Carbohydrate Digestion Flashcards Preview

Digestive System > Carbohydrate Digestion > Flashcards

Flashcards in Carbohydrate Digestion Deck (36):

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



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



Types of complex carbohydrates

1) starches: potatoes, bread, rice (glucose)

2) Dietary Fibres:
-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



found in milk / dairy products



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


What happens when storage of carbs runs out?

body protein > glucose
fat stores > ketones (ketosis)


Recommended servings of carbs a day

Preschoolers = 4
children = 5
adults = 6


Difference between intrinsic and free sugars?

Intrinsic found in fruit & vege (lactose, fructose)
Free sugar (sucrose) added by manufacturers, we need to reduce, 50% of NZ intake


Insoluble fibre?

provides mass to faeces. Fibres attract water ensure the stools are large and soft


Soluble fibre

-Binds w FAs
- prolong emptying (fuller for longer)
- lowers cholesterol + LDL cholesterol
-fermented by bacteria > SCFAs that feed gut enterocytes, ensure appropriate DNA methylation.
-regulates Blood sugar


What does your microbiota do?
How do we get it?
What happens if this changes?

Live synergistically, thrive off carbs/fibre (only thing they can proliferate off)

Unique to us, born with, also vaginal delivery and breast millk affects

Changes with: bad diet, illness, AB


Recommended intakes of carbs

45-65% carbs
of this 10% simple sugars

15% > 5%


What happens when you have a high glycaemic Diet?

1) eat food with HGI, is absorbed very quickly, we get a high peak of blood glucose and insulin (to decrease this)
2) then as your blood glucose & insulin rapidly drops > hyperglycaemic effect > hunger
3) snack again... cycle repeats


Why are people encouraged to eat things with a LGI?

creates a more plateau effect (not peaks), fully for longer


Symptoms of lactose malabsorption?

bloating, abdominal discomfort, diarrhoea
as sugar overload disrupts the osmotic balance of LI


Primary Lactase deficiency? Management?

Genetically predisposed

Managed by: removing milk products from diet
OR taking lactase enzyme tablets with your milk product


secondary lactase deficiency?

Due to a condition (gastroenteritis, celiac that destrys villi in SI) >> lactose malabsorption

Managed by: initially removing milk products, slowly introducing them back