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Biomolecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What are the functions of Carbohydrates?

A

-Energy source and energy storage
-structural component of cell wall and exoskeletons
-informational molecules in cell-cell signalling

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2
Q

What is the basic nomenclTURE OF CARBS?

A

Cn(H2O)n
Number of carbon atoms and add -ose e.g triose

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3
Q

What are the functional groups in carbs

A

-Aldehydes - aldose
-Ketones - ketose

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4
Q

Examples of enantiomers in sugars?

A

(MIRROR IMAGE)
D and L isomers of a sugar are enantiomers

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5
Q

Are most hexoses in living organisms L or D stereoisomers?

A

D stereoisomers
Some simple sugars occur in L form, e.g L-arabinose

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6
Q

How to know whether a sugar is L or D?

A

The -OH that is farthest from the carbon involved in the aldehyde/ketone group is the one to look at

If the -OH is on the right = D
If the -OH is on the left = L

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7
Q

What are diasteromers?

A

When 2 sugars have ientical molecular formulas, have different arrangement of atoms and are not enantimers (not mirror images)

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8
Q

What are Epimers?

A

A subgroup of diastereoisomers - sugrs differ at only one chiral center - not mirror images

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9
Q

Why do ring structure of carbohydrates predominate under normal physiological conditions?

A

They are lower in energy and more stable than open chains

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10
Q

How does this ring formation take place?

A

-The nucleophilic alcohol attacks the electrophilic carbonyl carbon, allowing formation of a hemiacetal
-As result linear carb forms ring structure

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11
Q

At the completion of ring formation, what is the carbonyl carbon reduced to?

A

An alcohol

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12
Q

What sugars readily undergo intramolecular cyclization?

A

Pentoses and hexoses

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13
Q

When does the anomeric carbon occur and where does it occur in and aldose and a ketone?

A

-The former carbonyl carbon (carbon that takes part in functional group) becomes a new chiral center, this is called the anomeric carbon.
-Occurs at C1 of an aldose and C2 of a ketose

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14
Q

What determines if the anomer is alpha or ß?

A

The position of the former carbonyl oxygen.

-If the hydroxl group (-OH) is on the opposite (trans) of the ring as the CH2OH then its alpha
(If the CH2OH is up and the OH is below the c1)

-If the hydroxyl group (-OH) is on the same side (cis) of ring as CH2OH then its ß
(If the CH2OH) is up and the OH is above C1)

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15
Q

What are pyranoses?

A

`6 membered oxygen containing rings

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16
Q

What are furanoses?

A

5 membered oxygen containing rings

17
Q

In amino sugars, what is replaced for what?

A

An NH2 group replaces one of the OH groups in the hexose

18
Q

How can 2 sugar molecules be joined?

A

Via an O-glycosidic bond between an anomeric carbon and a hydroxyl carbon.

19
Q

Glycosidic bond Vs hemiacetal

A

The glycosidic bond (an acetal) between monomers is more stable and less reactive than the hemiacetal at the second monomer

20
Q

What is the hemiacetal?

A

A carbon connected to 2 oxygen atoms where one oxygen is an alcohol (OH) and the other is an ether (O R)

21
Q

What is sucrose, lactose and maltose made of?

A

Sucrose - glucose + fructose
Lactose - Glucose + galactose
Maltose - Glucose + glucose

22
Q

How is a disaccharide formed?

A

Formed from 2 monosaccharides when an
-OH (alcohol) from one glucose molecule condenses with the intramolecular hemiacetal (C bonded to OH and OR)
-Eliminates H2O and forms a glycosidic bond

23
Q

What is the condensation of 2 glucose molecules via a 1 - 4 bond called?

A

alpha-1-4 glycosidic bond

24
Q

How to tell if a sugar is a reducing sugar or a non reducing sugar?

A

If the oxygen on anomeric carbon (the carbonyl group) of a sugar is not attached to any other structure, the sugar is a reducing sugar.
(If there is a hemiacetal then theres a reducing end)

25
Q

What are the different kinds of polymers?

A

-Homo-polysaccharides (one monomer unit)
-Hetero-polysaccharide (multiple monomer units)
-Linear (one type of glycosidic bond)
-Branched (multiple types of glycosidic bonds)

26
Q

Cellulose - subunit, bonds, branches

A

ß-glucose
1-4
No branches

27
Q

Starch-Amylose- subunit, bonds, branches

A

alpha glucose
1-4
No branches

28
Q

Starch-Amylopectin- subunit, bonds, branches

A

alpha-glucose
1-4 and 1-6
Yes branches

29
Q

Glycogen- subunit, bonds, branches

A

alpha-glucose
1-4 and 1-6
yes branches

found in animals not plants
(alpha is for the orientation of the hydroxyl group at C1 position)

30
Q

When are the (alpha-1-6) linkages in glycogen?

A

Every 8-12 residues

31
Q

When are the (alpha-1-6) linkages in Amylopectin?

A

Every 24-30 residues

32
Q

What is the solubilty of glycogen and starch like and why? what do they form in cells?

A

Insoluble due to their high molecular weight and often form granules in cells that contain enzymes that synthesize and degrade polymers.
Enzymatic rxns take place in non-reducing ends (only have one reducing end)

33
Q

What is chitin made of?

A

Chitin is a linear homoolysaccharide of N-acetylglucosamine
(ß1-4) linked chains

34
Q

What is agar and what is it made of?

A

Agar is a branched heteropolysaccharide composed of agarose and agaropectin
Agar serves as a component of cell wall in some seaweeds

35
Q

What are agarose solutions used for?

A

Forms gels used to separate DNA by electrophoresis

36
Q

What are glycosaminoglycans?

A

Polysaccharides that consist of repeating disaccharide units which contain an amino group and some neg charged groups
E.g: Hyaluronate, Chondroitin sulfate, Keratan sulfate, Heparin

37
Q

What are glycosamines actually composed of?

A

-One monomer is an amino sugar : N-acetyl-glucosamine or N-acetyl-galactosamine
-Second monomer is neg charged uronic acids or galactose and sulfate esters

Biomolecules (5 decks)

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