
Waxes have a variety of different chemical structure, often with long carbon chains. They are normally solid in room temperature.

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Introduction

We sometimes talk about fat as if it were a malevolent substance bent on our dietary destruction. In reality, fats are elegant little molecules, each one made of three long hydrocarbon tails attached to a little coathanger-like molecule called glycerol. Like the other large biological molecules, they play essential roles in the biology of humans and other organisms. (Also, many recent dietary studies see sugar as causing a lot more health problems than fat!)

Fats are just one type of lipid, a category of molecules united by their inability to mix well with water. Lipids tend to be hydrophobic, nonpolar, and made up mostly of hydrocarbon chains, though there are some variations on this, which we'll explore below. The different varieties of lipids have different structures, and correspondingly diverse roles in organisms. For instance, lipids store energy, provide insulation, make up cell membranes, form water-repellent layers on leaves, and provide building blocks for hormones like testosterone.

Here, we'll look in greater detail at some of the most important types of lipids, including fats and oils, waxes, phospholipids, and steroids.

Fats and oils

A fat molecule consists of two kinds of parts: a glycerol backbone and three fatty acid tails. Glycerol is a small organic molecule with three hydroxyl (OH) groups, while a fatty acid consists of a long hydrocarbon chain attached to a carboxyl group. A typical fatty acid contains 12-18 carbons, though some may have as few as 4 or as many as 36.

To make a fat molecule, the hydroxyl groups on the glycerol backbone react with the carboxyl groups of fatty acids in a dehydration synthesis reaction. This yields a fat molecule with three fatty acid tails bound to the glycerol backbone via ester linkages (linkages containing an oxygen atom next to a carbonyl, or C=O, group). Triglycerides may contain three identical fatty acid tails, or three different fatty acid tails (with different lengths or patterns of double bonds).

Fat molecules are also called triacylglycerols, or, in bloodwork done by your doctor, triglycerides. In the human body, triglycerides are primarily stored in specialized fat cells, called adipocytes, which make up a tissue known as adipose tissue. While many fatty acids are found in fat molecules, some are also free in the body, and they are considered a type of lipid in their own right.

Saturated and unsaturated fatty acids

As shown in the example above, the three fatty acid tails of a triglyceride need not be identical to each other. Fatty acid chains may differ in length, as well as in their degree of unsaturation.

If there are only single bonds between neighboring carbons in the hydrocarbon chain, a fatty acid is said to be saturated. (The thing that fatty acids are saturated with is hydrogen; in a saturated fat, as many hydrogen atoms as possible are attached to the carbon skeleton.)

When the hydrocarbon chain has a double bond, the fatty acid is said to be unsaturated, as it now has fewer hydrogens. If there is just one double bond in a fatty acid, it's monounsaturated, while if there are multiple double bonds, it's polyunsaturated.

The double bonds in unsaturated fatty acids, like other types of double bonds, can exist in either a cis or a trans configuration. In the cis configuration, the two hydrogens associated with the bond are on the same side, while in a trans configuration, they are on opposite sides (see below). A cis double bond generates a kink or bend in the fatty acid, a feature that has important consequences for the behavior of fats.

Saturated fatty acids tails are straight, so fat molecules with fully saturated tails can pack tightly against one another. This tight packing results in fats that are solid at room temperature (have a relatively high melting point). For instance, most of the fat in butter is saturated fat.

In contrast, cis-unsaturated fatty acid tails are bent due to the cis double bond. This makes it hard for fat molecules with one or more cis- unsaturated fatty acid tails to pack tightly. So, fats with unsaturated tails tend to be liquid at room temperature (have a relatively low melting point) - they are what we commonly call oils. For instance, olive oil is mostly made up of unsaturated fats.

At this point, you may be noticing that I've left something out: I didn't say anything about unsaturated fats with trans double bonds in their fatty acid tails, or . Trans fats are rare in nature, but are readily produced in an industrial procedure called partial hydrogenation.

In this process, hydrogen gas is passed through oils (made mostly of cis-unsaturated fats), converting some - but not all - of the double bonds to single bonds. The goal of partial hydrogenation is to give the oils some of the desirable properties of saturated fats, such as solidity at room temperature, but an unintended consequence is that some of the cis double bonds change configuration and become trans double bonds. Trans-unsaturated fatty acids can pack more tightly and are more likely to be solid at room temperature. Some types of shortening, for example, contain a high fraction of trans fats.

Partial hydrogenation and trans fats might seem like a good way to get a butter-like substance at oil-like prices. Unfortunately, trans fats have turned out to have very negative effects on human health. Because of a strong link between trans fats and coronary heart disease, the U.S. Food and Drug Administration (FDA) recently issued a ban on trans fats in foods, with a three-year deadline for companies to remove trans fats from their products.

Omega fatty acids

Another class of fatty acids that deserves mention includes the omega-3 and omega-6 fatty acids. There are different types of omega-3 and omega-6 fatty acids, but all of them are made from two basic precursor forms: alpha-linolenic acid (ALA) for omega-3s and linoleic acid (LA) for omega-6s.

The human body needs these molecules (and their derivatives), but can't synthesize either ALA or LA itself. Accordingly, ALA and LA are classified as essential fatty acids and must be obtained from a person's diet. Some fish, such as salmon, and some seeds, such as chia and flax, are good sources of omega-3 fatty acids.

Omega-3 and omega-6 fatty acids have at least two cis-unsaturated bonds, which gives them a curved shape. ALA, shown below, is quite bent but isn't the most extreme example - DHA, an omega-3 fatty acid made from ALA by the formation of additional double bonds, has six cis-unsaturated bonds and is curled up almost in a circle!

Omega-3 and omega-6 fatty acids play a number of different roles in the body. They are precursors (starting material) for the synthesis of a number of important signaling molecules, including ones that regulate inflammation and mood. Omega-3 fatty acids in particular may reduce the risk of sudden death from heart attacks, decrease triglycerides in the blood, lower blood pressure, and prevent the formation of blood clots.

Role of fats

Fats have received a lot of bad publicity, and it's true that eating large amounts of fried foods and other "fatty" foods can lead to weight gain and cause health problems. However, fats are essential to the body and have a number of important functions.

For instance, many vitamins are fat-soluble, meaning that they must be associated with fat molecules in order to be effectively absorbed by the body. Fats also provide an efficient way to store energy over long time periods, since they contain over twice as much energy per gram as carbohydrates, and they additionally provide insulation for the body.

Like all the other large biological molecules, fats in the right amounts are necessary to keep your body (and the bodies of other organisms) functioning correctly.

Waxes are another biologically important category of lipids. Wax covers the feathers of some aquatic birds and the leaf surfaces of some plants, where its hydrophobic (water-repelling) properties prevent water from sticking to, or soaking into, the surface. This is why water beads up on the leaves of many plants, and why birds don't get soaked through when it rains.

Structurally speaking, waxes typically contain long fatty acid chains connected to alcohols by ester linkages, although waxes produced by plants often have plain hydrocarbons mixed in as well.

Phospholipids

What keeps the watery goo (cytosol) inside of your cells from spilling out? Cells are surrounded by a structure called the plasma membrane, which serves as a barrier between the inside of the cell and its surroundings.

Specialized lipids called phospholipids are major components of the plasma membrane. Like fats, they are typically composed of fatty acid chains attached to a backbone of glycerol. Instead having three fatty acid tails, however, phospholipids generally have just two, and the third carbon of the glycerol backbone is occupied by a modified phosphate group. Different phospholipids have different modifiers on the phosphate group, with choline (a nitrogen-containing compound) and serine (an amino acid) being common examples. Different modifiers give phospholipids different properties and roles in a cell.

A phospholipid is an amphipathic molecule, meaning it has a hydrophobic part and a hydrophilic part. The fatty acid chains are hydrophobic and do not interact with water, whereas the phosphate-containing group is hydrophilic (because of its charge) and interacts readily with water. In a membrane, phospholipids are arranged into a structure called a bilayer, with their phosphate heads facing the water and their tails pointing towards the inside (above). This organization prevents the hydrophobic tails from coming into contact with the water, making it a low-energy, stable arrangement.

If a drop of phospholipids is placed in water, it may spontaneously form a sphere-shaped structure known as a micelle, in which the hydrophilic phosphate heads face the outside and the fatty acids face the interior of this structure. Formation of micelle is an energetically favored because it sequesters the hydrophobic fatty acid tails, allowing the hydrophilic phosphate head group to instead interact with the surrounding water.

Steroids are another class of lipid molecules, identifiable by their structure of four fused rings. Although they do not resemble the other lipids structurally, steroids are included in lipid category because they are also hydrophobic and insoluble in water. All steroids have four linked carbon rings and several of them, like cholesterol, also have a short tail. Many steroids also have an -OH functional group attached at a particular site, as shown for cholesterol below; such steroids are also classified as alcohols, and are thus called sterols.

Cholesterol, the most common steroid, is mainly synthesized in the liver and is the precursor to many steroid hormones. These include the sex hormones testosterone and estradiol, which are secreted by the gonads (testes and ovaries). Cholesterol also serves as the starting material for other important molecules in the body, including vitamin D and bile acids, which aid in the digestion and absorption of fats from dietary sources. It's also a key component of cell membranes, altering their fluidity and dynamics.

Of course, cholesterol is also found in the bloodstream, and blood levels of cholesterol are what we often hear about at the doctor's office or in news reports. Cholesterol in the blood can have both protective effects (in its high-density, or HDL, form) and negative effects (in its low-density, or LDL, form) on cardiovascular health.

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Lipids (article) | Macromolecules | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Triglyceride
Triglycerides that are saturated are generally solids at room temperature. These lipids are responsible for storing long term energy - an energy source used after carbohydrates and it acts as a cushion which protects organs. They also provide insulation from heat loss.

Phospholipid
Phospholipids are the main components in cell membrane and they are important to the cell's ability to function. They function by changing their shape to accommodate any changes in cellular volume, and adapts to the physical constraints. They function by allowing small molecules like oxygen or hydrocarbons to pass through freely, and preventing larger molecules such as glucose or water to pass through.

Steroid
Cholesterol is a type of steroid present in the blood of animals. They are used to make essential molecules such as hormones, and bile acid to digest food. Hormones such as testosterone is produced to regulate sexual function, and helps in building bones and muscles. Estrogen is produced to regulate sexual function in females, and acts as a storage of fat.

Waxes
Waxes have a variety of functions. In plants, waxes coat the surface of leaves to prevent water from escaping and repels insects. In animals, waxes are present on skin, fur, feather, and the exoskeleton of insects. The wax in animals form protective layers.

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#2 Lipids & Their Functions | The BioChemistry Guide | 2014

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Sothern, M. (2018). What Are the Primary Functions of Phospholipids?. Retrieved from https://sciencing.com/primary-functions-phospholipids-7349125.html

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Triglyceride - lard, butter, vegetable oil, olive oil

Phospholipid - phosphatidylcholine

Steroid - cholesterol, estrogen, testosterone, anabolic steroid

Waxes -  earwax, beeswax, spermaceti

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Carbohydrate are one of four major macromolecule in living things. They are composed of carbon, hydrogen and oxygen with the general formula of (CH₂O)n, in which n represents the number of carbon atoms.

Due to the high ratio of hydroxyl group and carbonyl groups, most carbohydrate are polar molecules and many dissolve in water.

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Overview of carbohydrates, including structure and properties of monosaccharides, disaccharides, and polysaccharides.

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Monosaccharide
When the number of Carbon atoms are 3-7, the carbohydrate is addressed as a simple sugar. These are referred to as monosaccharides, mono meaning one, and saccharide meaning sugar.  Monosaccharide are a single carbon monomer structure. Its 3D shapes differs, and the arrangement of hydrogen atoms and hydroxyl groups are differing as well. Despite its identical chemical composition, the differing isomers which are created, causes it to be different from one another.

Disaccharide
When two monosaccharides conjoin, they form a disaccharide, in which 'di' means two. As a result of the covalent bond, a glycosidic linkage is formed between the hydroxyl group of each monomer.

Polysaccharide
When many monosaccharide are joined together, they form a polysaccharide, in which 'poly' means many. The different ways in which the units are conjoined result in different shapes, thus results in having different functions.

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Monosaccharides

Carbohydrates are the most abundant biomolecule on Earth. Living organisms use carbohydrates as accessible energy to fuel cellular reactions and for structural support inside cell walls. Cells attach carbohydrate molecules to proteins and lipids, modifying structures to enhance functionality. For example, small carbohydrate molecules bonded to lipids in cell membranes improve cell identification, cell signaling, and complex immune system responses. The carbohydrate monomers deoxyribose and ribose are integral parts of DNA and RNA molecules.

To recognize how carbohydrates function in living cells, we must understand their chemical structure. The structure of carbohydrates determines how energy is stored in carbohydrate bonds during photosynthesis and how breaking these bonds releases energy during cellular respiration.

Biomolecules meet specific structural criteria to be classified as carbohydrates. Simple carbohydrates are modifications of short hydrocarbon chains. Several hydroxyls and one carbonyl functional group modify these hydrocarbon chains to create a monosaccharide, the base unit of all carbohydrates.

Monosaccharides consist of a carbon chain of three or more carbon atoms containing a hydroxyl group attached to every carbon except one. The lone carbon atom is double-bonded to an oxygen atom, and this carbonyl group may be in any position along the carbon chain. Therefore, one oxygen atom and two hydrogen atoms are present for every carbon atom in a monosaccharide. Consequently, we can define monosaccharides as possessing the molecular formula (CH ₂O) n, where n equals the number of carbon atoms and must be greater than or equal to three.

Monosaccharides (Greek, meaning "single sugar") are simple sugars and are frequently named using the suffix -ose. Sugars with the carbonyl group attached to a carbon at the end of the chain are aldoses ("aldehyde sugar") such as glucose. When the carbonyl group is located anywhere other than the end of the carbon chain, the monosaccharide is a ketose ("ketone sugar") such as fructose.

Because the position of individual atoms within a sugar molecule varies, many monosaccharides are isomers of one another. For example, glucose and fructose share the molecular formula C ₆H ₁₂O ₆, but are structurally different. Differences between isomers are not always as readily apparent as in structural isomers like glucose and fructose. More subtle stereoisomers share the same order of covalent bonds between atoms, but differ in the three-dimensional positions of the atoms around one or more individual carbon atoms. For example, glucose and galactose are stereoisomers, and appear very similar in drawings. Small details such as whether an - OH extends from the right or left side of each carbon atom are extremely important to taste, chemical reactivity, and human health.

In crystalline form, the majority of monosaccharides are present in a "long chain" structure. In contrast, sugars dissolved in a solution, such as the fluid of a cell's interior, frequently convert into a "ring" structure. The molecular formula of a sugar is not affected by conversions from a long chain to a ring structure. The ring forms of sugars are the structures that react to form carbohydrate dimers and polymers.

Some monosaccharides are modified by cellular enzymes to enhance or change their cellular function. Although modified sugars do not meet the formal definition for carbohydrates, they are formed through small modifications to common monosaccharides. Deoxyribose, a key sugar component of all DNA molecules, is a "deoxy sugar." To form deoxyribose, the 5-carbon monosaccharide ribose is "deoxygenated," removing one specific hydroxyl group and replacing it with a hydrogen atom. In contrast, "amino sugars" are modified by the addition of a new functional group. In an amino sugar, one or more hydroxyl groups are replaced by nitrogen-containing functional groups. Amino sugars play important roles in the immune system, neuronal processing, and structural support.

Functional Groups of Carbohydrates

This activity tests your ability to identify all of the functional groups of monosaccharides in carbohydrates.

Carbohydrate Structure and Function

Carbohydrate monomers, short chains, and polymers perform important cellular functions to maintain life. The number and type of monosaccharides used, as well as the position of the bond between them, determines the three-dimensional structure of each carbohydrate. By recognizing the structural and functional differences between common carbohydrate monomers and polymers, we can better understand the roles carbohydrates play inside cells and in the human diet.

Cells build carbohydrate polymers by using energy to form glycosidic linkages, the bonds between monosaccharides. A dehydration synthesis reaction forms a bond between carbon atoms in two monosaccharides, sandwiching an oxygen atom between them and releasing a water molecule. A disaccharide forms when two monomers are joined. Sucrose (table sugar) is made by joining two specific monomers, glucose and fructose. Different monosaccharide pairs produce many of the common disaccharide sugars we associate with food, including sucrose, maltose (malt sugar, two glucose monomers) and lactose (milk sugar, glucose and galactose monomers).

Carbohydrate chains are extended by additional dehydration synthesis reactions, adding one monomer at a time to a growing chain. Short chains called oligosaccharides are frequently attached to lipids and proteins. These carbohydrate "tags" support immune system functions, participate in cell communication, and help attach cells to extracellular surfaces and other cells.

Carbohydrate chains with hundreds or more monosaccharide units are polysaccharides. Unlike shorter chains, carbohydrate polymers are frequently composed of a single type of monosaccharide unit. Differences in the structure and function of these polymers arise mainly from differences in the glycosidic linkage, rather than the presence of different monosaccharides. Glycosidic linkages involve covalent bonds from one carbon atom in each monosaccharide to a single oxygen atom between them. However, which carbon atoms participate in this covalent bond may be different in each carbohydrate molecule.

The most common polysaccharides are built solely with glucose monomers, while significant structural differences between these polysaccharides arise mainly from the position and number of the glycosidic linkages in each glucose unit. Although these bond differences appear insignificant at first glance, the functional effect of minor structural differences in each glycosidic linkage is enormous.

Building and Breaking Carbohydrates

This activity tests your ability to identify the reactants and products in carbohydrate synthesis and hydrolysis.

Polysaccharides

Polysaccharides, the "complex carbohydrates," play vital energy storage and structural roles in living organisms, making carbohydrates the most abundant biomolecules on Earth. Polysaccharides are excellent energy storage molecules because they are easily built and broken down by enzymes. Forming fairly compact structures, polysaccharides allow energy storage without the space required by a pool of free glucose monomers. Other polysaccharides form strong fibers that provide protection and structural support in both plants and animals.

With small differences in the bond between monomers, polymers can function as compact energy storage units in starch and glycogen or as strong, protective fibers in cellulose and chitin. Understanding the structure, synthesis, and breakdown of carbohydrate polymers provides a framework for understanding their function in living cells.

Animals, including humans, create glucose polymers called glycogen. The position of the glycosidic linkage between glucose monomers causes glycogen polymers to coil into spiral shapes. Glycogen polymers are significantly branched, with several monomers in the primary chain containing a second glycosidic linkage to a different glucose. The second attachment sites allow shorter glucose chains to branch away from the main chain, packing more glucose units into the compact coiled structure.

Although glycogen's structure allows humans and other animals to store energy in a relatively compact form, the polymer can be degraded rapidly. Animals initiate enzyme-driven hydrolysis reactions to break down glycogen when energy is needed. For quick access to energy, glycogen is stored primarily in two locations in humans, the liver for easy delivery into the bloodstream and muscles for direct use as needed.

Plants synthesize two types of polysaccharides, starch and cellulose. The glycosidic bonds between glucose units in plant starch are similar to those in animal glycogen. Accordingly, starch molecules are structurally similar, forming compact coils, and play a similar role in energy storage for plants. Unlike glycogen, starch molecules vary widely in the level of branching. Most plants form a mixture of starch polymers with little to no branching and polymers with extensive branching.

In addition to providing energy for the plants that synthesize them, starches serve as the main food source for many animals. Humans and other animals produce enzymes that degrade starch molecules into small fragments during digestion. In humans, this digestion begins in the mouth by an enzyme called amylase, which degrades starch polymers into disaccharides (maltose). To experience starch digestion yourself, try chewing an unsalted cracker for a long time. After a while, did the cracker begin to taste sweet? This is the formation of maltose disaccharides in your mouth as the starch is digested. Salt may disguise many other tastes, so this mini-experiment works best with unsalted crackers.

Plants synthesize a structural polysaccharide called cellulose. Although cellulose is made with glucose, the glycosidic linkages between glucose monomers are different from the bonds in glycogen and starch. This unique bond structure causes cellulose chains to form linear flat strands instead of coils. The flat cellulose strands are able to form tightly packed bundles. Strong and rigid fibers result as hydrogen bonds form between polar hydroxyl groups in the bundled polymers. Cellulose fibers provide structural support to plants. Without cellulose, flower stems and tree trunks could not maintain their rigid, straight height.

Structural differences between the glycosidic linkages in starch and cellulose affect animals' ability to digest plant foods. Enzymes such as amylase cannot break down cellulose polymers. Some animals, including cows and termites, digest cellulose by hosting special microorganisms in their digestive tracts that produce cellulose-degrading enzymes. However, humans and most animals do not make an enzyme capable of degrading cellulose, leaving cellulose fibers undigested as they pass through the body. Humans do exploit plant cellulose in non-dietary ways by processing trees, cotton, and other plants to make paper, clothing, and many other common materials. Humans also harvest large trees to build structures with the cellulose-rich lumber.

Some animals synthesize a special polysaccharide, chitin, which forms a protective exoskeleton shell. The glycosidic linkages in chitin are very similar to cellulose bonds, causing chitin to also form linear, well-packed sheets of strong fibers. Unlike cellulose, chitin is synthesized from a modified monosaccharide called an amino sugar. The chitin monomer is derived from glucose by replacing one hydroxyl group with a nitrogen-containing functional group. Interactions between the nitrogen-containing groups and the remaining hydroxyl groups in chitin's polymer structure make it extremely strong and rigid. Chitin provides protection and structural support for many living organisms, including forming the exoskeletons of shellfish and insects and the cell walls of fungi.

Carbohydrate Ring Toss

In this activity, you will classify characteristics of several major carbohydrates.

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Carbohydrates are the most abundant biomolecule on Earth. Living organisms use carbohydrates as accessible energy to fuel cellular reactions and for structural support inside cell walls. Cells attach carbohydrate molecules to proteins and lipids, modifying structures to enhance functionality. For example, small carbohydrate molecules bonded to lipids in cell membranes improve cell identification, cell signaling, and complex immune system responses.

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What are Proteins?. Retrieved from https://learn.genetics.utah.edu/content/basics/proteins/

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Monosaccharide
The function of monosaccharides serves as a major fuel for cells and raw materials for building molecules. They are the main provider of energy source for most living things.

Dissacharide
The body digest disaccharides in foods and breaks them into two individual sugar molecules. Similar to monosaccharides, they store energy.

Polysaccharide
Plants store glucose in the form of starch, and animal store glucose in the form of glycogen. These molecules store short-term energy usage, where in glucose is easily accessible by the cell. On the other hand cellulose, provide structural support for plant cell walls.

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Jeffrey Traister

Jeffrey Traister is a writer and filmmaker. For more than 25 years, he has covered nutrition and medicine for health-care companies and publishers, also producing digital video for websites, DVDs and commercials. Trained in digital filmmaking at The New School, Traister also holds a Master of Science in human nutrition and medicine from the Columbia University College of Physicians and Surgeons.

Disaccharides play important functions in the human diet. Also called double sugars, disaccharides are a type of carbohydrate that contains two sugar molecules called monosaccharides that are linked together in a compound. Your body digests disaccharides in foods and breaks them into the two individual sugar molecules that are then absorbed through your small intestine. Disaccharides differ by chemical structure and function. Consult your doctor about the function of disaccharides in your diet.

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Three disaccharides exist in the human diet. Lactose is naturally found in the milk of mammals and contains glucose and galactose. Sucrose is found in beets and sugar cane. Sucrose, also called table sugar, contains glucose and fructose. Maltose is a disaccharide that contains two molecules of glucose. Maltose forms during the breakdown of certain starches, such as barley, during food manufacturing. Glucose is the simple sugar cell that your body uses for energy. Your body normally converts galactose and fructose, also called fruit sugar, into glucose.

Lactose, also called milk sugar, is the nutritional source of energy for infants during nursing. Lactose makes milk tastes sweet and is an ingredient in many processed foods that contain dairy. Manufacturers add whey, a byproduct of dairy production that contains lactose, to certain food products, such as breads, cookies, cakes, doughnuts, breakfast bars and ice cream. Lactose requires you have an enzyme called lactase to digest the disaccharide. Many people are lactose intolerant and do not produce sufficient amounts of lactase to digest lactose, causing such symptoms as nausea, diarrhea, gas, abdominal cramps and bloating. You can take a lactase supplement to help you digest lactose and ameliorate the symptoms.

Sucrose is the disaccharide present most in the human diet. The function of sucrose is to sweeten foods for more taste appeal. Manufacturers add sucrose as a sweetener to candies, ice cream, cookies, cakes, breads, sauces, ketchup and canned goods. An advantage of using sucrose as a sweetener is that it is stable in both liquid and crystallized solid states.

Manufacturers replaced sucrose as a sweetener in many food and beverage products with high-fructose corn syrup, a sweetener that contains a mixture of glucose and high concentrations of fructose and is less costly than sucrose. However, high-fructose corn syrup increases abdominal fat and weight more than sucrose does, according to research by scientists at Princeton University that was published in "Pharmacology, Biochemistry and Behavior" in November 2010.

Maltose does not have a specific function in the body. Manufacturers convert maltose to a disaccharide sugar alcohol called maltilol for use as a bulk sweetener in powder and syrup and added to many sucrose-free and diabetic foods, including chocolates, chewing gum, bakery goods, candies, ice cream and jam. Your body slowly absorbs only 50 to 60 percent of maltilol, with the remainder excreted or fermented in the large intestine.

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Disaccharides play important functions in the human diet. Also called double sugars, disaccharides are a type of carbohydrate that contains two sugar molecules called monosaccharides that are linked together in a compound. Your body digests disaccharides in foods and breaks them into the two individual sugar molecules that are then absorbed through...

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All About Carbohydrates in 6 min! From a HighSchool Student - BIOLOGY | HD

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Monosaccharide
Examples of common monosaccharides include glucose, fructose and galactose. All three are composed of C₆H₁₂O₆, however, due to its differing isomers, the properties of each are different.

Glucose in the body is commonly referred to as blood sugar, because it is the first source of sugar that cells in the body uses.

Fructose is found in fruits, known as fruit sugar.

Galactose is sugar found in milk

Dissacharide
Examples of disaccharide are sucrose, lactose and maltose. These disaccharide are formed by combining two monosaccharide with a glycosidic linkage, in which two molecules are combined to produce a large product and water.

Sucrose is known as common table sugar, which is composed of glucose bonded with fructose.

Lactose are formed by combining galactose and glucose. Lactose is found in milk and other dairy product, Those who are lactose intolerant will react negatively to lactose and experience side effects after consuming such as diarrhoea or cramps.

Polysaccharide
Three common polysaccharides are cellulose, glycogen and starch. Plants store glucose in the form of starch, and animals store glucose in the form of glycogen. Cellulose provide structure to plant cell walls. Due to the glycosidic linkage, two possible results are produced. The alpha glucose and beta glucose.