Carbohydrates

Question 1

Definition of carbohydrate

Answer 1

A biomolecule consisting of carbon, hydrogen and oxygen

Question 2

What is the formula for carbohydrates?

Answer 2

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

Question 3

When are aldoses and ketoses formed as carbohydrates?

Answer 3

When n=3

Question 4

Examples of aldoses and ketoses

Answer 4

Aldoses: glyceraldehyde
Ketoses: dihydroxyacetone

Question 5

What is the structure of aldoses?

Answer 5

Carbon double bond with oxygen and single bond with hydrogen

Question 6

What is the structure of ketoses?

Answer 6

Carbon double bond with oxygen

Question 7

Why are aldehydes (aldoses) called reducing sugars?

Answer 7

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

Question 8

What are enantiomers?

Answer 8

A pair of stereoisomers affected by mirror imaging

Question 9

D-form vs L-form mirror imaging

Answer 9

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

Question 10

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

Answer 10

A circular structure (α-D-glucose)

Question 11

What happens when n=5?

Answer 11

The alpha switches to beta and H and OH swap over

Question 12

Condensation reaction

Answer 12

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

Question 13

Name 3 disaccharides

Answer 13

Maltose, lactose and sucrose

Question 14

Name 2 oligosaccharides

Answer 14

Maltodextrins and inulin

Question 15

What are the 2 subgroups of polysaccharides?

Answer 15

Starch and non-starch polysaccharides

Question 16

Examples of starch polysaccharides

Answer 16

Amylose and amylopectin

Question 17

Examples of non-starch polysaccharides

Answer 17

Glycogen, cellulose and pectin

Question 18

What are the wheat properties that are good for bread?

Answer 18

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

Question 19

How is a high protein content achieved?

Answer 19

Nitrogen support through fertiliser and water

Question 20

Why does protein content drop?

Answer 20

When the drying temperature is too high

Question 21

How can alpha amylase content be reduced in wheat?

Answer 21

Prioritising wheat harvest to prevent sprouting

Question 22

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

Answer 22

Correct combine harvester settings

Question 23

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

Answer 23

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

Question 24

How can barley be improved?

Answer 24

• 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

Question 25

How do monosaccharides enter the body?

Answer 25

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

Question 26

Why is glucose needed?

Answer 26

Brain and nervous system and red blood cells

Question 27

How does glucose become energy?

Answer 27

Glycolysis, citric acid cycle and oxidative phosphorylation

Question 28

How much glucose is used as ATP?

Answer 28

40% and the rest is used as heat

Question 29

What are the average levels of blood glucose levels?

Answer 29

- Never below 5mM - Rises to 7-8mM after food

Question 30

What is glycogen?

Answer 30

A store of glucose chains synthesized in the liver

Question 31

What is glycogenesis?

Answer 31

The synthesis of glucose into glycogen and is dependent on insulin

Question 32

What is glycogenolysis?

Answer 32

Glycogen degraded into glucose catalysed by enzyme phosphorylase

Question 33

What is gluconeogenesis?

Answer 33

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

Question 34

Insulin

Answer 34

Promotes use of glucose to reduce blood sugar

Question 35

Glucagon

Answer 35

Completes glycogenesis and gluconeogenesis to increase blood sugar

Question 36

What are the 2 sub-groups for oligosaccharides?

Answer 36

Glycaemic and non-glycaemic glucans

Question 37

Glycaemic vs Non-glycaemic glucans

Answer 37

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

Question 38

What is alpha-amylase?

Answer 38

Enzyme in saliva which breaks down amylose and amylopectin

Question 39

What is the lumen?

Answer 39

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

Question 40

How are starchy polysaccharides digested in the small intestine?

Answer 40

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

Question 41

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

Answer 41

Fermentation by sugars

Question 42

What are the membranes on the enterocytes?

Answer 42

Apical and basolateral membranes

Question 43

How does the apical membrane transport monosaccharides?

Answer 43

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

Question 44

How does the basolateral membrane transport monosaccharides?

Answer 44

GLUT2 protein