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Pre-Vet 3 > 7. Carbohydrates 2 > Flashcards

7. Carbohydrates 2 Flashcards

1
Q

Explain sugar derivatives (3)

A
  1. Reduction of D-glyceraldehyde yields glycerol (alcohol)
  2. Reduction of D-glucose yields D-glucitol (sorbitol)
  3. Reduction of mannose yields mannitol
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2
Q

Epimers of sugar derivatives (1)

A

Glc and man are epimers at C2

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3
Q

What is mannitol and sorbitol used for? Why do they give a cool sensation? What happens if you have too much unabsorbed? (4)

A
  1. Low calorie sweeteners.
  2. Very slowly metabolized to glucose and stimulate little insulin secretion, a property helpful to diabetics.
  3. They have a positive heat of solution giving them a “cool”
    sensation.
  4. Any excess, unabsorbed sugar alcohols have a laxative effect as they prevent absorption of water.
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4
Q

Are monosaccharides reducing or oxidizing agents? Why? Whats an example? (3)

A
  1. Reducing agents.
  2. They give up electrons and are themselves oxidized.
  3. Oxidation of aldols yields the Aldonic acid family. This can be detected in an alkaline solution of Copper.
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5
Q

Explain this photo for monosacharides being a reducing agent (5) - Cu is what and forms what? which experiment is this? which form is reactive? How does ketosis react? Oxidation at c6 produces what?

A
  1. Cu+ is insoluble and precipitates from solution as brick-red Cu2O
  2. “Benedicts Test” (Experiment 4)
  3. Only straight chains forms of sugars are reactiv e
  4. Ketosis will react slowly because they must isomerize to the aldehyde first
  5. Oxidation at C6 produces Uronic acid
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6
Q

What are aldonic and uronic acids, and what do they form?

A
  1. Aldonic and uronic acids form stable intramolecular esters called sugar lactones - top photo
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7
Q

What is Vitamin C, and what type of compound is it? Which animals have lost the ability to make Vitamin C, making it an essential nutrient?

A

Vitamin C is L-ascorbic acid, a sugar acid lactone.

Primates and fruit bats have lost the ability to make Vitamin C, so it is an essential nutrient for them.

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8
Q

What role does uric acid play in humans, and why is Vitamin C important?

A

Humans have lost the ability to oxidize uric acid, so some of the antioxidant function of Vitamin C may be taken over by uric acid. The ancient DNA encoding L-glucoronolactone oxidase is still present in humans.

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9
Q

Explain sugar phosphate esters (1)

A
  1. They are intermediates in sugar synthesis that prevent transport of the sugar across hydrophobic membranes and charged
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10
Q

Explain the structure of amino sugars. Give example of epimers (1)

A
  • OH (usually C2) is replaced by an amino group

Glc and Gal are epimers at C4
- OH goes up in gluco
- OH points down in galacto

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11
Q

Whats an example of sugar amides? (3)

A
  1. N-acetyl-glucosamine
  2. Acetyl group (–COCH₃) is attached to the amine group (–NH₂) on the C2 carbon
  3. Hydrophobic
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12
Q

Explain deoxy-sugars (4)

A
  1. Component of DNA
  2. ribose = OH
  3. deoxyribose = H
  4. Greater stability when it’s just H
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13
Q

What is this structure and explain it (4)

A
  1. Maltose
  2. A disaccharide
  3. A reducing sugar
  4. It’s made from a starch by the enzyme amylase
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14
Q

What’s the difference between alpha and beta maltose structure?

A
  1. OH at C1 points down - alpha
  2. OH at C1 points up - beta
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15
Q

Explain this maltose structure (2)

A
  1. Left = Glc is an acetal (non-reducing and non-mutorotating
  2. Right = glucose is a hemiacetal (reducing end and mutarotates)
  3. Glycosidic bonds join sugars
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16
Q

What structure is this and explain it (3)

A
  1. Iso-maltose (disach)
  2. Glc (alpha1->6) Glc
  3. A reducing sugar43. Made from hydrolysis of dextran
17
Q

What structure is this and explain it (3)

A
  1. Cellobiose (disach)
  2. A reducing sugar
  3. Produced by acid hydrolysis of cellulose
18
Q

What structure is this and explain it (3)

A
  1. Lactose (disach)
  2. Milk reducing sugar
  3. Glc and Gal are epimers at C4
19
Q

What causes lactose intolerance? (2)

A
  1. People without the enzyme lactase and can’t digest lactose
  2. In the small intestine, bacteria switch their metabolism to digest lactose (fermentation) producing large amounts of gas and cramping
20
Q

What structure is this and explain it (3)

A
  1. Sucrose (disac)
  2. Non-reducing sugar
  3. Made by plants
21
Q

Explain the rotation light of sucrose and what happens with hydrolysis (3)

A
  1. Sucrose rotates light by +66
  2. Hydrolysis of sucrose results in a mixture that rotates light at -39 (invert sugar)
  3. ~2x sweeter than sugar
22
Q

Rotation of light for alpha+BD-Glc and alpha+BD-Fru (2)

A

alpha+BD-Glc = +53
alpha+BD-Fru = -92

23
Q

What structure is this and explain it (3)

A
  1. Trehalose (disach)
  2. Non-reducing sugar
  3. Energy stored in insects
24
Q

How are sugars stored? (2)

A
  1. Stored as polysaccharides = glycans
  2. Can be branched or unbranched
25
Q

Explain starch and the 2 types

A
  1. Storage of D-Glc in plants
  2. I Amylose and H Amylopectin
26
Q

Explain I-Amylose (3)

A
  1. A type of starch that is a polysaccharide
  2. Unbranched chains of alpha1->4 linked Glc
  3. helical structure stabilized by H-bonding with 6 residues per turn
  4. Iodine can insert into the middle of the helix giving starch a blue colour
27
Q

Explain H-Amylopectin (2)

A
  1. A type of starch that is a polysaccharide
  2. Up to 200 amylose chains linked alpha1->6 at branch points like iso-maltose
  3. Cannot form a helical structure
28
Q

How does starch relate to maltose and iso-maltose (1)

A
  1. Contains maltose and isomaltose units with 1 reducing end and many non-reducing ends
29
Q

Explain amylase in maltose (3)

A
  1. Saliva and pancreas secrete alpha-amylase that randomly cleaves alpha1,4 bonds
  2. Plants and bacteria secrete beta-amylase that removes maltose units starting at the non-reducing end
  3. Debranching enzymes hydrolyse the alpha1,6 bonds
30
Q

Explain 4 other types of polysaccharides

A
  1. Glycogen: animal cell storage of Glc
    - Similar to amylopectin but more branched (15-30 sugars per branch)
  2. Dextrans: bacterial with alpha1->6 links and some alpha1->2 and alpha1->4 glucose links
  3. Fructans/Levans: fructose storage forms in plants
  4. Cellulose: Glc B1->4Glc) - linear chain of Glc
31
Q

Explain where the irridescent blue colour comes from in Pollia condensata (4)

A
  1. Interaction of light with the helical rods of cellulose in the outer skin, no pigment
32
Q

Explain chitin (4)

A
  1. A polysaccharide
  2. rthropod exoskeleton, shells of crustaceans and peacock feathers
  3. N-acetlyglucosamine linked B1->4 in a linear chain
  4. Cellulose with a C2 N-acetyl
33
Q

Explain how glycoprotein sugars are linked

A
  1. O-linked to Ser-Thr-Tyr
  2. N-linked to Asn/Gln
  3. Great variety of sequence, branching and linkage
34
Q

Explain peptidoglycan vs proteoglycans

A
  1. Peptidoglycans: cell wall of bacteria that is a cross-linked network of short peptides
  2. Proteoglycans: in animals, the extracellular matrix, cartilage, tendons and skin. Proteins with large amounts of carbs

Pre-Vet 3 (11 decks)

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