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Cellulose - why is it fibrous and not granular?

Cellulose - why is it fibrous and not granular?



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I was reading a book where it said that the 1 - 4 Glycosidic bond of the Beta Glucose meant that cellulose isfibrousand notgranular.

First, what does it mean to begranularand why is notgranularunlike Amylose?

Thanks, Dave.


Cool I got something right :D

Cellulose is a linear polymer and therefore makes a fiber. I guess the linear in this case implies fiber. Amylose has a helical structure to it i think. Here is an image I found that shows the difference.


Microcrystalline Cellulose: Benefits, Side Effects & Dosage

Microcrystalline cellulose (MCC) is non-digestible plant matter in sources like wood pulp and tough plant stalks. These plants are harvested, cleaned and ground to create a fine, white powder. It is called “microcrystalline” because its tiny crystals can only be viewed under a microscope. Microcrystalline cellulose is a common addition to products not for nutritional value, but for various other purposes. And as strange as it may seem to add ground wood pulp to foods or pharmaceuticals, it is safe and legal.

You may find microcrystalline cellulose on ingredient lists under the names powdered cellulose, MCC, cellulose gum or carboxymethylcellulose. Microcrystalline cellulose is often present in supplements, pharmaceuticals and packaged foods, and its unique properties are used for a variety of reasons (x).

Where Does Microcrystalline Cellulose Come From?

Some people are unsure about the thought of having “wood pulp” in food. However, microcrystalline cellulose is not created from recycled industrial pallets. In fact, MCC is carefully processed cellulose from wood or other tough plant parts such as sorghum, cotton linen or hemp (x, x).


Cellulose is considered insoluble because it does not bind with water nor change form in the digestive tract. Another type of fiber, called soluble fiber, does bind with water and become a gel-like substance -- that type of fiber serves different purposes in your body. Because insoluble fiber travels through your digestive system unchanged, it helps move waste through your digestive tract, which prevents constipation.

Insoluble fiber is the type primarily responsible for preventing diverticular disease, a condition characterized by the development of pockets called diverticula along the colon wall. According to the Harvard School of Public Health website, diverticular disease is one of the most prevalent age-related conditions that affects the colon in Western society. Diverticulitis occurs when the diverticula become infected and inflamed. Diverticular disease is more common in people who don't eat enough fiber, according to the American Society of Colon & Rectal Surgeons website.


What is Cellulose

Cellulose is the polysaccharide which is made up of hundred to many thousands of glucose units. It is the major component of the cell wall of plants. Many algae and oomycetes also use cellulose to form their cell wall. Cellulose is a straight chain polymer in which 1,4-beta glycosidic bonds are formed between glucose molecules. Hydrogen bonds are formed between multiple hydroxyl groups of one chain with neighboring chains. This allows the two chains to be held together firmly. Likewise, several cellulose chains are involved in the formation of cellulose fibers. A cellulose fiber, which is made up of three cellulose chains, is shown in figure 2. Hydrogen bonds between cellulose chains are shown in cyan color lines.

Figure 2: A cellulose fiber


Classification of Polysaccharides

Ø Some polysaccharides are linear chains (Cellulose), while others are branched (Glycogen, Starch). Starch, Glycogen and Cellulose consist of monosaccharide unit – D-glucose. The term Glycans is used to denote polymers of medium to high sized carbohydrates.

Ø Polysaccharides differ in:

$ Composition (monomer units)

Ø Polysaccharides can be divided into TWO classes based on its function:

$ Storage polysaccharides (Starch in plants, Glycogen in animals)

$ Structural polysaccharides (Cellulose in plants, Chitin in insects)

Ø Polysaccharides are divided into two groups based on composition:

$ Homo-polysaccharides (single type of monomer)

$ Hetero-polysaccharides (different type monomers)

Ø Storage polysaccharides are usually homo-polysaccharides.

Ø Structural polysaccharides include both homo- & hetero-polysaccharides.

Ø Hetero-polysaccharides provide extracellular support to the organisms of all kingdoms

Ø Polysaccharides are synthesized enzymatically by the cells.

Ø Unlike proteins, polysaccharides generally do not have definite molecular weights.

Ø Proteins are synthesized on a template (messenger RNA) of defined sequence and length, by enzymes that follow the template exactly.

Ø There is NO template for the synthesis of polysaccharides in the cell.

Ø Thus, there is NO specific stopping point in the biosynthesis process hence, the size of polysaccharide greatly varies.


What is Cellulose

Cellulose was first revealed by the French chemist Anselme Payen in 1838 Payen isolated it from plant matter and determined its chemical formula. It is a structural polysaccharide where D-glucose units are joined to each other in order to form this structure. A large number of glucose molecules such as 3000 or more than that can participate in developing a cellulose molecule. In cellulose, glucose molecules are linked together by β (1→4) glycosidic bonds, and it does not branch. Thus, it is a straight chain polymer. Furthermore, as a result of the hydrogen bonds between glucose molecules, it can develop a very rigid structure. It is not soluble in water. It is plentiful in the cell walls of green plants and in algae and thereby giving strength, rigidity, firmness and shape to plant cells. Cellulose in the cell wall is permeable to any constituent thus, it allow passing constituents in or/and out of the cell. Cellulose is considered as the most common and abundant carbohydrate on earth. It is also used to create paper, biofuels, and other useful byproducts.

Cotton fibers represent the purest natural form of cellulose


4.1: Carbohydrates

Carbohydrates are one of the four main classes of macromolecules that make up all cells and are an essential part of our diet grains, fruits, and vegetables are all natural sources. While we may be most familiar with the role carbohydrates play in nutrition, they also have a variety of other essential functions in humans, animals, plants, and bacteria. In this section, we will discuss and review basic concepts of carbohydrate structure and nomenclature, as well as a variety of functions they play in cells.

Molecular structures

In their simplest form, carbohydrates can be represented by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule. For simple carbohydrates, the ratio of carbon-to-hydrogen-to-oxygen in the molecule is 1:2:1. This formula also explains the origin of the term &ldquocarbohydrate&rdquo: the components are carbon (&ldquocarbo&rdquo) and the components of water (&ldquohydrate&rdquo). Simple carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides, which will be discussed below. While simple carbohydrates fall nicely into this 1:2:1 ratio, carbohydrates can also be structurally more complex. For example, many carbohydrates contain functional groups (remember them from our basic discussion about chemistry) besides the obvious hydroxyl. For example, carbohydrates can have phosphates or amino groups substituted at a variety of sites within the molecule. These functional groups can provide additional properties to the molecule and will alter its overall function. However, even with these types of substitutions, the basic overall structure of the carbohydrate is retained and easily identified.

Nomenclature

One issue with carbohydrate chemistry is the nomenclature. Here are a few quick and simple rules:

  1. Simple carbohydrates, such as glucose, lactose, or dextrose, end with an "-ose."
  2. Simple carbohydrates can be classified based on the number of carbon atoms in the molecule, as with triose (three carbons), pentose (five carbons), or hexose (six carbons).
  3. Simple carbohydrates can be classified based on the functional group found in the molecule, i.e ketose (contains a ketone) or aldose (contains an aldehyde).
  4. Polysaccharides are often organized by the number of sugar molecules in the chain, such as in a monosaccharide, disaccharide, or trisaccharide.

For a short video on carbohydrate classification, see the 10-minute Khan Academy video by clicking here.

Monosaccharides

Monosaccharides ("mono-" = one "sacchar-" = sweet) are simple sugars the most common is glucose. In monosaccharides, the number of carbons usually ranges from three to seven. If the sugar has an aldehyde group (the functional group with the structure R-CHO), it is known as an aldose if it has a ketone group (the functional group with the structure RC(=O)R'), it is known as a ketose.

Figure 1. Monosaccharides are classified based on the position of their carbonyl group and the number of carbons in the backbone. Aldoses have a carbonyl group (indicated in green) at the end of the carbon chain and ketoses have a carbonyl group in the middle of the carbon chain. Trioses, pentoses, and hexoses have three, five, and six carbons in their backbones, respectively. Attribution: Marc T. Facciotti (own work)

Glucose versus galactose

Galactose (part of lactose, or milk sugar) and glucose (found in sucrose, glucose disaccharride) are other common monosaccharides. The chemical formula for glucose and galactose is C6H12O6 both are hexoses, but the arrangements of the hydrogens and hydroxyl groups are different at position C4. Because of this small difference, they differ structurally and chemically and are known as chemical isomers because of the different arrangement of functional groups around the asymmetric carbon both of these monosaccharides have more than one asymmetric carbon (compare the structures in the figure below).

Fructose versus both glucose and galactose

A second comparison can be made when looking at glucose, galactose, and fructose (the second carbohydrate that with glucose makes up the disaccharide sucrose and is a common sugar found in fruit). All three are hexoses however, there is a major structural difference between glucose and galactose versus fructose: the carbon that contains the carbonyl (C=O).

In glucose and galactose, the carbonyl group is on the C1 carbon, forming an aldehyde group. In fructose, the carbonyl group is on the C2 carbon, forming a ketone group. The former sugars are called aldoses based on the aldehyde group that is formed the latter is designated as a ketose based on the ketone group. Again, this difference gives fructose different chemical and structural properties from those of the aldoses, glucose, and galactose, even though fructose, glucose, and galactose all have the same chemical composition: C6H12O6.

Figure 2. Glucose, galactose, and fructose are all hexoses. They are structural isomers, meaning they have the same chemical formula (C6H12O6) but a different arrangement of atoms.

Linear versus ring form of the monosaccharides

Monosaccharides can exist as a linear chain or as ring-shaped molecules. In aqueous solutions, monosaccharides are usually found in ring form (Figure 3). Glucose in a ring form can have two different arrangements of the hydroxyl group (OH) around the anomeric carbon (C1 that becomes asymmetric in the process of ring formation). If the hydroxyl group is below C1 in the sugar, it is said to be in the alpha (&alpha) position, and if it is above C1 in the sugar, it is said to be in the beta (&beta) position.

Figure 3. Five- and six-carbon monosaccharides exist in equilibrium between linear and ring form. When the ring forms, the side chain it closes on is locked into an &alpha or &beta position. Fructose and ribose also form rings, although they form five-membered rings as opposed to the six-membered ring of glucose.

Disaccharides

Disaccharides ("di-" = two) form when two monosaccharides undergo a dehydration reaction (also known as a condensation reaction or dehydration synthesis). During this process, the hydroxyl group of one monosaccharide combines with the hydrogen of another monosaccharide, releasing a molecule of water and forming a covalent bond. A covalent bond formed between a carbohydrate molecule and another molecule (in this case, between two monosaccharides) is known as a glycosidic bond. Glycosidic bonds (also called glycosidic linkages) can be of the alpha or the beta type.

Figure 4. Sucrose is formed when a monomer of glucose and a monomer of fructose are joined in a dehydration reaction to form a glycosidic bond. In the process, a water molecule is lost. By convention, the carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the carbonyl group. In sucrose, a glycosidic linkage is formed between the C1 carbon in glucose and the C2 carbon in fructose.

Common disaccharides include lactose, maltose, and sucrose (Figure 5). Lactose is a disaccharide consisting of the monomers glucose and galactose. It is found naturally in milk. Maltose, or malt/grain sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose.

Figure 5. Common disaccharides include maltose (grain sugar), lactose (milk sugar), and sucrose (table sugar).

Polysaccharides

A long chain of monosaccharides linked by glycosidic bonds is known as a polysaccharide ("poly-" = many). The chain may be branched or unbranched, and it may contain different types of monosaccharides. The molecular weight may be 100,000 Daltons or more, depending on the number of monomers joined. Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.

Starch is the stored form of sugars in plants and is made up of a mixture of amylose and amylopectin both are polymers of glucose. Plants are able to synthesize glucose. Excess glucose, the amount synthesized that is beyond the plant&rsquos immediate energy needs, is stored as starch in different plant parts, including roots and seeds. The starch in the seeds provides food for the embryo as it germinates and can also act as a source of food for humans and animals who may eat the seed. Starch that is consumed by humans is broken down by enzymes, such as salivary amylases, into smaller molecules, such as maltose and glucose.

Starch is made up of glucose monomers that are joined by 1-4 or 1-6 glycosidic bonds the numbers 1-4 and 1-6 refer to the carbon number of the two residues that have joined to form the bond. As illustrated in Figure 6, amylose is starch formed by unbranched chains of glucose monomers (only 1-4 linkages), whereas amylopectin is a branched polysaccharide (1-6 linkages at the branch points).

Figure 6. Amylose and amylopectin are two different forms of starch. Amylose is composed of unbranched chains of glucose monomers connected by 1-4 glycosidic linkages. Amylopectin is composed of branched chains of glucose monomers connected by 1-4 and 1-6 glycosidic linkages. Because of the way the subunits are joined, the glucose chains have a helical structure. Glycogen (not shown) is similar in structure to amylopectin but more highly branched.

Glycogen

Glycogen is a common stored form of glucose in humans and other vertebrates. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis.

Cellulose

Cellulose is the most abundant natural biopolymer. The cell wall of plants is 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 &beta 1-4 glycosidic bonds.

Figure 7. In cellulose, glucose monomers are linked in unbranched chains by &beta 1-4 glycosidic linkages. Because of the way the glucose subunits are joined, every glucose monomer is flipped relative to the next one, resulting in a linear, fibrous structure.

Cellulose is not very soluble in water in its crystalline state this can be approximated by the stacked cellulose fiber depiction above. Can you suggest a reason for why (based on the types of interactions) it might be so insoluble?

As shown in the figure above, every other glucose monomer in cellulose is flipped over, and the monomers are packed tightly as extended, long chains. This gives cellulose its rigidity and high tensile strength&mdashwhich is so important to plant cells. While the &beta 1-4 linkage cannot be broken down by human digestive enzymes, herbivores such as cows, koalas, buffalos, and horses are able, with the help of the specialized flora in their stomach, to digest plant material that is rich in cellulose and use it as a food source. In these animals, certain species of bacteria and protists reside in the rumen (part of the digestive system of herbivores) and secrete the enzyme cellulase. The appendix of grazing animals also contains bacteria that digest 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. Termites are also able to break down cellulose because of the presence of other organisms in their bodies that secrete cellulases.

Interactions with carbohydrates

We have just discussed the various types and structures of carbohydrates found in biology. The next thing to address is how these compounds interact with other compounds. The answer to that is that it depends on the final structure of the carbohydrate. Because carbohydrates have many hydroxyl groups associated with the molecule, they are therefore excellent H-bond donors and acceptors. Monosaccharides can quickly and easily form H-bonds with water and are readily soluble. All of those H-bonds also make them quite "sticky". This is also true for many disaccharides and many short-chain polymers. Longer polymers may not be readily soluble.

Finally, the ability to form a variety of H-bonds allows polymers of carbohydrates or polysaccharides to form strong intramolecular and intermolocular bonds. In a polymer, because there are so many H-bonds, this can provide a lot of strength to the molecule or molecular complex, especially if the polymers interact. Just think of cellulose, a polymer of glucose, if you have any doubts.


Cellulose Insulation – A Smart Choice

Please note: This older article by our former faculty member remains available on our site for archival purposes. Some information contained in it may be outdated.

Cellulose insulation is a smart alternative to fiberglass. It provides a green, efficient, non-toxic, affordable thermal solution that’s worth considering.

The thermal protection of a home is essential controlling durability, cost of operation and homeowner comfort. Fiberglass insulation is the standard bearer. The ubiquitous bales of pink and yellow fiberglass insulate more than 90% of the new homes built in the United States. But homeowners have many good choices. Plastic foams, rock wool, cellulose and even cotton insulation are readily available. Insulation materials come in many forms. They are sprayed, stapled, blown, nailed or simply laid in place. The choices can be difficult to sift, but cellulose insulation passes as a strong contender.

The common standard by which insulation is measured, R-value, is the level of resistance to heat flow. R-value measures conductive resistance – the ability of a material to impede the flow of heat along the continuous chain of matter that makes up a solid material. Most of a home’s heat is typically lost through conduction. Cellulose is not unusual in this regard. Like many insulation materials, it provides an R-value of approximately R-3.5 per inch of thickness. But, air leakage through cracks, voids, and gaps is important, responsible for approximately one-third of an average home’s heat loss. Cellulose is a superb air-blocker. Heat and comfort are also lost through convection when drafty currents of air within the house, wall cavities or attics, move heat to other locations. This is technically different from air leakage where the heated air mass is actually expelled from the home. Tightly packed cellulose provides a thermally efficient, cost effective, and comfortable solution.

Cellulose is “green.” It’s made of 80% post-consumer recycled newsprint. The fiber is chemically treated with non-toxic borate compounds (20% by weight) to resist fire, insects and mold. The Cellulose Insulation Manufacturers Association (CIMA) claims that insulating a 1500 ft2 house with cellulose will recycle as much newspaper as an individual will consume in 40 years. If all new homes were insulated with cellulose this would remove 3.2 million tons of newsprint from the nation’s waste stream each year. There’s room to grow. Fewer than 10% of the homes built today use cellulose. Cellulose earns “green” points because it requires less energy than fiberglass to manufacture. Disciples claim 200 times less petro-energy than fiberglass. More realistically, Environmental Building News reports that fiberglass requires approximately 8 times more energy to make when adjusted to reflect energy cost per installed R-value unit.

Cellulose insulation is safe. It is made of paper, but the chemical treatment provides it with permanent fire resistance. There’s been static generated by the fiberglass industry warning that cellulose could burn. But independent testing confirms it’s safe and cellulose is approved by all building codes. In fact, many professionals consider cellulose to be more fire-safe than fiberglass. This claim rests on the fact that cellulose fibers are more tightly packed, effectively choking wall cavities of combustion air, preventing the spread of fire through framing cavities.

Wet insulation of any stripe is bad. But cellulose is hygroscopic. It’s able to soak and hold liquid water. Undetected leaks can wet cellulose causing it to sag within framing cavities. Water leaks can compress the blanket of fiber and in extreme cases, can create a void space, degrading its thermal value. Another concern is that chemicals used to protect cellulose from fire make it potentially corrosive in wet environments. Tests conducted by the Oak Ridge National Laboratory show chemical treatments used to treat cellulose can cause metal fasteners, plumbing pipes and electrical wires to corrode if left in contact with wet, treated cellulose insulation for extended periods of time.

The fact that R-value of cellulose is slightly better than fiberglass is perhaps a minor issue. Fiberglass batts and cellulose used in walls earn similar conductive ratings between R-3 and R-4 per inch depending on density. And while the low-density fiberglass insulation used in attics rates a much lower R-2.0 per inch – there is typically very little space restriction in attics. So you can simply pile fiberglass deeper to achieve the R-value you need.

Cellulose insulation provides greater resistance to air leakage and for me this is a biggie. The fiberglass industry points to tests demonstrating air leakage can be controlled with dedicated air-barrier systems. True. Install perfectly continuous sheathing, caulks, gaskets and sealants and you will block air leakage effectively with fiberglass or cellulose. But the simple fact remains: densely packed cellulose blocks air better than fiberglass. Fiberglass relies on trapped air for its insulation value. Cellulose is made from wood fiber and the cellular structure of wood is naturally more resistant to the conduction of heat. When dedicated air-barrier systems are not installed perfectly (which they seldom are), cellulose wins.

Preparation
Choosing the right insulation material is important. However, the quality of the installation is critical. Efficient insulation systems need thoughtful preparation. Armed with a trusty caulk gun and spray container of insulating foam, seal all penetrations in the structural envelope prior to insulation.

The greatest opportunities for air sealing exist at the top and bottom of the house because the greatest stack pressures exist there. Warm air rises and exhausts most vigorously high in the house. Replacement air infiltrates most forcefully at the lowest levels. Start by sealing air leaks in the attic. Seal around electrical lights, junction boxes, fan housings, pipes, and wires. Be sure to seal where wall plates intersect the attic floor. Seal duct connections and penetrations through the ceiling. Be careful around chimneys. Use a non-flammable sealing material there. Install baffles in each rafter bay at the eaves so you don’t block soffit vents. Leave enough room above the baffles for vent air to pass from soffit vents up into the attic where it can exhaust through the ridge vent system. Repeat this air-sealing strategy in the basement ceiling to block infiltration points. And lastly, when possible, seal the walls.

Seal all gaps in the wall sheathing and framing. Fill narrowly spaced studs and headers. Seal around window, electrical, and plumbing penetrations. Once all leakage points are sealed you are ready to install the cellulose insulation. Cellulose comes in two basic varieties: dry fiber that is blown into open attics and enclosed cavities damp fiber that is sprayed into open wall cavities.

Blown Cellulose
Blown cellulose can be installed in new or existing structures. It is popular in retrofit applications because existing wall finishes are not removed to install the insulation. It is favored in attic applications because you can blow unrestricted depths of fiber to achieve deep coverage with very little labor.

Blown cellulose is shredded newsprint that is installed with special equipment. Construction-savvy homeowners might be able to install blown cellulose in open attics not walls or cathedral roofs. You can use blowing machines from rental centers and building material dealers that sell cellulose insulation. But in general, this is a job for pros. On paper the application is simple. Dry cellulose fiber is blown through a hose into open attics or into enclosed wall, floor or cathedral-roof framing cavities.

Two people are required to run the equipment. One person feeds dry fiber into a hopper breaking up clumps of cellulose as it is passes into the blowing system. The hopper and blower can be located inside or outside the house. The other person operates a hose that is attached to the blower and extends to the locations where insulation will be deposited. The ratio of air to fiber is adjustable and with some experimenting the right balance is struck. A 3-inch diameter flexible hose is typically used to blow fiber into open attics. If an attic floor is already installed, remove some of the boards or drill holes at strategic locations to fill the floor cavities with insulation. If the floor cavities are already filled, blow an additional layer of cellulose directly over the floor sheathing to improve the level of protection. The job is dusty and wearing a mask is required.

Blowing fiber into enclosed wall and cathedral framing cavities is different. Here a smaller 1- or 2-inch diameter fill tube is attached to the end of the larger hose. The fill tube is inserted into enclosed cavities through a series of strategically placed holes. The general idea is to drill a series of 2-inch holes horizontally across the structural surface so that the holes are centered in each framing cavity. One or more holes per framing bay are required depending on the length of the framing cavity and the applicator’s fill technique.

Filling walls and cathedral roofs from the outside is the typical practice. Pieces of siding or roofing are removed, holes drilled and insulation fill tubes inserted. Air pressure is cranked up for cavity-fill applications to provide a more densely packed injection called dense-pack cellulose. The narrow fill tube is inserted into the holes and pushed to within a foot of the far end of the enclosed cavity as the blowing begins. When the packed insulation becomes dense enough to stall the blower, the hose is backed out a bit. The blower gears up and filling resumes. The process is repeated until the framing cavity is filled. Then jump over to the hole(s) in the adjacent cavity. The injected fiber compacts tightly around wires, plumbing, and other penetrations providing an airtight insulating blanket with a slightly elevated R-value approaching R-4 per inch. The holes are plugged and the siding and roof covering is patched or reinstalled when the blowing is completed.

Cellulose can be blown into wall or cathedral roof cavities from the inside as well. Remove interior trim, drill – or simply drill holes through the interior drywall surface – and blow. Replace trim and patch the holes after the cavities are filled. In new construction, walls must be enclosed with fiber-reinforced plastic sheeting or drywall before cellulose can be blown into the framing. The plastic sheeting doubles as a vapor barrier. Choose whichever strategy makes the most sense for your situation.

If you have a home that was insulated years ago with inadequate levels of insulation, you are not out of luck. Skilled cellulose professionals can snake fill tubes into a wall already filled with fiberglass batts. The installer fills the cavities with dense-pack cellulose in a way that crushes the existing insulation without balling up the batts, achieving a full uniform application of the new cellulose fiber. The goal on any application is to assure complete coverage that is installed at a density that will not settle over time.

Sprayed Cellulose
Blown cellulose is a great option for attics and retrofit applications where the dry fiber can be supported by an attic floor or enclosed wall cavity. But damp-sprayed cellulose provides an effective solution for open wall cavities in new construction.

Dampened cellulose is a sticky material. It is sprayed directly into open wall cavities between the studs, right against the exterior sheathing, where it stays put. It provides a solid, airtight and completely filled wall cavity. The basic cellulose fiber used in the sprayed application is the same as that used in the blown application: recycled newsprint with chemical additives. The difference is that sprayed cellulose is dampened with water and sometimes a little adhesive is blended into the mix.

Dry cellulose fiber is blown from a machine through a 2 1/2-inch hose much like its dry-blown counterpart. However, a water hose with high-pressure nozzle resembling a pressure washer is attached to the end of the fill hose. It sprays the fiber with a mist of water as it is fired from the hose. The spray dampens the surface of wall cavity at the same time to provide a sticky contact bond between the framing materials and the insulating fiber. The flow of water is adjusted by the applicator to establish an important balance. The fiber must be damp enough to stick permanently to the wall, yet not so wet to cause moisture problems. The damp fiber is shot until the wall cavities are overfilled, just proud of the wall thickness. The overfilled walls are then scraped flat to match the exact thickness of the wall framing using a rotating brush called a scrubber.

Adding moisture to the wall cavity of homes is a touchy subject. One the fiberglass industry likes to promote as dangerous to structural and human health. The truth is a bad application can be dangerous and ineffective. An inexperienced applicator can introduce an unsafe level of water into a wall system. Mold, mildew and even rot can result. On the other hand, skilled applicators achieve an effective and safe balance of moisture-to-fiber and provide a superb insulation system. A target of approximately 30% moisture content by weight is appropriate. Freshly sprayed cellulose should feel damp, but you should not be able to squeeze water out of a handful if you tried.

As the sprayed cellulose insulation dries it stiffens and is very resistant to settling. Sprayed walls should be left open until the Moisture Content (MC) of the fiber drops below 25%. This normally requires a 2-day drying out period depending on the climatic conditions. The installer should check the MC using a moisture meter to assure the fiber is dry before authorizing a close-in of the walls.

Sprayed cellulose is not all roses. An entire house can be insulated in one day, but it will be a very messy day. The inside of the house will resemble a combination of mid-winter blizzard and coastal fog. Windows, doors, and electrical boxes must be protected with plastic sheeting and tape prior to installation. Blowing fibers irritate the respiratory tract and eyes so a protective mask and goggles are a must. A sea of waste fiber must be vacuumed and shoveled on an ongoing basis. Spraying damp cellulose during freezing conditions is rough on equipment and drying time can drag to a crawl. And while priced competitively, it will cost a few hundred dollars more than fiberglass batt insulation. But the upside is worthy.

Sprayed cellulose is an eco-friendly material that is installed at a high density. Coverage is complete. There are no voids in the walls. All wire and plumbing penetrations are automatically and completely sealed. A professionally installed application is airtight, comfortable, energy efficient, and safe. There are fewer thermal short circuits and virtually no convective currents within the wall cavities. On the whole, customers report a less drafty, more comfortable living experience. As a bonus, many people think the superior air-tightness and absorptive qualities of sprayed cellulose provides a quieter indoor environment.

Comparing prices of competing insulation systems is difficult. Costs vary from location to location and even between applicators in any given area. As a rule, cellulose installations are competitively priced with fiberglass and much less expensive than foamed-in-place applications. But the Performance of any insulation system depends on the quality of its installation.

Demand high quality. Ask a lot of questions. Be sure installers list more than R/inch. Ask them how they achieve a high degree of air sealing and proper coverage. Ask for a list of references and be sure to call the references. Did the installers stay on schedule? Were they clean, organized, and courteous? Were customers satisfied with the completed project?

The Federal Trade Commission (FTC) regulates home insulation through its Home Insulation Rule 460 (see http://www.ftc.gov/bcp/rulemaking/rvalue/16cfr460.htm) The rule specifies:

DIY customers must be presented with fact sheets.

Consumers hiring contractors must receive fact sheets about installed insulation.

Customers must receive a contract or receipt for the insulation installed.

The receipt must show the coverage area, thickness, R-value and number of bags of fiber used.

The receipt must be dated and signed by the installer.

New home sellers must list the type, thickness, and R-value of each type of insulation installed in each part of the house on every sales contract.

Once you have chosen a contractor, be sure the total cost, payment schedule and warranty are clearly expressed. Be sure the installed R-value is documented. And be very cautious about contracts using wiggle words like “average” or “nominal.” Your antennae should rise if the job quote is expressed only in terms of thickness. You want to know the installed R-value.

There are many choices when it comes to insulating a home. The US Department of Energy provides consumers with a useful tool that helps you determine how much insulation you should use in your home, based on your zip code. Visit the DOE web site at http://www.ornl.gov/

roofs/Zip/ZipHome.html and use the ZIP-Code Insulation Program to learn the most economic level of insulation for your home. The program leads you through the important elements is needs to know about your house and climate.

Here is a table that lists some R-values DOE assigns to a variety of insulation materials.

Insulation Type R-value per Inch of Thickness
Fiberglass blanket or batt 3.2
High performance fiberglasss batt 3.8
Loose-fill fiberglass 2.5
Loose-fill rock wool 2.8
Loose-fill cellulose 3.5
Dense-pack cellulose 4.0*
Expanded polystyrene board 3.8
Extruded polystyrene board 4.8
Polyisocyanurate board, unfaced 5.8
Polyisocyanurate board, foil-faced 7.0
Spray polyurethane foam 5.9

* Dense-pack cellulose R-value provided by US Housing and Urban Development (HUD) ToolBase Services


Globular Proteins

  • Molecule forms a coiled shape ( globule )
  • Hydrophobic groups point into centre of molecule away from water
  • Only hydrophilic groups are exposed outside the molecule so globular proteins are soluble
  • Globular proteins have roles in metabolic reactions:
    • Enzymes - catalyse metabolic reactions
    • Haemoglobin - binds to oxygen to transport it around body

    Haemoglobin

    Haemoglobin has a quaternary structure made up of 4 separate polypeptide chains:

    • 2 identical alpha -chains with 141 amino acids each
    • 2 identical beta -chains with 146 amino acids each
    • Each polypeptide chain is folded/coiled into a compact shape due to hydrophobic interactions between the (hydrophobic) R groups
    • All 4 polypeptide chains are linked to form a roughly spherical haemoglobin molecule
    • The precise 3D-shape of the Haemoglobin molecule is absolutely critical to it's Oxygen-carrying function
    • The Hydrophilic R-groups are arranged around the outside of the molecule which allows Haemoglobin to mix with the watery medium inside red blood cells
    • Attached to each polypeptide chain is a prosthetic HAEM group with an Fe2+ ion
    • Each Fe2+ ion can combine with one O2 molecule
    • Human haemoglobin has four polypeptide chains and four haem groups and can therefore carry 4 x O2 molecules
    • When haemoglobin is bound to oxygen it is called oxyhaemoglobin and the colour changes from purplish red to bright red
    • The 3D-shape of globular proteins is critical to their function – slight changes can have radical effects – eg in sickle cell anaemia one amino acid change causes a shape change in the molecule that in turns reduces the ability of haemoglobin to bind to oxygen and changes the shape of the whole red blood cell from a biconcave disk to a sickle shape. Severe sickle cell anaemia can be fatal.

    Fibrous Proteins

    • Polypeptides form long chains running parallel to each other
    • These chains are linked by disulphide cross bridges – making the proteins very stable and strong
    • Fibrous proteins have Structural functions:
      • Keratin in skin and hair
      • Collagen - found in bone, cartilage, tendons and ligaments for tensile strength

      Collagen is the most abundant protein in the animal kingdom. It is found in many diverse organisms and organs:

      • in humans in tendons, the walls of blood vessels, cartilage, bone, gums
      • sea anemones
      • egg cases of dogfish

      Collagen is strong but still flexible – this is important in tendons which cannot be rigid

      The Primary structure of collagen

      The Secondary/Tertiary Structure of Collagen

      glycine is the smallest amino acid and this together with proline allow the polypeptide chain to be wound into a tightly coiled, straight and unbranched helix


      Summary – Fibrous vs Globular Proteins

      Fibrous and globular proteins are two types of proteins present in our body. Fibrous proteins are elongated strand like protein On the other hand, globular proteins are spherical in shape. Furthermore, fibrous proteins are insoluble in water, while globular proteins are soluble in water. Moreover, globular proteins act as catalysts of biochemical reactions while fibrous proteins provide structural functions. Compared to globular proteins, fibrous proteins are abundant in our body. This summarizes the difference between fibrous and globular proteins.

      Reference:

      1. “Structural Biochemistry/Proteins/Fibrous Proteins.” Development Cooperation Handbook/Guidelines/How to Manage Programmes for a Learning Organization That Is Projectized and Employee Empowering – Wikibooks, Open Books for an Open World, Wikimedia Foundation, Inc., Available here.

      Image Courtesy:

      1. “Hierarchical structure of hair in the cortex and cuticle” By Yang F, Zhang Y, Rheinstädter MC – [1] (CC BY 4.0) via Commons Wikimedia
      2. “1GZX Haemoglobin” By Zephyris at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia


      Watch the video: What is CELLULOSE FIBER? What does CELLULOSE FIBER mean? CELLULOSE FIBER meaning u0026 explanation (August 2022).