Carbohydrate Biochemistry Quiz
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Questions and Answers

Amino sugars are primarily composed of N-acetyl glucosamine and N-acetyl galactosamine.

True (A)

Glycosaminoglycans (GAGs) are synthesized exclusively in the cytoplasm.

False (B)

Chondroitin sulfate has a relatively long chain structure compared to other GAGs.

False (B)

Heparin is known for its anticoagulant properties and is utilized in medical settings to prevent clotting.

<p>True (A)</p> Signup and view all the answers

Glycoconjugates link carbohydrates to proteins and lipids, with proteoglycans and glycoproteins being the primary types.

<p>True (A)</p> Signup and view all the answers

Monosaccharides can be classified as either aldoses or ketoses.

<p>True (A)</p> Signup and view all the answers

All carbohydrates possess the empirical formula Cx(H2O)y.

<p>False (B)</p> Signup and view all the answers

Glycogen is a type of monosaccharide found in the human body.

<p>False (B)</p> Signup and view all the answers

Reducing sugars can easily oxidize due to the presence of a free anomeric carbon.

<p>True (A)</p> Signup and view all the answers

Complex carbohydrates include glycoproteins and proteoglycans.

<p>True (A)</p> Signup and view all the answers

Benedict’s test is a method used to identify non-reducing sugars.

<p>False (B)</p> Signup and view all the answers

Anomeric carbon is a term used to describe a carbon that can form a glycosidic bond.

<p>True (A)</p> Signup and view all the answers

Gluconic acid is derived from the oxidation of D-glucose.

<p>True (A)</p> Signup and view all the answers

Carbohydrates are primarily sourced from animal products.

<p>False (B)</p> Signup and view all the answers

The term 'mucous membranes' relates to the structural components of carbohydrates.

<p>True (A)</p> Signup and view all the answers

Glycogen is stored in the heart and spleen.

<p>False (B)</p> Signup and view all the answers

Starch is a structural polysaccharide predominantly found in plants.

<p>False (B)</p> Signup and view all the answers

Glycoproteins contain covalently attached oligosaccharides to proteins.

<p>True (A)</p> Signup and view all the answers

Amylopectin has a more branched structure than glycogen.

<p>False (B)</p> Signup and view all the answers

Iodine can produce a blue color when it interacts with amylose.

<p>True (A)</p> Signup and view all the answers

O-glycosidic bonds are formed through the amino acid aspartic acid.

<p>False (B)</p> Signup and view all the answers

N-glycosidic bonds involve the side chain NH2 of tyrosine.

<p>False (B)</p> Signup and view all the answers

Cellulose is the most abundant polysaccharide on Earth.

<p>True (A)</p> Signup and view all the answers

Glycosaminoglycans consist of linear polymers of repeating monosaccharides.

<p>False (B)</p> Signup and view all the answers

Transferrin is classified as a structural glycoprotein.

<p>False (B)</p> Signup and view all the answers

Sorbitol accumulation in the lens can lead to cataract formation due to osmotic stress.

<p>True (A)</p> Signup and view all the answers

B-d-glucose is linked by b(1®4) linkages in cellulose.

<p>True (A)</p> Signup and view all the answers

2’-deoxy ribose is the sugar found in RNA.

<p>False (B)</p> Signup and view all the answers

Immunoglobulins are examples of immunologic glycoproteins.

<p>True (A)</p> Signup and view all the answers

The formation of glycosidic bonds requires the loss of water.

<p>True (A)</p> Signup and view all the answers

The O antigen is associated with α-1,3-N-acetylgalactosaminytransferase.

<p>False (B)</p> Signup and view all the answers

Hydrolysis of glycogen releases glucose at the reducing end.

<p>False (B)</p> Signup and view all the answers

Blood group antigens are found solely on proteins within the erythrocyte membrane.

<p>False (B)</p> Signup and view all the answers

Ruminants are capable of digesting cellulose.

<p>True (A)</p> Signup and view all the answers

Maltose consists of glucose and galactose.

<p>False (B)</p> Signup and view all the answers

Glycosyltransferases are enzymes that assemble monosaccharide residues for blood group substances.

<p>True (A)</p> Signup and view all the answers

Proteoglycans are primarily made up of carbohydrate chains attached to a core protein.

<p>True (A)</p> Signup and view all the answers

Lactose is a disaccharide that consists of glucose and fructose.

<p>False (B)</p> Signup and view all the answers

Chitin is a type of homopolysaccharide found in fungi.

<p>False (B)</p> Signup and view all the answers

Gangliosides are simpler than glycosphingolipids due to their lack of complex oligosaccharides.

<p>False (B)</p> Signup and view all the answers

The terminal monosaccharide at the non-reducing end determines the blood group of an individual.

<p>True (A)</p> Signup and view all the answers

Insulin is required for glucose uptake in lens cells.

<p>False (B)</p> Signup and view all the answers

Glycation of proteins mainly involves the enzymatic reaction of sugars with amino groups.

<p>False (B)</p> Signup and view all the answers

Glycogen is hydrolyzed by glycogen phosphorylase from the non-reducing end.

<p>True (A)</p> Signup and view all the answers

In diabetes, HbA1c is used as a marker for short-term glycemic control.

<p>False (B)</p> Signup and view all the answers

The main sources of starch include rice, corn, and potatoes.

<p>True (A)</p> Signup and view all the answers

O-glycosidic bonds form between an -OH group of one monosaccharide and an -NH group of another compound.

<p>False (B)</p> Signup and view all the answers

Glycogen and starch are both structural polysaccharides.

<p>False (B)</p> Signup and view all the answers

The hyperosmotic effect caused by sorbitol results in fluid infusion to counteract the osmotic gradient.

<p>True (A)</p> Signup and view all the answers

Polysaccharides are generally sweet and soluble in water.

<p>False (B)</p> Signup and view all the answers

Hexokinase saturation leads to the activation of the aldose reductase pathway.

<p>True (A)</p> Signup and view all the answers

Glucose forms sorbitol through enzymatic reduction.

<p>True (A)</p> Signup and view all the answers

Deoxy sugars are monosaccharides that have additional hydroxyl groups compared to regular sugars.

<p>False (B)</p> Signup and view all the answers

Cataracts are primarily caused by the accumulation of polyols in the lens.

<p>True (A)</p> Signup and view all the answers

Sucrose consists of two monosaccharides joined by a β-1,2 glycosidic bond.

<p>False (B)</p> Signup and view all the answers

Flashcards

What are monosaccharides?

Monosaccharides are simple sugars, the basic building blocks of carbohydrates. They are polyhydroxy aldehydes or ketones with at least three carbon atoms. Examples include glucose, fructose, and galactose.

What are disaccharides?

Disaccharides are formed when two monosaccharides are joined together by a glycosidic bond. Common examples include sucrose (table sugar), lactose (milk sugar), and maltose (malt sugar).

What are polysaccharides?

Polysaccharides are complex carbohydrates formed by the linkage of many monosaccharide units. These can be linear or branched chains. Important examples include starch, glycogen, and cellulose.

What is anomeric carbon?

Anomeric carbon is the carbon atom in a monosaccharide that is attached to two oxygen atoms, one being part of the carbonyl group (aldehyde or ketone) and the other part of a hydroxyl group.

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What are reducing sugars?

Reducing sugars have a free anomeric carbon that can be oxidized. They can reduce other compounds, like the copper ions in Benedict's reagent.

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What are non-reducing sugars?

Non-reducing sugars lack a free anomeric carbon and cannot be oxidized. Their anomeric carbon is involved in a glycosidic bond, preventing oxidation.

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What is a glycosidic bond?

Glycosidic bond is the covalent bond that connects monosaccharides. It's formed by a condensation reaction where a water molecule is removed. The bond is named based on the carbon atoms involved in the linkage.

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What is glycogen?

Glycogen is a branched polysaccharide that serves as the primary energy storage molecule in animals. It's found mainly in liver and muscle cells.

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What is starch?

Starch is a branched polysaccharide that serves as the primary energy storage molecule in plants. It consists of two major components: amylose (linear) and amylopectin (branched).

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What is cellulose?

Cellulose is a linear polysaccharide that serves as a structural component in plant cell walls. It's composed of repeating glucose units linked by beta-1,4-glycosidic bonds.

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Reduction

A process where a molecule gains hydrogen atoms or electrons, often catalyzed by enzymes or using hydrogen and a catalyst.

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Polyol or Sugar Alcohol

A sugar alcohol formed by the reduction of a sugar, like glucose being reduced to sorbitol.

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Deoxy Sugar

A type of monosaccharide that lacks one or more hydroxyl (-OH) groups.

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O-glycosidic bond

A covalent bond formed between the anomeric carbon of a monosaccharide and the hydroxyl (-OH) group of another molecule.

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N-glycosidic bond

A covalent bond formed between the anomeric carbon of a monosaccharide and the amino (-NH) group of another molecule.

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Maltose

A disaccharide composed of two glucose molecules linked via an α-1,4 glycosidic bond.

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Sucrose

A disaccharide composed of glucose and fructose linked via an α-1,2 glycosidic bond.

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Lactose

A disaccharide composed of galactose and glucose linked via a β-1,4 glycosidic bond.

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Aldose

A type of monosaccharide that has a carbonyl group (C=O) which can exist in either an aldehyde or ketone form.

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Ketohexose

A type of monosaccharide that has a ketone group.

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Cataract

A condition where the lens of the eye becomes cloudy, often caused by the accumulation of sorbitol in diabetics.

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Aldose reductase pathway

A metabolic pathway that converts glucose into sorbitol using the enzyme aldose reductase.

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Sorbitol

A sugar alcohol that accumulates in the lens of the eye in diabetics, contributing to cataracts.

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Insulin-independent glucose uptake

The uptake of glucose into cells independently of insulin, often involving hexokinase.

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Hexokinase saturation

The state of an enzyme where it has reached its maximum activity due to saturation with substrate.

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Glycosaminoglycans (GAGs)

Composed of repeating disaccharide units, strongly negatively charged due to carboxyl groups. Synthesized in the ER and Golgi, degraded by lysosomal hydrolases.

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Chondroitin Sulfate

Type of GAG found in tendons, ligaments, cartilage, aorta, cornea, and skin. Relatively shorter chain, binds collagen to create a strong network in cartilage.

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Hyaluronic Acid

Unique GAG with no sulfation. Forms large molecules, found in the plasma membrane. Creates clear and viscous solutions. Essential for the extracellular matrix of cartilage and tendons.

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Heparin

Highly sulfated GAG with anticoagulant properties. Prevents clotting and is used in blood banks and for preventing clots in patients recovering from surgery.

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Glycoconjugates

Compounds with carbohydrates covalently linked to proteins and lipids. Two kinds of glycoconjugates containing proteins: proteoglycans and glycoproteins.

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Homopolysaccharide

A type of polysaccharide where all the monosaccharides are the same.

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Heteropolysaccharide

A type of polysaccharide where different types of monosaccharides are linked together.

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Glycogen

A type of polysaccharide that serves as an energy storage molecule, found in animals.

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Starch

A type of polysaccharide found in plants, serving as an energy storage molecule.

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Cellulose

A type of polysaccharide that forms the structural component of plant cell walls.

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Chitin

A type of polysaccharide found in the exoskeletons of insects and crustaceans, providing structural support.

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What is the function of glycogen?

A type of polysaccharide that functions as an energy reservoir in animals, particularly muscles and liver.

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How is glycogen structured?

Glycogen has a branched structure. The main chain is linked by α(1→4) glycosidic bonds, while the branches are formed by α(1→6) glycosidic bonds.

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How is glycogen broken down?

Glycogen is broken down into glucose molecules through a process called hydrolysis.

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What enzyme breaks down glycogen?

The enzyme glycogen phosphorylase breaks down glycogen from the non-reducing end.

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What are the components of starch?

Starch is composed of two types of polysaccharides: amylose and amylopectin.

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What is amylose?

Amylose is a linear chain of glucose molecules linked by α(1→4) glycosidic bonds.

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What is amylopectin?

Amylopectin is a branched chain of glucose molecules with α(1→4) glycosidic bonds in the main chain and α(1→6) glycosidic bonds at branch points.

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How can starch be detected?

The presence of starch can be detected using iodine, which forms a blue complex with the amylose helix.

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Glycoproteins

Proteins with covalently attached sugar chains called oligosaccharides.

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Functions of glycoproteins

They provide structural support, transport molecules, act as hormones, and serve as enzymes.

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Glycosyltransferases

Specific enzymes that add sugars to a growing oligosaccharide chain during glycoprotein synthesis.

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Blood group antigens

The ABO blood group system is based on different terminal sugars on glycoproteins present on red blood cell membranes.

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Glycocalyx

A sugar chain attached to a protein or lipid, often on the surface of cells.

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Glycosyltransferases in blood group systems

They help determine blood type by adding specific sugars to the ends of glycoprotein chains.

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Glycolipid

A type of carbohydrate molecule that is linked to a lipid (fat). They are important components of cell membranes and play a role in cell recognition and signaling.

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Glycation of Proteins

Process where sugar molecules bind to proteins without the help of enzymes. This happens when there's too much glucose in the blood, like in diabetes. It can cause damage to tissues and organs.

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Proteoglycans

A complex molecule found in cartilage and other tissues. It's made up of a protein core with attached sugar chains. They help keep tissues hydrated, flexible, and resilient.

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Galactocerebroside

A specific type of glycolipid found in the brain and nerve cells. It's made up of a ceramide molecule with a single sugar attached.

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Study Notes

Carbohydrates of Physiologic Significance

  • Carbohydrates are the most abundant compounds in nature, with cellulose being a notable example (100 billion tons annually).
  • Saccharides (sugars) are polyhydroxy aldehydes or polyhydroxy ketones.
  • They are synthesized in plants and animals.
  • A carbohydrate's definition is a polyhydroxylated compound containing at least 3 carbon atoms.
  • The molecular formula is generally Cx(H2O)y, but not all carbohydrates adhere to this formula (e.g., deoxy sugars, amino sugars).

Learning Objectives (ILOs)

  • Students will be able to identify major monosaccharides, disaccharides, and polysaccharides in humans.
  • They will understand the properties of monosaccharides, including nomenclature (number of carbons, functional groups), isomerism (structural, epimers, optical, D/L), anomeric carbons, and reducing/non-reducing sugars.
  • The students will be able to describe the structures and functions of disaccharides (e.g., maltose, lactose, sucrose), storage polysaccharides (glycogen, starch), and complex carbohydrates (GAGs, glycoproteins, proteoglycans).

Functions of Carbohydrates

  • Carbohydrates serve as energy sources.
  • They are components of DNA, RNA, and intermediates in the biosynthesis of fatty acids & proteins.
  • They also participate in biological transport, cell recognition, growth factors, and immune system modulation.
  • Carbohydrates act as lubricants for mucous membranes and are structural components (e.g., cellulose).

Classification of Carbohydrates

  • Carbohydrates are categorized into monosaccharides, oligosaccharides (disaccharides), and polysaccharides with further subdivisions.
  • Monosaccharides are the simplest form (e.g., aldoses, ketoses).
  • Oligosaccharides consist of a few monosaccharides linked together (e.g., disaccharides).
  • Polysaccharides are polymers of monosaccharides (e.g., homopolysaccharides, heteropolysaccharides).
  • Derived carbohydrates are formed by oxidation/reduction/amino/deoxy sugar derivations of the main classes.

Oxidation of Monosaccharides

  • Free anomeric carbons can be oxidized.
  • Benedict's test identifies reducing sugars, wherein the free anomeric carbon reacts changing a blue solution of copper ions to a brick red precipitate.
  • Oxidation by glucose oxidase is a highly specific test for glucose, yielding gluconic acid and hydrogen peroxide.

Clinical Applications of Glucose Testing (glucometers and dipsticks)

  • Glucose oxidase is utilized in glucometers to determine levels.
  • The enzyme reacts with glucose, producing hydrogen peroxide, which leads to a color change (indicating glucose level).
  • Similar reactions occur in urine dipsticks to measure glucose.
  • These methods provide diagnostic tools.

Reducing and Non-Reducing Sugars

  • Reducing sugars have free anomeric carbons which can be oxidized.
  • Benedict's tests use the oxidation of copper ions, which change color to show the reducing sugars.
  • Non-reducing sugars lack free anomeric carbons.

Reduction of Carbohydrates

  • Carbohydrates can be reduced catalytically (using hydrogen and a catalyst) or enzymatically.
  • The product is a polyol (sugar alcohol).
  • For instance, glucose can be reduced to sorbitol.
  • Glucose reduction/increase (especially in diabetes) can lead to cataract formation.

Special Monosaccharides: Deoxy Sugars

  • Deoxy sugars are monosaccharides that lack one or more hydroxyl groups.
  • 2-deoxyribose is an example, a component of DNA.

Glycosidic Bonds

  • Glycosidic bonds link monosaccharides.
  • These bonds form between an anomeric carbon of one monosaccharide and a hydroxyl or amine group of another compound by dehydration.
  • Bonds can be O-glycosidic or N-glycosidic, depending on linking groups involved.
  • Glycosidic bonds create di-, oligo-, and polysaccharides.

Naming Glycosidic Bonds

  • Glycosidic bonds are named based on the carbon atoms involved and the orientation of the anomeric carbon.
  • Example: Maltose (α-1, 4) bond, indicates a bond between carbons 1 and 4.

Disaccharides

  • Two monosaccharides linked by an O-glycosidic bond form disaccharides.
  • Examples include glucose + glucose (maltose), glucose + fructose (sucrose), and galactose + glucose (lactose).

Disaccharides: Structure and Function

  • Disaccharides have unique structures (determined by which carbons are linked).
  • These structures determine their functions.

Lactose Intolerance

  • Lactose intolerance is the inability to digest lactose (glucose and galactose linkages).
  • The inability to digest the disaccharide lactose causes symptoms like gas, bloating, and abdominal pain.
  • Lactose intolerance arises from decreased or absent Lactase activity.

Polysaccharides

  • Polysaccharides are complex carbohydrates, long chains of monosaccharides linked together.
  • They have characteristics like being white, amorphous (glassy), and non-reducing.
  • Polysaccharides are categorized as homopolysaccharides (single monosaccharides) like glycogen, cellulose, and heteropolysaccharides.

Glycogen

  • Glycogen is a branched storage polysaccharide.
  • It is found in liver and muscle.
  • It provides short term glucose storage, and its branches facilitate quick glucose mobilization.

Starch

  • Starch, a storage polysaccharide in plants, consists of amylose and amylopectin.
  • Amylose is a linear chain, while amylopectin is a branched chain.
  • Iodine staining of starch yields diagnostic blue colors due to interactions with amylose.

Cellulose

  • Cellulose, a structural polysaccharide in plants, is a linear polymer with β-1, 4 linkages of glucose that our bodies cannot digest
  • It provides structural support.

Glycosaminoglycans (GAGs)

  • GAGs are linear polymers of repeating disaccharides with amino sugars (acetylglucosamine or galactosamine) and uronic acids (glucuronic or iduronic).
  • They are strongly negatively charged due to carboxyl groups.
  • GAGs are synthesized in the ER and Golgi and degraded in lysosomes.
  • They function in ground substance (to bind water producing gel-like matrix), lubrication, and cell signaling/adhesion.

Members of GAGs

  • Notable GAGs include chondroitin sulfates, keratan sulfates, hyaluronic acid, heparin, and dermatan sulfate which have diverse roles within the body.

Proteoglycans

  • Proteoglycans consist of a core protein attached to glycosaminoglycans.
  • They are found on cell surfaces and in the extracellular matrix.
  • Proteoglycans modulate cell growth, provide elasticity, and influence properties of connective tissues like cartilage and skin.

Glycoproteins

  • Glycoproteins are proteins with covalently attached oligosaccharides.
  • The attachment can be O-linked (serine/threonine) or N-linked (asparagine).
  • Abundant in various proteins throughout the body: structural, transport, hormones, enzymes, immunoglobulins/antigens, and in blood groups.

Blood Group Antigens

  • Blood group antigens are glycoproteins or glycolipids.
  • They are on red blood cells.
  • ABO blood group systems are based on sugar molecules present, determined genetically.

ABO blood group system

  • ABO blood groups are determined by specific glycosyltransferases.
  • These enzymes add sugar molecules to a precursor protein or lipid, leading to the formation of A, B, or O antigens.

Glycolipids

  • Glycolipids are lipids with attached carbohydrate chains.
  • Classified into glycosphingolipids (ceramide backbone) including glycocerebrosides and gangliosides.
  • Glycolipids have diverse roles, for instance, in cell recognition and development.

Glycation of Proteins

  • Glycation is a nonenzymatic process.
  • Sugars (e.g., glucose) react with proteins, forming stable products.
  • Glycation is a long-term glycemic indicator, and high levels indicate poor management of blood glucose levels (diabetes).

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Carbohydrates of Physiologic Significance (Lecture I & II) PDF

Description

Test your knowledge on carbohydrates, including amino sugars, glycosaminoglycans, and their functions. This quiz covers important concepts such as reducing sugars, glycoproteins, and biochemical tests like Benedict’s test. Ideal for students studying biochemistry or molecular biology.

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