STORAGE POLYSACCHARIDE- STARCH

STORAGE POLYSACCHARIDE - STARCH 

• Starches are glucose polymers in which glucopyranose units are bonded by alpha-linkages.
• It is made up of a mixture of amylose(15%-20%) and amylopectin (80%- 85%).
• Amylose consists of a linear chain of several hundred glucose molecules and amylopectin is a branched molecule made of several thousand glucose units(every chain of 24-30 glucose units is one unit of amylopectin).Starches are insoluble in water.
• They can be digested by hydrolysis, catalysed by enzymes called amylases, which can break the alpha-linkages(glycosidic bonds).
• Humans and other animals have amylases, so they can digest starches. Potato, Rice, Wheat, and maize are major sources of starch in the human diet.
• It is exclusively formed in plants and not in Animals.

Figure: Amylopectin is a glucose polymer with mainly a(1-->4) linkages, but it also has branches formed by a(1--->6) linkages. The branches are generally longer than shown above. The branches produce a compact structure, and provide multiple chain ends at which enzymatic cleavage of the polymer can occur. 

Figure: Amylose is a linear polymers of glucose mainly linked with a(1-->4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.

POLYSACCHARIDES OR OLIGOSACCHARIDES

POLYSACCHARIDES OR OLIGOSACCHARIDES 

• Polysaccharide is an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related.
• Starch is a polymer of glucose is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopetcin.
• In Animals, the structurally similar glucose polymer is the more densly branched glycogen, sometimes called 'animal starch'.
• Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.
• Structural Polysaccharides: Cellulose, Pectin and Chitin
• Cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on earth.
• It has many uses such as a significant role in the paper and textile industries, and is used as a feedback for the production of rayon (via viscose process),cellulose acetate, celluloid, and nitrocellulose.
• Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi.
• Chitin is also has multiple uses, including surgical threads.
• Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan, and galactomannan.
• Monosaccharides can be linked together into polysaccharides(or Oligosaccharides)in a large variety of ways.
• Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed.
• Pectins are a family of complex polysaccharide that contain 1,4-linked α-D-galactosyluronic acid residues.
• They are present in most primary cellwalls and in the non-woody parts of terrestrial plants.

STORAGE POLYSACCHARIDE-GLYCOGEN

• Glycogen serves as the secondary long-term energy storage in animals and fungal cells, with the primary energy stores being held in adipose tissue.
• Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.
• Glycogen is the analogue of starch, a glucose polymer in plants, and is sometimes referred to as animal starch, having a similar structure to amylopectin but more extensively branched and compact than starch.
• Glycogen is a polymer of α(1--->4) glycosidic bonds linked, with α(1--->6)-linked branches.
• Glycogen is found in the form of granules in the cytosol/cytoplasm in may cell types, and plays an important role in the glucose cycle.
• Glycogen forms an energy reserves that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact than the less immediately available energy reserves of triglycerides(lipids).
• In the Liver hepatocytes, glycogen can compose up to eight percent(100-120 g in an adult) of the fresh weight soon after a meal.
• Only glycogen stored in the liver can be made accessible to other organs. In the muscles, glycogen is found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells.
• The Uterus also stores glycogen during pregnancy, to nourish the embryo.
• Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles.

          1. It is an energy reserves for animals.

          2. It is the chief form of carbohydrate stored in animal body.

          3. It is insoluble in water. It turns red when mixed with iodine.

          4. It also yields glucose on hydolysis.

 DISACCHARIDES

• When the alcohol component of a glycoside is provided by a hydroxyl function on another monosaccharide, the compound is called a Dissacharide.
• Ex. Cellulose : 4-O-β-D-Glucopyranosyl-D-Glucose(the beta-anomer is drawn)
• Maltose : 4-O- α-D-Glucopyranosyl-D-Glucose (the beta-anomer is drawn)
• Gentiobiose : 6-O-β-D-Glucopyranosyl-D-Glucose (the alpha-anomer is drawn)
• Trehalose : α-D-Glucopyranosyl-α-D-Glucopyranoside
• Although all the disaccharides shown here are made up of two glucopyranose rings, their properties differ in interesting ways.
• Maltose, sometimes called malt sugar, comes from the hydrolysis of starch. It is about one third as sweet as cane sugar(Sucrose),is easily digested by humans, and is fermented by yeast. 
•  Cellobiose is obtained by the hydrolysis of cellulose.
• It has virtually no taste, is indigestible by humans, and is not fermented by yeast.
•  Some bacteria have beta-glucosidase enzymes that hydrolyse the glycosidic bonds in cellobiose and cellulose. 
• The presence of such bacteria in the digestive tracts of cows and termites permits these animals to use cellulose as a Food. 
• Finally, it may be noted that trehalose has a distinctly sweet taste, but gentiobiose is bitter.

Figure. A four examples of disaccharides composed of two glucose units are shown

• Disaccharides made up of other sugars are known, but glucose is often one of the components. 
• Two important examples of such mixed disaccharides will be displayed above by clicking on the diagram.
• Lactose, also known as milk sugar, is a galactose-glucose compound joined as a beta-glycoside.

Figure. Lactose is a disaccharide found in milk.

• It is a reducing sugar because of the hemiacetal function remaining in the glucose moiety. Many adults, particularly those from regions where milk is not a dietary staple, have a metabolic intolerance for lactose.
• Infacts have a digestive enzyme which cleaves the beta-glycoside bond in lactose, but production of this enzyme stops with weaning.
• Cheese is less subject to the lactose intolerance problem, since most of the lactose is removed with the whey.
• Sucrose, or cane sugar, is our most commonly used sweetening agent. It is a non-reducing disaccharide composed of glucose and fructose joined at the anomeric carbon of each by glycoside bonds(one alpha and one beta).
• In the formula shown here the fructose ring has been rotated 180° from its conventional perspective.

Microbiology terms and definitions from Y

 MICROBIOLOGY TERMS AND DEFINITIONS FROM Y

Yaws definition

• A tropical disease caused by Treponema pertenue that produces granulomatous ulcers on the extremities and occasionally on the bone but does not produce a central nervous system or cardiovascular complications. (Foundation in Microbiology by Talaro and Chess)

Yeast definition

• (1) A type of unicellular, nonfilamentous fungus that resembles bacterial colonies when grown in culture. (2) A term sometimes used to denote the unicellular form of pathogenic fungi. (Alcamo’s Fundamentals of Microbiology)
• The single-celled growth form of various fungi. (Brock Biology of Microorganisms)
• Single-celled, budding fungi. (Foundation in Microbiology by Talaro and Chess)
• Nonfilamentous, unicellular fungi. (Microbiology: An Introduction by Tortora, Funke, and Case)
• A unicellular, uninuclear fungus that reproduces either asexually by budding or fission, or sexually through spore formation. (Prescott’s Microbiology)

Yeast Artificial Chromosome (YAC) definition

• A genetically engineered chromosome with yeast origin of replication and centromere sequence. (Brock Biology of Microorganisms)
• Engineered DNA that contains all the elements required to propagate a chromosome in yeast and is used to clone foreign DNA fragments in yeast cells. (Prescott’s Microbiology)

Yeast infection definition

• Disease caused by the growth of certain yeasts in a susceptible host. (Microbiology: An Introduction by Tortora, Funke, and Case)

Yellow fever definition

• Best-known arboviral disease. Yellow fever is transmitted by mosquitoes. Its symptoms include fever, headache, and muscle pain that can proceed to oral hemorrhage, nosebleeds, vomiting, jaundice, and liver and kidney damage. (Foundation in Microbiology by Talaro and Chess)

 

MICROBIOLOGY TERMS AND DEFINITIONS FROM X

X-factor definition

• Substances from the heme fraction of blood hemoglobin. (Microbiology: An Introduction by Tortora, Funke, and Case)

X-ray definition

• The ionizing radiation that can be used to sterilize objects. (Alcamo’s Fundamentals of Microbiology)

Xenobiotic definition

• A synthetic compound not produced by organisms in nature. (Brock Biology of Microorganisms)
• Synthetic chemicals that are not readily degraded by microorganisms. (Microbiology: An Introduction by Tortora, Funke, and Case)

Xenodiagnosis definition

• A method of diagnosis based on exposing a parasite-free normal host to the parasite and then examining the host for parasites. (Microbiology: An Introduction by Tortora, Funke, and Case)

Xenograft definition

• A tissue graft between members of different species, such as between a pig and a human. (Alcamo’s Fundamentals of Microbiology)
• The transfer of a tissue or an organ from an animal of one species to a recipient of another species. (Foundation in Microbiology by Talaro and Chess)
• A tissue graft from another species. (Microbiology: An Introduction by Tortora, Funke, and Case)
• A tissue graft between animals of different species. (Prescott’s Microbiology)

Xerophile definition

• An organism adapted to growth at very low water potentials. (Brock Biology of Microorganisms)
• Microorganisms that grow best under low water activity (aw) conditions, and may not be able to grow at high aw values. (Prescott’s Microbiology)

STRUCTURE AND FUNCTIONS

 STRUCTURE AND FUNCTION

Formerly the name "carbohydrate" was used in chemistry for any compound with the formula Cm(H2O)n. Following this definition, Some chemists considered formaldehyde(CH2O) to be the simplest carbohydrate while other claimed that title for glyceraldehyde Today the term is generally understood in the biochemistry sense, which exclude compounds with only one or two carbons.

MONOSACCHARIODES

• Natural saccharide are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more.
• A typical monosaccharide has the structure H-(CHOH)x(C=O)-(CHOH)y-H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group.
• Examples of monosaccharides are Glucose, Fructose and Glyceraldehyde. However, Some Biological Substances Commonly called "Monosaccharide" do not conform to this formula(e.g; Uronics Acids and  Deoxy-Sugars Such as fucose), and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g; Formaldehyde CH2O and inositol(CH2O)6)
• The open-chain form of a monosaccharide often coexists with a closed rong form where the aldehyde/ketone carbonyl group carbon(C=O) and hydroxyl group (-oh) react forming a hemiacetal with a new C-O-C bridge.

α-D-Glucopyranose

 HAWORTH PROJECTION

• The Three Dimensional structure of a monosaccharide in cyclic form is usually represented by its Haworth Porjections.
• In the Diagram, the α-isomer has the -OH of the anomeric carbon below the plane of the carbon atoms, and the β-isomer has the-OH of the anomeric carbon above the plane.

• Pyranose typically adopt a chair Conformation,similar to cyclohexane. In this conformation, the α-isomer has the -OH of the anomeric carbon in an axial position, whereas the β-isomer has the OH- of the anomeric carbon in equatorial position.

COMPOSITION,STRUCTURE AND FUNCTION OF BIOMOLECULES

 1.2 COMPOSITION,STRUCTURE AND FUNCTION OF BIOMOLECULES 

BULLET POINTS

• There are four major classes of biomolecules - Carbohydrates, Proteins, Nucleotides and Lipids.
• carbohydrates, or Saccharides, are the most abundant of the four. Carbohydrates have several roles in living organisms, including energy transportation, as well as being structural components of plants and arthropods.
• Carbohydrate derivatives are actively involved in fertilization, immune systems, and the development of diseases, blood clotting and development.
• Carbohydrates are called carbohydrates because the carbon, oxygen and hydrogen they contain are generally in proportion to form water with general formula Cn(H2O)n.
• Carbohydrates (saccharides)- Molecules consist of carbon, hydrogen and oxygen atoms. 
• A major polymers, carbohydrates can function as long term food storage molecules, as protective membranes for organisms and cells, and as the main structural support for plants and constituents of many cells and their contents.
• Lipids (fats) - Molecules consist of carbon, hydrogen and oxygen atoms. 
• The main constituents of all membranes in all cells (cell walls), food storage molecules, intermediaries in signalling pathways, vitamin A,D,E and K, cholestrol.
• Proteins - molecules contain nitrogen, carbon, hydrogen and oxygen. They act as biological catalyst (enzymes), form structural parts of organisms, participate in cell signal and recognition factors, and act as molecules of immunity. proteins can also be a source of fuel.
• Nucleic Acids(Nucleotides) - DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).These molecules are involved in genetic information, as well as forming structure within cells.
• They are involved in the storage of all heritage information of all organisms, as well as the conversion of this data into proteins. 

1.2.1 CARBOHYDRATES

    Carbohydrates are one of the main types of nutrients. They are the most important source of energy for your body. Your digestive system changes carbohydrates into glucose( Blood Sugar). 

Your body uses this sugar for energy for your cells, tissues and organs. It stores any extra sugar in your liver and muscles for when it is needed.

Carbohydrates are called simple or complex, depending on their chemical structure. Simple Carbohydrates include Sugars found naturally in foods such as Fruits, vegetables, Milk and Milk products.

They also include Sugars added during food processing and refining. Complex Carbohydrates include whole grain breads and cereals, Starchy vegetables and Legumes.

Many of the complex Carbohydrates are good sources of Fibre. For a Healthier Diet, limit the amount of added Sugar that you eat and choose whole grains over refined grains.

The Term is Most common in Biochemistry, it is called Saccharide. The Carbohydrates (Saccharides) are divided into four chemical grouping:

1. Monosaccharide

2. Disaccharide

3. Oligosaccharide

4. Polysaccharide

In general, the Monosaccharides and disaccharides,  which are smaller ( lower molecular weight). Carbohydrates, are commonly reffered to as sugars. while the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix-ose. For example, grape sugar is the monosaccharide glucose, cane sugar is the dissacharide sucrose, and milk sugar is the disaccharide lactose.