Carbs Flashcards
Source of carbs
- Plants convert sunlight into carbohydrates through photosynthesis (process in which green
plants use sunlight to make their own food)
What are simple carbs?
Monosaccharides
-Single-sugar units
- glucose
- fructose
- galactose
What is glucose?
Most important carb
- Focuses on CHO metabolism
-Most cells rely on glucose -> Brain and nervous system
What is fructose?
- Fruit sugar
-naturally in fruits, veggies, honey and part of table sugar
What is galactose?
- Mostly occurs as part of lactose
-Byproduct of digestion
What are disaccharides?
-Pairs of sugar units bonded together
-Combination of pairs of monosaccharides
1. Maltose
2. Sucrose
3.Lactose
How to link two monosaccharides?
Condensation
How to break up into two monosaccharides?
Hydrolysis
What is condensation?
Form a bond between two compounds
-Water is released
What is hydrolysis?
Bond is broken
-Water is required for this reaction
What is maltose
-Plant sugar
-Composed of two glucose units
-Occurs in plants during break down of stored starch and in humans during carb digestion
What is sucrose?
Composed of glucose and fructose
-Table sugar
What is lactose?
Glucose and galactose
What ars complex carbs?
Oligosaccharides & polysaccharides
-More than two monosaccharides (starch, glycogen, fibre)
What are major polysaccharides?
- Starch
- Glycogen
- Fibre
What is starch?
Multiple glucose units
(occasionally branched or
unbranched)
Storage form in plants (grains
e.g. rice, legumes e.g. beans,
tubers e.g. potatoes)
What is glycogen?
Multiple glucose units
Not a significant food source of carbs
Important role in carb storage in the body
What os fibre?
Non-starch polysaccharides
- Indigestible
What are the three types of fibre?
- Dietary fibre: non-digestible of plants (grains, rice, seed, legumes, fruits)
- Functional fibre: non-digestible carbs extracted from plants and added to food (cellulose, pectin)
How to calculate total fibre?
dietary + functional
What is soluble fibre?
absorbed water to form a gel
Fermented and broken down by bacteria in colon producing gasses and short chain fatty acids
Slow GI motility
What are non-soluble fibres?
-Do not dissolve in water and do not form a gel
- Non-fermentable
-Provide bulk and feeling of fullness
-Help with weight management
-Help with constipation
Digestion of carbs in mouth
– salivary amylase
– breaks down starch into small polysaccharides and maltose
Digestion of carbs in stomach
– acid inactivates salivary
amylase, halting starch
digestion
Digestion of carbs in pancrease
– pancreas secretes pancreatic amylase into
small intestine to digest starch into small
polysaccharides and maltose
Digestion of carbs in small int.
– Enzymes (maltase, sucrase, lactase) hydrolyze
disaccharides (maltose, sucrose, lactose) into
monosaccharides (glucose, fructose and
galactose)
– Monosaccharides are absorbed across the
microvillus membrane of the small intestine
into the portal blood system for transport to
the liver.
What is glycemic response?
glucose absorption after a meal
What is glycemic index?
-Potential to raise Blood glucose
-Measures how quick carbs absorb
Factors that influence GI
-starch structure,
-fiber content,
-presence of fat and protein,
-food processing,
-mixture of foods in a meal,
-individual glucose tolerance
What are excess carbs stored as?
glycogen
What is insulin?
– produced by beta cells of the pancreas
– helps cells take in glucose from the
blood
– facilitates glucose uptake by muscles
and adipose tissue
– stimulates the liver and muscle to take
up glucose and convert it to glycogen
What is glucagon?
– produced by alpha cells of the pancreas
– stimulates the breakdown of glycogen
to glucose (glucose is exported from liver but not muscle)
– more glucose is available to cells of the body
What is glucogenesis?
the production of glucose from amino acids in liver
RDA for carbs is?
130g of digestible carbs per day for adults
- Adequate for normal brain function
Carb recommendations
Total carbohydrates: 45-65% caloric
input (Health Canada’s recommendation)
– 200-330 g/day men
– 180-230 g/day women
What happens when carb intake is low?
Proteins are used for gluconeogenesis
Recommended total fibre?
About 14 g of dietary +
functional fibre/1000
kcal/day
What are non-nutritive sweeteners?
- Aspartame
- Saccharin
- Sucralose
- Stevia
