Monosaccharides and Their Configurations

Questions and Answers

What determines the D or L configuration of a monosaccharide?

The –OH group of the highest chiral carbon

What is a triose?

A monosaccharide with five carbon atoms

A monosaccharide with three carbon atoms (correct)

A monosaccharide with six carbon atoms

A monosaccharide with four carbon atoms

Which of the following are types of monosaccharides based on the number of carbon atoms?

Triose

Pentose

Hexose

All of the above (correct)

An aldose contains a ketone functional group.

False Signup and view all the answers

What is the difference between D-glucose and D-galactose?

They differ in the placement of the -OH group on carbon 4. Signup and view all the answers

What are cyclic monosaccharides formed from?

The reaction between a carbonyl group and a hydroxyl group Signup and view all the answers

Which cyclic sugar form has a six-atom ring?

Pyranose Signup and view all the answers

What is an anomeric carbon atom?

The hemiacetal carbon atom in a cyclic monosaccharide. Signup and view all the answers

Haworth projection formulas accurately represent the stereochemistry of sugars.

True Signup and view all the answers

What is the biochemical importance of D-Ribose?

Structural elements of nucleic acids and coenzymes. Signup and view all the answers

Are all carbohydrates sweet?

No Signup and view all the answers

Give at least one medical use for carbohydrates.

Carbohydrates can be used in medical applications such as intravenous glucose solutions. Signup and view all the answers

What are carbohydrates primarily classified on?

Molecular size Signup and view all the answers

The human diet should ideally be about two-thirds carbohydrate by mass.

True Signup and view all the answers

What process do green plants use to produce carbohydrates?

Photosynthesis Signup and view all the answers

What is a chiral center?

A carbon atom bonded to four different groups. Signup and view all the answers

What does the term 'enantiomers' refer to?

Stereoisomers that are nonsuperimposable mirror images Signup and view all the answers

Achiral molecules possess handedness.

False Signup and view all the answers

Which phrase correctly describes an optically active compound?

It rotates the plane of polarized light. Signup and view all the answers

What is the role of insulin in the body?

Insulin helps cells absorb blood sugar for energy or storage. Signup and view all the answers

What happens when blood sugar levels drop too low?

Alpha cells in the pancreas release glucagon. Signup and view all the answers

What can result from high glucose levels in cells?

Insulin resistance Signup and view all the answers

Why should carbohydrates be eaten before exercise?

To top up energy stores in muscles and the liver, improving performance. Signup and view all the answers

What happens to performance when all carbohydrates are used?

Performance decreases, and the body starts to use protein as its energy source. Signup and view all the answers

Eating carbohydrates is unnecessary for high endurance sports.

False Signup and view all the answers

What are the two structural polysaccharides mentioned?

Cellulose and Chitin Signup and view all the answers

What is the structural component of plant cell walls?

Cellulose Signup and view all the answers

Chitin is the most abundant naturally occurring polysaccharide.

False Signup and view all the answers

What are glycosaminoglycans (GAGs) also known as?

Mucopolysaccharides Signup and view all the answers

What is the role of proteoglycans?

They provide mechanical support and cushioning to joints. Signup and view all the answers

Which of the following is associated with the inflammatory response after tissue injury?

Heparin Signup and view all the answers

The 2nd most abundant naturally occurring polysaccharide, next to __________.

cellulose Signup and view all the answers

Hyaluronic acid is a small polysaccharide with 15–90 disaccharide residues.

False Signup and view all the answers

What is the medical condition characterized by an inability to metabolize galactose?

Galactosemia Signup and view all the answers

Match the following GAGs with their descriptions:

Chondroitin Sulfate = Structural polysaccharide of ligaments, cartilage, and tendons Dermatan Sulfate = Structural polysaccharide in skin Keratan Sulfate = Found primarily in the cornea of the eye Heparan Sulfate = Component of cell-surface proteoglycans Signup and view all the answers

Which type of diabetes is generally diagnosed in children and teenagers?

Type 1 Signup and view all the answers

Match the following terms related to stereoisomerism and carbohydrates:

Enantiomers = Nonsuperimposable mirror image Diastereomers = Not mirror images of one another Chiral molecule = Has a non-superimposable mirror image Achiral molecule = Superimposable mirror image Epimers = Stereoisomers that differ at one specific chiral center Carbohydrate = Most abundant class of bioorganic molecules on Earth Starch = Energy reserve in plants Cellulose = Structural component in plants Photosynthesis = Process of converting light energy into chemical energy Signup and view all the answers

Diastereomers are _____ of each other.

not mirror images Signup and view all the answers

What is the structure being illustrated? (1) a-D-altrose, (2) b-D-altose, (3) a-L-altrose, (4) b-L-altrose.

a-D-altrose Signup and view all the answers

Which of the following monosaccharide structural relationships is CORRECT?

1 and 2 are enantiomers, while 2 and 3 are diastereomers Signup and view all the answers

What form must all carbohydrates be in for cells to use them as an energy source?

Glucose Signup and view all the answers

Polysaccharides are saccharide units that contain 3 to 10 units.

False Signup and view all the answers

What is the primary source of energy for cells?

D-Glucose Signup and view all the answers

The process that forms glycosides from cyclic monosaccharides involves a reaction with _____ in acid solution.

alcohols Signup and view all the answers

D-Fructose is the sweetest tasting sugar.

True Signup and view all the answers

What metabolic condition leads to the presence of D-Glucose in urine?

Diabetes mellitus Signup and view all the answers

Match the following disaccharides with their common names:

Maltose = Malt sugar Cellobiose = Intermediate in the hydrolysis of cellulose Lactose = Milk sugar Sucrose = Table sugar Signup and view all the answers

What is the structure of the glycosidic linkage in Maltose?

α(1-4) Signup and view all the answers

Which of the following is a common reaction of monosaccharides?

Oxidation to acidic sugars Signup and view all the answers

What are the three common natural amino sugars?

D-glucosamine, D-galactosamine, N-acetyl derivatives Signup and view all the answers

Which type of polysaccharide serves as an energy storage polysaccharide in animals?

Glycogen Signup and view all the answers

Polysaccharides are typically sweet and soluble in water.

False Signup and view all the answers

Study Notes

Carbohydrates Overview

Carbohydrates are the most abundant bioorganic molecules on Earth.
They constitute about 75% of dry plant materials, produced through photosynthesis (reactants: carbon dioxide, water; energy source: sunlight).
Major carbohydrate sources for humans and animals come from dietary plant materials, ideally two-thirds of the average diet by mass.

Classification of Carbohydrates

Carbohydrates are classified based on molecular size into:
- Monosaccharides: Single sugar units (e.g., glucose and fructose).
- Disaccharides: Two sugar units linked (e.g., sucrose).
- Oligosaccharides: Short chains of sugar units.
- Polysaccharides: Long chains of sugar units (e.g., starch, cellulose).

Molecular Structure and Chirality

Carbohydrates can be polyhydroxy aldehydes or polyhydroxy ketones.
Chirality refers to "handedness" in molecules; chiral molecules have non-superimposable mirror images.
The presence of a chiral center (a carbon atom bonded to four different groups) determines chirality.
Chiral molecules exhibit different biological responses; the body may respond differently to left-handed versus right-handed forms.

Importance of Chiral Molecules

Right-handed and left-handed forms can elicit different responses in biological systems.
Example: Human body reacts 20 times more effectively to the right-handed form of epinephrine compared to its left-handed counterpart.

Stereoisomerism

Stereoisomers share the same molecular formula but differ spatially:
- Enantiomers: Non-superimposable mirror images (e.g., right and left-handed forms).
- Diastereomers: Stereoisomers that are not mirror images (e.g., cis-trans isomers).

Designating Handedness Using Fischer Projections

Enantiomers can rotate polarized light (dextrorotatory = clockwise, levorotatory = counterclockwise).
D,L system helps determine configuration based on the highest-numbered chiral center's hydroxyl group:
- If -OH is right, it is a D-isomer.
- If -OH is left, it is an L-isomer.
Fischer projections visually represent spatial arrangement around chiral centers.

Summary

Understanding carbohydrates involves reviewing molecular structures, classifications, and the importance of chirality in their biological functions.
Applications of carbohydrates extend to their roles in energy storage, structural roles in plants, and their implications in health, notably in carbohydrate-related diseases.### Structures and Classification of Monosaccharides
Monosaccharides typically contain 3 to 7 carbon atoms.
Three-carbon monosaccharides are called trioses (e.g., glyceraldehyde).
Four-carbon monosaccharides are tetroses (e.g., erythrose).
Five-carbon monosaccharides are pentoses (e.g., ribose, arabinose).
Six-carbon monosaccharides are hexoses (e.g., glucose, fructose).
Aldoses contain an aldehyde functional group; ketoses contain a ketone functional group.
Classification can be based on both the number of carbon atoms and functional groups (e.g., aldohexose, ketopentose).
"Sugar" refers to both monosaccharides and certain disaccharides, often associated with sweetness.

Optical Isomers and Chiral Centers

The number of possible optical isomers is determined by the number of chiral centers in the monosaccharide.
Each chiral carbon can result in varying configurations, affecting the sugar's stereoisomers.
Aldohexose (6C) can produce 16 optical isomers; aldohexose has 4 chiral centers.
Ketoses have fewer optical isomers due to fewer chiral centers.

Epimers

Epimers are forms of carbohydrates that differ at only one chiral center (e.g., D-glucose and D-galactose differ at carbon 4).
Unlike enantiomers, epimers are not mirror images of each other.

Cyclic Monosaccharides: Haworth Projection

Monosaccharides can exist in cyclic forms, represented by Haworth projection formulas.
Cyclic structures result from the reaction of carbonyl groups with hydroxyl groups.
Pyranoses (six-atom rings) and furanoses (five-atom rings) are the two cyclic forms.
The formation of cyclic monosaccharides usually leads to two stereoisomers known as anomers (alpha and beta forms).
The anomeric carbon is the hemiacetal carbon; its configuration defines the type of anomer.

Biochemically Important Monosaccharides

D-Ribose: Essential component of nucleic acids and ATP; involved in various metabolic pathways.
D-Ribulose: An intermediate in the pentose phosphate pathway.
D-Arabinose: Present in various plant gums; constituent of glycoproteins.
D-Glucose: Known as the "sugar" of the body; normal concentration is 70-100 mg/dL; key energy source.
D-Fructose: Found in fruit juices; used by the liver and considered the sweetest sugar.
D-Galactose: Derived from lactose; crucial for brain function and appears in glycolipids.
D-Mannose: Found in plant mannans; a constituent of glycoproteins used for prevention of certain diseases.### Urinary Tract Infections (UTIs)
UTIs are common infections affecting the urinary system, often treated with antibiotics.
Understanding carbohydrate metabolism can help manage genetic disorders like carbohydrate-deficient glycoprotein syndrome.

Reactions of Monosaccharides

Five major reactions include oxidation to acidic sugars, reduction to sugar alcohols, glycoside formation, phosphate ester formation, and amino sugar formation.

Oxidation to Acidic Sugars

Involves redox reactions of monosaccharides, transforming them into acidic forms:
- Aldonic Acid: Acid group at terminal carbon.
- Alduronic Acid: Acid group at the terminal carbon opposite the aldehyde.
- Aldaric Acid: Acid groups at both ends of the molecule.

Reduction to Sugar Alcohols

Carbonyl group can be reduced to a hydroxyl group.
The product is a sugar alcohol (e.g., D-glucose reduced to D-glucitol or D-sorbitol) used in cosmetics and as a sweetener.

Glycoside Formation

Hemiacetal forms of monosaccharides react with alcohols to create acetals, termed glycosides.
Glycosides can exist in alpha and beta forms, defined by the orientation of the -OH group.

Phosphate Ester Formation

Hydroxyl groups of monosaccharides may react with oxyacids to form phosphates.
Forming glucose 1-phosphate and glucose 6-phosphate is important for carbohydrate metabolism.

Amino Sugar Formation

A hydroxyl group replaced by an amino group leads to amino sugar formation (common examples: glucosamine and galactosamine).
Amino sugars are crucial in constructing polysaccharides like chitin and hyaluronic acid.

Disaccharides

Formed from the glycosidic linkage between two monosaccharides functioning as a hemiacetal and an alcohol.
Glycosidic linkages consist of carbon–oxygen–carbon bonds.

Features of Disaccharides

Maltose: Comprised of two D-glucose units, linked by α(1-4) linkage.
Cellobiose: Comprised of β(1-4) glucose and galactose units.
Lactose: Composed of D-galactose and D-glucose with β(1-4) linkage.
Sucrose: Comprising glucose and fructose via α,β(1-2) linkage.

Oligosaccharides

Contain 3 to 10 monosaccharides linked via glycosidic bonds.
Example trisaccharide: Raffinose (α-D-galactose, α-D-glucose, β-D-fructose).
Example tetrasaccharide: Stachyose (two α-D-galactose, one α-D-glucose, one β-D-fructose).

Importance of Oligosaccharides

Blood types (O, A, B, AB) are defined by specific oligosaccharides on red blood cells.

Polysaccharides

Polymers of numerous monosaccharide units, often non-sweet and limited in solubility.
Used as thickeners in cooking due to the hydrophilic nature of -OH groups.

Types of Polysaccharides

Storage Polysaccharides:
- Starch: Energy storage in plants, includes amylose (linear) and amylopectin (branched).
- Glycogen: More branched than amylopectin, serves as energy storage in animals.
Structural Polysaccharides:
- Cellulose: Main component of plant cell walls, indigestible by humans.
- Chitin: Structural element in exoskeletons of arthropods, similar structure to cellulose.
Acidic Polysaccharides:
- Composed of disaccharide repeating units with amino sugars and negative charges (e.g., hyaluronic acid and heparin).

Glycosaminoglycans (GAGs)

Also known as mucopolysaccharides, consist of repeating disaccharide units.
Often contain one amino sugar, playing essential roles in biological processes such as joint lubrication and cellular hydration.

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Explore the crucial concepts surrounding monosaccharides, including their D or L configurations, types such as trioses, and the structural differences between D-glucose and D-galactose. This quiz will test your understanding of the formation and classification of these important carbohydrates.