Carbohydrate Digestion Flashcards
3 Functions of carbs?
1) supplies energy (from glucose)
2) Protein sparing
3) prevents ketosis
Main energy source and how is this stored?
Glucose, stored as glycogen in the liver and muscle
How much energy of the NZ diet do carbohydrates produce
40-60%
the link between carbs and many ethnicities?
carbs form a staple food for majority of ethnicities around the world.
asian = rice
european = wheat/potatoes
Complex carbs and simple sugars eventually end up as
Glucose
Types of complex carbohydrates
1) starches: potatoes, bread, rice (glucose)
2) Dietary Fibres:
- INSOLUBLE (bran)
- SOUBLE (lentils, beans)
Types of simple carbohydrates?
Sugars: (glucose)
1) Dissacharides - sucrose, maltose, lactose
2) monosaccharides - fructose, glucose, galactose
compounds that make up carbs
aldehydes + ketones
Types of monosaccharides
glucose, fructose, galactose
Galactose
found in milk / dairy products
Fructose
found in veges + fruit
Types of disaccharides and what makes the
Maltose= glucose + glucose Sucrose= glucose + fructose Lactose = glucose + galactose
maltose is for
fermentation and alcohol production
Sucrose is found in
table sugar + processed foods
What are polysaccharides. What is their purpose?
A chain of two or more monosaccharides. Chain may be branched (amylose) or branched (amylopectin + glycogen)
They function as food storage as glycogen
Amylose and amylopectin are…?
Both storage polysaccharides of plants. Made up of glucose polymers, they are starches (not water soluble)
-found in cereals, grains, root veges, legumes
Features of glycogen (liver & skeletal muscle)
- storage form of glucose
- 12-14 hrs worth stores
- Provides a rapid release of energy when needed
- liver releases first (bloodglucose control)
Non-starch polysaccharides are, and what are the types?
polysaccharies with glucose links that can’t be broken (so can’t be digested) = “NSP dietary fibre”
-give very little E
1) SOLUBLE FIBRE: dissolves in water, forms gels, easily digested by bacteria (fermented)
2) INSOLUBLE FIBRE: doesn’t dissolve or form gels, not easily fermented
Digestion of Carbs in the mouth?
S: salivary glands secrete saliva into the mouth. Moistens food, amylase hydrolyses starch > small PS
DF: mechanical action of the mouth crushes/mixes DF with saliva for swallowing
Digestion of carbs in the stomach?
S: stomach acid inactivates salivary enzymes
DF: DF not digested, delays gastric emptying
Digestion of starch carbs in SI?
S: chyme stimulates pancreas to release amylase. This breaks starch down > small PS
PS go to surface of micro villi
DS enzymes on surface of SI cells hydrolyse DS into MS that can now be absorbed
(*DS enzymes specific to specific DS)
Digestion of Dietary Fibre in SI and LI
SI: DF is not digested, delays absorption
LI: bacterial enzymes digest DF into SCFA, gas
The steps of monosaccharide absorption?
takes place mainly in the SI
1) MS enter capillaries of the intestinal villi
- Glucose & galactose via AT of GLUT-1 transport protein
- Fructose via facilitated diffusion
2) MS travel to liver via Hepatic portal vein
3) in the liver, galactose & fructose > glucose
4) Glucose now available to be used to either control blood sugar or be stored as glycogen
Why are people concerned for those who consume excessive amounts of fructose
That they may have issues with excess storage of fructose within the liver > fatty liver
