Biochemistry: Chapter 5

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What type of bond connects two monosaccharides in a disaccharide?

N-glycosidic bond

Hydrogen bond

O-glycosidic bond (correct)

Peptide bond

What is a function of homopolysaccharides?

Form the cell membrane

Contribute to genetic information

Serve as storage forms of monosaccharides (correct)

Provide extracellular support

What is the composition of peptidoglycan in bacterial cell envelopes?

Cellulose and chitin

Two alternating monosaccharide units (correct)

A single type of sugar

Only amino acids

How does boiling with dilute acid affect disaccharides?

Hydrolyzes them into monosaccharides Signup and view all the answers

What are the two components of starch?

Amylose and amylopectin Signup and view all the answers

What type of linkages are found in the chains of amylose?

(a1-4) linkages Signup and view all the answers

What distinguishes amylopectin from amylose?

Amylopectin is highly branched Signup and view all the answers

What is the primary role of heteropolysaccharides in animal tissues?

Support and protection for cells and tissues Signup and view all the answers

Which of the following is NOT a characteristic of glycosidic bonds?

They can only form between similar sugars Signup and view all the answers

What structural feature distinguishes glycoproteins from proteoglycans?

Glycoproteins have smaller, branched, and more diverse glycan structures. Signup and view all the answers

What is the primary role of lectins in organisms?

To bind carbohydrates and facilitate cell recognition and signaling. Signup and view all the answers

Which statement about glycolipids is correct?

Glycolipids are membrane lipids that contain oligosaccharides as hydrophilic head groups. Signup and view all the answers

What is the significance of proteoglycan aggregates?

They are large assemblies that provide strength and resilience to cartilage. Signup and view all the answers

What functional role do glycoproteins serve in the cell membrane?

They provide specific sites for recognition and binding by other proteins. Signup and view all the answers

Which of the following accurately describes the oligosaccharide linkages in glycoproteins?

They are less complex compared to the glycosaminoglycan chains in proteoglycans. Signup and view all the answers

What type of interactions stabilize the three-dimensional structure of polysaccharides?

Weak interactions, including hydrogen bonds and van der Waals interactions Signup and view all the answers

What is the three-dimensional structure of starch and glycogen primarily characterized by?

A tightly coiled helix Signup and view all the answers

What color does iodine solution give when it interacts with starch?

Blue Signup and view all the answers

What are the two major components of agar?

Agarose and agaropectin Signup and view all the answers

What property of agarose makes it useful in biochemistry laboratories?

Gel-forming property Signup and view all the answers

What is the extracellular matrix primarily composed of?

Heteropolysaccharides and fibrous proteins Signup and view all the answers

Which monosaccharide is always present in glycosaminoglycans?

N-acetylglucosamine or N-acetylgalactosamine Signup and view all the answers

What role do glycosaminoglycans play in the body?

Creating structural support in the extracellular matrix Signup and view all the answers

What is a common feature of glycosaminoglycans regarding their structure?

They consist of repeating disaccharide units Signup and view all the answers

What can happen to the hydroxyls of amino sugars in some glycosaminoglycans?

They can be esterified with sulfate Signup and view all the answers

What role does heparin play in blood samples and transfusions?

It inhibits blood coagulation. Signup and view all the answers

What type of bond is hydrolyzed by lysozyme to kill bacteria?

(b1-4) glycosidic bond Signup and view all the answers

Which macromolecule primarily serves as a rigid component of bacterial cell walls?

Peptidoglycan Signup and view all the answers

What is the primary function of proteoglycans in the extracellular matrix?

To act as information carriers Signup and view all the answers

What substance is known to prevent the synthesis of cross-links in bacterial cell walls?

Amoxicillin Signup and view all the answers

What is known to have the highest negative charge density among biological macromolecules?

Heparin Signup and view all the answers

Which of the following best describes the structure of peptidoglycan?

Heteropolymer of sugars and peptides Signup and view all the answers

What is the main consequence of osmotic lysis in bacteria?

Cellular swelling and rupture Signup and view all the answers

Which carbohydrate-containing molecules are important for cell-cell recognition?

Glycoconjugates Signup and view all the answers

What purpose do glycosaminoglycan chains serve in proteoglycans?

To mediate specific cell interactions Signup and view all the answers

What is the repeating disaccharide unit found in hyaluronate?

D-glucuronic acid and N-acetylglucosamine Signup and view all the answers

How many disaccharides does hyaluronate contain per chain?

50,000 Signup and view all the answers

What is a key function of chondroitin sulfate?

Contribute to the tensile strength of tissues Signup and view all the answers

Which glycosaminoglycan is known for having variable sulfate content?

Keratan sulfate Signup and view all the answers

What type of enzyme is hyaluronidase and what does it do?

An enzyme that hydrolyzes glycosidic linkages of hyaluronate Signup and view all the answers

Heparin is produced in which type of cell?

Mast cells Signup and view all the answers

What function does heparin serve in the body?

Inhibits blood coagulation Signup and view all the answers

Which glycosaminoglycan primarily contributes to the pliability of skin?

Dermatan sulfate Signup and view all the answers

How do other glycosaminoglycans generally differ from hyaluronate?

They are covalently linked to specific proteins Signup and view all the answers

What is the molecular weight of hyaluronate typically greater than?

1 million daltons Signup and view all the answers

Study Notes

Disaccharides

Disaccharides are composed of two monosaccharides, joined by an O-glycosidic bond.
This bond forms when a hydroxyl group of one sugar reacts with the anomeric carbon of the other.
Disaccharides can be hydrolyzed to yield their free monosaccharide components by boiling with dilute acid.
N-glycosyl bonds join the anomeric carbon of a sugar to a nitrogen atom in glycoproteins and nucleotides.

Polysaccharides

Homopolysaccharides contain only a single type of monomer, e.g. starch.
Heteropolysaccharides contain two or more different kinds of monomers, e.g. peptidoglycan.

Functions of Polysaccharides

Homopolysaccharides like starch and glycogen serve as storage forms of fuel for cells.
Homopolysaccharides like cellulose and chitin serve as structural elements.
Heteropolysaccharides provide extracellular structural support for organisms of all kingdoms.
Heteropolysaccharides in animal tissues form a matrix that holds individual cells together and provides shape and support.

Starch

Starch contains two types of glucose polymer: amylose and amylopectin.
Amylose consists of long, unbranched chains of D-glucose residues connected by (α1→4) linkages.
Amylopectin is highly branched.
The branch points in amylopectin are (α1→6) linkages.

Folding of Homopolysaccharides

Polysaccharides form 3-dimensional structures stabilized by weak interactions: hydrogen bonds, hydrophobic interactions, van der Waals interactions, and electrostatic interactions.
The most stable 3-dimensional structure for starch and glycogen is a tightly coiled helix.
The helix can accommodate iodine, which can be used as a qualitative test for amylose.

Agarose

Agarose is a mixture of sulfated heteropolysaccharides made up of D-galactose and an L-galactose derivative.
The two major components of agar are agarose and agaropectin.
The gel-forming property of agarose makes it useful in the biochemistry laboratory.

Glycosaminoglycans

Extracellular matrix (ECM) is a gel-like material that holds cells together and provides a porous pathway for nutrient and oxygen diffusion.
The ECM is composed of an interlocking meshwork of heteropolysaccharides and fibrous proteins.
Glycosaminoglycans are linear polymers of repeating disaccharide units.
One of the two monosaccharides is always either N-acetylglucosamine or N-acetylgalactosamine; the other is usually a uronic acid (D-glucuronic or L-iduronic acid).
Some glycosaminoglycans have hydroxyl groups esterified with sulfate.
Attached to extracellular proteins, glycosaminoglycans form proteoglycans.

Hyaluronate

Hyaluronate has alternating residues of D-glucuronic acid and N-acetylglucosamine.
Hyaluronate has a molecular weight greater than 1 million and forms clear, highly viscous solutions.
The viscous properties make it a lubricant in synovial fluid and contribute to the strength and elasticity of cartilage and tendons.

Hyaluronidase

Hyaluronidase is an enzyme secreted by some bacteria.
It hydrolyzes the glycosidic linkages of hyaluronate, making tissue more susceptible to bacterial invasion.
Sperm also uses similar enzymes to hydrolyze an outer coat surrounding the ovum to allow for penetration.

Chondroitin Sulfate

Chondroitin sulfate is a glycosaminoglycan with repeating disaccharide units of N-acetylgalactosamine and glucuronic acid.
Chondroitin sulfate contributes to the tensile strength of cartilage, tendons, ligaments, and the walls of the aorta.

Dermatan Sulfate

Dermatan sulfate is similar to chondroitin sulfate but with glucuronic acid replaced by iduronic acid.
Dermatan sulfate contributes to the pliability of skin and is also present in blood vessels and heart valves.

Keratan Sulfate

Keratan sulfates have no uronic acid and variable sulfate content.
They are present in cornea, cartilage, bone, and in horny structures like hair, nails, hoofs, and claws.

Heparin

Heparin is a natural anticoagulant made in mast cells.
It binds to and inhibits the protein antithrombin, which in turn inhibits thrombin, a protease essential to blood clotting.
Heparin is routinely added to blood samples and donated blood to prevent clotting.

Glycoconjugates

In addition to functions as stored fuels and structural materials, polysaccharides and oligosaccharides act as information carriers.
Glycoconjugates are biologically active molecules containing carbohydrates covalently joined to proteins or lipids.

Bacterial Cell Wall: Peptidoglycan

The rigid component of bacterial cell walls is a heteropolymer of alternating (β1→4)-linked N-acetylglucosamine and N-acetylmuramic acid residues.
Linear polymers are cross-linked by short peptides to create a strong sheath that envelops the cell—preventing lysis due to osmotic pressure.
The enzyme lysozyme kills bacteria by hydrolyzing the glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid.
Penicillin and related antibiotics kill bacteria by preventing synthesis of the cross-links.

Proteoglycans

Proteoglycans are macromolecules containing glycosaminoglycan chains covalently joined to a membrane protein or a secreted protein.
They are major components of connective tissue, contributing to strength and resilience.
Proteoglycans can form proteoglycan aggregates, which are enormous supramolecular assemblies of many core proteins bound to a single molecule of hyaluronic acid.

Glycoproteins

Glycoproteins are carbohydrate-protein conjugates with smaller, branched, and more diverse glycans than the glycosaminoglycans of proteoglycans.
They are found on the outer face of the plasma membrane, in the ECM, and in the blood.
The oligosaccharide portions of glycoproteins are less complex than the glycosaminoglycan chains of proteoglycans.
Glycoproteins form highly specific sites for recognition and binding by other proteins.

Glycolipids

Glycolipids are membrane lipids with oligosaccharide head groups.
They act as specific sites for recognition by carbohydrate-binding proteins.
Glycolipids are involved in intercellular communication.
Oligosaccharides in glycolipids and glycoproteins serve as cell recognition factors in cell membranes.
The carbohydrate residues in these oligosaccharides are the antigens of the ABO blood group substances.

Carbohydrate-Protein Interaction

Lectins bind carbohydrates with high affinity and specificity.
Lectins serve in cell-cell recognition, signaling, adhesion processes, and intracellular targeting of proteins.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on disaccharides and polysaccharides with this quiz. Explore their structures, functions, and differences between homopolysaccharides and heteropolysaccharides. Understand how these carbohydrates play crucial roles in biological systems.