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Carbohydrates Intro Flashcards

1
Q

What are the major characteristic features of monosaccharides?

A

1) they contain an aldehyde or a ketone

2) they contain multiple hydroxyl group

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2
Q

How are monosaccharides named?

A

It’s a combination of information about the number of carbons and the functional group, adding -ose at the end

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3
Q

How can you classify monosaccharides?

A

1) aldoses or ketoses (either aldehyde or ketone)

2) based on the number of carbons it contains (heptoses, pentoses, etc)

With one limitation of the carbon being 3 at least

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4
Q

What is the formula for monosaccharides?

A

CnH2nOn

With one limitation of the carbon being 3 at least

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5
Q

What are the cellular functions of carbohydrates?

A

1) energy

2) structure

3) communication

4) precursor for other biomolecules

  • Direct link between solar & chemical bond energy (we can synthesize glucose only from intermediate levels not from scratch)
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6
Q

What is a monosaccharide?

A

Simple sugars they are polyhydroxy aldehyde or ketones (aldehyde = aldoses, ketone = ketoses)

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7
Q

What are the most abundant type of carbohydrate in living cells?

A

Hexoses (the aldehyde must be at carbon number 1) & ketoses (the ketone must be at carbon number 2)

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8
Q

How to know the number of isomers/optical of monosaccharides?

A

2^n of the number of chiral centers. (two stereoisomers D (right) & L (left) the way you look at the page)
If you have more than one chiral center you name it D or L based on the OH of the farthest carbon from the carbonyl group (CHO)

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9
Q

In which form does the monosaccharides occur mainly, and mainly derived from what?

A

D- form, D-Glyceraldehyde and dihydroxyacetone

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10
Q

What is an Enantiomers?

A

Optical isomer Compounds that have the same structural formula forming a mirror images

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11
Q

What is a Diastereomer?

A

Optical isomer Compounds that have the same structural formula but don’t form mirror images in more than one carbon

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12
Q

What is an epimer?

A

Diastereomers that only differ in one carbon

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13
Q

What is the structural link between D-Glucose and D-galactose?

A

C4-Epimers

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14
Q

In which Form do we find monosaccharides in nature and why?

A

In sugars with 4+ carbons they exist as a Cyclic form as they can form hemiacital and hemiketal with the most common form being in the interaction of C1 (aldehydes) /C2 (ketones) with C5 as it’s the most stable this is a reversible reaction

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15
Q

What is an anomeric carbon?

A

A term associated with cyclic sugars which refers to the carbon that was either a aldehyde or a ketone in the open chain structure which is a new type of isomers giving alpha and beta (in a structure you can depict it as it’s the only carbon bound to two oxygen atoms)

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16
Q

What is meant by anomers?

A

The two possible diastereomers that form due to cyclization

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17
Q

What defines alpha and beta isomers?

A

Based on the OH at the anomeric carbon if it’s down then it’s alpha (right in Fischer projection) if it’s up then it’s beta (left in Fischer projection)

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18
Q

What are the different ways to draw the structure of monosaccharides?

A

1) Haworth structure

2) Fischer projection

3) conformational structure (shows the puckered nature of sugar rings,

4) space filling

5) X-ray and bond analysis

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19
Q

How many different type of cycles do we have in sugars?

A

1) five membered ring (furanoses, usually by ketoses)

2) six membered ring (pyranoses, usually by aldohexoses)

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20
Q

What is meant by mutarotation?

A

The change between a- and b- forms of monosaccharides, it is a spontaneous process producing a mixture of a- & b- in both furanoses and pyranoses in an aqueous environment mostly 62% in b-form (we should maintain this equilibrium)

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21
Q

What are the reactions of monosaccharides?

A

Their carbonyl and hydroxyl groups can undergo several reactions,

1) oxidation

2) reduction

3) isomerization

4) Esterification

5) glycoside formation

6) glycosylation reactions

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22
Q

What is the oxidation reaction of monosaccharides and which type of monosaccharides are capable of doing it?

A

Aldoses, usually ketoses don’t undergo oxidation reaction due to the nature of the ketone group, it can occur in the aldehyde group (producing an -onic acid “Aldonic acid”) or in the last hydroxyl group (-uronic acid) so from the name you can tell which group have been oxidized if both are oxidized at the same time they will produce (-aric acid “aldaric acid”) this reaction can undergo in the presence of metal ions or certain enzymes

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23
Q

What is a lactone?

A

Cyclization of an aldonic/uronic acid reacting with an OH in the molecule

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24
Q

What is ascorbic acid?

A

Vitamin C, reducing agent, important as an antioxidant and a cofactor for some enzymes

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25
What is a reducing sugar?
Sugars that can be reduced by weak oxidizing agents (Benedict’s reagent) (usually, all monosaccharides are reducing sugars, in disaccharides only when the anomeric carbon is free)
26
What is the reduction reaction?
“Sugar alcohols” (alditols) produced by the reaction of aldehyde and ketone groups of monosaccharides, used in commercial food processing and in pharmaceuticals (sorbitol used to prevent moisture loss “preservative”) they produce alcohols
27
What is an isomerization reaction?
1) D-glucose incubation in an alkaline solution can produce two isomers (A) D-mannose & B) D-fructose) having an enediol as an intermediate (it is the conversion of a sugar to its isomer)
28
What is meant by epimerization?
The transformation of carbohydrate (glucose) into one of its Epimers (mannose) catalyzed by epimerase (enzyme)
29
What is meant by Aldose-ketose interconversion?
The transformation of glucose to fructose
30
What is Esterification?
The conversion of the OH group to esters via acids -changing the physical and helical property of the sugar (polarity, type of attachments) & participates in the salt bridge formation
31
Where is sulfate esters of carbohydrates found?
Proteoglycan component of the connective tissue
32
What is glycoside formation?
It is the. Linkage that monosaccharides form to produce polysaccharides (which is the interaction of hemiacetal or hemiketal with an alcohol/or hemiketal/acetal forming acetal “glucoside” or a ketal “fructoside” (glycoside) respectively)
33
What is the linkage in polysaccharides?
Glycosidic linkage
34
What is a glycosylation reaction?
The attachment of sugars/sugar polymers (glycane) to proteins or lipids catalyzed via glycosyl transferases, forming a bond between anomeric carbons in certain glycans and oxyggen or nitrogen of the other molecule (producing N-GLYCOSYLATION AND O-GLYCOSYLATION)
35
What is a glycation reaction?
Interaction of sugar to a nitrogen in a non-enzymatic reaction producing an amadori product (Millard reaction) this reaction can form a product named AGEs (advanced glycation end products, associated with atherosclerosis and many clinical symptoms like glucotoxicity, promotes inflammatory processes and age related diseases)
36
What are the important monosaccharides?
1) glucose (D-Glucose) 2) fructose (D-Fructose) 3) galactose
37
What is glucose?
AKA dextrose, found in large quantities in the world, it is the primary fuel for living cells, and the preferred source of energy for the brain and cells without a mitochondria (erythrocytes)
38
What is fructose?
Fruit sugar, used as a sweetening agent in processed food, and in sperms as a source of energy, it has 7 times the potency to by glycated which makes it more dangerous than glucose
39
What is galactose?
is necessary to synthesize a variety of important biomolecules (lactose), Important biomolecules include lactose, glycolipids, phospholipids, proetoglycan, and glycoproteins
40
What is Galactosemia?
a genetic disorder resulting from a missing enzyme in galactose metabolism
41
What are the monosaccharides derivatives?
1) uronic acids (a-D-glucuronate in the liver its used to improve water solubility and remove wastes , b-L-iduronate) 2) Amino sugars (D-Glucosamine, D-Galactoseamine where the hydroxyl group in the second carbon is replaced with an amine group) 3) deoxygenated sugars (monosaccharides with a replaced -OH with an -H or -CH3 “2-Deoxygenated-D-ribose”)
42
What is a disaccharide?
When a hemiacetal “at carbon number 1”/hemiketal “carbon number 2” interacting with an -OH of another molecule forming an acetal or a ketal (depending on the origin of the anomeric carbon), the linkage is named by a- or b-conformation and by which carbon are connected (a(1,4), b-(2,4) “note it will always start with 1 or 2”
43
Examples of disaccharides
1) lactose (milk sugar) 2) maltose (malt sugar) 3) cellobiose (cellulose degradation) 4) sucrose (cane/beat sugar “table sugar”)
44
What is lactose and what is its structure?
Its a reducing sugar (its has a free anomeric carbon) found in milk, (B(1,4) between GLUCOSE & GALACTOSE “glycosidic linkage”) broken down by lactase There is alpha and beta lactose depending on the orientation of the OH around the “free” anomeric carbon (the anomeric carbon of glucose (whether its OH is up one down)
45
What is maltose and what is its structure?
It is an intermediate product of starch hydrolysis (a(1,4) between two glucoses) two conformation alpha and beta based on the free anomeric carbon - It doesn’t exist free in nature - reducing sugar - broken down by maltase
46
What is cellobiose and what is its structure?
It is a degradation product of cellulose, composed of two molecules of glucose linked by (b(1,4) glycosidic bond) - doesn’t exist free in nature - reducing sugar - we don’t have its enzyme
47
What is the structure of sucrose?
Glucose linked to fructose by (a,b(1,2)) glycosidic bond at both anomeric carbons -non-reducing sugar
48
What is meant by polysaccharides?
Polysaccharides (glycans) it is composed of large number of monosaccharides connected by glycosidic linkage
49
What is meant by oligosaccharides?
Small glycans (polysaccharides) composed of 10-15 monosaccharides, they are often connected to polypeptides as glycoprotein with two classes (N- & O-LINKED oligosaccharides)
50
What is an N-linked oligosaccharide?
They are attached to polypeptides by an N-glycosidic bond with the side chain amide nitrogen of the amino acid usually of “asparagine” with three types based on the carbohydrate linked 1) high mannose 2) hybrid 3) complex
51
What is an O-linked oligosaccharide?
The attachment of the oligosaccharide (glycan) to the side chain hydroxyl of serine, threonine, or the hydroxyl oxygens of the membrane lipids
52
What is the two structural variations of polysaccharides, & into which classes are they divided?
1) linear or branched 2) homoglycans (composed of one repeated monomer) & heteroglycans (composed of several monomers)
53
what are some of the homoglycans examples?
1) starch (energy storage) 2) glycogen (energy storage) 3) cellulose (structural molecule, plant cell wall) 4) chitin (structural molecule, cell wall of fungi) - they don’t have a fixed molecular weight (size may vary based on the number of monosaccharides)
54
What is starch?
The energy reservoir in plants, a source of carbohydrate in human diet, composed of two polysaccharide types: 1) Amylose (long, unbranched chains of D-glucose with a(1,4) linkage in between) 2) amylopectin (branched polymer of glucose, containing both a(1,6 “branching points”) & a(1,4) linkages, with their branch being every 20-25 residues)
55
What is glycogen?
Energy storage form in humans and animals, (great amount in liver “8-10% of its weight” and muscle cells “2-3%”), its structure is similar to amylopectin (glucose a(1,6) & a(1,4) but with more branch points, every 8-10) - Easily mobilized compared to other polysaccharides
56
What is cellulose?
Its a polymer of unbranched, D-glucopyranosides, linked by b(1,4) glycosidic bonds, most important structural polysaccharide in plants - most abundant organic substance on earth - pairs of unbranched cellulose molecule are held together by hydrogen bonds forming microfibrils (sheetlike strips) which has great strength - it is important dietary fiber, wood, paper and textiles
57
What is lactose intolerant?
It is the absence of the enzyme lactase, making the person is unable to digest lactose, resulting in the accumulation of lactose in the intestine absorbing water leading to diarrhea (osmolitic activity), also the micro biome will ferment it releasing CO2 causing cramps/spasm
58
What is a heteroglycan?
A high molecular-weight carbohydrate polymer containing more than one type of monosaccharide, its major types are: 1) N-linked (core of N-acetyl glucose amino “anomeric carbon” will attach to amide of aspargine R group via b-glycosidic linkage) & O-linked (disaccharide core of galactosyl-b-(1,3)-N-acetylgalactosamine linked to serine or threonine via a-glycosidicbond) glycosaminoglycan 2) glycosaminoglycan 3) glycan component of amino lipids 4) GPI (Glycosylphosphatidylinositol) “anchor proteins”
59
What is a glycosaminoglycan (GAG’s)?
Linear polymer with disaccharide repeating unit it has five classes: 1) hyaluronic acid 2) chondroitin sulfate 3) dermatan sulfate 4) heparin & heparin sulfate 5) keratin sulfate They have lots of uses based on the repeating units, important in connective tissues
60
What is glycoconjugate?
When a protein (glycoprotein) or a lipid (glycolipid) attached to a carbohydrate molecule
61
What is a proteoglycan?
A form of glycoprotein but with high carbohydrate content (95%), which occurs on cell surfaces or secreted to the ECM, usually have a lot of GAG’s attached to core protein which are classified into groups: attached to protein surface 1) syndicans (heparin sulfate proteoglycan “high heparin sulfate GAG component”, protein attached to transmembrane protein) 2) glypicans (heparin sulfate proteoglycan “high heparin sulfate GAG component”,protein attached to peripheral protein) 3) Aggricans (disc of the intervertebra, extracellular composed more than 100 GAG) They have roles in organizing the ECM and involved in signal transduction, and their metabolism involves lots of genetic disorders like (Hurler syndrome)
62
What is a glycoprotein?
Proteins that are covalently linked to carbohydrates through N-linked & O-Linkage Functions: 1) enzyme 2) immunoglobulin 3) hormone 4) membrane protein 5) blood clotting 6) transport protein 7) cell adhesion “CAM’s” (selectin, integrin, cadherins) 8) receptor protein glyccocalyx important component (
63
What is the differences between n-linked & o-linked glycoprotein
(N-linked are in the lumen of Endoplasmic reticulum & Golgi complex, usually asparagine linked protein) while o-linked (initiates in the golgi complex)
64
Glucose and galactose are
C4 Epimers
65
Glucose and mannose are
C2 EPIMERS
66
Smallest carbohydrate is
Glyceraldehyde & dihydroxyacetone
67
An example of a Diastereomers
D-ribose & D-arabinose
68
What are the stereoisomers produced by glucose
produces two isomers: D-mannose and D-fructose

Carbohydrates (1 decks)

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