Carbohydrates in Human Biology

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Questions and Answers

Which of the following is NOT a biomedical importance of carbohydrates?

Certain carbohydrate derivatives are used as drugs, such as cardiac glycosides and antibiotics.

Carbohydrates are crucial for the formation of structural components like bones and teeth. (correct)

Serving as a chief energy source for the body.

Acting as constituents of compound lipids and conjugated proteins.

What is the defining characteristic of a monosaccharide?

They are the simplest form of carbohydrates and cannot be further hydrolyzed. (correct)

They are primarily found in plant-based foods.

They contain two or more sugar units linked together.

They are composed of a long chain of sugar units.

Which of the following statements accurately describes the relationship between carbohydrates and metabolic diseases?

Inherited deficiencies in carbohydrate metabolism do not lead to any significant health problems.

Lactose intolerance is exclusively caused by environmental factors and not genetic predisposition.

Disorders of carbohydrate metabolism, like galactosemia and GSDs, can arise from inherited enzyme deficiencies. (correct)

Carbohydrate metabolism is unaffected in individuals with diabetes mellitus.

What is the primary carbohydrate found in milk?

Lactose (B) Signup and view all the answers

Which of the following is an example of an oligosaccharide?

Maltose (B) Signup and view all the answers

Which of the following statements accurately describes the breakdown products of carbohydrates?

They can be utilized to synthesize other substances like fatty acids, cholesterol, and amino acids. (B) Signup and view all the answers

What is the general formula for monosaccharides?

CnH2nOn (D) Signup and view all the answers

Which of the following statements best describes the significance of mucopolysaccharides in the body?

They form the ground substance of mesenchymal tissues. (B) Signup and view all the answers

Which of the following carbohydrates can be converted into glucose in the liver?

Fructose (A), Galactose (B), All of the above (D) Signup and view all the answers

In which specific cells is fructose utilized for energy?

Sperm cells (C) Signup and view all the answers

Which of the following is NOT a component of galactose?

Glycoproteins (C) Signup and view all the answers

What is the primary function of glucose in erythrocytes and brain cells?

Energy production (D) Signup and view all the answers

What type of ring structure is formed when a carbonyl group reacts with an alcoholic hydroxyl group?

Furanose ring (A), Pyranose ring (B) Signup and view all the answers

What determines whether a sugar is an alpha (α) or beta (β) isomer?

The position of the hydroxyl group attached to the anomeric carbon (B) Signup and view all the answers

What property allows a substance containing asymmetric carbon atoms to rotate plane polarized light?

Optical activity (B) Signup and view all the answers

Which of the following carbohydrates is a constituent of glycoproteins?

Mannose (C), All of the above (D) Signup and view all the answers

Which of the following statements correctly describes the relationship between glucose and galactose?

Glucose and galactose are epimers, differing in the configuration of only one chiral center. (A) Signup and view all the answers

Which of the following sugars is a deoxy sugar?

Deoxyribose (D) Signup and view all the answers

If a monosaccharide rotates plane-polarized light to the left, it is considered:

Levorotatory (C) Signup and view all the answers

Which of the following statements about anomers is CORRECT?

Anomers are formed by the change of position of a hydroxyl group attached to the anomeric carbon. (A) Signup and view all the answers

How many asymmetric carbon atoms are present in glucose?

4 (B) Signup and view all the answers

Which of the following pairs of sugars are epimers?

Glucose and Mannose (B), Glucose and Galactose (C) Signup and view all the answers

The simplest carbohydrate, glyceraldehyde, has ____ asymmetric carbon atoms.

1 (A) Signup and view all the answers

Fructose is sometimes called levulose because it is ______ .

Levorotatory (D) Signup and view all the answers

Which of the following is TRUE about the role of amino sugars in antibiotic activity?

The presence of amino sugars in certain antibiotics may contribute to their antibiotic activity. (B) Signup and view all the answers

Why is neuraminic acid rarely found in nature in its pure form?

Neuraminic acid is highly unstable and degrades quickly in biological environments. (B) Signup and view all the answers

What is the primary function of muramic acid in bacterial cells?

Muramic acid is the primary building block for the bacterial cell wall, providing structural support and protection. (A) Signup and view all the answers

How does the presence of fructose contribute to the sweetness of honey?

Fructose interacts with taste receptors differently than glucose, producing a stronger sensation of sweetness. (C) Signup and view all the answers

What is the significance of the term 'Invert Sugar' in relation to sucrose?

Invert sugar refers to the mixture of glucose and fructose produced by the enzymatic hydrolysis of sucrose. (B) Signup and view all the answers

What distinguishes glycosides from other carbohydrate-containing compounds?

Glycosides are characterized by the presence of a non-carbohydrate residue attached to the carbohydrate molecule. (D) Signup and view all the answers

Why is parenteral administration of sucrose ineffective for providing energy?

Sucrose requires the presence of digestive enzymes in the gut to be broken down into usable energy sources. (B) Signup and view all the answers

What is the primary therapeutic benefit of administering sucrose in cases of cerebral edema?

Sucrose helps to increase the osmotic pressure of the blood, drawing water out of the tissues into the bloodstream. (B) Signup and view all the answers

What is the main reason why deficiency of the appropriate enzyme in the gut leads to diarrhea?

The unhydrolyzed disaccharides draw water into the gut, causing osmotic pressure. (B) Signup and view all the answers

Which of the following accurately describes the relationship between starch and amylose?

Amylose is a linear polymer of glucose units and is a component of starch. (C) Signup and view all the answers

What is the primary difference between amylopectin and glycogen?

Amylopectin has a higher degree of branching than glycogen. (C) Signup and view all the answers

What is the significance of the process known as glycogenolysis?

It breaks down glycogen into glucose for energy. (C) Signup and view all the answers

Which of the following is a characteristic of dextrins?

They are intermediate products of starch hydrolysis. (C) Signup and view all the answers

What is the main function of mucopolysaccharides?

They provide lubrication and cushioning in various tissues and fluids. (A) Signup and view all the answers

Which of the following statements correctly describes the relationship between starch and glycogen?

Glycogen is a branched polymer of glucose units and is similar to amylopectin, a component of starch. (A) Signup and view all the answers

Which of the following is a TRUE statement based on the information provided?

Glycogen is the storage form of carbohydrates in animals and is also found in plants with chlorophyll systems. (A) Signup and view all the answers

What is the primary function of erythrose, a tetrose, in the body?

It serves as a precursor to the synthesis of other important molecules. (A) Signup and view all the answers

What is the chemical difference between an aldotetrose and a ketotetrose?

An aldotetrose contains an aldehyde group, while a ketotetrose contains a ketone group. (A) Signup and view all the answers

Which of the following statements is TRUE regarding the importance of pentoses in biological systems?

Pentoses are essential components of nucleic acids and coenzymes. (A) Signup and view all the answers

What is the condition called when excessive intake of cherries and grapes leads to the presence of arabinose in urine?

Alimentary pentosuria (A) Signup and view all the answers

Which of the following is NOT a characteristic of glucose, the chief carbohydrate for mammals?

It is a common constituent of plant cell walls. (A) Signup and view all the answers

Which of the following statements BEST describes the classification of monosaccharides?

Monosaccharides are classified based on the number of carbon atoms they contain and the presence of either an aldehyde or a ketone group. (B) Signup and view all the answers

What is the significance of the suffix '-ulose' in the classification of monosaccharides?

It indicates the presence of a ketone group. (C) Signup and view all the answers

Which of the following monosaccharides IS NOT directly linked to the structure of nucleic acids (DNA and RNA)?

Arabinose (A) Signup and view all the answers

Study Notes

Carbohydrate Chemistry

Carbohydrates are chemically defined as aldehyde or ketone derivatives of higher polyhydric alcohols, or compounds that yield these derivatives on hydrolysis.
Key components include aldehyde groups and ketone groups, with many hydroxyl groups.

Biomedical Importance of Carbohydrates

Carbohydrates are the primary source of energy.
They are components of complex lipids and proteins.
Degradation products act as catalysts.
Some carbohydrate derivatives are used as drugs (e.g., cardiac glycosides and antibiotics).
Lactose is the main sugar in milk produced by lactating mammary glands.
Degradation products are used to create other substances such as fatty acids, cholesterol, and amino acids.
Carbohydrates are constituents of mucopolysaccharides, which form the fundamental substance of mesenchymal tissues.
Inherited deficiencies in carbohydrate metabolic pathways can cause diseases (e.g., galactosemia, glycogen storage diseases, lactose intolerance).
Glucose metabolism abnormalities are observed in diabetes mellitus.

Carbohydrate Classification

Carbohydrates are categorized into four main groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
Monosaccharides have one sugar unit.
Disaccharides have two sugar units.
Oligosaccharides have 3-10 sugar units.
Polysaccharides have more than 10 sugar units.
The ratio between carbon and water is typically 1: 2 in carbohydrates.

1. Monosaccharides

Also known as simple sugars or glycoses.
Cannot be further hydrolyzed.
Subclassified based on carbon atoms (trioses, tetroses, pentoses, hexoses, etc.).
Further distinguished as aldoses or ketoses depending on the presence of an aldehyde or ketone group, respectively.
Trioses include Glyceraldehyde and Dihydroxyacetone.
Tetroses include Erythrose and Erythrulose.
Pentoses include Ribose, Arabinose, Lyxose, and Xylose. (Ribose, arabinose, xylose, and lyxose are aldopentoses; ribulose and xylulose are ketopentoses).
Hexoses include Glucose, Mannose, Galactose, and Fructose.
- Glucose is the chief carbohydrate, the primary metabolic fuel for mammals and a universal fuel for the fetus.
- Fructose is found in fruits, honey, and semen. It's converted to glucose in the liver, and is utilized by seminal fluid and sperm for energy production.
- Galactose is synthesized in mammary glands to produce lactose (milk sugar). It can be converted to glucose in the liver and found in glycosaminoglycans, glycolipids, and agar.
- Mannose is not found freely in nature, but found as constituent of many glycoproteins.

1. Monosaccharides (continued)

Monosaccharides exist in cyclic forms due to the reaction between the carbonyl group (C=O) and a hydroxyl (alcohol) group.
Cyclic forms are either pyranose (5-membered ring) or furanose (4-membered ring).
Different ring forms of a monosaccharide are called anomers. Alpha (α) and Beta (β) forms differ by the position of a hydroxyl group on the anomeric carbon (C1 in aldoses, C2 in ketoses).
Asymmetric Carbon atoms result in optical activity.
A substance with an asymmetric carbon atom can exist in different optical isomers.
- Glucose is dextrorotatory, hence called dextrose.
- Fructose is levorotatory, hence called Levulose.

Sugar Derivatives

Deoxy sugars are formed by replacing hydroxyl groups with hydrogen atoms. Deoxyribose is an example of a deoxy sugar.
Amino sugars contain an amino group (-NH2). Glucosamine, galactosamine, and mannosamine are important examples. Some antibiotics also contain amino sugars.
Neuraminic acid is an unstable amino sugar acid found naturally in acylated derivative form called sialic acids. It is a vital part of peptidoglycan composition.
Glycosides are compounds composed of a carbohydrate and a non-carbohydrate molecule (aglycone). The carbohydrate moiety is attached to the non-carbohydrate residue via a carbon-1 acetal linkage. Cardiac glycosides, such as digitalis, are examples of this type of compound.

2. Disaccharides

Disaccharides are formed from two monosaccharides linked together.
Common disaccharides: maltose, isomaltose, trehalose, lactose, and sucrose.
Maltose contains two glucose monomers.
Isomaltose also contains two glucose monomers.
Trehalose also contains two glucose monomers.
Lactose is made up of glucose and galactose.
Sucrose is made up of glucose and fructose.

3. Polysaccharides

Polymers made up of many monosaccharides.
Homopolysaccharides are composed of a single type of monosaccharide. Examples include starch, glycogen, cellulose, and inulin.
Heteropolysaccharides are made up of more than one type of monosaccharide and may also contain other groups such as hexuronic acid. Mucopolysaccharides are an example of heteropolysaccharides.
Starch is composed of amylose and amylopectin. Amylose is linear, while amylopectin is branched.
Glycogen is the primary storage polysaccharide in animals, similar in structure to amylopectin but more extensively branched.
Dextrins are products of starch partial hydrolysis.
Cellulose is a linear polysaccharide composed of glucose units joined by β(1→4) glycosidic linkages.
Agar is a sulphated polysaccharide derived from seaweed.
Inulin is a storage polysaccharide composed of fructose units, found in roots and tubers.

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Test your knowledge about the role of carbohydrates in human biology with this quiz. From their metabolic significance to specific types like monosaccharides and oligosaccharides, explore key concepts that underscore their importance in health and disease. Perfect for students studying biochemistry or those interested in nutrition.