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Carbohydrate Structure and Role

March 2024

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Carbohydrates are essential biomolecules that play a variety of structural and functional roles in living organisms. As one of the three major macronutrients, along with proteins and fats, carbohydrates are a vital energy source and metabolic fuel. However, carbohydrates contribute much more than just calories. This review provides an in-depth examination of carbohydrate chemistry, structure, function, and metabolism. Focus is given to how the specific molecular structures of different carbohydrate classes including monosaccharides, disaccharides, oligosaccharides, and polysaccharides determine their physiological activities. Key topics covered include carbohydrate digestion and absorption, glycoprotein and glycolipid synthesis, energy storage, and cell signaling roles. Special attention is paid to glucose metabolism and homeostasis due to the critical importance of blood sugar regulation. Potential links between carbohydrate structures and the development of metabolic disorders are also discussed. Tables and figures are provided to illustrate key concepts and summarize important information. Current areas of research and future directions are highlighted to demonstrate how continued elucidation of carbohydrate structural chemistry may lead to improved understanding of carbohydrate biology and better therapeutic interventions for carbohydrate-related diseases. This broad review provides a structural perspective to improve comprehension of the diverse functional roles of carbohydrates in biological systems. INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH & REVIEWS j o u r n a l h o m e p a g e : w w w. i j m r r. o n li n e / in d e x. p h p / h o m e Shailja and Parul Singh (2024). Carbohydrate Structure and Role.

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Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

___________________________________________________________________________

under Attribution-NonCommercial 4.0 International

Carbohydrate Structure and Role

Shailja1, Parul Singh2*

1Tikaram PG Girls College, Sonipat, Haryana- 131001, India.

2 Department of Chemistry, Deshbandhu College, University of Delhi, Delhi-110019, India.

*Corresponding author: Parul Singh, Department of Chemistry, Deshbandhu College, University

of Delhi, Delhi-110019, India.

How to Cite the Article: Shailja and Parul Singh (2024). Carbohydrate Structure and Role.

International Journal of Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

Keywords

Abstract

Carbohydrate,

Metabolism,

Glycoproteins,

Glycosylation,

Glycolysis, Protein,

glycosylation

Carbohydrates are essential biomolecules that play a variety of structural

and functional roles in living organisms. As one of the three major

macronutrients, along with proteins and fats, carbohydrates are a vital

energy source and metabolic fuel. However, carbohydrates contribute

much more than just calories. This review provides an in-depth

examination of carbohydrate chemistry, structure, function, and

metabolism. Focus is given to how the specific molecular structures of

different carbohydrate classes including monosaccharides, disaccharides,

oligosaccharides, and polysaccharides determine their physiological

activities. Key topics covered include carbohydrate digestion and

absorption, glycoprotein and glycolipid synthesis, energy storage, and

cell signaling roles. Special attention is paid to glucose metabolism and

homeostasis due to the critical importance of blood sugar regulation.

Potential links between carbohydrate structures and the development of

metabolic disorders are also discussed. Tables and figures are provided

to illustrate key concepts and summarize important information. Current

areas of research and future directions are highlighted to demonstrate

how continued elucidation of carbohydrate structural chemistry may lead

to improved understanding of carbohydrate biology and better

therapeutic interventions for carbohydrate-related diseases. This broad

review provides a structural perspective to improve comprehension of

the diverse functional roles of carbohydrates in biological systems.

INTERNATIONAL JOURNAL OF

MULTIDISCIPLINARY RESEARCH & REVIEWS

jo ur nal ho mepa ge

www.ij mrr. online /index.p hp/h ome

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

___________________________________________________________________________

under Attribution-NonCommercial 4.0 International

1. INTRODUCTION

Carbohydrates are a vital class of biomolecules that play numerous critical roles across all

domains of life. As their name indicates, carbohydrates are hydrate carbon compounds that

contain carbon, hydrogen, and oxygen atoms. The basic molecular formula for carbohydrates

is (CH2O)n where n is at least 3. Carbohydrates are synthesized by plants through

photosynthesis and serve as the primary metabolic fuel utilized by cells to produce energy

through cellular respiration [1]. In addition to their well-established function as an energy

source, carbohydrates have many other important structural and functional roles. They

contribute to cell membrane structure, facilitate cellular recognition, provide protection and

support, and participate in numerous biological processes as activating or signaling

molecules [2].

Figure 1: General classification of carbohydrates

With such widespread involvement in living systems, a thorough understanding of

carbohydrate chemistry and structure is essential. The diverse physiological functions of

carbohydrates are directly determined by their underlying molecular structures. Even subtle

differences in molecular configuration can have significant impacts on carbohydrate

metabolism and activity. Therefore, this review provides an in-depth examination of

carbohydrate structure-function relationships. Focus is given to how the specific molecular

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

___________________________________________________________________________

under Attribution-NonCommercial 4.0 International

structures of different carbohydrate classes and functional groups contribute to their

biological roles.

Carbohydrates can be divided into four primary categories: monosaccharides,

disaccharides, oligosaccharides, and polysaccharides. Monosaccharides are the simplest and

smallest carbohydrates. They cannot be further hydrolyzed to smaller carbohydrates and

serve as the building blocks for all higher order carbohydrate structures. Disaccharides

contain two monosaccharide units, oligosaccharides three to ten, and polysaccharides more

than ten monosaccharide units linked together [3]. Each carbohydrate category contains

distinct subgroups with unique structural attributes that determine their functional

capabilities.

This review will provide a thorough overview of carbohydrate chemistry starting with

monosaccharide structure. Key carbohydrate classes will be covered highlighting how their

molecular configurations give rise to specific biological activities. Important physiological

processes involving carbohydrates such as digestion, nutrient absorption, energy

metabolism, glycoprotein synthesis, cell signaling, and disease development will be

discussed throughout to demonstrate the form-function relationships of carbohydrate

structures. Tables and figures will be incorporated to summarize key information and

illustrate structural concepts. The goal is to provide a comprehensive structural perspective

to improve understanding of the varied functional roles of carbohydrates in biological

systems.

2. MONOSACCHARIDE STRUCTURE AND FUNCTION

Monosaccharides are the most basic carbohydrate units. They contain a single

polyhydroxy aldehyde or ketone unit making them the simplest form of a sugar molecule.

Monosaccharides are further classified by the number of carbon atoms they contain which is

typically three to seven carbons long. The most abundant monosaccharides relevant to

human physiology are the hexoses, which contain six carbon atoms [4].

The six carbon hexoses share a common chemical formula of C6H12O6. However, they

can exist as different structural isomers depending on the position of the carbonyl group

within the carbon chain and the spatial arrangements around asymmetric carbons. These

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

subtle structural differences confer each hexose with unique chemical properties that

determine their physiological functions (See Table 1).

Table 1. Structures and functions of common hexose monosaccharides.

Monosaccharide

Primary Functions

Glucose

Major energy source, metabolic intermediate

Galactose

Component of lactose, glycoproteins, glycolipids

Fructose

Sweetener, glycolysis intermediate

Mannose

Component of glycoproteins, glycolipids

Glucose is the most abundant monosaccharide in nature and the primary product of

photosynthesis [5]. As such, glucose plays a central role in carbohydrate metabolism and

bioenergetics. Glucose in its ring form can exist in either an α-pyranose or β-pyranose

structure which interconvert through mutarotation. These two anomers differ in the position of

the hydroxyl group on the anomeric carbon. This structural flexibility of glucose allows it to

adopt different conformations required to fit into active sites of metabolic enzymes and

transport proteins [6].

Fructose and galactose are structural isomers of glucose. Fructose, also known as fruit

sugar, differs from glucose only in the position of the hydroxyl group on carbon 2. This subtle

change causes fructose to be much sweeter than glucose and gives it distinct metabolic

properties. Fructose is metabolized independently of insulin by the liver which can lead to

adverse effects when consumed in excess [7]. Galactose differs from glucose in the

configuration around carbon 4 which is critical for its role in lactose synthesis and

incorporation into glycoproteins and glycolipids.

Mannose is an epimer of glucose, meaning it differs only in the stereochemistry around

one carbon. This C2 epimerization causes mannose to be metabolically inert compared to

glucose. Instead of energy metabolism, mannose is primarily utilized for protein glycosylation

[8]. Overall, the distinct structures of the various hexoses enable each one to play unique

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

biological roles critical to health. Further elucidation of monosaccharide structure-function

relationships will provide key insights into improving carbohydrate metabolism and

preventing metabolic disorders.

3. DISACCHARIDE STRUCTURE AND FUNCTION

Disaccharides are composed of two monosaccharide units linked together by a

glycosidic bond. The particular monosaccharides joined and type of glycosidic linkage

determine the classification and function of each disaccharide. The four main disaccharides

relevant to human nutrition are sucrose, lactose, maltose, and trehalose (See Table 2).

Table 2: Structures and functions of common dietary disaccharides.

Disaccharide

Linkage

Primary Functions

Sucrose

α-D-glucose, β-D-fructose, 1→2

glycosidic bond

Sweetener, energy source

Lactose

β-D-galactose, β-D-glucose , 1→4

glycosidic bond

Primary sugar in milk, probiotic

Maltose

α-D-glucose, α-D-glucose , 1→4

glycosidic bond

Product of starch digestion

Trehalose

α-D-glucose, α-D-glucose , 1→1

glycosidic bond

Energy storage, stress protection

Sucrose, also known as table sugar, is composed of glucose and fructose bonded

together. This makes sucrose very sweet and provides a readily absorbed energy source.

Lactose is the primary carbohydrate found in milk consisting of galactose and glucose. It

requires lactase enzyme to digest. Maltose, made of two glucose units, is an intermediate

product of starch breakdown. Trehalose has two glucose monomers linked in an atypical 1→1

bond, allowing it to provide stress protection [9]. Overall, the different disaccharides each

serve specialized roles in nutrition, metabolism, and homeostasis. Further study of how

disaccharide structures relate to their digestion, absorption, and utilization will provide

insights to help optimize carbohydrate benefits.

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

4. Oligosaccharide Structure and Function

Oligosaccharides are carbohydrate polymers containing between three to ten

monosaccharide units. They can be linear or branched chains with a variety of glycosidic

linkages. Oligosaccharides have many structural forms and are abundant on cell surfaces as

components of glycoproteins and glycolipids where they facilitate molecular recognition and

cell signaling [10]. Key dietary oligosaccharides include raffinose, stachyose, and

fructooligosaccharides (FOS). Their structures and functions are outlined in Table 3.

Table 3: Structures and functions of common dietary oligosaccharides.

Oligosaccharide

Composition

Primary Functions

Raffinose

Galactose, glucose, fructose

Gas production, prebiotic

Stachyose

Galactose, glucose, fructose (2 units)

Gas production, prebiotic

FOS

Fructose polymers

Prebiotic, soluble fiber

Raffinose and stachyose contain galactose, glucose, and varying numbers of fructose

units. They are indigestible oligosaccharides that provide prebiotic and gas-producing effects.

Fructooligosaccharides (FOS) are short polymers of fructose that also display prebiotic

activities. Overall, the structural diversity of oligosaccharides allows them to interact with gut

microbes and gut epithelia in ways that modulate health [11]. Additional oligosaccharide

research is needed to determine how best to leverage their structures for improved nutrition

and disease prevention.

5. POLYSACCHARIDE STRUCTURE AND FUNCTION

Polysaccharides contain long chains of monosaccharide units linked together by

glycosidic bonds. They are the most abundant carbohydrate class representing the primary

storage and structural forms of carbohydrates. Plant polysaccharides include starch and

cellulose, while animal polysaccharides include glycogen and chitin. The monosaccharide

composition, chain length, branching structure, and glycosidic linkages influence the

physical properties and functions of each polysaccharide (See Table 4).

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

Table 4: Structures and functions of key dietary polysaccharides.

Polysaccharide

Composition

Primary Functions

Starch

α-D-glucose , α-1,4 linear

with α-1,6 branches

Energy storage in plants

Cellulose

β-D-glucose , β-1,4 linear

Structural fiber in plants

Glycogen

α-D-glucose , α-1,4 linear

with α-1,6 branches

Energy storage in animals

Chitin

β-D-N-acetylglucosamine ,

β-1,4 linear

Structural fiber in fungi, insects

Starch and glycogen are highly branched glucose polymers that serve as compact energy

stores in plants and animals, respectively. Cellulose is an unbranched glucose chain that

provides structural rigidity to plant cell walls. Chitin is an unbranched N-acetylglucosamine

polymer that forms exoskeletons of insects and cell walls of fungi. These examples

demonstrate how polysaccharides are structurally optimized for key biological roles. Further

insights into polysaccharide conformations will lead to better use of dietary fibers and

improved utilization of carbohydrate energy reserves.

6. Carbohydrate Digestion and Absorption

In order to utilize ingested carbohydrates, the digestive system must first break down

polysaccharides into their monosaccharide constituents. Digestion begins in the mouth with

salivary amylase which hydrolyzes some starch into maltose and dextrin disaccharides [12].

The bulk of carbohydrate digestion then occurs in the small intestine aided by pancreatic

enzymes that further break down polysaccharides into oligosaccharides and disaccharides for

absorption.

Intestinal cells lining the small intestine, called enterocytes, complete carbohydrate

digestion through intracellular hydrolysis. Enterocytes express various membrane-bound

disaccharidases and cytosolic glycosidases that split disaccharides, oligosaccharides, and any

remaining polysaccharides into monosaccharides [13]. The monosaccharides glucose,

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

galactose, and fructose are then absorbed across the intestinal epithelium into circulation via

facilitated transport. Once absorbed, monosaccharides enter circulation and travel to tissues

for utilization.

The efficiency of carbohydrate digestion and absorption depends heavily on molecular

structure. For example, the glycosidic bonds of starch amylose and amylopectin differ in

position and branching, leading amylopectin to be more readily digested. Fiber

polysaccharides like cellulose are resistant to hydrolysis which prevents their breakdown and

absorption [14]. Disaccharides also require their specific disaccharidases in order to be

digested (See Table 5). Lactose cannot be absorbed without intestinal lactase to cleave it.

These examples illustrate the critical impact carbohydrate molecular structure has on

determining its fate and physiological effects during and after digestion.

Table 5: Digestive enzymes involved in carbohydrate breakdown.

Enzyme

Production Site

Substrate

Products

Salivary amylase

Salivary glands

Starch(amylose, amylopectin)

Maltose, dextrin

Pancreatic α-amylase

Pancreas

Starch, glycogen

Maltose, dextrin

Oligo-1,6-glucosidase

Small intestine

Oligosaccharides

Glucose

Sucrase

Small intestine

Sucrose

Glucose, fructose

Maltase

Small intestine

Maltose

Glucose

Lactase

Small intestine

Lactose

Glucose, galactose

7. CARBOHYDRATE ENERGY METABOLISM

Following digestion and absorption, carbohydrates undergo cellular metabolism to

produce energy. The monosaccharides glucose and fructose enter glycolysis, a cytoplasmic

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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pathway that breaks down 6-carbon sugars into two 3-carbonglycolytic intermediates called

pyruvate. Glycolysis yields a net gain of two ATP molecules and two NADH coenzymes.

Pyruvate can then enter the mitochondria where it is completely oxidized by the

tricarboxylic acid (TCA) cycle producing additional energy equivalents and substrates for

cellular respiration [15].

Glucose serves as the primary input for glycolysis in most cells. Phosphorylation traps

glucose inside the cell. Hexokinase then converts glucose to glucose-6-phosphate,

committing it to further catabolism. The intermediates of glycolysis include three-carbon

sugars such as glyceraldehyde 3-phosphate and dihydroxyacetone phosphate as well as the

phosphoesters 2,3-bisphosphoglycerate and phosphoenolpyruvate. Multiple isozyme forms

of glycolytic enzymes exist with differences in kinetic parameters, allosteric regulation, and

tissue distribution reflecting the varied metabolic needs of cells [16].

All aerobic organisms completely oxidize glucose for maximum energy yield. Under

anaerobic conditions, glycolysis allows net ATP production through substrate level

phosphorylation alone. This makes glycolysis a fundamental pathway conserved across

species. However, glycolysis is regulated differently in various tissues to match

carbohydrate utilization to energetic and biosynthetic demands. For example, liver uptakes

and metabolizes glucose as needed whereas brain glycolysis is constantly active to provide

its high glucose requirement [17].

Besides glucose, galactose and fructose also feed into glycolysis after initial processing

steps. Galactose is converted to glucose-6-phosphate by the Leloir pathway in the liver and

then metabolized like glucose [18]. Fructose enters its eponymous pathway involving

phosphorylation by fructokinase and cleavage by aldolase B ultimately generating glycolytic

intermediates. However, fructose metabolism bypasses key regulatory steps leading to

unrestrained production of substrates that drive lipogenesis [19]. This provides a molecular

mechanism for the association between excess fructose consumption and adverse metabolic

effects.

Overall, the glycolytic pathway exemplifies how carbohydrate structure relates to

function. The distinct fates of glucose versus fructose during metabolism combined with

tissue-specific control of glycolysis allows this conserved catabolic route to support diverse

physiological needs. Additional insights into carbohydrate structures and fluxes through

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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intersecting metabolic pathways will further unveil the complexities of systemic energy

homeostasis relevant to health and disease.

8. GLYCOPROTEIN SYNTHESIS AND FUNCTION

In addition to energy metabolism, carbohydrates play a crucial role in protein

glycosylation. Glycoproteins contain one or more covalently attached glycan chains that

affect protein folding, distribution, stability, and activity. Glycans contribute to protein

structure while also serving as vital cell surface recognition elements mediating cell-cell and

cell-matrix interactions [20].

Glycoprotein glycans are assembled in a step-wise manner from monosaccharide building

blocks. The most prevalent sugars incorporated are glucose, mannose, galactose, fucose, N-

acetylglucosamine and N-acetylneuraminic acid which comprise over 90% of all mammalian

glycan structures [21]. Hundreds of glycosyltransferase enzymes catalyze the formation of

glycosidic linkages to extend glycans via the various sugar monomers. Branch points and

chain termination are mediated by glycosidases. This enzymatic balance determines the

ultimate glycan structures attached to proteins [22].

The particular glycan configurations synthesized create distinct binding epitopes for

lectins and other carbohydrate-binding proteins that induce downstream signaling effects

[23]. For example, glycans attached to cell surface receptors can alter ligand binding and

activation. Changes in glycan structures are associated with cancer, autoimmunity, and

congenital disorders of glycosylation highlighting the essential contributions of glycans to

protein activities [24]. Therapeutics targeting glycan biosynthesis pathways continue to be

explored for modulating protein functions in disease contexts [25].

In summary, the step-wise synthesis of glycoprotein glycans from carbohydrate substrates

coupled with their subsequent recognition by binding partners represents a fundamental form

of post-translational modification regulating protein structure and function. Continued

efforts to elucidate glycan assembly pathways and decode glycan structural motifs will

further unlock the secrets of this complex carbohydrate signaling system.

9. CARBOHYDRATES IN CELL SIGNALING

Beyond protein glycosylation, carbohydrates participate directly in cellular

communication systems as well. They can form ligands that bind cell surface receptors to

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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trigger signaling cascades that alter cell behavior and physiology. Key examples include

glycan-binding receptors of the C-type lectin family and glycosphingolipid signaling [26].

C-type lectins include selectins, collectins, and other receptors that bind carbohydrate

chains in a calcium-dependent manner. Selectins facilitate cell adhesion and migration

during inflammation and wound repair by interacting with sialylated and fucosylated glycans

[27]. Collectins are soluble lectins that recognize glycan pathogen-associated molecular

patterns (PAMPs) as part of the innate immune response [28]. Changes in carbohydrate

structures provoked by inflammatory stimuli, hormones, or disease processes can

dynamically alter lectin activities.

Glycosphingolipids contain carbohydrate head groups attached to a ceramide lipid

backbone embedded in cell membranes. As both glycans and lipids transduce signals,

glycosphingolipids integrate these pathways eliciting downstream effects on growth,

differentiation, and motility through direct receptor binding or membrane domain

organization [29]. Gangliosides are sialic acid-containing glycosphingolipids abundant in

neuronal membranes where they modulate ion channel activities [30]. Defects in ganglioside

catabolism lead to GM1 and GM2 gangliosidoses characterized by severe neurological

impairment.

Together these examples demonstrate that carbohydrates directly participate in cell-cell

communication mechanisms beyond their roles as passive protein modifiers. Specific

carbohydrate motifs interact with various glycan-binding proteins and lipids to initiate

signaling cascules that dynamically regulate cell functions. Further research into glycomic

and glycobiological mechanisms will continue elucidating the diverse signaling roles of

carbohydrates.

10. CARBOHYDRATES IN HEALTH AND DISEASE

Given the widespread involvement of carbohydrates in human physiology, it follows that

aberrations in carbohydrate metabolism provoke development of disease. Changes in

carbohydrate structures, concentrations, and fluxes through metabolic pathways have all

been associated with pathology [31]. One of the most prevalent diseases linked to

carbohydrate dysregulation is diabetes mellitus which is characterized by hyperglycemia

arising from defects in insulin secretion, insulin action, or both [32].

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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Chronic hyperglycemia leads totissue damage through increased protein glycation and

generation of reactive oxygen species. Major complications of diabetes include retinopathy,

nephropathy, neuropathy, and cardiovascular disease which all involve biomolecular damage

from elevated blood glucose [33]. Strict control of carbohydrate intake and metabolism

through insulin therapy, other drugs, diet, and exercise provides the cornerstone of diabetes

management to prevent long-term sequelae.

Beyond diabetes, alterations in specific carbohydrate structures have been implicated in

congenital disorders, cancer, autoimmunity, and susceptibility to pathogens. For example,

defects in N-glycan synthesis pathways underlie congenital disorders of glycosylation

associated with severe developmental impairment [34]. Thedensity of cell surface glycan

branching is increased in tumorigenic cells which may impact metastasis [35]. Antibodies

against glycoprotein glycans and glycolipids attack self-tissues in Guillain-Barre syndrome

and other autoimmune neuropathies [36]. Viral and bacterial lectins that bind cell surface

glycans facilitate infection highlighting the pivotal roles carbohydrates play on both sides of

host-pathogen interactions [37].

In summary, precise regulation of carbohydrate chemistry is required to maintain normal

physiology. Perturbations in carbohydrate structures, metabolism, or signaling contribute

broadly to the pathogenesis of diverse diseases. Continued efforts to define carbohydrate

involvement in disease processes may reveal novel glycan biomarkers and therapeutic

targets to improve prevention and treatment.

11. CURRENT TRENDS AND FUTURE DIRECTIONS

Carbohydrate research remains an active field as the critical importance of glycobiology

in human health becomes increasingly apparent. Major research directions include:

● Development of improved analytical methods for characterizing carbohydrate structures.

Advances in mass spectrometry and NMR enable detailed compositional and conformational

analysis of glycans to define structure-function relationships [38].

● Mapping of glycan biosynthesis pathways. Genomic, transcriptomic, proteomic, and

metabolomic approaches are combining to identify glycosyltransferases, glycosidases,

substrates, products, and regulators to model cell-specific glycan assembly [39].

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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● Investigation of glycan recognition and signaling. Glycan arrays, glycan binding assays, and

co-crystal structures precisely define lectin-glycan interactions while improving

understanding of downstream signaling effects [40].

● Engineering of synthetic glycans and glycomimetics. Chemical and enzymatic glycan

synthesis allows generation of homogeneous glycan probes to study and modulate glycan

activities in vivo [41].

● Integration of glycomic data into systems biology models. Databases of glycan structures and

biosynthetic pathways support systems-level modeling of glycan functions in metabolism,

signaling, and overall network dynamics [42].

● Development of glycan-based biomarkers and therapeutics. Aberrant glycans show promise

as early disease indicators while glycan biosynthetic enzymes are emerging drug targets [43].

Overall, recent technological and bioinformatic advances have propelled the

glycosciences forward into the post-genomic era. The coming decades will continue to see

major discoveries related to fundamental glycan biology that translate into clinical tools for

managing carbohydrate-related diseases. These future glycomic applications will firmly

establish carbohydrates as essential biomolecules crucial for supporting human life and

health.

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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Figure 2: Interplay of the instrumental and computational methods in the 3D structure

determination of carbohydrates, proteins, and protein–glycoconjugate complexes

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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Figure 3 (a) Original glycan structure model from the PDB entry. 3(b) PDB-REDO model

with properly renamed fucose residue and improved fit to the electron density. 3(c) Manually

rebuilt model based on PDB-REDO results. 3(d) CARP distribution plot for glycosidic φ-ψ

torsions of FUC(1-6)NAG (from panel (a)) in PDB.

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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Figure 4: Deposition statistics of carbohydrate-containing structures in Protein Data Bank

based on carbohydrate remediated list data. Data for 2020 cover seven of twelve months

12. CONCLUSION

In conclusion, this broad review integrates principles from carbohydrate chemistry,

biochemistry, physiology, and pathology to provide a structural perspective on the diverse

functional roles of carbohydrates in biological systems. Key topics covered include:

● Carbohydrate classification, nomenclature, and molecular structures

● Monosaccharide, disaccharide, oligosaccharide, and polysaccharide configurations in

relation to their biological activities

● Carbohydrate digestion, absorption, and intracellular metabolism

● Glycoprotein synthesis and function

● Roles of carbohydrates in cell-cell signaling mechanisms

● Involvement of carbohydrates in health and disease processes

● Current trends and future research directions in the glycosciences

The form-function relationships of carbohydrate structures give rise to their widespread

capabilities as energy sources, metabolic intermediates, stable polymers, dynamic post-

translational modifiers, cell surface ligands, and more. Appreciation of these structure-

Shailja and Parul Singh (2024). Carbohydrate Structure and Role. International Journal of

Multidisciplinary Research & Reviews, Vol 03, No. 02, pp. 52-72.

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under Attribution-NonCommercial 4.0 International

activity correlations is critical for improving carbohydrate utilization and developing glycan-

targeted therapeutics. This overview of carbohydrate chemistry and biology provides a

foundation for ongoing research efforts seeking to fully elucidate the diverse molecular roles

of these essential biomolecules.

13. CONFLICT OF INTEREST

The authors declared no potential conflicts of interest with respect to the research, authorship,

and/or publication of this article.

14. PLAGIARISM POLICY

All authors declare that any kind of violation of plagiarism, copyright and ethical matters will

taken care by all authors. Journal and editors are not liable for aforesaid matters.

15. SOURCES OF FUNDING

The authors received no financial aid to support for the research.

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Bioactive Profile Analysis and Inhibitory Activity of Prostaglandin Synthase from Sungkai Leaf Extract (Peronema canescens Jack) In Silico

Article

Full-text available

Mar 2025

Sungkai leaves (Peronema canescens Jack) have antipyretic properties that have been proven ethnobiologically. However, research on sungkai leaves is scarce, especially in silico and in vitro. The aim of this study was to prove the ability of sungkai leaves to accelerate the process of decreasing body temperature during fever using the silico method. Sungkai leaves were extracted using a 70% ethanol solvent. The extract solution was concentrated using a rotary evaporator and then analyzed using an LC-MS device. Compounds obtained from the LC-MS analysis were screened in silico using Lipinski's rule of 5 and ADMET. The compounds that successfully passed the screening were docked with the target enzyme mPGES-1 using the Yasara Structure application. Extraction with 70% ethanol solvent resulted in an extract yield of 14.75%. The results of the LC-MS analysis showed the presence of 22 known compounds and one unknown compound. The screening results showed that ten compounds had successfully passed. Compounds 2-oxo-6-(piperidine-1-sulfonyl)-benzoxazole-3-carboxylic acid isobutyl ester; 2-(5-{[Isopropyl (methyl)amino] methyl} – 1 - tetrazolidinyl) – N – methyl – N - [ 2 - ( 2 – methyl – 1 – imidazolidinyl) ethyl] acetamide; 2-({2-[4-(2-Hydroxyethyl)-1-piperazinyl]-2-oxoethyl} sulfanyl)-5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one;2-({4 amino -5-[3-(diethylsulfamoyl) phenyl]-4H-1,2,4-triazol-3-yl}sulfanyl)-N-dimethylacetamide; and 3, 4,5-trimethoxycinnamate obtained from this study could inhibit mPGES-1 based on the binding energy and inhibition constant that each test ligand had.

Chemical Composition And Aphrodisiac Activity Of Aqueous And Hydroalcoholic Extracts Of Corynaea crassa Hook f

Article

Full-text available

Feb 2025

Introduction: corynaea crassa is a hemiparasitic plant, traditionally used in Ecuador and Peru as a male aphrodisiac, but scientific evidence is required to validate its use. Especially, the species from Ecuador has not been studied for this purpose.Objective: compare the chemical composition and aphrodisiac activity of aqueous and hydroalcoholic extracts of C. crassa collected in Ecuador and Peru.Methods: the chemical composition of aqueous and hydroalcoholic extracts was determined through the quantification of phenols by Folin-Ciocalteu, flavonoids by the aluminum trichloride technique, alkaloids and carbohydrates by the bromocresol green and phenol-sulfuric methods, respectively. The aphrodisiac activity of the extracts was tested at doses of 100, 200 and 300 mg/kg in male Wistar rats, using sildenafil (50 mg/kg) as a positive control. Parameters of sexual behavior, nitric oxide concentration in plasma and corpus cavernosum, and testosterone concentration in blood serum were evaluated.Results: significant differences were seen in the content of each metabolite. The hydroalcoholic extracts showed the highest concentration of phenols, flavonoids and alkaloids, higher for the Ecuadorian sample. The aqueous extract from Peru recorded the highest concentration of carbohydrates. All extracts promoted sexual activity in rats, increasing the levels of nitric oxide and testosterone, highlighting the aqueous and hydroalcoholic extracts (300 mg/kg) with a behavior comparable to sildenafil. Conclusions: the study justified the popular use of C. crassa as a male aphrodisiac, given the variety of chemical compounds quantified, providing the first scientific evidence of the Ecuadorian species.

Resistant Starch Type 2 from Wheat Reduces Postprandial Glycemic Response with Concurrent Alterations in Gut Microbiota Composition

Article

Full-text available

Feb 2021

The majority of research on the physiological effects of dietary resistant starch type 2 (RS2) has focused on sources derived from high-amylose maize. In this study, we conduct a double-blind, randomized, placebo-controlled, crossover trial investigating the effects of RS2 from wheat on glycemic response, an important indicator of metabolic health, and the gut microbiota. Overall, consumption of RS2-enriched wheat rolls for one week resulted in reduced postprandial glucose and insulin responses relative to conventional wheat when participants were provided with a standard breakfast meal containing the respective treatment rolls (RS2-enriched or conventional wheat). This was accompanied by an increase in the proportions of bacterial taxa Ruminococcus and Gemmiger in the fecal contents, reflecting the composition in the distal intestine. Additionally, fasting breath hydrogen and methane were increased during RS2-enriched wheat consumption. However, although changes in fecal short-chain fatty acid (SCFA) concentrations were not significant between control and RS-enriched wheat roll consumption, butyrate and total SCFAs were positively correlated with relative abundance of Faecalibacterium, Ruminoccocus, Roseburia, and Barnesiellaceae. These effects show that RS2-enriched wheat consumption results in a reduction in postprandial glycemia, altered gut microbial composition, and increased fermentation activity relative to wild-type wheat.

Flexibility of Gut Microbiota in Ageing Individuals during Dietary Fiber Long‐Chain Inulin Intake

Article

Full-text available

Dec 2020

Scope During ageing, dysbiosis in the intestinal microbiota might occur and impact health. There is a paucity of studies on the effect of fiber on the elderly microbiota and the flexibility of the aged microbiota upon prebiotic intake. We hypothesized that chicory long‐chain inulin consumption can change microbiota composition, microbial fermentation products and immunity in the elderly. Methods and results A double‐blind, placebo‐controlled trial was performed in healthy individuals (55‐80 years), in which microbiota composition was studied before, during and after two months of chicory long‐chain inulin consumption. Fecal SCFA concentrations, T cell subsets and antibody responses against a Hepatitis B (HB) vaccine were measured as well. Inulin consumption modified the microbiota composition, as measured by 16S rRNA sequencing. Participants consuming inulin had a higher microbial diversity and a relative higher abundance of the Bifidobacterium genus, as well as Alistipes shahii, Anaerostipes hadrus, and Parabacteroides distasonis. While the immune responses remained unchanged, the isobutyric acid levels, an undesired fermentation product, tended to be lower in the inulin group. Conclusions Overall, we show for the first time that the gut microbiota composition is still sensitive to chicory long‐chain inulin induced changes in an ageing population, although this did not translate into an improved immune response to a HB vaccine. This article is protected by copyright. All rights reserved

An Online Survey on Consumer Knowledge and Understanding of Added Sugars

Article

Full-text available

Jan 2017

Evidence of an association between added sugars (AS) and the risk of obesity has triggered public health bodies to develop strategies enabling consumers to manage their AS intake. The World Health Organisation (WHO) has strongly recommended a reduction of free sugars to 10% of total dietary energy (TE) and conditionally recommended a reduction to 5% TE to achieve health benefits. Despite food labelling being a policy tool of choice in many countries, there is no consensus on the mandatory addition of AS to the nutrition panel of food labels. An online survey was conducted to explore consumer ability to identify AS on food labels and to investigate consumer awareness of the WHO guidelines in relation to sugar intakes. The questionnaire was tested for participant comprehension using face-to-face interviews prior to conducting the online study. The online survey was conducted in Northern Ireland during May 2015 and was completed by a convenient sample of 445 subjects. Results showed that just 4% of respondents correctly classified 10 or more ingredients from a presented list of 13 items, while 65% of participants were unaware of the WHO guidelines for sugar intake. It may be timely to reopen dialogue on inclusion of AS on food product nutrition panels.

The Importance of Dietary Carbohydrate in Human Evolution

Article

Full-text available

Jan 2015

Abstract We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. Although previous studies have highlighted a stone tool-mediated shift from primarily plant-based to primarily meat-based diets as critical in the development of the brain and other human traits, we argue that digestible carbohydrates were also necessary to accommodate the increased metabolic demands of a growing brain. Furthermore, we acknowledge the adaptive role cooking played in improving the digestibility and palatability of key carbohydrates. We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus. We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia. Although uncertainties remain regarding the antiquity of cooking and the origins of salivary amylase gene copy number variation, the hypothesis we present makes a testable prediction that these events are correlated.

An Evolutionary Perspective on Food and Human Taste

Article

Full-text available

May 2013

Paul Breslin

The sense of taste is stimulated when nutrients or other chemical compounds activate specialized receptor cells within the oral cavity. Taste helps us decide what to eat and influences how efficiently we digest these foods. Human taste abilities have been shaped, in large part, by the ecological niches our evolutionary ancestors occupied and by the nutrients they sought. Early hominoids sought nutrition within a closed tropical forest environment, probably eating mostly fruit and leaves, and early hominids left this environment for the savannah and greatly expanded their dietary repertoire. They would have used their sense of taste to identify nutritious food items. The risks of making poor food selections when foraging not only entail wasted energy and metabolic harm from eating foods of low nutrient and energy content, but also the harmful and potentially lethal ingestion of toxins. The learned consequences of ingested foods may subsequently guide our future food choices. The evolved taste abilities of humans are still useful for the one billion humans living with very low food security by helping them identify nutrients. But for those who have easy access to tasty, energy-dense foods our sensitivities for sugary, salty and fatty foods have also helped cause over nutrition-related diseases, such as obesity and diabetes.

Research on risk scorecard of sick building syndrome based on machine learning

Article

Dec 2021
BUILD ENVIRON

Sick building syndrome (SBS) negatively affects numerous aspects of human health. To date, few studies have used machine learning to establish SBS risk prediction models. In this study, we investigated 2370 buildings in Chongqing, China and collected 29,785 questionnaires as the basic dataset. Logistic regression was used as the machine learning algorithm. Based on the weight of evidence and information value, features with significant effects were selected, and prediction models were established for mucosal irritation, dermal symptoms, neurotoxic symptoms, and respiratory symptoms. Through verification based on the accuracy, receiver operating characteristic curve, and Kolmogorov–Smirnov values, the model performed well on the test set. Thus, the prediction models were further transformed into a scorecard that could provide quantitative results for each environment, and the impact of each level of each feature on the results could be observed. The results indicated that when there was an indoor pollution source, the risks of the four SBS models increased. In addition, the indoor thermal environment had a significant impact on SBS. If the indoor thermal environment deviated from the range of thermal comfort, the prevalence of SBS increased, particularly when the indoor and outdoor thermal environments had opposite thermal sensations to the occupants. Finally, we initially established four SBS rating systems based on quantiles, which can provide a reference for establishing a rating system for healthy indoor environments.

Functionality of Sugars in Foods and Health: Functionality of sugars…

Article

May 2016
COMPR REV FOOD SCI F

Overweight and obesity are global health problems that affect more than 1.9 billion adults who are overweight, and of these 600 million are obese. In the United States, these problems affect 60% of the population. Critical to these statistics is the association with increased risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome among other noncommunicable diseases. Many factors, including sugars, have been charged as potential causes. However, obesity and overweight and their attendant health problems continue to increase despite the fact that there is a decline in the consumption of sugars. Sugars vary in their types and structure. From a food science perspective, sugars present an array of attributes that extend beyond taste, flavor, color, and texture to aspects such as structure and shelf-life of foods. From a public health perspective, there is considerable controversy about the effect of sugar relative to satiety, digestion, and noncommunicable diseases. This comprehensive overview from experts in food science, nutrition and health, sensory science, and biochemistry describes the technical and functional roles of sugar in food production, provides a balanced evidence-based assessment of the literature and addresses many prevalent health issues commonly ascribed to sugar by the media, consumer groups, international scientific organizations, and policy makers. The preponderance of the evidence indicates that sugar as such does not contribute to adverse health outcomes when consumed under isocaloric conditions. The evidence generally indicates, as noted by the 2010 Dietary Guidelines Advisory Committee, that sugar, like any other caloric macronutrient, such as protein and fat, when consumed in excess leads to conditions such as obesity and related comorbidities. More recently, the 2015-2020 Dietary Guidelines for Americans recommended limiting dietary sugar to 10% of total energy in an effort to reduced the risk of these noncommunicable diseases.

Medical food and meal replacement nutritional supplements

Article

Jan 2015
Pharm Times

Y.C. Terrie

A review of reviews: A new look at the evidence for oral nutritional supplements in clinical practice

Article

Dec 2007
Clin Nutr Suppl

Decisions about the treatment of disease-related malnutrition should be guided where possible by evidence. Increasing numbers of systematic reviews and meta-analyses have reviewed the efficacy of oral nutritional supplements for treating disease-related malnutrition. In order to consolidate this evidence, an overview of systematic reviews and meta-analyses (‘review of reviews’) in which oral nutritional supplements were compared with routine care was undertaken, focussing primarily on clinical outcomes. Thirteen systematic reviews and meta-analyses were reviewed (up to August 2006), either of trials in adults, including the elderly, with a variety of conditions (6 reviews), or in specific groups, including chronic renal disease, diabetes, cancer, chronic obstructive pulmonary disease (COPD), hip fracture and gastrointestinal surgery (7 reviews). This review of reviews found largely consistent clinical benefits with oral nutritional supplements in meta-analyses of trials across patient groups. Benefits included significant reductions in mortality and complications (e.g. infections, pressure ulcers), particularly in acute settings and acutely ill geriatrics. In some specific groups there were reductions in complications (in gastrointestinal surgery, hip fracture) but in other groups (e.g. COPD, chronic renal disease) more research is needed to assess relevant clinical outcomes. Across reviews of all patient groups, oral nutritional supplements consistently improved total nutritional intake, with little suppression of food intake. In general, reviews indicated improvements in weight (weight gain or less weight loss) with oral nutritional supplements. The only systematic review comparing oral nutritional supplements with dietary advice showed greater intakes and weight gain with oral nutritional supplements. In summary, there is increasing evidence to support the use of oral nutritional supplements in clinical practice, particularly in acutely ill and older patients. Future research must be well designed in order to ascertain the most effective ways of using oral nutritional supplements and other dietary strategies to optimally treat disease-related malnutrition.

Oral Nutritional Supplementation

Article

Feb 2013
AM J MANAG CARE

Gordon L Jensen

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