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GI- Week 3 > Skildum: Nutrition, Proteins, Carbohydrates > Flashcards

Skildum: Nutrition, Proteins, Carbohydrates Flashcards

1
Q

What are the main dietary carbohydrates?

A 
fructose
lactose (Gal + Glu)
sucrose (Fru + Glu)
amylose (a1,6 bonds)
amylopectin (a1,6 & a1,4 branches)
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2
Q

What are the dietary disaccharides and their linkages?

A

lactose (Gal + Glu); b-1,4
sucrose (Fru + Glu); a-1,2
trehalose (Glu + Glu); a-1,1 (mushrooms)

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3
Q

How are starches that enter the mouth broken down?

A

Starch is broken down by salivary amylase to maltose, maltotriose, and alpha dextrin. Pancreatic amlase breaks these products down further to maltose maltriose and limit dextrans. They are then transported into intestinal epithelial cells by brush border enzymes.

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4
Q

Where is amylase activity highest?

A

Duodenum

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5
Q

What type of enzyme is amylase? What does it do?

A

Endoglycosidase

Cuts alpha 1-4 bonds in polysaccharides

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6
Q

What are the 4 disaccharidases of the brush border?

A

Glucoamylase
Sucrase/isolmaltase complex
trehalase
b-glycosidase complex

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7
Q

What does glycoamylase/maltase do?

A

Exoglycosidase that cuts glucose off the NON-REDUCING ends of starch

Cleaves alpha 1-,4 bonds of MALTOSE to form two molecules of GLUCOSE.

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8
Q

What is isomaltose?

A

Disaccharide w/ alpha 1-6 bond

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9
Q

Where is glucoamylase activity the highest?

A

ileum

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10
Q

What is the sucrase?

A

ISOMALTASE COMPLEX w/ TWO extracellular domains w/ diff substrate specificities.

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11
Q

What is the difference between the sucrase and isomaltose ends of the sucrase?

A

Sucrase cuts sucrose into glucose and fructose

Isomaltose cuts the a-1,6 bond in isomaltose

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12
Q

Where is sucrase isomaltase activity the highest?

A

jejunem

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13
Q

Trehalase has ONE catalytic site. What is it’s ONE substrate?

A

Trehalose

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14
Q

What is trehalose and where is it found?

A

Two glucose units bonded through the number 1 carbons.

Found in insects, algae, mushrooms and other fungi.

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15
Q

What is a beta glycosidase complex?

A

A glycophosphatidylinositol (GPI) glycan anchored protein with two catalytic domains.

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16
Q

What are the two catalytic domains of a beta glycosidase complex?

A
  1. Glucosyl ceramide domain: A glycophosphatidylinositol (GPI) glycan anchored protein with two catalytic domains.
  2. Lactase domain: Splits the 1,4 bond in lactose to make galactose and glucose.
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17
Q

How are carbs absorbed when then conc in the lumen exceeds that of the blood?

A

facilitated diffusion

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18
Q

How are carbs absorbed when the conc in the lumen is LOWER than that of the blood?

A

cell must expend ENERGY get the monosaccharides inside

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19
Q

What is fructose?

A

Naturally occurring monosaccharide found in honey

or….

product of SUCRASE acting on SUCROSE–> glucose and FRUCTOSE

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20
Q

What is high fructose corn syrup?

A

mix of fructose and glucose

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21
Q

What are substrates for fermentation by gut bacteria?

A

amylose and amylopectin

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22
Q

Short chain fatty acids (acetate, propionate and butyrate) are produced by bacteria and used as fuel by…

A

colonocytes

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23
Q

What causes lactose intolerance?

A

No lactose>
bacteria ferment lactose to LACTIC ACID>
water enters gut to balance diff in H conc>
DIARRHEA

24
Q

glycolysis

A

all tissues

25
Q

glycogenogenesis

A

all tissues

26
Q

fatty acid synthesis

A

liver

27
Q

cholesterol synthesis

A

liver

28
Q

AA synthesis

A

mainly liver, but most tissues

29
Q

glycosylation of proteins/lipids

A

all tissues

30
Q

Describe how protein is broken down.

A

Mechanically chewed>

Low pH DENATURES proteins; activates PEPSINOGEN>

LUMENAL PROTEASES digest to tripeptides, dipeptides, and amino acids>

Tripeptides, dipeptides and amino acids are transported into the intestinal epithelial cell>

INTRACELLULAR PEPTIDASES digest tri- and dipeptides to amino acids>

AMINO ACIDS are transported into the blood

31
Q

PEPSINOGEN + H

A

PEPSIN

32
Q

TRYPSINOGEN + ENTEROPEPTIDASE

A

TRYPSIN

33
Q

CHYMOTRYPSINOGEN + TRYPSIN

A

CHYMOTRYPSIN

34
Q

PROELASTASE + TRYPSIN

A

ELASTASE

35
Q

PROCARBOXYPEPTIDASES + TRYPSIN

A

CARBOXYPEPTIDASES

36
Q

What do endopeptidases do and what determines their specificity?

A

cleave peptide bonds w/in a chain

side chain of the carbonyl containing acid

37
Q

What does trypsin do?

A

cuts peptide bonds in which carbonyl is provided by arginine or lysine

38
Q

What do exopeptidases do?

A

cut SINGLE AA from ends of peptide chains

39
Q

What protein transporters are Na dependent?

A

all but L

40
Q

What are sources of the intracellular AA pool?

A

Extracellular amino acids

Protein degradation

de novo synthesis from glycolysis or TCA cycle intermediates

41
Q

What are the three key cofactors for enzymes in AA metabolism?

A

PLP
FH4
BH4

42
Q

PLP is a cofactor for…

A

transaminations
deaminations
carbon chain transfers

43
Q

PLP deficiency

A

seizures
diarrhea
anemia
EEG abnormalities

44
Q

FH4 is a cofactor for

A

one carbon transfers

45
Q

FH4 def

A

megaloblastic anemia

46
Q

BH4 is a cofactor for

A

ring hydroxylations (Phe> Tyr)

47
Q

BH4 def

A

seizures

developmental delays

48
Q

What controls protein synthesis and degradation?

A

the metabolic state in the cell

49
Q

What is the role of the mTORC1 complex in protein synthesis?

A

It ACTIVATES protein synthesis and INHIBITS autophagy

50
Q

What inhibits protein synthesis and PROMOTES autophagy?

A

activation of AMPK

51
Q

What does AMPK block?

A

TSC2 autophagy / protein synthesis
p53 cell cycle, DNA repair
p27 cell cycle
ACC acetyl CoA carboxylase; fatty acid synthesis
HMGCR cholesterol synthesis
PFKBF3 key subunit of PFK-2; regulation of glycolysis

52
Q

What are the dietary protein requirements for an infant?

A

?

53
Q

What is the most important circulating carbohydrate?

A

glucose

54
Q

Does our diet contain glucose?

A

Almost none!

We eat other carbs (polysaccharides, disaccharides, fructose) that are converted to glucose by our body

55
Q

What dietary carbohydrate’s structure most resembles glycogen?

A

Amylopectin (linear glucose chain w/ 1,4 linkage and 1,6 branch points)

56
Q

What happens to ingested fructose and disaccharides?

A

They go straight to the small intestines and are broken down by brush border enzymes there.

57
Q

Protein malnutrition is called…

A

kwashiorkor

GI- Week 3 (15 decks)

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