Carbs - Fibre

Question 1

humans lack the enzyme to hydrolyze what bond

Answer 1

B-1,4 glycosidic bonds

Question 2

what is the definition of fibre

Answer 2

edible carbohydrate polymer with 3+ units that are not hydrolyzed by the enzymes in the small intestine
- naturally occurring
- obtained from food/synthetically derived that have physiological benefit to health

Question 3

digestible carbs come from the _____ of a plant

indigestible carbs come from the _____ of a plant

Answer 3

dig = cell lumen

indig = cell wall

Question 4

what type of starch id not susceptible to enzymatic digestion + physically inaccessible to enzymes

Answer 4

resistant starch

Question 5

why is resistant starch resistant to enzymes

Answer 5

• physical factors (fibre/protein/high starch)
• starch structure (dense/granular/processed)
• fermentable by colonic microflora

Question 6

how does resistant starch form

Answer 6

during processing, baking/cooling/storage

Question 7

what foods contain resistant starch

Answer 7

unripe bananas, oats, cooked + cooled rice/potatoes

Question 8

amylopectin is more prone to irreversible retrogradation, T or F

Answer 8

false, amylose is more prone + broken down more efficiently

amylopectin can be reversed with gentle heating

Question 9

fibre that is intrinsic + intact from plants is ____

Answer 9

dietary fibre

Question 10

fibre that is isolated, non-digestible with beneficial physiological effects in humans from plants/animals/extracted/synthesized is _____

Answer 10

functional fibre

Question 11

fibre is classified by

Answer 11

composition + physical properties

Question 12

properties of all indigestible fibres are:

Answer 12

• increase distension/stretch receptors
• add bulk w/o energy = increase satiety/decrease kcals

Question 13

differences in fibre properties determine _____

Answer 13

how each fibre functions

Question 14

fibres that delay gastric emptying + increase transit time + decrease/delay nutrient absorption are _____

Answer 14

soluble fibres

Question 15

properties of soluble fibre

Answer 15

• attract water + form gel
• delays gastric emptying/slows digestion
• increases satiety
• lowers postprandial blood glucose levels
• more fermentable that insoluble fibres

Question 16

what are sources of soluble fibre

Answer 16

oatmeal, apples, psyllium

Question 17

fibres that decrease transit time + increase fecal bulk are _____

Answer 17

insoluble

Question 18

properties of insoluble fibre

Answer 18

• don’t dissolve, pass through intact
• decreases transit time
• adds bulk to food, laxative effect
• poorly fermented

Question 19

sources of insoluble fibre

Answer 19

whole grains, seeds, broccoli

Question 20

how do soluble fibres decrease absorption of nutrients

Answer 20

• viscous gel traps nutrients
• lowers mixing of contents with digestive enzymes = lowers enzyme function + contact with brush border
• lower diffusion rate to bloodstream

Question 21

how do insoluble fibres decrease absorption of nutrients

Answer 21

• decreased transit time = not enough time for efficient absorption to even occur
• physical barrier for enzyme function

Question 22

how does fibre impact lipid binding

Answer 22

• lowered absorption of lipids interferes with micelle formation
• increased fecal bile acid excretion
• decreased enzymatic breakdown = lower serum cholesterol levels

Question 23

what types of fibre are mostly fermentable

Answer 23

fructans, pectin, gums, psyllium, resistant starch

Question 24

what type of fibre are slowly fermented

Answer 24

cellulose, hemicellulose

Question 25

what are products formed by fibre metabolism

Answer 25

• lactate = lower pH
• SCFA (propionate, acetate, butyrate) = energy sources

Question 26

what does the production of SCFAs result in

4

Answer 26

• increased water/Na absorption
• increased mucosal cell turnover
• energy
• acidification of luminal environment

Question 27

what does acidification of the lumen result in

Answer 27

• increased excretion of bile = lower solubility of free bile acids + increased Ca binding
• lowered rate of conversion of primary to secondary bile acids

Question 28

why is the rate of primary to secondary bile acids reduce from an acidic environment

Answer 28

bacterial dehydrogenase activity lowered

Question 29

fecal bulk increases as fermentability increases, T or F

Answer 29

false, fecal bulk increases as fermentability decreases

Question 30

how does fibre detoxify

Answer 30

mix of fibres increasing bulk + bacterial mass = diluting effect of toxins + less contact time on intestinal wall
- some bacteria scavenge toxins = less carcinogenic substance formation + inhibit tumor cell formation

Question 31

classified by resistant to digestion/absorption by SI + partial/complete fermentation by microbiota + ability to stimulate growth of bacteria = ______

Answer 31

prebiotics

Question 32

human gut flora is dominated by what bacteria

Answer 32

Bacteroides + firmicutes

Question 33

Fibre affecting the entrance of chyme into SI + affecting rate of carb/lipid absorption + influencing insulin secretion/lipoprotein formation = what mechanism

Answer 33

delayed gastric emptying

Question 34

viscous fibres that sequester lip/pro/carb from digestive enzymes + impairing their absorption = what mechanism

Answer 34

interference with digestive enzymes

Question 35

fibres binding to bile acids/interfere with micelle formation + impairing the absorption of cholesterol/bile acids/lipids = what mechanism

Answer 35

interference with micelle formation

Question 36

fibres interfering with micelle formation + ability of digestive enzymes to hydrolyze lip/pro/carb = what mechanism

Answer 36

interference with mixing of intestinal contents

Question 37

absorption of propionate (produced by fermentation of fibre in colon) inhibits HMG-CoA reductase activity (rate limiting enzyme for cholesterol biosynthesis) = what mechanism

Answer 37

inhibition of cholesterol biosynthesis