Disaccharides and Glycosidic Linkages Quiz

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Questions and Answers

What are disaccharides primarily composed of?

Two monosaccharides (correct)

One monosaccharide and one oligosaccharide

Three monosaccharides

Two polysaccharides

What type of reaction is responsible for the formation of glycosidic linkages in disaccharides?

Hydrolysis reaction

Reduction reaction

Dehydration reaction (correct)

Oxidation reaction

In the synthesis of maltose, which carbon of the first glucose unit bonds with which carbon of the second glucose unit?

2 of the first glucose with 4 of the second glucose

1 of the first glucose with 4 of the second glucose (correct)

1 of the first glucose with 2 of the second glucose

1 of the first glucose with 1 of the second glucose

What is the effect of changing the bonding arrangement of glucose monomers in a disaccharide?

It results in a different disaccharide Signup and view all the answers

Which disaccharide is formed from two glucose units?

Maltose Signup and view all the answers

In the context of glycosidic linkages, what distinguishes a 1–4 linkage from a 1–2 linkage?

The specific carbons bonded together Signup and view all the answers

What is the characteristic feature of a glycosidic linkage?

It connects monosaccharides Signup and view all the answers

Which reaction releases water as a byproduct during the formation of disaccharides?

Dehydration Signup and view all the answers

What is the primary structure of glucose when dissolved in water?

It predominantly forms a ring structure. Signup and view all the answers

What connects carbon 1 of glucose to carbon 5 to form its ring structure?

A glycosidic linkage Signup and view all the answers

Which of the following is NOT a characteristic feature of monosaccharides?

They contain glycosidic linkages. Signup and view all the answers

Which carbon atom in glucose is involved in forming the glycosidic linkage in the ring structure?

Carbon 1 Signup and view all the answers

How does the stability of ring forms of monosaccharides compare to linear forms in solution?

Ring forms are more stable than linear forms. Signup and view all the answers

Which of these statements best describes the structure of monosaccharides in aqueous solutions?

They mainly exist as ring structures. Signup and view all the answers

What type of bond would most likely be formed when two monosaccharides link together?

Glycosidic linkage Signup and view all the answers

In which scenario would the linear form of monosaccharides be favored over the ring form?

In extreme pH conditions. Signup and view all the answers

What type of glucose monomers does cellulose primarily consist of?

Beta glucose Signup and view all the answers

Which of the following describes the glycosidic linkage in cellulose?

1–4 linkage Signup and view all the answers

How does the glycosidic linkage in starch differ from that in cellulose?

Starch has a 1–4 linkage of alpha glucose, cellulose has a 1–4 linkage of beta glucose Signup and view all the answers

Which structure primarily forms cellulose?

Unbranched chain of beta glucose Signup and view all the answers

What type of polymer is cellulose categorized as?

Structural polysaccharide Signup and view all the answers

What is the primary difference between starch and cellulose concerning their glycosidic bonds?

Starch contains 1–4 linkages of alpha glucose while cellulose contains 1–4 linkages of beta glucose Signup and view all the answers

What structural feature of cellulose contributes to its strength?

Unbranched polymer chains with hydrogen bonding Signup and view all the answers

In terms of solubility, how does cellulose compare to starch?

Starch is more soluble than cellulose Signup and view all the answers

What type of bond primarily holds the monomers together in cellulose?

Covalent bonds Signup and view all the answers

What property of cellulose is largely due to its long straight chains of beta glucose?

Strong tensile strength Signup and view all the answers

Which of the following statements about glycosidic linkages is false?

All glycosidic linkages are the same in structure. Signup and view all the answers

Why is cellulose not easily digestible by humans?

Humans do not produce the enzyme necessary to break down beta linkages. Signup and view all the answers

Study Notes

Life and Chemistry: Large Molecules

Large biological molecules are called macromolecules
These large molecules are present in all living things, in similar proportions
Macromolecules are giant polymers
Polymers are formed by covalent linkages of smaller units called monomers
Molecules with molecular weights greater than 1,000 Daltons (1 kDa = 1000 Daltons) are usually classified as macromolecules
The functions of macromolecules are related to their shape and the chemical properties of their monomers
Some functions of macromolecules include: energy storage, structural support, transport, protection and defense, regulation of metabolic activities, means for movement, growth, and development, Heredity

Macromolecules: Condensation and Hydrolysis

Macromolecules are made from smaller monomers by dehydration (condensation) reaction.
In a condensation/dehydration reaction, an OH from one monomer links to an H from another monomer.
A water molecule is released in this reaction (H₂O)
The reverse reaction, where polymers are broken into monomers, is called a hydrolysis reaction.
Energy is required to make or break polymers

Biological Macromolecules

There are four major types of biological macromolecules: proteins, nucleic acids, carbohydrates, and lipids
Of the four, only three are polymers: proteins, nucleic acids, and carbohydrates.

1. Proteins

Proteins are polymers of amino acids. They are molecules with diverse structures and functions
Each type of protein has a characteristic amino acid composition and order.
Proteins range in size from a few amino acids to thousands
Protein folding is crucial to function and is influenced largely by the amino acid sequence
An amino acid has four groups attached to a central carbon atom: a hydrogen atom, an amino group (NH₃⁺), a carboxyl group (COO⁻), and a variable side chain (R group.)
Differences in amino acids come from the side chains or R groups.
There are twenty different amino acids found in cells
Amino acids are linked by peptide bonds.
A condensation reaction links the carboxyl group of one amino acid to the amino group of the next, releasing a water molecule
Polypeptides have an amino-terminal (N-terminus) end and a carboxyl-terminal (C-terminus) end.
The polypeptide backbone is relatively inflexible.
Various interactions between the R groups cause the polypeptide to fold into a specific 3D shape, crucial to their function.
Proteins can be classified into four levels of structure: primary, secondary, tertiary, and quaternary
The primary structure of a protein is its amino acid sequence.
The precise sequence of amino acids is called primary protein structure
Secondary structure describes local folded structures like a-helices and ß-sheets
Tertiary structure describes the overall, 3D folded structure of a single polypeptide chain.
Quaternary structure describes how multiple polypeptide chains (subunits) interact to form a functional protein.

2. Nucleic Acids

Nucleic acids are polymers of nucleotide monomers
Nucleotides are composed of a phosphate group, a sugar (ribose in RNA and deoxyribose in DNA), and a nitrogenous base (purines or pyrimidines).
There are two groups of nitrogenous bases: purines (adenine and guanine), and pyrimidines (cytosine, uracil, and thymine)
Uracil is found only in RNA, and thymine is found only in DNA
Nucleic acid strands are formed by a phosphodiester linkage (phosphodiester bond)
The phosphodiester linkage is formed between the phosphate group of one nucleotide and the 3' hydroxyl group of an adjacent nucleotide.
The sugar-phosphate backbone is directional, running 5' → 3'
DNA has a double helix, with two antiparallel strands held together by complementary base pairing. The hydrophilic sugar-phosphate backbone is facing the outside, while nitrogenous bases are inside the structure.
DNA has complementary base pairing of purines and pyrimidines; adenine pairs with thymine, and guanine pairs with cytosine
The base-pairs are held together by hydrogen bonds.
DNA strands are antiparallel. The structure of DNA is a double helix.
The information necessary to maintain hereditary information is encoded in the DNA base sequences.
Closely related species have more similar base sequences.

3. Carbohydrates

Carbohydrate polymers are called glycans
Carbohydrates serve as fuel and building material
Carbohydrates include both sugars and their polymers
Monosaccharides are the simplest sugars. They can be used for fuel and converted into other organic molecules and combined into polymers.
Examples include glucose, galactose, fructose.
Disaccharides are two monosaccharides joined by a glycosidic linkage. Examples include sucrose (glucose + fructose) and maltose (glucose + glucose).
Polysaccharides are polymers of monosaccharides. Polysaccharides include: -Storage polysaccharides (starch and glycogen): -Starch is the main storage polysaccharide of plants, consisting entirely of α-glucose monomers; and used as energy storage in plants -Glycogen is the major storage polysaccharide in animals, also composed of α-glucose monomers, used as energy storage in animals -Structural polysaccharides (cellulose, chitin): -Cellulose is an unbranched polymer of β-glucose; forms plant cell wall structures -Chitin is a structural polymer present in fungal cell walls and the exoskeletons of arthropods
Glycoproteins (proteins with covalently bound carbohydrates) are part of the cell’s surface, used for cell-cell recognition

4. Lipids

Lipids are a diverse group of hydrophobic molecules
Lipids are not polymers
Lipids include a variety of molecules, including fats, phospholipids, steroids, and carotenoids
Lipids share the common feature of being hydrophobic
Fats (triglycerides): Composed of glycerol and three fatty acid chains. They store energy. Saturated fats have no double bonds and are solid at room temperature, and unsaturated fats have one or more double bonds and are liquid at room temperature.
Phospholipids: Structure includes two fatty acid chains bound to glycerol, and a phosphate modified group. Part of cell membranes, they are amphipathic with hydrophobic tails and hydrophilic heads.
Steroids: Have a four-ring carbon skeleton. Important signaling molecules in hormones and part of cell membranes. Cholesterol is an example, important in cell membranes and the precursor to other steroids.
Carotenoids: Light-absorbing pigments. Examples include beta-carotene (a plant-based pigment that converts to vitamin A in animals)
Additional Roles for lipids: energy storage, insulation, cushioning, part of cell membranes, capture of light energy, components of hormones and vitamins, thermal insulation, electrical insulation of nerves, water repellence

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Description

Test your knowledge on disaccharides, their composition, and glycosidic linkages. This quiz covers the key reactions and structural aspects of disaccharides like maltose, including the formation and characteristics of glycosidic bonds. Challenge yourself with questions about glucose linking and structural features!