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Introduction to Carbohydrates Flashcards

1
Q

what happens when carbohydrates are oxidised in living cells?

A

produce energy, carbon dioxide and water

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2
Q

what are the different types of carbohydrate?

A

monosaccharides, disaccharides,, polysaccharides

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3
Q

what are monosaccharides?

A

simplest carbohydrate

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4
Q

what are disaccharides?

A

consist of 2 monosaccharides

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5
Q

what are polysaccharides?

A

contain many monosaccharides

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6
Q

monosaccharides consist of…

A

3-6 carbons, a carbonyl group(aldehyde/ketone), several hydroxyl groups

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7
Q

what are aldoses?

A

monosaccharides with an aldehyde group, many hydroxyl groups eg triose, tetrose, pentose

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8
Q

what are ketoses?

A

monosaccharides with a ketone group, many hydroxyl groups eg ketohexose (fructose)

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9
Q

what is a fischer projection?

A

used to represent carbohydrates, places the most oxidised at the top eg carbonyl group, shows chiral carbons as the intersection of vertical and horizontal lines

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10
Q

how to determine the L or D isomer…

A

in Fischer projection, the hydroxyl group on the chiral carbon furthest from the carbonyl group determines the L or D isomer, if on left it is L if on right it is D (sugars usually D, amino acids usually L) and causes polarised light rotation

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11
Q

where is D-glucose found?

A

honey and fruits

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12
Q

what is D-glucose?

A

aldohexose C6H12O6, known as blood sugar in the body, it is the monosaccharide of starch, cellulose, glycogen

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13
Q

what is the difference between D-glucose and D-galactose?

A

the hydroxyl group on the 4th carbon is on different sides, right for glucose, left for galactose - these are epimers (one pair of stereoisomers)

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14
Q

how does D-galactose convert to D-glucose?

A

enzymes move the hydroxyl group from the left to right side of the carbon

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15
Q

what is galactosemia?

A

lack of enzymes required for galactose metabolism

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16
Q

effects of galactosemia…

A

galactose intermediates (toxic) accumulates and there is a toxic effect on liver, brain, kidney, eyes

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17
Q

how can galactosemia be detected and controlled?

A

screened using the heel prick test on newborns and controlled using a low galactose diet

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18
Q

what are cyclic structures?

A

the prevalent form of monosaccharides with 5/6 carbon atoms

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19
Q

how do cyclic structures form?

A

when the hydroxyl group on C5 reacts with the aldehyde or ketone group (condensation)

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20
Q

the cyclic structure for glucose…

A
  1. number carbon chain and obtain linear open chain 2. bond C5 -O- to C1 3. place C6 (long chain) above ring 4. write -OH groups for C2 and C4 below the ring 5. write -OH for C3 above the ring 6. write new -OH on C1 in either alpha/beta form
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21
Q

what happens when alpha and beta forms are placed in solution?

A

they convert into each other and at any time only a small amount of open chain forms as they are constantly going between forms

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22
Q

what is D-glyceraldehyde?

A

simplest sugar

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23
Q

what is D-glucose?

A

most important in diet

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24
Q

what is D-fructose?

A

sweetest sugar

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25
what is D-galactose?
part of milk sugar
26
what is D-ribose?
used in RNA
27
what is a reducing sugar?
a sugar that will reduce inorganic ions eg Cu++ (Fehling's reagent)
28
what sugars are reducing sugars?
all monosaccharides regardless of aldehyde or ketone
29
what is not a reducing sugar?
sucrose
30
colour change of Fehling's...
blue Cu++ to orange Cu+ when reduced
31
absorbance using colorimeter...
more colour = higher absorbance reading
32
what happens in the glucose oxidase test?
glucose converted to gluconate which produces hydrogen peroxide that converts another compound into a different colour which can be read off of a dipstick
33
how does glucose enter red blood cells?
in a non-insulin dependent matter
34
what does uncontrolled hyperglycemia result in?
a covalent linkage between glucose and the NH2 terminal amino acid of the haemoglobin beta chain - HbA1c
35
what is the half life of a red blood cell?
about 120 days
36
what are good levels of blood glucose?
up to 10mmol/l or 180mg/dL
37
what are good levels of HbA1c?
up to 8
38
what is glucose + glucose?
maltose and water
39
what is glucose + galactose?
lactose and water
40
what is glucose + fructose?
sucrose and water
41
what is lactose?
a disaccharide of beta D-galactose and alpha or beta D-glucose
42
what type of bond does lactose contain?
a beta 1,4-glycosidic bond
43
where is lactose found?
milk and milk products
44
what is lactose intolerance?
lack of lactase enzyme in small intestine, this can happen as a person gets older and their body closes down the expression of the lactose enzyme
45
what happens as a result of lactose intolerance?
lactose passes into colon where bacteria ferments it causing stomach cramps, bloating, flatulence
46
what is a homopolymer?
polymer formed from subunits that are the same
47
what is the most common homopolymer in animals?
glycogen
48
what is glycogen?
the storage form of glucose, a highly branched polysaccharide made of multiple glucose units linked by alpha 1,4 and alpha 1,6-glycosidic bonds
49
where is glycogen found?
in liver and muscle
50
what is starch?
the plant form of carbohydrate ingested by humans
51
what is amylose?
an unbranched starch comprised of glucose units, alpha 1,4 linkage
52
what is amylopectin?
a branched form of starch with alpha 1,4 linkage (1 every 30 sugar monomers) to the alpha 1,6 linkage
53
where is alpha amylase secreted from?
salivary glands
54
where is amylose and amylopectin hydrolysed?
the pancreas
55
what is cellulose?
main storage of glucose in plants
56
what link does cellulose contain?
beta 1,4 that we cannot break down as we do not have the required enzyme (cellulase)
57
what happens to neighbouring glucoses?
they are inverted - alpha bond, beta bond, alpha bond etc
58
importance of glycoproteins...
how cells recognise each other
59
importance of glycolipids...
structure of membranes
60
how do sugars on the surface play an important role in blood cells?
they determine how blood cells are recognised by the immune system
61
how do sugars on the surface play an important role in viral coats?
in the way the virus attacks the cell
62
what is a nucleotide?
a nitrogen ring linked to a 5 carbon sugar which can be made of ribose or deoxyribose with a phosphate group attached

Week 2 (7 decks)

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