Session 2 - Carbs

Question 1

Carbohydrates are compounds composed of?

Answer 1

carbon, oxygen and hydrogen

Question 2

Carbohydrates are synthesised by plants from…

Answer 2

The sun (solar energy), carbon dioxide and water through the process of photosynthesis.

The carbohydrate produced via photosynthesis can be used by the plant for

• energy or transported to the roots, stems and fruits

where it can be stored as starch or converted into other constituents.

Question 3

2 ways to classify carbohydrates?

Answer 3

• Chemical structure –e.g. monosaccharides, polysaccharides, etc.
• Physiological properties –e.g. effect on blood glucose levels, effect on gut microbiota, etc.

Question 4

Dietary sources (carbs)

Answer 4

• Grains –breads and cereals, including corn
• Legumes –lentils, beans, peas
• Fruit and root vegetables
• Dairy foods –mainly milk and yoghurt
• Processed foods –sweets and hidden

Question 5

Simple carbohydrates include?

Answer 5

Fruits, milk and veggies

Cake, candy and other refined sugar products are simple sugars which provide energy but lack vitamins, minerals and fiber

Question 6

Classify simple and complex carbohydrates

Answer 6

Simple = sugars - disaccharides, monosaccharides, sucrose

Complex = starches ( potatoes, bread etc) and dietary fibre ( insoluble & soluble )

Question 7

Explain psychological classification of carbohydrates

Answer 7

Dietary carbohydrates can be classified based on physiological properties:

• Low, medium or high glycaemic effect.
• Effect on colonic health and stool output –e.g. fermentable or non-fermentable; increase stool output or no effect on stool output.

Question 8

Function of carbohydrates

Answer 8

• Substrates for energy metabolism - Brains preferred source of energy, other organs - about 50% come from carbohydrates
• Can also combine structurally with proteins and lipids to form glycoproteins and glycolipids.
• Some oligosaccharides and non-starch polysaccharides can be metabolised by gut microbiotato produce short chain fatty acids. ( good for colon health)
• Some oligosaccharides (e,g, found in breastmilk) can have an immunomodulatory effect.

Question 9

Name two sugar alcohols, where they come from and their use

Answer 9

•Sorbitol and Xylitol

• Found in nature and are prepared commercially
• Not digested or absorbed in small intestine → fermented by large gut micro flora → less energy

Commonly used as a sweetner alternative to sugar

•Glucose aldose reductase sorbitol

• Used in diabetic foods
• Slower absorption

Question 10

What are Oligosaccharides?

Answer 10

oComprised of 3-10 monosaccharides

oOccur in many foods - e.g legumes

•Raffinose, stachyose and verbascose

Galactose, glucose and fructose

Indigestible -fermented in large intestine > that is why some people experience flatulence after consuming legumes

Question 11

What are polysaccharides ?

Poly = many

Answer 11

•Starch, cellulose, and glycogen are all polysaccharides.

•Starch

• Energy source
• Cereals, fruits and tuber vegetables
• Amylose and amylopectin

Question 12

How are unused starches and simple sugars stored in the body?

Answer 12

•Unused → triglycerides → stored in adipose tissue

Question 13

What are the 3 parts that make a wholegrain?

And what is their nutritional function?

Answer 13

•Bran

• “Outer shell”
• Fibre, B vitamins, trace minerals

•Endosperm

• Provides energy
• CHO, protein

•Germ

• Nourishment for the seed
• Antioxidants, vitamin E, B vitamins

Question 14

What part of the grain do they used in processed foods?

Answer 14

When grains are processed, the endosperm is what is used! This section contains carbohydrates (energy)

The bran and germ (which is important for nutritional value) are sold off to health food shops etc..