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Carbohydrates > Carbohydrates-1 part final > Flashcards

Carbohydrates-1 part final Flashcards

1
Q

What is the sub composition of Macromolecues?

A
  1. Monomers

2. Polymers

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2
Q

What are there four classes of biological molecules?

A
  1. Lipids
  2. Carbohydrates
  3. Proteins
  4. Nucleic acids
  • Lipids
  • Saturated, Unsaturated, trans fats
  • Phospholipids
  • Steroids
  • Carbohydrates
  • Monosaccharides, Disaccharides, Polysaccharides
  • Proteins
  • Amino acids
  • Primary, Secondary, Tertiary, Quarternary structure
  • Nucleic acids
  • Nucleotides
  • DNA & RNA
  • ALL FOUR CLASSES ARE ORGANIC MOLECULES (NOT ALL ORGANIC MOLECULES ARE PART OF ONE OF THE FOUR CLASSES OF BIOLOGICAL MOLECULES)
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3
Q

What are the three of the four classes of life’s organic molecules which is polymers?

A
  1. Carbohydrates
  2. Proteins
  3. Nucleic Acids
  • Polymer - a long molecule consisting of many similar building blocks
  • Monomers - the building block
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4
Q

What is the literally means of Carbohydrates?

A

It literally means hydrates of carbon, but actually carbohydrates may be defined as POLYHYROXYALDEHYDES or POLYHYDROXYKETONES.

  • The term SUGARS is utilized just for those carbohydrates soluble in water and sweet in taste.
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5
Q

What are the functions of Carbohydrates?

A
  1. Source of energy
  2. Storage form of energy
  3. Structural component.
  4. RNA & DNA Constituent
  5. Conjugated with proteins and lipids
  6. Involved in cell-cell interaction and recognition events
  • Glucose is the principal fuel of metabolism, supplying energy to all living cells, both plants and animals.
  • Also it serves as the storage form of energy (starch in plants and glycogen in animals) to satisfy the immediate energy demands of the organism.
  • They form structural components of many organism
  • Cellulose : the fibers of plants
  • Chitin : exoskeleton of some insects or crustaceans
  • Bacteria : the cell wall of microorganism
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6
Q

What are their characteristics chemical features made functions of carbohydrate?

A
  1. The existence of at least one, or more, asymmetric center.
  2. The ability to exist either in linear or ring structure.
  3. The capacity to form polymeric structures by means of glycosidic bonds.
  4. The potential to form multiple hydrogen bonds with water, or other molecules, in their environment.
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7
Q

What is the basic composition of carbohydrates?

A

(CH2O)n , n is at least 3.

The simplest form is represented by MONOSACCHARIDES (simple sugars with multiple OH groups)

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8
Q

What is the standard for classification of carbohydrates?

A
  1. It is based on the number of carbon atoms
  2. It is based on the functional group
  • Triose , Tetrose, Pentose, Hexose and Heptose
  • Aldoses = have an aldehyde group at C1.
    Ketoses = have a ketone group at C2.
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9
Q

What are the disaccharides?

A

Disaccharides are 2 monosaccharides covalently linked.

  • Maltose = Glucose + Glucose
  • Sucrose = Glucose + Fructose
  • Lactose = Glucose + Galactose
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10
Q

What are the oligosaccharides?

A

From 2 at up to 10-15 monosaccharidic residues covalently linked.

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11
Q

What are the polysaccharides?

A

Polysaccharides are polymers consisting of long chains of monosaccharidic or disaccharidic units.

  • They have high molecular weight.
  • They are generally tasteless (non sugars) and form colloidal solution with water.
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12
Q

What are there two types of polysaccharides?

A
  1. Homopolysaccharides
  2. Heteropolysaccharides
  • Monosaccharides of a single type
  • Monosacchrides of 2or more different types, or their derivatives.
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13
Q

The nomenclature of monosaccharides is also directly related to what?

A

It directly related to the configuration of each asymmetric carbon.

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14
Q

What is the asymmetric carbon?

A

An asymmetric carbon atom (chiral carbon) is a carbon atom that is attached to four different types of atoms or groups of atoms.

  • Chiral Carbon = all different carbon atoms
  • Non Chiral Carbon = not all different carbon atoms
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15
Q

Considering the simple aldotriose glyceraldehyde, having just 1 asymmetric C (C*), we can have what?

( Aldotriose glyceraldehyde is CHIRAL CARBON)
( Dihydroxyacetone is same NO CHIRAL CARBON)
* They are same chemical formulas. But different structural formulas.

A

We can have 2 configurations named as D&L. ( D-glyceraldehyde , L-glyceraldehyde)

  • D : OH is attached to right side of molecular.
  • L : Hydroxide is attached to left side of molecular.
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16
Q

In sugars with more than one chiral carbon, D or L refers to what?

A

D or L refers to the position of the oxydrylic group in the asymmetric carbon farthest from the functional group ( aldehydic or ketonic )

  • D = OH group is on the right.
  • L = OH group is on the left.
  • Most naturally occurring sugars are D isomers.
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17
Q

What is the stereoisomers?

A

The stereoisomers are the compounds that have same structural formulae but differ in their spatial arrangement.

  • For instance, hexoses have the same chemical formula C6H12O6 but exist different stereoisomers having exclusive names : GLUCOSE , MANNOSE , GALACTOSE , etc.
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18
Q

What are the ENANTIOMERS?

A

The ENANTIOMERS are stereoisomers whose molecules are the mirror image ( and not superimposable) of the other one.

  • According to convention, D&L sugars are mirror images of each other.
  • They have the same name, D-glucose & L-glucose.
  • The aldoses have 4 asymmetric centers (2 times to the four), there 16 stereoisomers (8 D-hexoses and 8 L-hexoses).
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19
Q

What are the EPIMERS?

A

Epimers are two sugars different in configuration of only one chiral carbon.

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20
Q

What is the part of discount of monosaccharides?

A

Usually monosaccharides are presented and reported usingthe linear molecular structure (Fischer projections) but they discount the most intersting aspects of sugar structure : THEIR ABILITY TO FORM CYCLIC STRUCTURES.

  • An aldehyde can react with an alcohol to form a hemiacetal.
  • A ketone can react with an alcohol to form a hemiketal.
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21
Q

The linear form of glucose ( and other aldoses ), undergoes to a similar INTRAMOLECULAR reaction forming what?

A

The linear form of glucose (and other aldoses), undergoes to a similar INTRAMOLECULAR reaction forming a CYCLIC HEMIACETAL.

  • This reaction occurs between the aldehydic functional group (C1) and the alchoholic group of the last asymmetric carbon (C5).
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22
Q

What is the results from the cyclization of Glucose?

A

The cyclization of Glucose forms a 6-membered ring (containing 5 carbon and 1 oxygen atoms) that is similar to the PYRAN structure.

  • Consequently the ring of the cyclized glucose is defined as PYRANOSE RING or GLUCOPYRANOSE. ( it is an arrangement reminiscent of pyran )
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23
Q

The linear form of D-Fructose (and other ketoses) undergoes to a similar INTRAMOLECULAR reaction forming what?

A

The linear form of D-Fructose undergoes to a similar INTRAMOLECULAR reaction forming a CYCLIC HEMIKETAL.

  • This reaction occurs between the ketonic functional group (C2) and the alchoholic group of the last asymmetric carbon (C5).
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24
Q

What is the result from the cyclization of fructose?

A

The cyclization of fructose forms a 5-membered ring that is similar to the FURAN arrangement.

  • Consequently the ring of the cyclized fructose is defined as FURANOSE RING or FRUCTOFURANOSE. ( it is an arrangement reminiscent of furan )
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25
Q

Cyclization of HEXOSE produce what?

A

Cyclization of HEXOSE produces a new asymmetric center at the C1.

The 2 stereoisomers are called ANOMERS, alpha&beta, and C1 becomes the ANOMERIC CARBON.

26
Q

What is ANOMER?

A

An anomer is an epimer at the hemiacetal/hemiketal carbon in a cyclic saccharide, an atom called the anomeric carbon.

  • Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1 :
  • alpha (OH below the ring)
  • beta (OH above the ring).
27
Q

In similar manner with Glucopyranose, also for FRUCTOFURANOSE it is possible to distinguish by what?

A

It is possible to distinguish the two ANOMERS and C2 is the ANOMERIC CARBON.

  • Also in this case :
  • alpha (OH below the ring)
  • beta (OH above the ring).
28
Q

At Haworth projections are convenient for displaying monosaccharides structures, they don’t accurately represent what?

A

They don’t accurately represent the conformations of pyranose rings.

Since just tetrahedral nature of carbon bonds with bond angles of 109(degrees) renders stable the molecule, PYRANOSE 120(degrees) cannot adopt the correct planar structures.

  • In fact, it is distorted in space assuming 2 different conformation :
  • BOAT CONFORMATION
  • CHAIR CONFORMATION
29
Q

In fact, pyranose sugars assume a which configuration?

A

In fact, pyranose sugars assume a “CHAIR CONFIGURATION”, since THIS is more stable as 3-dimensional spatial arrangement.

30
Q

A variety of chemical and enzymatic reactions produces what?

A

A variety of chemical and enzymatic reactions produces DERIVATIVES of the simple sugars (monosaccharides)

  • These modifications generate a VARIED COLLECTION OF SACCHARIDE DERIVATIVES.
31
Q

What is the example of the most common modifications?

A
  1. Phosphate Sugars , Amino Sugars , Deoxy Sugars , Sugar Acids
  2. Glucose-1-Phosphate , Glucose-6-Phosphate , Fructose-6-Phosphate , Fructose-1,6,-Phosphate.
32
Q

AMINO SUGARS present an what?

A

It is present an AMINO GROUP (NH2) instead of a HYDROXYL GROUP (OH , C2).
An example is the GLUCOSAMINE instead of GLUCOPYRANOSE.

  • The amino group can be acetylated by adding a molecule of acetic acid, as in N-ACETYLGLUCOSAMINE (Component of bacterial cell wall)
33
Q

(AMINO SUGAR)

Glucosamine can be modified bt addition of what?

A

Glucosamine can be modified by addition of a LACTIC ACID MOLECULE at C3 (loss of OH) = MURAMIC ACID

  • In case of N-acetylglucosamine the same modification leads to the N-ACETYLMURAMIC ACID (the other component of bacterial cell wall)
34
Q

(SUGAR ACIDS)

Sugars with free anomeric C1 are reasonably good reducing agents and with reduce what?

A

It will reduce hydrogen peroxide, certain metals (iron-Fe, Copper-Cu) and other oxidizing agents.
Such reactions convert the sugar to SUGAR ACIDS.

  • Carbohydrates that can reduce oxidizing agents in this way are considered as REDUCING SUGARS.
35
Q

D-hexose is oxidized to what?

A

D-hexose is oxidized to a carboxylic acid :

1) at C1 : ALDONIC acid (D-Gluconic acid)
2) at C6 : URONIC acid (D-Glucouronic acid)
3) at C1 + C6 = ALDARIC acid (D-Glucaric acid)

36
Q

N-acetylneuraminic acid and other derivatives of the what, are known as what?

A

N-acetylneuraminic acid and other derivatives of the NEURAMINIC ACID, are known as SIALIC ACIDS, often found as terminal residue of oligosaccharide chains of glycoproteins.

  • Sialic acid residues impart negative charge to glycoproteins, because the carboxyl group tends to dissociate a proton at physiological pH (as shown in figure).
37
Q

Where are the SUGAR ALCOHOLS (alditols) derived from?

A

These sugars derived from aldoses and ketoses by the mild reduction of their functional group.

38
Q

What cannot the alditols do inthe manner of aldoses?

A

The alditols are only linear molecules that cannot cyclize in the manner of aldoses.

  • They have sweet taste and are utilized to sweeten sugarless gums and mints : SORBITOL (GLUCITOL), MANNITOL, XYLITOL (pentose).
  • In diabetic people, high concentrations of glucose and galactose in blood, provoke a higher amount of these sugars in lens of the eye, where are reduced to the repective alditols.
  • GLUCOSE -> SORBITOL
  • GALACTOSE -> GALACTITOL
  • These are often induce the cataract formation.
39
Q

What are the DEOXY SUGARS?

A

They are monosaccharides with one or more hydroxyl groups replaced by hydrogens.

  • Deoxyribose = DNA
  • FUCOSE AND RAMNOSE are frequent in polisaccharides and in glycoproteins.
40
Q

L-Fucose is in where with respect the C6 that is modified as CH3 and is below the plane of the ring.

A

L-Fucose is in the BETA CONFIGURATION with respect the C6 that is modified as CH3 and is below the plane of the ring.

  • L-Rhamnose is in the ALPHA CONFIGURATION with respect the C6 (below the plane of the ring).
41
Q

The anomeric hydroxyl group of a monosaccharide and a hydroxyl of another sugar can join together, splitting out a water molecule to form what?

A

GLYCOSIDIC BOND.

  • R-OH + HO-R’ = R-O-R’ + H2O
42
Q

(DISACCHARIDES)

Maltose, is a what with what?

A

Maltose, is a disaccharide with an ALPHA (1->4) GLYCOSIDIC BOND between (-OH-C1) and (-OH-C4) of 2 glucoses. It is the ALPHA ANOMER.

43
Q

CELLOBIOSE, a product of what?

A

Cellobiose, a product of the cellulose breakdown, is an example of BETA ANOMER.

*The BETA (1->4) glycosidic bond is represented as an oblique link.

44
Q

What are the other DISACCHARIDES?

A
  1. SUCROSE (common table sugar) has a glycosidic bond linking the two ANOMERIC CARBONS : C1 of GLUCOSE + C2 of FRUCTOSE.
  2. LACTOSE, milk sugar, is composed by galactose + glucose, with BETA (1->4) LINKAGE (it utilizes the anomeric OH of galactose).

*(SUCROSE)
Because of the configuration at the glucose ANOMERIC CARBON is ALPHA, the resulting linkage is ALPHA (1->2) (the fructose is inverted!!!).

  • The complete name of sucrose is alpha-D-glucopyranosyl-(1->2)-D-fructofuranose.

*(LACTOSE)
Its complete name is beta-D-galactopyranosyl-(1->4)-D-glucopyranose

45
Q

(OLIGOSACCHARIDES)

How they are made up of?

A

They are made up of 4~15 monosaccharides and their major function is intercellular recognition.

46
Q

What are the OLIGOSACCHARIDES biologically active?

A

They are biologically active CARBOHYDRATES if conjugated with PROTEINS (GLYCOPROTEINS) or LIPIDS (GLYCOLIPID).

  • As free sugars, they are mainly present in some edible plants (garlic, lentils and beans) and are not easily digested in the upper gastrointestinal tract; they arrive unchanged in the colon and fermentation takes place here.
47
Q

The GLYCOGEN it is present as GRANULES in where?

A

The GLYCOGEN it is present as GRANULES in the CYTOPLASM of hepathocytes and of the muscle cells.

48
Q

The STARCH it is present as GRANULES in where?

A

The STARCH it is present as GRANULES in the CLOROPLASTS of all of the plant cells.

49
Q

Plants store glucose as what?

A

Plants store glucose as STARCH, it is formed of two different components : AMYLOSE and AMYLOPECTIN.

50
Q

How can the starch is stored in plant cells in granules in the stroma of plastids?

A

Thanks to its CONDENSED STRUCTURE, starch is stored in plant cells in granules in the stroma of plastids, particularly in seeds and tubers.

  • It is the most abundant dietary carbohydrate (rice, potatoes, pasta)
51
Q

AMYLOSE is what?

A

AMYLOSE is homopolymer of D-glucopyranose with alpha(1->4) linkages.

  1. It forms the 15-20% of the total amount of starch.
  2. It has a molecular weight from several thousands up to million of daltons.
  3. It has a NON-BRANCHED LINEAR STRUCTURE and the chains are of varying length.
  • Although poorly soluble in water, it forms MICELLES in which amylose assumes a HELICAL CONFORMATION, because of the distorted form (chair) of each glucose unit.
52
Q

AMYLOPECTIN (80-85% of total starch) is what?

A

AMYLOPECTIC (80-85% of total starch) is a GLUCOSE HOMOPOLYMER with mainly alpha(1->4) linkages, but it also has branches formed by alpha(1->6) linkages.

Branches (1 every 20 residues) are chain generally composed by 24-30 glucose units.

  • These RAMIFICTIONS
  • are an important advantage for the macromolecule
  • produce a compact structure
  • provide multiple chain ends at which enzymatic cleavage can occur.
53
Q

The end of the polysaccharide with an anomeric C1 not involved in a glycosidic bond, is called what?

A

It is called the REDUCING END.

54
Q

What is the GLYXCOGEN?

A

GLYCOGEN is the glucose storage polymeric compound in ANIMALS.

  • It is similar in structure to AMYLOPECTIN and present in granules inside liver muscle and cells.
55
Q

GLYCOGEN has more which branches?

A

It has more a
ALPHA (1->6) BRANCHES : 1 every 8 residues (instead of 1 every 20 residues in amylopectine)

The highly branched structure permits rapid glucose release from glycogen stores, e.g., in muscle during exercise.

  • The ability and possibility to quickly mobilize glucose is very important in animals, in response to the energy demand of metabolic pathways.
56
Q

What are the three main features of CELLULOSE?

A
  1. The plants do not synthesize structural fibrous proteins as animals, then their function is performed by the structural polysaccharides.
  2. Cellulose is the major constituent of plant cell walls.
    ( It’s always a carbohydrate but forms extended structures similar to the beta sheet of proteins)
  3. THE ROLE OF CELLULOSE IS TO IMPART STRENGTH AND RIGIDITY TO PLANT CELL WALLS, IN ORDER TO PREVENT THE OSMOTIC SWELLING.
57
Q

CELLULOSE, consists of which chain and linkages?

A

CELLULOSE, consists of long linear chains of glucose with beta(1->4) linkages.

58
Q

Why CELLULOSE cannot be digested by mammals?

A

It’s because of the absence of CELLULASE ENZYME that catalyzes that cleavage of the beta(1->4) linkages.

59
Q

The LINEAR STRUCTURE promotes what?

A

It promotes INTRA-CHAIN and INTER-CHAINS H-bonds and VAN DER WAALS INTERACTIONS, and RENDERS CELLULOSE CHAINS STRAIGHT and RIGID, PACKED with a CRYSTALLINE ARRANGEMENT in thick bundles.

60
Q

What is the CHITIN?

A

CHITIN is a polymer of N-acetylglucosamine with beta(1->4) linkage.

  • It represents the structural part of the exoskeleton of shellfish (shrimps, lobster), insects and spiders.
  • It is present in the cell wall of fungi.
  • Is the earth’s second most abundant carbohydrate polymer after cellulose.
61
Q

What is the AGAR?

A

POLYSACCHARIDE isolated from marine red algae and forms a gel containing large amount of water.

62
Q

What are the two components of AGAR?

A
  1. AGAROSE = D-galactose + 3,6,-anhydro-L-galactose
  2. AGAROPECTIN = Agaropectin which has the same structure as the agarose but is different for the e sterification of some alcoholic groups with sulfuric acid.
    - The polymer chain of AGAROSE (and AGAROPECTINE) forms helical fibers that aggregate in SUPER-COILED STRUCTURES.

Carbohydrates (2 decks)

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