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BIOL1007 > Structural carbohydrates > Flashcards

Structural carbohydrates Flashcards

1
Q

What are the main functions of carbohydrates?

A
  • main source of energy
  • serve as strucutral components
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2
Q

Name 3 monsaccharides?

A
  1. Glucose
  2. fructose
  3. galactose
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3
Q

What are the 2 forms that enantiomers can be? For glucose enantiomers, what form occurs in nature?

A

D or L.

For glucose enantiomers, only the D enantiomer occurs in nature. L has to be synthesised in a lab

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4
Q

When glucose is in cyclic form, what is it called?

A

Glucosepyranose

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5
Q

Whats the position of the OH group in alpha and beta forms?

A

Alpha: The OH is down position

Beta: the OH is in the up position

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6
Q

Draw the most stable chain conformation of beta-D-galactopyranose

A
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7
Q

What are structural carbohydrates?

A

Polysaccharides (glycans) in which monosaccharide units are joined as in these disaccharides

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8
Q

What bond joins monosaccharides together?

A

glycosidic bonds

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9
Q

Name some strucutral carbohydrates in plants? (4 of them)

A
  1. cellulose
  2. Hemi-cellulose
  3. Pectin
  4. Agarose
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10
Q

Tell me about cellulose and about it’s linkages?

A
  • most abundant polymer on the planet
  • major structural components in plants
  • organised into microfibrils
  • important biofuel
  • Linear polymer of D-glucose connected by beta1–> 4
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11
Q

What structural carbohydrate is this?

A
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12
Q

What type of sugar is Hemi-cellulose?

A

pentose sugar

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13
Q

Tell me about the structure of Hemi-cellulose ?

A
  • Beta1–>4 polymer of D-xylopyranose
  • sidegroups of various carbohydrates such as xylose, mannose, galactose, rhanmose and arabinose
  • 500-3000 sugar units per polymer
  • good as cross-linking (branched polymer)
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14
Q

Tell me about pectins structure and what its used for?

A
  • family of a mixture of branched polysaccharides rich in alpha1-4
  • linked D-galacturonic acid
  • gelling agent in jams and marmalades
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15
Q

Tell me about the structure of Agarose? and where it can be found?

A
  • D-galactose Beta1-4 with galactose
  • ether bridge connecting C3 and C6 (some of these molecules also have a sulphate group)
  • complex polysaccharide with lots of substitutions
  • carbon 6 has an ether bond between the oxygen and CH2

Some plants such as red algae use agarose in their cell walls

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16
Q

What structural carbohydrate is this?

A
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17
Q

Name some structural carbohydrates found in animals?

A
  1. chitin
  2. Glycosaminoglycans
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18
Q

What is chitin the main component of?

A

the exoskeleton of nearly a million species of arthropod e.g. insects and crabs

19
Q

What is chitin a polymer of and what bonds/linkages does it contains?

A
  • Polymer of N-acetyl glucosamine (glucose with an acetylated amino group at C2)
  • contains Beta 1–>4 linkages arranged in extended fibres in a similar way to cellulose
20
Q

What strucutral carbohydrate is this?

A

Chitin

21
Q

Why is the carbohydrate Glycosaminoglycans important?

A

its important as a matrix to hold together protein components of skin and connective tissue

22
Q

What is proteoglycan? what is it made of/ its structure?

A
  • it is a structure in cartilage
  • made of protein and sugar units

Explanation of the structure in the image:

  • dark blue are core proteins
  • proteins stem off of the core proteins and then there are carbohydrate polymers coming off of those proteins on the stems
23
Q

What are bacterial cell walls made of?

A

polysaccharides

24
Q

What is the name of the polysaccharide-peptide complex that bacterial cells walls are made from?

A

peptidoglycan

25
Q

What are the two classes that bacteria fall into?

A

Gram positive and gram negative

26
Q

Tell me the properties of gram +ve bacteria

A
  • cytoplasmic lipid membrane
  • thick peptidoglycan layer
  • retains the gram stain of dye-iodine complex which shows a blueish colour (helps to identify if gram +ve or -ve)
27
Q

Tell me the properties of gram negative bacteria?

A
  • cytoplasmic membrane
  • thin peptidoglycan layer
  • outer membrane containing lipopolysaccharides
  • periplasmic space between cytoplasmic membrane and outer membrane
28
Q

What is peptidoglycan composed of?

A

alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked tetrapeptides of (L-Ala)-(D-Glu)-(L-Lys)-(D-Ala)

29
Q

Does this show a gram +ve or gram -ve bacteria?

A

gram +ve

30
Q

Does this show a gram +ve or gram -ve bacteria?

A

gram -ve

31
Q

What’s meant by the word glycan?

A

its another term for a polysaccharide

32
Q

Whats glycosylation?

A

The attachment of oligosacchrides (sugars) to proteins

33
Q

Proteins that are glycosylated mostly pass thorugh where?

A

the secretory pathway (ER and golgi)

34
Q

Do cytoplasmic proteins tend to be glycosylated?

A

no

35
Q

Whats are the two types of glycosylation? which one is most common? where does each occur?

A

1. N-linked

Occurs in the ER

modified in golgi

most common type

2. O-linked

occurs in golgi

36
Q

What enzyme in golycosylation attaches the N-linked oligosaccharide in the ER?

A

oligosaccharyl transferase

37
Q

What species lipid helps the precursor oligosaccharide in the ER membrane duirng glycosylation?

A

dolichol

38
Q

in N-linked oligosaccharides, what is it linked to?

A

The -NH2 groups of an asparagine residue

39
Q

What are the three major types of N-glycans?

A
  1. High-mannose oligosaccharide
  2. Hybrid oligosaccharide
  3. Complex oligosaccharide
40
Q

What are O-linked oligosaccharides linked to?

A

either serine, threonine or hydroxyproline

41
Q

what type of protein functions does glycosylation lead to?

A
  • helps proteins fold in the ER
  • help direct proteins to their final destination
  • helps proteins function
42
Q

What helps proteins fold in the ER?

A
  • ER chaperones calnexin and calreticulin bind to oligosaccharide of partially folded proteins to stop aggragate and reain them in the ER
43
Q

What helps to direct proteins to their final destination?

A

carbohydrate proteins called lectins help guide ER to golgi transport and protein sorting in the trans-golgi network

44
Q

What types of protein functions does glycosylation help with?

A
  • improve stability
  • inprove solubility
  • cell signalling

BIOL1007 (8 decks)

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