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Biomolecules (Y2,S1) > Carbohydrates & Glycobiology > Flashcards

Carbohydrates & Glycobiology Flashcards

1
Q

Functions of Carbohydrates (4)

A
  1. Energy source
  2. Energy storage
  3. Structural component of cell walls and exoskeletons
  4. Informational molecules in cell - cell signalling (regulates cell - cell communication)
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2
Q

Carbohydrate formula

A

Cn(H2O)n

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3
Q

What is an aldose

A

A carbohydrate with aldehyde functionality

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4
Q

What is a ketose

A

A carbohydrate with ketone functionality

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5
Q

What are enantiomers

A

Stereoisomers that are non superimposable mirror images

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6
Q

What are diasteromers

A

Two sugars that have identical molecular formulas, different arrangement of atoms and are not enantimers (mirror images)

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7
Q

What are epimers

A

Sugars that differ in stereochemistry at only one chiral center. They are not mirror images and are not enantiomers.

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8
Q

What carbohydrate structure predominates under normal physiological conditions and why?

A

Cyclic/ ring structure. Because they are lower in energy and are more stable than open chain structures.

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9
Q

Alpha anomer of glucose structure

A

The OH group (hydroxyl grp) is facing the opposite direction than the CH2OH group

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10
Q

Beta anomer of glucose structure

A

OH (hydroxyl) group is facing the same direction as the CH2OH group.

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11
Q

How is the cyclic structure formed?

A

The nucleophilic alcohol attacks the electrophilic carbonyl carbon, allowing formation of a hemiacetal. This results in the linear carbohydrate forming a ring structure. The carbonyl carbon is reduced to an alcohol.

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12
Q

After the cyclisation of monosaccharides what does the former carbonyl carbon become?

A

It becomes a new chiral center, called the anomeric carbon at C1 of an aldose & C2 of a ketose.

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13
Q

What is a pyranose

A

Six membered oxygen containing ring

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14
Q

What is a furanose

A

Five membered oxygen containing ring

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15
Q

What occurs to form amino sugars

A

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

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16
Q

What occurs to form deoxy sugars

A

Substitution of H for OH produces a deoxy sugar

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17
Q

What occurs to form acidic sugars

A

Made by oxidation of carbonyl carbon or hydroxyl carbon or both.

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18
Q

What is the O-glycosidic bond formed between

A

An anomeric carbon and a hydroxyl carbon

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19
Q

Which part of the molecule is reducing

A

The second molecule, with the hemiacetal is reducing

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20
Q

Which part of the molecule is non reducing

A

The anomeric carbon involved in the glycosidic bonding is non reducing

21
Q

What is sucrose made of

A

Glucose + fructose

22
Q

What is lactose made of

A

Glucose + galactose

23
Q

What is maltose made of

A

Glucose + glucose

24
Q

How is a disaccharide formed

A
  • Formed from two monosaccharides
  • The OH of one glucose molecule condenses with the hemiacetal of the other glucose molecule
  • This happens with the elimination of H2O
  • A glycosidic bond is formed
25
Q

Reducing sugar

A

Sugar has the ability to participate in oxidation or reduction rxns due to the free oxygen in the OH group at the end of the molecule

26
Q

Non reducing sugar

A

Sugar doesn’t have the ability to participate in oxidation or reduction rxns due to the oxygens in the anomeric carbons being bound by the glycosidic bond

27
Q

What does the product have after an O-glycosidic bond (bond between two anomeric carbons) is formed

A

The product has two acetal groups and no hemiacetals

28
Q

What linkages do glucose monomers form to form glycogen

A

Alpha 1 - 4 linkages

29
Q

What is glycogen

A
  • A branched homopolysaccharide of glucose
30
Q

Function of glycogen

A

It is the main storage polysaccharide in animals

31
Q

What is starch a mixture of

A

Two homopolysaccharides of glucose: amylose & amylopectin

32
Q

Function of starch

A

It is the main storage polysaccharide in plants

33
Q

How is cellulose structured

A

It’s a linear homopolysaccharide of glucose

34
Q

What linkages are found in cellulose

A

Glucose monomers form beta 1 - 4 glycosidic linkages

35
Q

How is chitin structured

A

It’s a linear homopolysaccharide of N-acetylglucosamine

36
Q

What linkages are in chitin

A

N-acetylglucosamine monomers form beta 1-4 linked chains

37
Q

Structure of amylose (tyoe & repeating unit)

A

Linear homopolysaccharide of glucose with alpha 1-4 glycosidic bonds

38
Q

Structure of amylopectin (type & repeating unit)

A

Branched homopolysaccharide of glucose with alpha 1-4 glycosidic bonds

39
Q

What are glycosaminoglycans

A

A special type of polysaccharides that consist of repeating disaccharide units which are modified to contain an amino grp (either N-acetyl-glucosamine or N-acetyl-galactosamine) and some negatively charged grps (uronic acids or galactose and sulfate esters)

40
Q

Where are glycosaminoglycans found and what is their function

A

Found in our joints and act as a shock absorber/ buffer/ lubricant

41
Q

What are proteoglycans

A

Proteins that are attached to glycosaminoglycans

42
Q

What are glypicans

A

protein that is anchored to a lipid membrane

42
Q

What are syndecans

A

protein has a single transmembrane domain

43
Q

4 functions of proteoglycans

A
  1. Joint lubricants
  2. Structural components of connective tissue
  3. Bind cell to ECM
  4. Regulate movement of molecules through the matrix
44
Q

Main components of ECM

A
  • proteoglycan aggregates
  • collagen fibres
  • elastin (a fibrous protein)
45
Q

What is a glycoprotein

A

Carbohydrate attached to a protein via its anomeric carbon to amino acids on the protein

46
Q

What amino acids commonly form glycoproteins

A

Ser, Thr, Asn
(Serine, Threonine, Asparagine)

47
Q

What are glycolipids

A

Lipids with covalently bound oligosaccharide

Biomolecules (Y2,S1) (5 decks)

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