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Biochemistry > Carbohydrates (disaccharides and polysaccharides) > Flashcards

Carbohydrates (disaccharides and polysaccharides) Flashcards

1
Q

Important groups often attached to monosaccharides (in place of -OH)

A

●
Substitution of an -NH2 group for an -OH group results in an amino sugar.●
Substitution of an -H for an -OH group results in a “deoxy” sugar, like deoxyribose in DNA.●
Acidic sugars contain a carboxylate group (-ate), giving them a negative charge at neutral pH.●
A phosphate group can be added to the C6 carbon of glucose to form glucose-6-phosphate, an important intermediate in metabolic pathways like glycolysis.

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2
Q

How reducing sugars can be detected and why?

A

Reducing sugars have a free anomeric carbon that can be oxidized. This allows the sugar to act as a reducing agent, meaning it can donate electrons to another molecule. This property is used to detect the presence of reducing sugars.

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3
Q

Fehling’s test

A

The aldehyde group of a reducing sugar can reduce Cu2+ to Cu+, forming a “brick red” precipitate of copper(I) oxide.

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4
Q

Tollens’ test

A

he aldehyde group can also reduce Ag1+ to Ag0, precipitating silver metal and forming a “mirror” on clean glassware

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5
Q

Enzymatic methods:

A

Enzymes like glucose oxidase can be used to quantify reducing sugars like glucose. Glucose oxidase catalyzes the conversion of glucose to glucono-δ-lactone and hydrogen peroxide. The hydrogen peroxide then oxidizes organic molecules, creating highly colored compounds that can be measured colorimetrically

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6
Q

Electrochemical detection

A

This method is used in portable glucose sensors

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7
Q

Glycated Hemoglobin (HbA1c)

A

Glycated hemoglobin (HbA1c) is a form of hemoglobin that has glucose non-enzymatically attached to it. It serves as a measure of long-term blood glucose levels, providing valuable information for managing diabete

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8
Q

How glucose joins to the globin protein:

A

Glucose reacts with the amino group of the N-terminal valine residue of the β-globin chain of hemoglobin, forming a stable ketoamine linkage

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9
Q

How HbA1c is measured:

A

The percentage of glycated hemoglobin in the blood is measured. Higher HbA1c levels indicate higher average blood glucose levels over the preceding 2-3 months

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10
Q

Why HbA1c is important:

A

It provides a more reliable indicator of long-term blood glucose control than a single blood glucose measurement.●
It helps healthcare professionals assess the effectiveness of diabetes management and make adjustments to treatment plans as needed.

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11
Q

glycosidic bond

A

is a bond between two sugar molecules that joins them together.●
It forms between an anomeric carbon of one sugar and a hydroxyl carbon of another sugar. Is an acetal

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12
Q

Hemiacetals forms

A

Hemiacetals form when an alcohol attacks an aldehyde

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13
Q

Hemiketals forms

A

Hemiketals form when an alcohol attacks a ketone.

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14
Q

Mutarotation

A

s the interconversion between the α and β anomers

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15
Q

Is an anomeric carbon chiral?

A

Yes, in pentose and hexose

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16
Q

Pyranoses

A

Six-membered oxygen-containing rings. Named after the pyran ring structure.

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17
Q

Furanoses

A

Five-membered oxygen-containing rings. Named after the furan ring structure.

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18
Q

Which is more stable, the acetal or the hemiacetal?

A

The acetal is more stable and less reactive

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19
Q

the disaccharide formed by two glucose molecules joined by a 1→4 bond is named

A

α-D-glucopyranosyl-(1→4)-D-glucopyranose

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20
Q

O-glycosidic bonds

A

The anomeric carbon of a sugar is linked to the oxygen atom of an alcohol group (–OH). This is the most common type of glycosidic bond found in polysaccharides

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21
Q

N-glycosidic bonds

A

The anomeric carbon of a sugar is linked to a nitrogen atom, as seen in glycoproteins and nucleotides

22
Q

Reducing disaccharides vs
Nonreducing disaccharides

A

RDS have a free anomeric carbon (hemiactetal). Can be reduced. NRDS do not have have free anomeric carbons. Both are involved in glycosidic bonds, forming two acetal groups. Are stable and resistant to ocidationm. Good for energy storage and transport

22
Q

What are polysaccharides?

A

-Glycans
- Large carbohydrate polymers composed of many monosaccharide units linked by glycosidic bonds

23
Q

Do polysaccharides have a definite molecular weight? How often are the changed?

A

No. they are assembled without a template, resulting in variations in their size and chain length.

Have a constant state of flux. Individiual monosaccharides are continously added and removed as needed by enzyme

24
Q

Homopolysaccharides

A

have a single type of monosaccharide. They serve as fuel and structural elements. Examples are starch, glycogen, cellulose, and chitin

25
Q

Heteropolysaccharides

A

have more than 1 type of monosaccharide in chaoin. Provide extracellular support. Ex: peptifohlycans and glycoaminoglycans

26
Q

What is the structure of a polysaccharide?

A

It can be linear or unbranched with one type of glycosidic bond, or branched with multiple types of glycosidic bonds

27
Q

What are the similarites between glycogen and starch?

A

Both are homosaccharides with a1->4 glycosidic linkages.
Both function as energy storage. Glycogen for animals, starch in plants
- both form insoluble granules in cells, making them osmotically inactive and preventing them from affecting the cell’s water potential
- have one reducing end and many non-reducing ends

28
Q

What are the differences between glycogen and starch?

A

Branching: glycogen is very branched, a1->6 branch points every 8-12 residues.
starch is very 24-30 residues in amylopection, while amylose is unbranched.

Molecular weight: Glycogen weights less than amylopection

29
Q

Where is a branch point? What do they retain? What is the benefit?

A

α1→6. They retain nonreducing end. Allows for simultaneous enzymatic processing at multiple points, increasing the efficiency of glucose release or storage

30
Q

What is the role of glycogen phosphorylase?

A

breaking down glycogen by removing glucose-1-phosphate units from the nonreducing ends

31
Q

What is the role of glycogen synthase?

A

synthesize glycogen by adding glucose units to the nonreducing ends

32
Q

What is the role of starch phosphorylase?

A

Breaking down starch by removing glucose-1-phosphate units from the non-reducing ends

33
Q

What is the role of starch synthase?

A

Synthesizes starch by adding glucose to the non-reducing ends

34
Q

What is starch?

A

mixture of amylose and amylopectin

35
Q

Why is it important to store glucose as glycogen or starch?

A

Storing glucose as an insoluable large, polymer stops the change in osmolarity pressure. It keeps water from moving into the cell because of the presence of glucose, potentially causing it to burst.

Good energy reserve - if glucose is needed, can be easily broken off

Synthesis and degradation of glucose and starch are strictly regulated, resulting in precise control of blood glucose levels.

36
Q

Why is cellulose not a good energy storage molecule?

A

Because of B1->4 glycosidic linkage. Most animals lack enzyme cellulase, which is required to breakdown this linkage. Makes cellulose indigestible. Good for structure

37
Q

Why is cellulose great for structure, and why is it insoluble?

A

Cellulose contains B(1->4) linkages, which results in a straight, extented chain conformation. This chain allows for molecules to be packed tightly together, forming strong hydrogen bonfd between adjacent chains. This is why it is insoluble in water and good for structure

38
Q

How can cellulose be used as biofuel?

A

The glucose obtained from cellulose can be fermented to produce biofuels, such as ethanol, which can be used as a substitute for gasoline. However, the fibrous structure and insolubility make it a very challenging substrate to process

39
Q

What is chitin composed of?

A

linear, Homopolysaccharide composed of N-acetylglucosamine units linked by B1->4 glycosidic bonds.

40
Q

What does chitin form? Where can it be found?

A

Forms extened fibers that are hard, insoluble and can’t be digested by vertebrates. These factors make it good for structural support. It is found in cells walls of mushrooks and exoskeletons

41
Q

What are the differences between cellulose, amylose, and dextran?

A

Cellulose: Linear polymer with β1→4 linkages, forming extended, straight chains. This allows for strong hydrogen bonding between adjacent chains, resulting in high tensile strength and water insolubility.●
Amylose: Linear polymer with α1→4 linkages, forming a helical structure. It is less rigid than cellulose and can be digested by enzymes like amylase.●
Dextran: Branched polymer with α1→6 linkages as the main chain and α1→3 branches. Its branched structure and different linkage type make it distinct from both cellulose and amylose.

42
Q

What is agar?

A

A branched heteropolysaccharide composed of agarose and agaropectin, found in marine red algae. It is used in the laboratory as a surface for growing bacteria and in various food and pharmaceutical applications.

43
Q

What is agarose?

A

A component of agar with the fewest charged groups. It forms a double helix when heated and cooled, trapping water in the central cavity to form a gel. This makes it useful for separating DNA by gel electrophoresis.

44
Q

What are GAGs?

A

Glycoaminoglycans are linear polymers of repeating disaccharide units found in animals and bacteria, but not plants. They. form the extracellular matrix. This is meshwork with bibrous proteins

45
Q

What are the 2 monomers of GAG?

A

either N-acetyl-glycoamine or N-acetyl-galactosamine and uronic acid (glucuronic acid or L-iduronic acid).

46
Q

What causes a negative charge of glycosaminoglycans?

A

presence of uronic acids sulfate, which contributes to their extended, hydrated conformation and their role in forming the extracellular matrix.

47
Q

What is the function of GAGs?

A

GAGs form a meshwork with fibrous proteins, creating the extracellular matrix (ECM). The ECM provides structural support, lubrication of joints, and a barrier for tumor cell invasion

48
Q

Describe the conformation of GAGs.

A

The negatively charged groups repel each other, leading to an extended, rod-like helix, with negative charges on alternate sides of the helix. This minimizes charge repulsion and allows for interaction with other molecules.

49
Q

How does Heparin prevent blood clotting?

A

By activating the protease inhibitor antithrombin

50
Q

What is Heparan sulfate?

A

similar GAG that is attched to proteins. Has a high negative charge density and plays various roles in regualting development and blood vessel formation

Biochemistry (6 decks)

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