19 Questions
What is the empiric formula for many of the simpler carbohydrates?
(CH2O)n, n ≥3
Which sugar is converted to glucose in the liver?
Galactose
What is the major metabolic fuel of mammals?
Glucose
What are the structural components of many organisms including the cell walls of bacteria and the fibrous cellulose of plants?
Carbohydrates
Which disease is associated with carbohydrate metabolism?
Diabetes mellitus
What is the precursor for synthesis of all other carbohydrates in the body?
Glucose
What is the entire complement of sugars produced by an organism, whether free or in more complex molecules?
Glycome
What serves as a storage form of energy in the body and as cell membrane components that mediate some forms of intercellular communication?
Carbohydrates
What is the most common storage polysaccharide in animals?
Glycogen
Which of the following is a structural polysaccharide found in plant cell walls?
Chitin
What is the measure of a carbohydrate-containing food's effect on blood sugar levels?
Glycemic index
Which complex carbohydrate provides hydration and support to various tissues?
Hyaluronic acid
What is the most common disaccharide among the important disaccharides mentioned in the text?
Sucrose
Which of the following is an example of a disaccharide?
Maltose (glucose + glucose)
What is the most abundant monosaccharide?
D-glucose
What determines the D- and L-Isomerism of sugars?
Arrangement of atoms around the asymmetric carbon atom
Which type of sugar cannot be hydrolyzed into simpler carbohydrates?
Monosaccharides
What confers optical activity on a compound?
Presence of asymmetric carbon atoms
What is the main component of dietary fiber?
Foods with a polysaccharide structure
Study Notes
- Monosaccharides: i. Sugars that cannot be hydrolyzed into simpler carbohydrates. ii. Classified based on the number of carbon atoms (3-7) and whether they have an aldehyde or ketone group. iii. Most abundant monosaccharide is D-glucose (6-carbon sugar).
- Disaccharides: 1. Condensation products of two monosaccharide units. 2. Bonds are formed through glycosidic bonds. 3. Examples include lactose (glucose + galactose), maltose (glucose + glucose), and sucrose (glucose + fructose).
- Oligosaccharides: 1. Condensation products of 3 to 10 monosaccharides. 2. Most are not digested by human enzymes and have glycosidic bonds. 3. Foods with a polysaccharide structure form the main component of dietary fiber. 4. Examples include cellulose (from plant cell walls) and inulin (storage carbohydrate in some plants).
- Polysaccharides: 1. Condensation products of more than 10 monosaccharide units. 2. Formed by glycosidic bonds. 3. Examples include glycogen (branched glucose polymers), starches, and dextrins.
- D- and L-Isomerism: 1. Isomers with the same chemical formula but different structures. 2. Determined by the arrangement of atoms around the asymmetric carbon atom, not optical rotation. 3. Natural sugars are mostly D- and natural amino acids are mostly L-isomers.
- Optical Isomerism: 1. Presence of asymmetric carbon atoms confers optical activity on the compound. 2. Rotation of plane-polarized light can determine the compound’s optical activity and is independent of the stereochemistry.
- Pyranose and Furanose Ring Structures: 1. Monosaccharide ring structures similar to pyran (a six-membered ring) or furan (a five-membered ring). 2. Important for understanding the arrangement of the atoms in monosaccharides.
- Alpha- and Beta-Anomers: 1. Ring structure of aldoses and ketoses formed by a hemiacetal or hemiketal respectively. 2. In alpha-configuration, the hydroxyl group on the anomeric carbon projects to the same side as the ring. 3. In beta-configuration, the hydroxyl group projects to the opposite side of the ring.
- Epimers: 1. Isomers differing in configuration of hydroxyl and hydrogen on carbon atoms 2, 3, and 4 of glucose. 2. Important epimers of glucose are mannose (epimerized at carbon 2), galactose (epimerized at carbon 4).
- Aldose-Ketose Isomerism: 1. Aldoses are reducing sugars and can be tested for in urine through reduction of copper solution. 2. Reducing sugars include glucose, galactose, and mannose.
- Glycosides: 1. Formed by condensation between the hydroxyl group on the anomeric carbon and a second compound. 2. If hemiacetal is glucose, the resulting compound is a glucoside; if galactose, a galactoside. 3. Can be formed with amines to form N-glycosidic bonds, such as those found in nucleotides.
- Cardiac Glycosides: 1. Glycosides containing steroids as the aglycone. 2. Important in medicine due to their action on the heart. 3. Examples include digoxin and ouabain, which inhibit Na+-K+-ATPase of cell membranes.
- Antibiotic Glycosides: 1. Contain glycosides and are used as antibiotics. 2. Examples include streptomycin.
- Deoxy Sugars: 1. Monosaccharides in which one hydroxyl group has been replaced by hydrogen. 2. Example: deoxyribose in DNA.
- Amino Sugars (Hexosamines): 1. Monosaccharides with an amino group on the carbon chain. 2. Important components of glycoproteins, gangliosides, and glycosaminoglycans. 3. Examples include D-glucosamine and D-galactosamine.
- Disaccharides: 1. Sugars composed of two monosaccharide residues linked by a glycoside bond. 2. Examples include sucrose (glucose + fructose), lactose (glucose + galactose).
Learn about the most abundant organic molecules in nature with this introduction to carbohydrates. Discover their structural and metabolic roles, and their significance as a source of dietary calories and energy storage in the body.
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