Carbohydrates

Question 0

What bond is formed between two monosaccharides in maltose and which monosaccharides are these?

Answer 0

α 1-4 glycosidic bond between two α-D- glucose units

Question 1

What is the structure of α-D-glucose?

Answer 1

http://herboristen.wikidot.com/inhoudsstoffen:d-glucose

Question 2

In α- limit dextrin what bond forms the branched structure?

Answer 2

α 1-6 glycosidic bond

Question 3

What are the main disaccharides in the diet and what bonds are involved?

Answer 3

Sucrose- α 1-2 (glucose + fructose)
Maltose- α 1-4 (glucose)
Lactose- β 1-4 (glucose + galactose)

Question 4

What are the main dietary sources of the disaccharides?

Answer 4

Maltose in wheat, lactose in milk/dairy, sucrose in refined sugars

Question 5

How much sugar is there in the UK diet?

Answer 5

103g (total)
38g (milk and intrinsic)
65g (extrinsic)

Question 6

What are the main sources of starch in the UK diet?

Answer 6

Cereal products, vegetables

Question 7

How much starch in g is eaten by an average person per day in the UK?

Answer 7

137g (total available carbohydrate is 240g- starch= around 60% carbohydrate intake)

Question 8

What is the Atwater factor for carbohydrate?

Answer 8

3.75

Question 9

What are the two main forms of starch found in food and which is more prevalent?

Answer 9

Amylose and amylopectin*

Question 10

What are the nutritional classes of starch?

Answer 10

Rapidly digestible
Slowly digestible
Resistant

Question 11

How much non-digestible (resistant) starch is present in processed food?

Answer 11

1-10%

Question 12

Which enzymes initiate the digestion of starch?

Answer 12

α amylase (salivary and pancreatic)

Question 13

Which enzyme is essential in the breakdown of α limit dextrin?

Answer 13

Isomaltase, also known as α dextrinase

Question 14

Name 3 brush border enzymes involved in carbohydrate digestion

Answer 14

Isomaltase
Sucrase
Lactase
Glucoamylase

Question 15

Give 3 examples of classes on carbohydrate that reach the colon

Answer 15

Non-starch polysaccharide
Resistant starch
Oligosaccharides
Polyols

Question 16

What energy providing metabolites are formed?

Answer 16

Short chain fatty acids (butyrate, acetate, propionate)

Question 17

How much energy is derived from dietary fibre?

Answer 17

2kcal/g

Question 18

How many bacteria reside in the colon (per g faeces)?

Answer 18

100 trillion in large intestine

10^11-10^12 per g of faeces

Question 19

How much does the bacteria in the colon contribute to faecal mass?

Answer 19

50% dry weight

Question 20

Give in example of beneficial and one example of pathogenic colonic bacteria

Answer 20

Beneficial- bifidobacteria, lactobacilli, eubacteria, anaerobic cocci

Pathogenic- escherichia coli, clostridia, staphylococci, proteus, pseudomonas

Question 21

How much NSP is in the UK diet?

Answer 21

14g per day

Question 22

What are the main dietary sources?

Answer 22

Cereals and vegetables

Question 23

What is the DRV for NSP and what is the scientific basis of this DRV?

Answer 23

18g per day. Should increase stool weight to 100g per day

Question 24

What is the main storage form of carbohydrate in humans?

Answer 24

Glycogen

Question 25

Which organs store glycogen?

Answer 25

Liver, Muscle

Question 26

How is glycogen "used" by its storage organs?

Answer 26

Hydrolysed to glucose to maintain blood sugar levels (liver) and utilised for energy for contraction (muscle)

Question 27

Which hormone controls the formation of stored carbohydrate and which hormone controls the release of glucose from these stores?

Answer 27

Insulin | Glucagon/adrenaline

Question 28

Name 2 non-carbohydrate substances that can be converted into glucose (gluconeogenesis)?

Answer 28

Amino acids Fatty acids Lactate

Question 29

What does insoluble fibre do to stool weight and how does is have his effect?

Answer 29

Increases stool weight by adding physical bulk

Question 30

What does soluble fibre do to stool weight and how does it have this effect?

Answer 30

Increases stool weight by micro floral amplification

Question 31

What are some of the factors that affect glycaemic index?

Answer 31

``` Physical/chemical properties of food- degree of starch gelatinisation, degree of starch retrogradation, particle size Starch type Fibre content Fat content Protein content ```

Question 32

What is the laxative effect of dietary fibre?

Answer 32

Increases bulk of stool, decreases transit time, increases stool frequency, treats constipation

Question 33

What is the advantage of dietary fibre increasing the bulk of the stool?

Answer 33

Increase water content, softens stool, less straining, reduced abdominal pressure. Decreased pressure minimises risks of haemorrhoid, Harris hernia and diverticulum (weakened muscle wall in large intestine) Dilutes toxins due to decreases transit time (less time in contact with colonocytes=less reabsorption)

Question 34

What are some of the health benefits of NSP?

Answer 34

Reduced risk of colorectal cancer Reduced CVD Lowers blood cholesterol Useful in Diabetics and those who are obese Reduced abdominal pressure- haemorrhoids, haetus hernia, diverticulum