week 3

Question 1

define and name the monosaccharides

Answer 1

simplest carbohydrate - 1 sugar unit

hexoses
glucose, fructose, galactose

pentoses
- ribose and deoxyribose

Question 2

define and name the disaccharides

Answer 2

two monosaccharides linked by a condensation reaction to form an alpha or beta glycosidic bond

maltose: glucose and glucose with alpha1,4 bond

lactose: galactose and glucose with beta1,4 bond

sucrose: glucose and fructose with alpha1,2 bond

Question 3

Explain why some people can have lactose and others can’t

Answer 3

as we transit from breast/ bottle feeding to solids we start to production of lactase

some people who can digest lactose have lactase persistence, where they persist to produce this lactase into adulthood

Question 4

what are polyols?

Answer 4

derived from mono-, di- or poly saccharides
1 OH group attached to EACH carbon
occur naturally in many fruit and vegetables, but also produced from hydrogenation of sugars or via fermentation of sugars
- primarily used as low energy sweeteners because they are not fully absorbed in the small intestine => fermented by bacteria in the large intestine
- may induce bloating, diarrhoea and flatulence in large quantity, as water is drawn into the colon and bacterial fermentation occurs, producing gas

Question 5

what are oligosaccharides?

Answer 5

• contain 3-10 monosaccharides
• e.g. raffinose and stachyose (onion, legumes, cabbage, broccoli)
• mainly indigestible by human digestion enzymes => fermented by bacteria
• may cause digestive discomfort depending on gut bacteria profile

Question 6

what are polysaccharides?

Answer 6

• > 10 monosaccharides: 100-1000+ glucose molecules
• starch, cellulose, glycogen
• digestibility depends on type of glycosidic bonds binding the glucose molecules: alpha1,4 0r alpha1,6 are digestible

Question 6

how many kj in 1g CHO

Answer 6

16.7 / 17 kj

Question 7

what is CHO AMDR

Answer 7

45-65% EER

Question 8

what is a high GI food

Answer 8

carbohydrate foods that are digested quickly, resulting in glucose absorbed rapidly, have the highest glycemic index (GI more than 70). The “blood glucose response” is fast with high peaks

Question 9

what is a low GI food

Answer 9

carbohydrates foods that are digested slowly result in gradual glucose absorption and a gradual, moderate rise in BGL. They have low GI (GI less than 55). The “blood glucose response” is slower and flatter

Question 10

factors affecting GI of a food or meal

Answer 10

• amylose to amylopectin ratio
• degree of processing, e.g., wholemeal flour versus refined flour; micronised starch versus whole grain
• acidity
• sugar content + type of sugar
• other macronutrients contained in the food/ meal (e.g. lactose in whole fat milk vs low fat milk)
• ripeness of fruit
• fiber content

Question 11

what is glycemic load and how is it calculated

Answer 11

• based on the amount of CHO in the serving being consumed of test food
• CHO gram x GI / 100 = GL
• ideally want GL below 10
• above 20 is high GL