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Week 2 > Introduction to Carbohydrates > Flashcards

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
Q

what is D-galactose?

A

part of milk sugar

26
Q

what is D-ribose?

A

used in RNA

27
Q

what is a reducing sugar?

A

a sugar that will reduce inorganic ions eg Cu++ (Fehling’s reagent)

28
Q

what sugars are reducing sugars?

A

all monosaccharides regardless of aldehyde or ketone

29
Q

what is not a reducing sugar?

A

sucrose

30
Q

colour change of Fehling’s…

A

blue Cu++ to orange Cu+ when reduced

31
Q

absorbance using colorimeter…

A

more colour = higher absorbance reading

32
Q

what happens in the glucose oxidase test?

A

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
Q

how does glucose enter red blood cells?

A

in a non-insulin dependent matter

34
Q

what does uncontrolled hyperglycemia result in?

A

a covalent linkage between glucose and the NH2 terminal amino acid of the haemoglobin beta chain - HbA1c

35
Q

what is the half life of a red blood cell?

A

about 120 days

36
Q

what are good levels of blood glucose?

A

up to 10mmol/l or 180mg/dL

37
Q

what are good levels of HbA1c?

A

up to 8

38
Q

what is glucose + glucose?

A

maltose and water

39
Q

what is glucose + galactose?

A

lactose and water

40
Q

what is glucose + fructose?

A

sucrose and water

41
Q

what is lactose?

A

a disaccharide of beta D-galactose and alpha or beta D-glucose

42
Q

what type of bond does lactose contain?

A

a beta 1,4-glycosidic bond

43
Q

where is lactose found?

A

milk and milk products

44
Q

what is lactose intolerance?

A

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
Q

what happens as a result of lactose intolerance?

A

lactose passes into colon where bacteria ferments it causing stomach cramps, bloating, flatulence

46
Q

what is a homopolymer?

A

polymer formed from subunits that are the same

47
Q

what is the most common homopolymer in animals?

A

glycogen

48
Q

what is glycogen?

A

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
Q

where is glycogen found?

A

in liver and muscle

50
Q

what is starch?

A

the plant form of carbohydrate ingested by humans

51
Q

what is amylose?

A

an unbranched starch comprised of glucose units, alpha 1,4 linkage

52
Q

what is amylopectin?

A

a branched form of starch with alpha 1,4 linkage (1 every 30 sugar monomers) to the alpha 1,6 linkage

53
Q

where is alpha amylase secreted from?

A

salivary glands

54
Q

where is amylose and amylopectin hydrolysed?

A

the pancreas

55
Q

what is cellulose?

A

main storage of glucose in plants

56
Q

what link does cellulose contain?

A

beta 1,4 that we cannot break down as we do not have the required enzyme (cellulase)

57
Q

what happens to neighbouring glucoses?

A

they are inverted - alpha bond, beta bond, alpha bond etc

58
Q

importance of glycoproteins…

A

how cells recognise each other

59
Q

importance of glycolipids…

A

structure of membranes

60
Q

how do sugars on the surface play an important role in blood cells?

A

they determine how blood cells are recognised by the immune system

61
Q

how do sugars on the surface play an important role in viral coats?

A

in the way the virus attacks the cell

62
Q

what is a nucleotide?

A

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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