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BL2306 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Name 6 functions of carbohydrates

A
  1. Energy
  2. Structure
  3. Extracellular matrix
  4. Signalling and development
  5. Protein folding
  6. Components of DNA
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2
Q

What are the basic properties of all carbohydrates?

A
  • Carbon based molecules rich in hydroxyl groups

- Empirical formula: (CH2O)n

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3
Q

What are monosaccharides?

A
  • Most simple form of carbohydrates

- Either aldehydes (aldose) or ketones (ketose) with >2 hydroxyl groups

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4
Q

What is the configuration of a monosaccharide defined by?

A
  • Asymmetric carbon atom furthest from the aldehyde/keto group
    (Most sugars have a D configuration)
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5
Q

When can diasterioisomers occur?

A
  • > 3 carbon atoms

- Number of isomers = 2^n (where n= number of asymmetric carbon atoms)

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6
Q

What are constitutional isomers?

A

Have identical molecular formula but differ in how their atoms are ordered

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7
Q

How do epimers and anomers differ?

A

epimers - differ at one of several asymmetric carbon atoms

anomers - differ at a new asymmetric carbon atom formed on ring closure

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8
Q

Why do monosaccharides adopt cyclical forms?

A

Lower energy conformation

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9
Q

What types of rings to glucose and fructose form?

A

Glucose - C5 hydroxyl group attacks O of C1 aldehyde to form 6 C ring hyranose (hemiacetal - aldehyde)
Fructose - C5/C6 hydroxyl group attacks O of C2 ketone to form 5C ring of furanose/pyranose (Hemiaketal - ketone)

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10
Q

What are the two common forms of pyranose?

A

Boat and chair

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11
Q

What is the difference between axial and equatorial?

A

axial - nearly perpendicular to the average plane of the molecule
equatorial - nearly parallel to the average plane of the molecule

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12
Q

What is the common conformation of furanose rings?

A

envelope - either C-2 or C-3 is out of plan on the same side as C5 (endo-pucker)

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13
Q

What are anomers?

A

Different forms of carbohydrates created by an assymetric carbon

  • In glucose this is C1
  • In fructose this is C2
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14
Q

How do alpha and beta anomers differ?

A

alpha - hydroxyl group is on the opposite side of the ring as C6
beta - hydroxyl group is on the same side of the ring as C6
note: C5 on fructose

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15
Q

What are 3 common reactants for monosaccharides

A
  • alcohols
  • amines
  • phosphates
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16
Q

How does an O-glycosidic bond form?

A
  • oxygen atom of n alcohol and anomeric carbon of a monosaccharide
  • between two sugars
17
Q

How does an N-glycosidic bond form?

A

Anomeric carbon of sugar linked to nitrogen atom of an amine group

18
Q

Name 3 common disaccharides

A

sucrose, lactose, maltose

19
Q

What differentiates a reducing and non-reducing sugar

A

reducing - free hydroxyl at anomeric position allowing ring to open, exists in equilibrium (e.g glucose)
non-reducing - anomeric carbon is involved in bonding

20
Q

Describe the structure of glycogen

A
  • Branched

- Mostly consists of alpha 1,4 glycosidic bonds between glucose

21
Q

Describe the structure of starch

A
  • Linear
  • glucose joined by alpha 1,4 glycosidic bonds (amylose)
  • alpha 1,6 glycosidic bonds ( amylopectin)
22
Q

What is the structure of chitin and cellulose

A

cellulose - linear polymer of glucose B-1,4

chitin - linear molecules of N-acetyly glucosamine joined by B-1,4 glycosidic bonds

23
Q

By which type of linkage do carbohydrates link to nulceic acids?

A

N-glycosidic bonds

24
Q

How do carbohydrates typically attach themselves to proteins?

A
  • Attach to asparagine via N-glycosidic

- Attach to serine/threonine via O-glycosidic

25
Q

What is the typical function and structure of proteoglycans?

A
  • protein conjucated to a polysaccharide glycosaminoglycan
  • structural components and lubricants
  • tethered to cell membrane
  • highly sulfanated
26
Q

Where does glycolysation occur?

A

In the ER and Golgi apparatus, aids in protein folding

27
Q

Which enzymes are responsible for the assembly and breaking down of carbohydrates?

A

Broken down by glycoside hyrolayses (GHs) - general

Synthesized by glycosytransferases (GTs) - very specific

28
Q

How does the influenza virus exploit GHs?

A

Uses neurominidase to release new virus particles using own acid

29
Q

Which compounds typically act as GT donor substrates and which act as acceptors?

A

nucleotide phosphates - donors

hydroxl in protein, lipid, small molecule or another sugar - acceptor

BL2306 (8 decks)

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