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Sustainable agriculture > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Definition of carbohydrate

A

A biomolecule consisting of carbon, hydrogen and oxygen

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2
Q

What is the formula for carbohydrates?

A

CnH2nOn or Cn(H2O)n where n varies for each carbohydrate

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3
Q

When are aldoses and ketoses formed as carbohydrates?

A

When n=3

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4
Q

Examples of aldoses and ketoses

A

Aldoses: glyceraldehyde
Ketoses: dihydroxyacetone

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5
Q

What is the structure of aldoses?

A

Carbon double bond with oxygen and single bond with hydrogen

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6
Q

What is the structure of ketoses?

A

Carbon double bond with oxygen

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7
Q

Why are aldehydes (aldoses) called reducing sugars?

A

Because they are more reactive than ketone (ketoses) due to the hydrogen

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8
Q

What are enantiomers?

A

A pair of stereoisomers affected by mirror imaging

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9
Q

D-form vs L-form mirror imaging

A

D-form: OH group on right of carbon
L-form: OH group on left of carbon

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10
Q

What does D-glucose form when it reacts with itself?

A

A circular structure (α-D-glucose)

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11
Q

What happens when n=5?

A

The alpha switches to beta and H and OH swap over

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12
Q

Condensation reaction

A

When 2 monosaccharides form a disaccharide with the release of a water molecule

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13
Q

Name 3 disaccharides

A

Maltose, lactose and sucrose

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14
Q

Name 2 oligosaccharides

A

Maltodextrins and inulin

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15
Q

What are the 2 subgroups of polysaccharides?

A

Starch and non-starch polysaccharides

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16
Q

Examples of starch polysaccharides

A

Amylose and amylopectin

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17
Q

Examples of non-starch polysaccharides

A

Glycogen, cellulose and pectin

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18
Q

What are the wheat properties that are good for bread?

A
  • Easy to mill
  • Strong flour (high gluten)
  • > 13% protein
  • Hard endosperm
  • High water absorption
  • <16% moisture content
  • 98% sample purity
19
Q

How is a high protein content achieved?

A

Nitrogen support through fertiliser and water

20
Q

Why does protein content drop?

A

When the drying temperature is too high

21
Q

How can alpha amylase content be reduced in wheat?

A

Prioritising wheat harvest to prevent sprouting

22
Q

How can ergot (highly toxic) be avoided in rye?

A

Correct combine harvester settings

23
Q

What are some of the properties required for barley in distillation?

A
  • 100% germinated
  • <1.6% nitrogen
  • 2.2-2.8mm grain size
  • Uniform grains
  • 14.5% moisture content
24
Q

How can barley be improved?

A
  • Soil should be drained properly
  • Soil should not be drought prone
  • Early sowing date
  • On time harvest
  • Nitrogen nutrition should be adequate and on time
25
Q

How do monosaccharides enter the body?

A

Absorbed by the gut and transferred to the liver through epithelial cells via the portal vein

26
Q

Why is glucose needed?

A

Brain and nervous system and red blood cells

27
Q

How does glucose become energy?

A

Glycolysis, citric acid cycle and oxidative phosphorylation

28
Q

How much glucose is used as ATP?

A

40% and the rest is used as heat

29
Q

What are the average levels of blood glucose levels?

A
  • Never below 5mM
  • Rises to 7-8mM after food
30
Q

What is glycogen?

A

A store of glucose chains synthesized in the liver

31
Q

What is glycogenesis?

A

The synthesis of glucose into glycogen and is dependent on insulin

32
Q

What is glycogenolysis?

A

Glycogen degraded into glucose catalysed by enzyme phosphorylase

33
Q

What is gluconeogenesis?

A

Synthesis of glucose from non-carbohydrates (amino acids, glycerol, lactate)

34
Q

Insulin

A

Promotes use of glucose to reduce blood sugar

35
Q

Glucagon

A

Completes glycogenesis and gluconeogenesis to increase blood sugar

36
Q

What are the 2 sub-groups for oligosaccharides?

A

Glycaemic and non-glycaemic glucans

37
Q

Glycaemic vs Non-glycaemic glucans

A

Glycaemic- Digested and absorbed in small intestine
Non-glycaemic- Can’t be broken down and absorbed in large intestine

38
Q

What is alpha-amylase?

A

Enzyme in saliva which breaks down amylose and amylopectin

39
Q

What is the lumen?

A

An area in the small intestine which hydrolyses starch into maltose and dextrin

40
Q

How are starchy polysaccharides digested in the small intestine?

A

Enzymes on enterocytes in villi break down to monosaccharides which can be absorbed into small intestine

41
Q

How are non-starchy polysaccharides absorbed in the large intestine?

A

Fermentation by sugars

42
Q

What are the membranes on the enterocytes?

A

Apical and basolateral membranes

43
Q

How does the apical membrane transport monosaccharides?

A

Sodium-glucose transport protein (SGLT1)
Fructose transport protein (GLUT5)

44
Q

How does the basolateral membrane transport monosaccharides?

A

GLUT2 protein

Sustainable agriculture (9 decks)

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