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GI- Week 4 > Skildum: Fiber and Lipids > Flashcards

Skildum: Fiber and Lipids Flashcards

1
Q

What is fiber?

A

carbs that aren’t digestible

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2
Q

Why is fiber impt?

A 
it effects:
GI motility
absorption of nutrients
TI microbiome
immunity
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3
Q

How is fiber classified?

A
  1. soluble- viscous/non-viscous

2. insoluble- non-viscous

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4
Q

What is a major component of plant cell walls that is also abundant in bran, beans, nuts, roots, vegetables and apples?

A

Cellulose

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5
Q

How does the structure of a simple starch compare to cellulose? How does this relate to amylase?

A

Cellulose unlike starches is NOT a substrate for amylase

Both are glucose polymers but:

starch: a 1,4 bonds
cellulose: B 1,4 bonds

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6
Q

What are lignins (insoluble fiber)?

A

branched polymers of phenolic subunits

Found in the stems and seeds of fruits

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7
Q

What is hemicellulose (insoluble fiber)?

A

a branched polymer abundant in bran, whole grains, and nuts. (Hemicelluloses with acidic side chains can be soluble.)

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8
Q

What forms hte backbone of hemicellulose?

A

xylose
mannose
galactose

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9
Q

What forms the side chains of hemicellulose?

A

arabinose
glucuronic acid
galactose

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10
Q

What are pectins?

A

SOLUBLE FIBER!

branched polymers abundant in apples, strawberries and apples.

Almost completely degraded by gut bacteria

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11
Q

What are forms the backbone and side chains of pectins?

A

backbone: galacturonic acid

side chains: rhamnose, arabinose, xylose, fucose, and galactose

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12
Q

Gums (hydrocolloids) are secreted by …

A

plants to close wounds.

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13
Q

What are common food additives that are completely fermented by gut bacteria?

A

Gums– soluble fiber!

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14
Q

Where are B-glucans found?

A

oats
barley
mushrooms

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15
Q

B glucans are fermented by gut bacteria to…

A

short fatty chain acids

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16
Q

What subunits form B glucans?

A

homopolymers of glucopyranose subunits

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17
Q

What soluble fiber is found in asparagus, leeks, onions, garlic, tomatoes and bananas?

A

fructans

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18
Q

What soluble fiber is a prebiotics, that promotes the growth of bifidobacteria (gram positive anaerobes) in the gut?

A

fructans

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19
Q

What is a synthetic fructan used as a fat substitute in salad dressings?

A

inulin

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20
Q

What is a soluble fiber that has a structure similar to gums, is quite indigestible and holds a lot of water?

A

psyllium

*fun note–commonly used in india for diarrhea (i’ve used it:)

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21
Q

What are chitin and chitosan?

A

Insoluble fibers found in the exoskeletons of insects and crustaceans.

Their structure is similar to cellulose, but with amino group substitutions on the glucoses

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22
Q

What is polydextrose?

A

polymer of glucose and sorbitol used as a food additive to replace sugar. It is soluble, and partially fermented by the gut

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23
Q

How does soluble fiber affect gastric emptying?

A

Delays gastric emptying and INCREASES transmit time through the GI thus decreasing nutrient uptake

24
Q

How does insoluble fiber affect intestinal transit time?

A

DECREASES intestinal time and increases fecal bulk

25
Q

How do viscous fibers affect gastric emptying?

A

delay emptying

decrease mixing of food w/ digestive enzymes

decrease nutrient diffusion

increase SI transit time

26
Q

What does hte glycemic index measure?

A

How much blood glucose levels increase after ingestion

27
Q

Where are high fiber foods on the glycemic index

A

LOW

28
Q

How does fiber decrease lipid absorption?

A

prevents micelle formation required for fat uptake

29
Q

How does fiber lower serum cholesterol concentrations?

A

Increased excretion (and reduced uptake) of bile acids

30
Q

How does fiber affect the gut microbiome?

A

promotes the growth of lactobacilli and bifidobacteria

used by bacteria to generate short chain fatty acids

31
Q

Fiber increases fecal bulk. Why is this good?

A

Decreased intraluminal pressure decreases diverticulitis

32
Q

Fiber fermented by gut bacteria forms….

A

SCFA

33
Q

SCFA act as an accessible fuel for gut…

A

colonocytes

34
Q

SCFA are ligands for what receptor?

A

GRP43

35
Q

How do SCFA affect the immune system?

A

SCFA are ligands for GPR43. Stimulation leads to an anti-inflammatory signal that decreases inflammation and makes the IS more tolerant to GOOD bacteria.

36
Q

SCFA binding to GPR43 increases what cytokine? How does it affect histone deacytation?

A

increases IL-10–> Puts the BRAKES on inflammation

Competitor of histone deacytlation> changes the transcriptional patterns in cells

37
Q

SCFA activation of GPR43 leads to waht?

A

Inhibits insulin dependent storage of FA in adipose tissue and increases insulin use in other tissues (muscle, liver)

38
Q

What are the non-digestible oligosaccharides in human breast milk?

A

HMO (human milk oliogosaccharides)

39
Q

How are HMOs metabolized? What are they metabolized to?

A

Gut bacteria (bifidobacterium bifidum and B. infantis)

SCFA which then enter the blood and have immunomodulatory effects

40
Q

How do HMOs alter gut microbiome and metabalome?

A

Increase bifidobacterium present in the gut

Lead to more diverse species composition in the gut–> HEALTH

41
Q

How are HMOs anti-pathogenic?

A

HMOs can act as decoy receptors and prevent the attachment of pathogens to cellular glycolipids and glycoproteins.

This has been documented to improve the incidence of bladder infections!

42
Q

The cytosolic and extracellular isoforms of superoxide dismutase use two metal ion cofactors. What are these metal ion cofactors? An inherited disorder in the transport of one of those cofactors results in _____________.

A

Zn and Cu

Menkes: Deficiency in copper transporter at basolateral membrane of gut epithelial cells

43
Q

Rickets

A

vit D def

44
Q

Scurvy

A

vit C def

45
Q

Dents

A

Hypophophatemia

Mutation in a renal chloride channel

46
Q

CRC vit def?

A

Vit D contributes

47
Q

Gitelman

A

MG def d/t mutation in renal transporter

48
Q

If present in a polymer of glucose, which of the bonds below is not a substrate for human carbohydrate digestive enzymes?

a1,4
a1,6
b1,4
a1,1

A

B 1,4

lactose has a B1.4 bond but it is a glucose/galactose disaccharide and NOT a glucose polymer

49
Q

Indigestible fiber can be converted to _____by bacteria in the lumen of the gut.

A

acetate

50
Q

What component of human breast milke can be coverted to SCFA in the gut of a healthy infant?

A

Non digestible oligosaccharides

51
Q

What cytokine acts as a brake on inflammation?

A

IL-10

52
Q

What diet is best for infants?

A

breast milk

53
Q

Which dietary fibers DECREASE intestinal transit time?

A

Insoluble fibers

Cellulose, hemicellulose, lignin

54
Q

Which dietary fibers INCREASE intestinal transit time?

A

Soluble

Pectins, gums, B-glucans, fructans

55
Q

Which dietary fibers decrease nutrient uptake?

A

ALL of them

GI- Week 4 (12 decks)

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