Table of Contents
- Structure of Carbohydrates
- There are two main types of carbohydrates:
- Monosaccharide classes are ketoses and aldoses
- Classification of polysaccharides
- Functions of carbohydrates
- Glycolipids and lipopolysaccharides as membrane components
- Get help to do your homework
- Cite this article in APA
Structure of Carbohydrates
Carbohydrates are molecules made up of hydrogen, oxygen, and carbon
There are two main types of carbohydrates:
- Monosaccharides– known as simple sugars eg glucose
- Polysaccharides- they are complex carbohydrates
- This is single sugars
- They have a generic formula; CH2O
- They are colorless and crystalline solids which are water-soluble and insoluble in nonpolar solvents
- They have a sweet taste
- Monosaccharides have the following common features
- 3,4,5,6,7 carbon backbone
- A hydroxyl group (OH) is attached to every group of carbon. This group makes these sugars polar
- One double-bonded oxygen that is attached to the carbon backbone. This is called a carbonyl group.
Monosaccharide classes are ketoses and aldoses
- Aldoses – carbonyl group is found at the carbon chain end
- Ketoses – carbonyl group is found on any carbon group within the carbon chain
- Simplest monosaccharides include; two carbon chains aldotriose and glyceraldehyde and three carbon chains ketotrioses and dihydroxyacetone
- Polysaccharides are polymers of monosaccharides.
- To generate polysaccharides, Monosaccharides are combined by the condensation process.
- During condensation, a molecule of water is removed and a bond is generated between atoms of the growing polysaccharide chain.
- Homopolysaccharides contain a single monomer type
- Heteropolysaccharides– contain two or more types of monomers
Classification of polysaccharides
- Disaccharides- these are chains of two monosaccharides. An example is a fructose and lactose
- Oligosaccharides-this are short chains of monosaccharides. They are part of plasma membrane receptors.
- Polysaccharides- are long chains of monosaccharides. Consist of starch and cellulose
- Starch-contains two types of polymers of glucose, amylopectin, and amylose
- Glycogen– it is the main polysaccharide store in animal cells
- Glycogen is more branched than starch
Functions of carbohydrates
- Carbohydrates are great energy producers in living cells.
- They perform the following important functions in cells
- Carbohydrates are an important energy source for cells. Glucose is widely used as a source of cellular energy.
- Carbohydrates are used as important structural molecules of cells. Cell walls of plants are majorly made up of polysaccharides. Cellulose with residues of D- glucose provides rigidity and strength to cell walls
- Carbohydrates are useful cellular identity markers. Various cellular surfaces are marked by glycoproteins.
- Carbohydrates are useful extracellular molecules. The sticky matrix surrounding the cell is composed of polysaccharides.
- Polysaccharides serve also as information carriers
- The polysaccharides also help in blood clotting, migration of cells during migration and healing of wounds.
- Glycoconjugate– a carbohydrate that is covalently attached to a lipid or protein
- Proteoglycans-are cell surface macromolecules where one or more chains of glycosaminoglycan are attached covalently to secreted proteins
- Glycoproteins –have oligosaccharides of different complexity attached covalently to a protein
- Glycolipids– are lipids in membrane whose hydrophilic head group is an oligosaccharide.
Glycolipids and lipopolysaccharides as membrane components
- Many proteins on the cell surface are glycoproteins
- Oligosaccharides attached facilitate folding of the proteins and stability
- Lipopolysaccharides are the most common feature of the outer membrane surface of gram-negative bacteria like escherichia coli and salmonella Typhi
- They read the sugar code
- They mediate several biological processes
- Serve widely in cell signaling, adhesion, and cell-cell recognition
- Selectins- a group of lectins of the plasma membrane that facilitate adhesion and cell-cell recognition
|Structure of Carbohydrates
|Carbohydrates are molecules made up of hydrogen, oxygen, and carbon.
|Types of Carbohydrates
|Monosaccharides – Single sugars with a generic formula of CH2O. Polysaccharides – Complex carbohydrates made up of monosaccharide units.
|Single sugars with a sweet taste, a carbon backbone, hydroxyl groups attached to each carbon, and a carbonyl group. Divided into aldoses and ketoses based on the location of the carbonyl group.
|Polymers of monosaccharides formed by condensation. Homopolysaccharides contain a single monomer type, while heteropolysaccharides contain multiple monomer types.
|Classification of Polysaccharides
|Disaccharides – Chains of two monosaccharides. Oligosaccharides – Short chains of monosaccharides. Polysaccharides – Long chains of monosaccharides, such as starch and cellulose.
|Functions of Carbohydrates
|Energy production, carbon supply for cell component synthesis, chemical energy storage, and structural molecules in cells and tissues.
|Functional Groups in Carbohydrates
|Carbohydrates have hydroxy-aldehydes/ketones (polyhydroxy aldehydes and polyhydroxy ketones) as functional groups.
|A single polyhydroxy aldehyde or ketone unit.
|Two monosaccharide units linked together by acetal or ketal linkages.
|Short chains of 3-10 monosaccharide units.
|Very large chains of linked monosaccharide units, often consisting entirely of D-glucose units.
|Types of Monosaccharides
|Glucose, fructose, and galactose.
|Structure of D-Aldoses
|At the top, H-C=O. At the bottom, CH2OH. Differences in carbon rungs in between.
|Shape of L- or D-Glyceraldehyde
|A pair of molecules that are mirror images of each other.
|A carbon atom with four different groups attached.
|Chirality in Compounds
|Compounds are chiral when they cannot be superimposed on their mirror image despite having the same molecular and structural formulas.
|Placement of Carbonyl Carbon
|The carbonyl carbon is placed at or near the top in carbohydrates.
|The oxygen of the carbonyl group at the top determines which side of the polyhydroxide rungs cycles to the above side of the cyclic formation ring.
|Enantiomer Distinguishing Labels
|L- (levo) for left and D- (dextro) for right.
|L- and D- Labels in Enantiomers
|The L- and D- labels apply to the side of the molecule that contains the -OH farthest from the first chiral carbon.
|Sugars with 3, 4, 5, and 6 Carbons
|Trioses, tetroses, pentoses, and hexoses, respectively.
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|What is a monosaccharide?
|A simple sugar consisting of a single sugar unit.
|What is the most common monosaccharide?
|What are the two types of monosaccharides based on the functional groups they have?
|Aldose (has an aldehyde group) and ketose (has a ketone group).
|What are trioses, pentoses, and hexoses?
|Monosaccharides with three, five, and six carbon atoms, respectively.
|Name two other common monosaccharides.
|Galactose and fructose.
|What is the difference between glucose, galactose, and fructose?
|They have the same chemical formula (C6H12O6) but different structures due to the arrangement of functional groups.
|What are disaccharides?
|Carbohydrates formed by the joining of two monosaccharides through a glycosidic bond.
|Give examples of common disaccharides.
|Lactose, maltose, and sucrose.
|What are the monomers of lactose?
|Glucose and galactose.
|What is maltose composed of?
|Two glucose molecules.
|What are the monomers of sucrose?
|Glucose and fructose.
|What is a polysaccharide?
|A long chain of monosaccharides linked by glycosidic bonds.
|Name examples of polysaccharides.
|Starch, glycogen, cellulose, chitin, and peptidoglycans.
|What is the main function of starch in plants?
|It serves as the stored form of sugars in plants.
|What is glycogen?
|The storage form of glucose in humans and other vertebrates.
|Where is glycogen primarily stored in the body?
|Liver and muscle cells.
|What is cellulose and its function?
|It is a major component of plant cell walls and provides structural support.
|What is chitin and where is it found?
|It forms the exoskeleton of arthropods and is a major component of fungal cell walls.
|What are peptidoglycans and their role?
|They are the primary component of bacterial cell walls, providing structural support.
|What are the functions of carbohydrates in cells?
|Energy storage, structural support, and as building blocks for complex molecules.
|What is the role of carbohydrates in photosynthesis?
|They are synthesized by plants, algae, and some bacteria using energy from the sun.
|What are the functions of fiber in the diet?
|Promoting regular bowel movement, regulating blood glucose, and reducing cholesterol levels.
|What is the primary source of energy in cellular respiration?
|Glucose, which is broken down to produce ATP.
|Why is it important to consume carbohydrates in a well-balanced diet?
|They provide instant energy and are necessary for overall health and function.
|What is a sensible approach to weight loss?
|A low-calorie diet rich in whole grains, fruits, vegetables, lean meat, exercise, and proper hydration.
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