Capítulo 5. Discusión general ........................................... ¡Error! Marcador no definido
5.2. Potencial de los bloques multinutrientes, que incluyen subproductos de invernaderos,
5.2.2. Fermentación ruminal y síntesis de proteína microbiana
Carbohydrates-I 53 Q. Name some important monosaccharides.
(Page 61) A. Glucose, fructose, galactose, mannose.
Q. What are pentoses? (Page 61)
A. Monosaccharides with five carbon atoms.
Q. Name a few pentoses. (Page 61) A. Arabinose, Xylose, Ribose.
Q. Which is the reference carbon atom in sugars?
(Page 62) A. Penultimate carbon atom.
Q. What is the difference between D and L sugars?
(Page 62) A. They are mirror images with reference to
penultimate carbon atom.
Q. Which isomer is common in nature? (Page 62) A. D variety of sugars are common in nature.
Q. Which is the most common monosaccharide in the body?
A. Glucose. (Page 62)
Q. What is the difference between glucose and
ga-lactose? (Page 62)
A. They are different with regard to the H and OH groups at the 4th carbon atom. Galactose is the 4th epimer of glucose (Fig.8.3).
Q. Galactose is present in which food? (Page 62) A. Lactose is present in milk. Lactose contains
ga-lactose and glucose.
Q. What is epimerism? (Page 62) A. When sugars are different from one another, only
in configuration with regard to a single carbon atom (other than the reference carbon atom), they are called epimers.
Q. Give an example. (Page 62)
A. For example, glucose and mannose are an epimeric pair which differ only with respect to carbon atom 2. Similarly, galactose is the 4th epimer of glucose. (Fig. 8.3).
Q. Anomerism is produced with reference with
which carbon atom? (Page 62)
A. Anomers are produced by the spatial configura-tion with reference to the first carbon atom in al-doses and second carbon atom in ketoses. (Fig.
8.4).
Q. How alpha and beta forms of sugars are
pro-duced? (Page 62)
A. These are anomers. The difference lies in the spa-tial configuration with reference to the first car-bon atom in aldoses and second carcar-bon atom in ketoses. (Fig. 8.4).
Q. What is the basis of mutarotation? (Page 62) A. It is due to the anomeric carbon atom.
Q. What is the difference between glucose and fruc-tose?
A. Glucose is an aldohexose, and fructose is a ketohexose.
Carbohydrates-I 55
Q. Name a ketose. (Page 63)
A. Fructose.
Q. What is the principle of Benedict’s test?
(Page 64) A. In alkaline medium, sugar will cause reduction
of cupric ions, to form red coloured precipitate.
Q. What is the composition of Benedict’s reagent.
(Page 64)
A. It contains sodium carbonate, copper sulfate and sodium citrate. In the alkaline medium provided by sodium carbonate, the copper remains as cu-pric hydroxide. Sodium citrate acts as a stabilising agent to prevent precipitation of cupric hydrox-ide.
Q. Benedict’s test is commonly employed for what?
(Page 64) A. To detect the presence of glucose in urine.
Q. Name a few reducing sugars. (Page 64) A. Glucose, fructose, mannose.
Q. Keto group is non-reducing, but fructose reduces Benedict’s solution, what is the cause for this
anomaly? (Fig. 8.10)
A. In alkaline medium, ketone group is converted to aldehyde, through enediol formation.
Q. In the case of sugars, which of the properties go hand in hand?
A. Reducing property, osazone formation and
mu-tarotation. (page 64)
Q. Glucose and fructose will form identical osazones, why?
A. The difference in glucose and fructose is depen-dent on the first and second carbon atoms, and this is masked by the osazone formation.
(Page 64) Q. On oxidation of glucose, what are produced?
(Page 64) A. Glucuronic acid, gluconic acid and
glucos-accharic acid.
Q. Reduction of glucose produces what? (Page 64) A. Sorbitol.
Q. Name some deoxy sugars. (Page 66) A. Deoxy ribose, fucose (deoxy galactose).
Q. Which is the stain used to identify deoxysugar?
(Page 66) A. Feulgen staining.
Q. Name some important disaccharides. (Page 67) A. Sucrose, lactose, maltose.
Q. What is the glycosidic linkage in lactose?
(Page 67) A. Beta 1-4 linkage.
Q. What is the glycosidic linkage in sucrose?
(Page 67) A. 1-2 linkage.
Carbohydrates-I 57 Q. Which disaccharide has no free aldehyde or
ke-tone group?
A. Sucrose. (Page 67)
Q. Glucose and fructose are reducing sugars, but sucrose (containing glucose and fructose) is a non-reducing sugar, why? (Page 67) A. Because the glycosidic linkage in sucrose involves
1st carbon of glucose and 2nd carbon of fructose, so both reducing groups are masked.
Q. Hydrolysis of maltose will give rise to what ? (Page 67) A. Two glucose units.
Q. Which is the sugar found in milk? (Page 67) A. Lactose.
Q. What are the component monosaccharides of
lac-tose? (Page 67)
A. Galactose and glucose.
Q. Sucrose consists of what monosaccharides?
(Page 67) A. Glucose + fructose.
Q. Name reducing disaccharides. (Page 67) A. Lactose and maltose.
Q. How polysaccharides are classified? (Page 68) A. Homopolysaccharides (homoglycans) and
heteropolysaccharides (heteroglycans).
Q. What is a homopolysaccharide? (Page 68) A. They are composed of single kind of
monosac-charides.
Q. Give examples of homopolysaccharides.
(Page 68) A. Starch, and glycogen.
Q. What are heteropolysaccharides? (Page 68) A. They are composed of two or more different
monosaccharides.
Q. What are the characteristics of glycogen?
(Page 69) A. It is composed of glucose units. It is the stored
form of carbohydrate in animal kingdom. It has a highly branched structure.
Q. What is the reserve carbohydrate in plant
king-dom? (Page 69)
A. Starch.
Q. What is the end product of action of pancreatic
amylase on starch? (Page 69)
A. Maltose.
Q. Cellulose and starch are polysaccharides made of glucose, but cellulose cannot be digest by
human beings, why? (Page 69)
A. Cellulose contains beta 1,4 linkages, which can-not be digested by human enzymes.
Q. What is inulin? (Page 69)
A. It is a homopolysaccharide, composed of fructose units.
Q. What is the use of inulin? (Page 69) A. It is used to find renal clearance and glomerular
filtration rate.
Carbohydrates-I 59 Q. Give examples of heteropolysaccharides.
(Page 70) A. Agar, hyaluronic acid, heparin, chondroitin
sul-fate.
Q. What are mucopolysaccharides? (Page 70) A. They contain uronic acid and amino sugars.
Q. Which heteropolysaccharide does not contain
uronic acid? (Page 70)
A. Keratan sulfate.
Q. Hyaluronic acid is seen in which tissues?
(Page 70) A. Connective tissue, synovial fluid, tendons,
vitre-ous humor.
Q. What is the difference between glycoprotein and
mucoprotein? (Page 71)
A. If the carbohydrate content is less than 10%, it is called a glycoprotein. If the carbohydrate content is more than 10% it is a mucoprotein.
Q. The rate of absorption of sugars in intestine is highest for which monosaccharide? (Page 71) A. Absorption rate of galactose is more than glucose,
while fructose is absorbed at a lesser rate than glucose.
Q. Glucose is absorbed at the luminal side of gastro intestinal cells by which mechanism?
(Page 72, and Fig. 8.30) A. Carrier mediated co-transport with sodium,
named as sodium dependent glucose transporter (SGluT).
Q. How glucose is released from intestinal cells into the blood stream?
A. Glucose transporter type 2 (GluT2) (Fig.8.30).
Q. How glucose is taken up by cells from blood
stream? (Page 72)
A. In tissues GluT2 is involved in absorption of glu-cose from blood.
Q. What is the importance of GluT4? (Page 72) A. It is the glucose transporter present in muscle and
adipose tissues. Insulin induces these transport-ers. In diabetes mellitus, entry of glucose into muscle is decreased, because GluT4 is reduced in insulin deficiency.
Q. What is the glucose sensor in the beta cells of
pancreas? (Page 72)
A. GluT2 acts as the glucose sensor mechanism, for the controlled supply of insulin into blood stream.
Carbohydrates-II 61