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NUT1009 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What are carbohydrates

A

Diverse class of compounds in all cells

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2
Q

What is the typical formula for monosaccharides

A

CnH2nOn

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3
Q

What is the typical formula for larger carbohydrates

A

CnH2n-2xOn-x where x is the number of glycosidic bonds present

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4
Q

What three elements are carbohydrates composed of

A

Carbon, hydrogen and oxygen

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5
Q

What technical roles can carbohydrates play in food manufacture and processing

A

Texture, viscosity, flavour, colour formation and bulking

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6
Q

What three ways can carbohydrates be classified

A

Chain length, number of carbons per monomer and digestible vs non-digestible

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7
Q

What is the chain length of the carbohydrates responsible for/determine

A

Behaviour of carbohydrate

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8
Q

What does the number of carbons determine

A

Application of sugar in biological source

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9
Q

How many kcal/g are in digestible carbohydrates

A

3.75-4kcal/g

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10
Q

What is the difference in metabolism between glucose and fructose

A

Glucose is used in most cells and is insulin mediated while fructose is metabolised by the liver and bypasses some glycolysis steps

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11
Q

What us fructose associated with in the body

A

Increased VLDL cholesterol and reduced insulin response

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12
Q

How are digestible carbohydrates absorbed

A

Larger carbohydrates e.g oligo and polysaccharides are enzymically degraded into sugar monomers

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13
Q

What is the Glycaemic index

A

The rate at which sugar is absorbed from food

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14
Q

What is the difference between High GI and low GI foods

A

High are rapidly absorbed and result in a sugar spike while low GI require greater digestion before sugars are absorbed

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15
Q

What are high GI foods associated with

A

Snacking behaviour, high blood sugar and increased insulin response

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16
Q

What are nutrition claims

A

Claims that relate to the specific composition of a food

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17
Q

What is the low sugar nutrition claim in the UK

A

No more than 5g/100g in solid and no more than 2.5g/100gmL in liquid foods

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18
Q

What is the sugar free nutrition claim in the UK

A

No more than 0.5g/100g in solids and no more than 0.5g/100mL in liquid foods

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19
Q

What is the no added sugars nutrition claim in the UK

A

Does not contain any added mono or disaccharides or any other food used for its sweetening properties

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20
Q

What should naturally present sugars be labelled with

A

Contains naturally occurring sugars

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21
Q

What is the nutrition claim for sources of fibre

A

At least 3g/100g or 1.5g/100kcal

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22
Q

What is the nutrition claim for high fibre

A

At least 6g/100g or 3g/100kcal

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23
Q

Why is it beneficial for manufacturers to receive a nutrition claim

A

Demonstrates improved nutrition vs competitors

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24
Q

What two forms can monosaccharides exist in

A

Cyclic and linear

25
Q

What projection are cyclic monosaccharides depicted as

A

Haworth projection

26
Q

When do sugars transition between the linear and cyclic form

A

In solution

27
Q

When do sugars contain an aldehyde or ketone group

A

When in linear form

28
Q

What projection are linear monosaccharides depicted as

A

Fischer projection

29
Q

Why do polar sugars have a high solubility

A

Hydroxyl group forms H bonds between molecules of water keeping them in solution

30
Q

What type of bond are glycosidic bonds

A

Covalent bonds

31
Q

Where do glycosidic bonds form

A

Between a sugar and another organic compound

32
Q

What is a condensation reaction

A

A reaction that liberates one molecule of water

33
Q

What does bond labelling tell us

A

What atoms in a molecule are involved in the bond

34
Q

What do alpha and beta bonds refer to

A

The position of the hydroxyl on C1

35
Q

Where has an alpha-1-4 bond formed

A

On carbon 1 and the 4th carbon of another sugar

36
Q

Where does an alpha-1-6 bond form and what does it produce

A

Between C1 and C6 producing branching between sugars

37
Q

Why can sugars not be simply substituted for eachother by manufacturers

A

Variable in intensity, profile of sweetness and properties

38
Q

What are Advanced glycation end-products (AGEs) are what are they associated with

A

Reactive sugar-protein or sugar-lipid complexes that form during high temperature food processing and are associated with loss of cellular function, reduced elasticity and cardiovascular stress

39
Q

What are oligosaccharides

A

3-10 unit carbohydrates

40
Q

What are polysaccharides

A

11+ unit polysaccharides

41
Q

What are linear form carbohydrates

A

Single chain of monomers with the same glycosidic bond linking them

42
Q

What are branched chain carbohydrates

A

Several branches due to multiple different bonds

43
Q

What is amylose

A

Helical component of starch that is long chains of alpha 1-4 bonded glucose monomers

44
Q

What is amylopectin

A

Branched shorter chain component of starch with alpha 1-4 glycosidic bonds and frequent alpha 1-6 branching

45
Q

What are the crystalline regions of starch

A

Long unbranched chains where separate chains can self-associate decreasing hydrogen bonding opportunities and therefore interact with water less

46
Q

What are amorphous regions of starch

A

Regions with a high degrees of branching and limited self-association so increased hydrogen bonding availability for interaction with water molecules

47
Q

What are starch granules

A

A long term energy store found in storage organs (tubers, roots) and seeds, grains and some legumes

48
Q

Why does starch need to be gelatinised to be digested

A

In granule form it is poorly soluble as the outermost region is crystalline

49
Q

What is starch gelatinisation

A

Mixing starch into water to suspend the granules and then heating to break the hydrogen bonds involved in self association to hydrate the amorphous regions, leading to irreversible breakdown of the granule and increasing viscosity

50
Q

What is starch retrogradation

A

Starch reassociation by releasing bound water and recrystallising without returning to a granule structure resulting in hardness/ unpalatable texture modification

51
Q

Why can fibre not be digested

A

Primarily composed of beta glycosidic bonds which humans do not synthesise the enzymes to break down beta bonds so the oligo- or polysaccharides remain intact until the colon

52
Q

What are insoluble fibres

A

Fibres that are not fermented and pass through the colon intact contributing to stool frequency, bulk and bind to harmful components (bile acids, toxins)

53
Q

What are soluble fibres

A

Fibres that can be fermented by saccharolytic colonic bacteria which liberates short chain fatty acids for use by the body as energy or in gluconeogenesis (passively providing energy)

54
Q

What is dietary fibre

A

Carbohydrates polymers with 3 or more units which are not hydrolysed by endogenous enzymes in the small intestine

55
Q

What is the carbohydrate recommendations by the eatwell guide

A

1/3 of diet, higher fibre and whole grain varieties are recommended

56
Q

What are the daily recommendations for fibre for over 16s

A

30g a day

57
Q

What is the daily recommended intake for free sugars

A

No more than 5% of total energy

58
Q

What is the daily recommendations for carbohydrates

A

50% of total energy intake

59
Q

What does free sugars not include

A

Naturally occurring sugars in dairy or fresh/cooked/dried fruit and veg

NUT1009 (11 decks)

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