Carbohydrates and Their Functions

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Questions and Answers

What characterizes two sugars as epimers?

They have the same molecular formula but different structural formulas.

They differ in configuration around all carbon atoms.

They differ in configuration around only one specific carbon atom. (correct)

They are mirror images of each other.

What is the purpose of Molisch’s test?

To identify the type of sugar present in a solution.

To confirm the presence of carbohydrates in a solution. (correct)

To confirm the presence of proteins in a solution.

To confirm the presence of lipids in a solution.

Which of the following components is NOT part of the procedure for Molisch’s test?

Amino acid solution (correct)

5% alpha-naphthol solution in ethyl alcohol

Concentrated sulphuric acid

A clean and dry test tube

What color indicates a positive result for Molisch’s test?

Purple Signup and view all the answers

Which statement best defines enantiomers in carbohydrate chemistry?

They are mirror images of each other. Signup and view all the answers

Which compound is associated with the N-glycosidic linkage?

Amine group (-NH2) Signup and view all the answers

Which group of substances does Molisch's test primarily identify?

Carbohydrates Signup and view all the answers

Which of the following is true regarding the isomers mentioned in the content?

Glucose and Galactose are epimers. Signup and view all the answers

What is measured in the hydrogen breath test after the patient consumes a lactose-loaded beverage?

Concentration of hydrogen in the breath Signup and view all the answers

What is the initial phase of glycolysis known for?

Energy-investment phase Signup and view all the answers

Which of the following products is NOT produced during glycolysis?

Lactic acid Signup and view all the answers

What color indicates the presence of amylose during H. Bial's test?

Deep blue Signup and view all the answers

What condition does the stool acidity test help assess in infants and children?

Amount of acid from undigested lactose Signup and view all the answers

What is the initial step in the procedure for Bial's test?

Add 3mL of Bial’s reagent in an empty test tube. Signup and view all the answers

Which carbohydrate bond is unlikely to be hydrolyzed during digestion?

α-1,2 glycosidic bond Signup and view all the answers

Which component of starch is responsible for producing a purple color in Bial's test?

Amylopectin Signup and view all the answers

What condition might lead to the symptoms of bloating, gas, and diarrhea described in the clinical case?

Lactose intolerance Signup and view all the answers

What reaction occurs with furfural in the presence of ferric ion during Bial's test?

It yields a blue-green colored complex. Signup and view all the answers

How long does it typically take to obtain results from the hydrogen breath test?

2-3 hours Signup and view all the answers

Which sugar is specifically identified by the reaction producing violet or no color with iodine in Bial's test?

Pentoses Signup and view all the answers

During what process is hydrogen produced from undigested sugars?

Bacterial fermentation Signup and view all the answers

What role do salivary and pancreatic alpha amylase play in carbohydrate metabolism?

They initiate the breakdown of polysaccharides in the mouth. Signup and view all the answers

How does glycogen appear when subjected to Bial's test?

Reddish brown Signup and view all the answers

What is the purpose of heating the test tube in Bial's test?

To enable the formation of furfural. Signup and view all the answers

What is the primary consequence of lactase deficiency in individuals?

Incapable of hydrolyzing lactose Signup and view all the answers

Which glycosidic bond is specifically hydrolyzed by lactase?

β-bonds connecting glucose and galactose Signup and view all the answers

What type of disorder is associated with sucrase-isomaltase deficiency?

Autosomal-recessive disorder Signup and view all the answers

What symptoms are commonly associated with lactose intolerance?

Pain, nausea, and flatulence Signup and view all the answers

Which enzyme is coded by the LCT gene?

Lactase Signup and view all the answers

What happens in the intestines when lactose is not broken down?

Bacterial contamination and gas production Signup and view all the answers

What is the prevalence of individuals affected by sucrase-isomaltase deficiency?

1 in 5,000 Signup and view all the answers

Which catalytic site of the beta-glycosidase complex hydrolyzes the α-1,6 glycosidic bond?

Isomaltase-maltase Signup and view all the answers

What is the primary consequence of hexokinase deficiency in red blood cells?

Decreased production of 2,3 BPG Signup and view all the answers

Which of the following deficiencies is most commonly associated with glycolysis malfunction?

Pyruvate kinase deficiency Signup and view all the answers

What type of inheritance pattern is primarily associated with mutations affecting glycolytic enzymes?

Autosomal recessive Signup and view all the answers

What is the role of glucokinase in glucose metabolism?

Glucose sensing in blood glucose homeostasis Signup and view all the answers

Which diagnosis is commonly associated with hexokinase deficiency?

Jaundice Signup and view all the answers

Which enzyme is specifically known for converting acetaldehyde to ethanol?

Alcohol dehydrogenase Signup and view all the answers

What biochemical outcome is primarily caused by inactivating mutations of glucokinase?

Type 1 diabetes in young patients Signup and view all the answers

Which condition is a direct result of hexokinase deficiency in pediatric patients?

Nonspherocytic hemolytic anemia Signup and view all the answers

Study Notes

Carbohydrate Linkages and Isomers

Purines, aromatic rings, proteins, and lipids are non-carbohydrate molecules linked to sugars.
Isomers include glucose and fructose; they differ structurally but share the same molecular formula.
Epimers, a specific type of isomer, differ at only one carbon atom, such as glucose and galactose.

Tests for Carbohydrates

Molisch’s Test:
- Confirms the presence of carbohydrates using a reagent of 5% alpha-naphthol in ethyl alcohol.
- Procedure: Combine CHO solution with Molisch reagent and add concentrated sulfuric acid. A purple ring indicates a positive result.
Bial’s Test:
- Distinguishes pentoses from hexoses by forming a blue-green complex with furfural in the presence of orcinol and ferric ion.
- Procedure: Heat Bial’s reagent with the test solution. A blue-green color indicates a positive result.

Enzyme Function and Disorders

Salivary and pancreatic alpha-amylase initiate the breakdown of polysaccharides.
Lactase Deficiency:
- Causes lactose intolerance (pain, gas, nausea) due to insufficient lactase enzyme.
- Genetic basis linked to LCT gene mutations affects lactose breakdown.
Sucrase-Isomaltase Deficiency:
- Autosomal-recessive disorder affecting 1 in 5,000 individuals; leads to abdominal pain and gas from undigested sugars.
- Diagnosis may include hydrogen breath tests that evaluate hydrogen levels from bacterial fermentation of lactose.

Glycolysis

Glycolysis occurs in two stages: an energy-investment phase (first five steps) and an energy-generation phase (last five steps).
End products of glycolysis include 2 pyruvate, 2 ATP, and 2 NADH.
Hexokinase is known as HK4, acting as a glucose sensor critical in blood glucose regulation.

Malfunctions in Glycolysis

Genetic mutations can disrupt glycolysis, leading to enzyme deficiencies such as phosphofructokinase, aldolase, enolase, and pyruvate kinase deficiencies.
Hexokinase Deficiency:
- Results in hereditary non-spherocytic hemolytic anemia, particularly in pediatric patients due to poor oxygen delivery to tissues.
- Diagnosis includes increased levels of lactate dehydrogenase (LDH).

Clinical Case Insights

Symptoms of lactase deficiency include abdominal issues, flatulence, and diarrhea.
Symptoms suggest possible lactose intolerance or malabsorption, warranting further investigation through stool acidity tests or hydrogen breath tests.

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Description

Explore the fascinating world of carbohydrates, including their linkages, isomers like glucose and fructose, and important tests such as Molisch’s and Bial’s tests. Additionally, discover the role of enzymes in carbohydrate breakdown and related disorders. This quiz covers essential biochemical concepts you need to know.